DE102021004831A1 - METHOD FOR MACHINING OPTICAL WORKPIECES, ESPECIALLY PLASTIC GLASSES LENSES - Google Patents

Abstract

A method for machining optical workpieces, in which a semi-finished product (HZ) with predetermined surface geometries on the front side (FS) and rear side (RS) and a contoured edge (RA) of a predetermined edge thickness (D2) is formed from a blank (RL). comprises the following main steps: i) providing the blank to be machined at least on the back and edge with a blank thickness (D1); ii) non-blocking picking up of the blank for support at the rear; iii) Processing the blank on the front side using a first tool (WZ1) to form a circumferential geometric shape (NU) with a depth (TI) greater than or equal to the edge thickness of the semi-finished product to be formed, with a circumferential surface (UF) remaining on the workpiece, which defines the contoured edge of the stock to be formed; iv) picking up the workpiece for support at the front; and v) machining the workpiece on the rear using at least one second tool to form the semi-finished product with the predetermined surface geometry on the rear.

Description

TECHNICAL AREA

The present invention relates generally to a method of machining optical workpieces. In particular, the invention relates to a method for machining spectacle lenses made of plastic, for example polycarbonate, CR39 or so-called "high index" materials, as is the case in so-called "RX workshops", i.e. production facilities for the production of individual spectacle lenses according to prescription in very large extent is practiced.

STATE OF THE ART

In RX workshops, the following process steps are usually carried out as part of the industrial production of spectacle lenses (see also the 16 to the prior art): First, a suitable right and / or left eyeglass lens blank (also called "blank") from a semi-finished goods store or the like. removed. Semi-finished products insofar as the spectacle lens blanks, which are generally round or oval when viewed from above and have not yet been edged, already have their final geometry on one of their two optically effective surfaces. The spectacle lens blanks are then prepared for the blocking process, namely by applying a suitable protective film or a suitable protective lacquer to protect the already finished, injection-molded prepared or otherwise shaped optically active surface with its final geometry.

Next is done according to 16 the so-called "blocking" of the spectacle lens blanks. In this case, the spectacle lens blank is connected to a suitable, so-called “block piece”, for example a block piece in accordance with the German standard DIN 58766. When blocking, the position and, if necessary, the shape of the spectacle lens blank are first determined by measurement, before the spectacle lens blank is then positioned in six degrees of freedom relative to the block piece, so that the block piece assumes a predetermined position in relation to the protected, already finished surface of the spectacle lens blank.

This set position is then fixed. The space between the block piece and the spectacle lens blank is filled with a molten material - for example "alloy", ie a metallic alloy that is usually bismuth-based, or wax (see, for example, the publication EP 1 593 458 A2 ). After the filling material has solidified, the block piece represents a receptacle for processing the spectacle lens blank or forms a machine interface, which subsequently remains on the spectacle lens during several processing operations in different machines and must reliably hold the spectacle lens in a defined position. As an alternative to the aforementioned solidifying block materials, it has already been proposed (cf., for example, the publications DE 10 2007 007 161 A1 and EP 2 011 604 A1 ), to use a special - if necessary under UV light - hardening adhesive to connect the block piece and the spectacle lens blank, with the adhesive as a layer in between. The process step of blocking can also be fully automated (see, for example, the publication WO 2009/135689 A1 ) .

Only then can the spectacle lens blanks be processed in the next process step 16 , the so-called "generating", can be pre-machined into a semi-finished product. Depending on the material, this pre-processing is carried out - in the case of plastic by means of a geometrically defined cutting edge, i.e. regularly milling and/or turning - in a special processing machine (see, for example, the publications EP 1 719 585 A2 and EP 2 011 603 A1 ), also called "generator", in which the blocked spectacle lens blank is held by means of the block piece on or in a receptacle of a rotating workpiece spindle. Here, the optically effective surface of the respective spectacle lens blank that has not yet been processed is given its macro geometry (optically active shape) according to the recipe.

According to 16 generation usually includes two sub-steps (see also the publication EP 1 203 626 B1 , 1 ), namely edge pre-processing (also known as pre-edging or "cribbing"), in which the edge of the spectacle lens blank is processed from the so-called "raw diameter" to the so-called "finished diameter", and subsequent surface processing. In the case of plastic lenses, this is done regularly first by milling using, for example, a high-speed rotary driven disc milling cutter TF, which is 17 is shown in principle for the prior art.

As for example in the pamphlet EP 0 758 571 B1 described, the milling can be done in such a way that the circular milling cutter TF, whose tool center path is in 17 is indicated by a thick line, coming from the edge RA over the transition between the edge RA and the surface in the surface on the back RS of the spectacle lens blank RL, which is driven rotating about its central axis MA, "rolls in" in a rotating manner. A prerequisite for this milling operation is that the block piece BS temporarily attached to the front side FS of the spectacle lens blank RL has a maximum diameter smaller than the finished diameter of the workpiece, since it otherwise there would be a collision between milling tool TF and block piece BS. In this milling operation, the connection between workpiece RL and block piece BS must also withstand considerable forces and moments, also due to the leverage effect due to the relatively large distance between the machining engagement of tool TF and workpiece RL at workpiece edge RA and the connection point of workpiece RL and block piece BS. At the end of this milling process, most of the blank material to be removed has already been removed.

As a further sub-step of surface machining with a geometrically defined cutting edge on the rear RS of the workpiece, turning usually follows with the aid of a so-called “fast tool” arrangement (see, for example, the publication EP 1 779 967 A2 ), which is used to reciprocately move a lathe tool with a rotary cutting edge in order to work (also) non-rotationally symmetrical surface sections (e.g. free-form surfaces for varifocal glasses) on the rotating surface of the workpiece to be machined in a so-called "single-point cutting" process . At the end of this turning operation, in which the cutting edge can also be guided in several gears from radially outwards to radially inwards (or vice versa) over the rotating workpiece, pre-processing traces such as milling marks or the like are present on the semi-finished product produced. eliminated and the workpiece has the macro geometry according to the recipe on its machined surface on the rear side RS.

Then the in 16 (Micro)fine machining of spectacle lenses, generally referred to as "polishing", in which the pre-machined optically effective surface of the respective semi-finished product is given the desired micro-geometry (surface quality) by means of a geometrically undefined cutting edge. For this purpose, the pre-machined, blocked semi-finished product is removed from the generator and further processed in a fine processing or polishing machine. The positioning and fixing of the semi-finished product in the polishing machine also takes place using the block piece.

Depending on the material of the spectacle lenses, among other things, the fine machining is usually divided into a fine grinding process and a subsequent polishing process (see, for example, the publications EP 1 473 116 A1 and EP 1 698 432 A2 ), or if a surface that can be polished has already been created during the pre-processing - which will usually be the case with plastic lenses that have been machined by turning - only includes a polishing process in the polishing machine (see, for example, the publication EP 2 308 644 A2 ). During polishing, a liquid polishing agent containing abrasive particles is added by means of a flexible polishing tool or disk, as described, for example, in the publication WO 2016/058661 A1 disclosed is driven in defined paths over the pre-machined surface in order to reduce the surface roughness.

The next optional process step takes place according to 16 the marking of the semi-finished product. In this case, two small circles, for example, are produced on the back surface of the semi-finished product, for example by means of a laser beam or mechanically by means of an engraving tool. This is necessary, for example, with free-form surfaces in order to be able to reliably find the position of the semi-finished product in later process steps via the markings made. Since a high degree of positioning accuracy is required here, the block piece is also used for positioning and fixing during marking. The marking can already be done in the generator (see, for example, the pamphlet EP 1 916 060 B1 ) or a separate machine.

Only after this processing is the semi-finished product separated from the block piece (so-called "blocking" in 16 ). This is done, for example, in the case of the above-mentioned adhesive connection, by means of a high-pressure water jet emitted by a nozzle, which hits an edge point between the block piece and the semi-finished product in order to detach the semi-finished product from the block piece by applying hydraulic forces (see, for example, the publication WO 2011/042091 A1 or WO 2011/107227 A1 ). As a result, the processed semi-finished product is available individually, the separated block piece is cleaned and returned to the blocking process step.

In further processing, the semi-finished product is cleaned according to 16 optionally coated on its front and/or back to achieve additional effects (increased scratch resistance through hard coating, anti-reflection properties, color, mirroring, hydrophobic properties, etc.).

According to 16 the final process step is the so-called "edging", in which the semi-finished product is processed again at the edge to fit it into a desired spectacle frame, so that it takes on the shape of the respective spectacle frame. Since the semi-finished product is no longer fixed on the block piece, the position must be determined again here (e.g. using the aforementioned markings) before the semi-finished product is suitably fixed and used in a so-called "Edger" as an edge processing device (see e.g. the publication EP 1 243 380 A2 ) can be finally processed with regard to its edge shape and attachment in the spectacle frame.

The extent based on the 16 The process chain described from the prior art includes the steps “blocking” and “blocking” two processes that represent necessary auxiliary processes, but do not themselves increase the value of the spectacle lens produced. A process chain that does not require these auxiliary processes would therefore be desirable. In particular to increase efficiency and also for ecological reasons, it has already been proposed in the prior art to work "without blocks" in the production of the optically effective surfaces of spectacle lenses (see, for example, the publications WO 2015/059007 A1 , US 9,969,051 B2 and DE 10 2016 112 999 A1 ).

In this context, for example, the document discloses WO 2015/059007 A1 a method for non-blocking surface processing of spectacle lenses, which are held (among other things) by vacuum. A special feature of this state of the art is that the lens is held "in two stages" during surface processing: If the cutting tool in the form of a lathe chisel or milling cutter attacks the surface with a large lever in the area of the lens edge, the lens is held on the front surface Application of a vacuum to a suction chamber sealed against the front surface of the lens by means of a circumferential seal and a central counterholder in the form of a rotating stamp on the rear surface, i.e. from both sides. Then, as the surface processing progresses and approaches the center of the lens with smaller processing forces, the central anvil is withdrawn and the lens is held solely by the vacuum. Any edging of the lens is not addressed in this prior art. The edge of the lens is only addressed as a possible (alternative) holding surface for surface processing.

A problem with this prior art is seen in particular in the fact that the lens is placed “hollowly” on the seal surrounding the central suction chamber. In the case of comparatively thin lenses, there is a risk that the lens will experience elastic deformation or deflection as a result of the holding forces applied by the central counter-holder or the processing forces acting centrally when the counter-holder is retracted. During processing, this can lead to intolerable deviations between the actual geometry generated on the rear surface and the target geometry desired there, which then become noticeable when the lens "springs out" again after processing. Such lens deformations that are detrimental to the processing quality and are caused by the holding system are particularly critical when relatively complex surface geometries (ie surfaces other than just spherical or toric surfaces) are to be produced. Although in the pamphlet WO 2015/059007 A1 also an example ( 3 ) having in the suction chamber a plurality of concentrically arranged, individually axially moveable, support rings which are spring biased towards the lens to be held. However, if the lens to be held has a non-rotationally symmetrical geometry on its surface to be held, cavities will develop locally between the lens and the rings, with the above-mentioned risk of an undesirable deformation of the lens under the processing forces acting in these unsupported cavities.

In order to remedy this, in the prior art according to the publication US 9,969,051 B2 proposed a specially designed receptacle or holder for pneumatically blocking or holding optical lenses on a surface processing machine. The fixture disclosed herein generally has a clamping member for securing the fixture to an associated component of the surfacing machine and a lens blocking assembly comprising a base from which protrude abutments intended to rigidly seat the lens provide, and a seal against which the lens can be brought into contact to define a vacuum chamber with the body. The stops comprise a plurality of first rods mounted to slide with respect to the body so as to bear with their free ends on the lens, and three second rods integral with the body. Furthermore, return elements in the form of springs are provided on the first rods in order to return the first rods to the lens, ie to apply them.

In this prior art, the rods provided in the area of the vacuum chamber also provide axial support radially inside the seal on the front surface of the optical lens sucked onto the receptacle when machining forces act on the rear surface of the lens during machining of the lens. Here too, however, there are relatively large cavities between the individual rods, which are elastically bridged by the lens. In addition, the spring preloading of the rods reduces the holding force generated by the effective suction surface of the holder, so that there is a risk that the lens will become detached from the holder in the event of high machining forces, in particular as a result of the leverage effect on the edge of the lens.

Also the print DE 10 2016 112 999 A1 deals with the design of a workpiece holder for holding optical lenses in lens processing machines, which has a blockless Clamping of the lens should allow for surface processing. The workpiece holder disclosed here is also designed for various "clamping techniques": On the one hand, to suck the lens onto a receiving surface of an insert made of a porous material, a vacuum can be applied via an air duct, after which the lens can be (finely) machined with moderate forces (turning, grinding, polishing). On the other hand, the lens can be clamped at its round peripheral edge by mechanical clamping using clamping areas provided on a clamping chuck, which is intended to enable "stronger" (pre)processing (milling, turning).

With this prior art, however, there is also the risk of deformations of the lens that are detrimental to the processing quality if the latter is mechanically clamped at the peripheral edge with radial clamping forces. In addition, the mechanical clamping of the lens at the peripheral edge impedes or prevents pre-machining in the edge region of the lens, as described above.

Finally, the reference discloses EP 1 037 727 B1 an edger, i.e. a spectacle lens edging machine with a spectacle lens holder having a suction cup for a raw lens held at least on one side and with a small-format processing device having only a high-speed driven end milling cutter or a mounted point or a laser beam as the only processing tool for completely machining the shape of the raw lens by means of a separating cut a roof facet or a peripheral groove or grooves for fixing a spectacle frame by means of clips or bores. However, this prior art does not provide anything for processing the optically effective surfaces of the spectacle lens.

TASK

In contrast to the prior art described in this respect, the object of the invention is to provide the simplest possible method for machining optical workpieces, in particular spectacle lenses made of plastic, which addresses the problems described above, in particular enables reliable workpiece machining without workpiece deformations that are detrimental to the machining quality and ideally without blocks can be carried out.

PRESENTATION OF THE INVENTION

This object is achieved by a method with the method steps according to patent claim 1. Advantageous or expedient refinements and developments of the invention are the subject matter of the dependent patent claims.

A method for machining optical workpieces, in particular spectacle lenses made of plastic, in which, starting from a blank, a semi-finished product with predetermined surface geometries on a front side and a rear side facing away from it and with a contoured edge of a predetermined edge thickness between the front side and the rear side is formed, according to the invention comprises the following main steps taking place in the order given: i) providing the blank, which has a blank thickness, can already have the predetermined surface geometry on the front side and is to be machined at least on the rear side and the edge; ii) rear non-blocking picking up of the blank to support the workpiece; iii) Machining of the blank on the front side using a first tool to form a circumferential groove or step with a depth that is greater than or equal to the edge thickness of the semi-finished product to be formed and smaller than the thickness of the blank, or a circumferential groove that at least partially has a depth equal to the thickness of the blank, leaving a peripheral surface on the workpiece which defines the contoured edge of the stock to be formed; iv) receiving the workpiece at the front to support the workpiece; and v) machining the workpiece on the back using at least one second tool to form the semi-finished product with the predetermined surface geometry on the back.

Due to the fact that in the main step iii) the groove, the step or the indentation on the front side of the blank is formed circumferentially with a depth that is greater than (equal to) the edge thickness of the semi-finished product to be formed, it comes - at the latest - in the main step v ), when the predetermined surface geometry of the semi-finished product is generated by machining on the back, leads to a complete separation of the semi-finished product from the excess, radially outer material of the blank. "At the latest" in connection with the main step v) insofar as the circumferential recess - depending on the radial dimensions of the rear receptacle, which should not collide with the first tool - can have a depth equal to the thickness of the blank completely and not only partially , so that such a deep puncture already in the main step iii) leads to a separation of the excess, radially outer material of the blank in the sense of a circumferential "pierce". As a result of the depth of the groove, the step or the indentation in the thickness direction of the workpiece, a peripheral surface remains on the workpiece in the main step iii), which invent according to the invention defines the contoured edge of the semi-finished product to be formed.

In connection with the claimed geometric shapes of groove, step and recess, which are produced in the main step iii) on the front side of the blank, the conjunction "or" used should be understood as non-exclusive. Accordingly, in addition to full-circumferential grooves, steps or punctures, mixed forms of these geometries are also conceivable, which should therefore not be excluded. An example of such a mixed form would be a circumferential groove that “leaves” the blank material in some areas, forming a step in the radial direction and/or forming a puncture in the axial direction. This can result from the predetermined surface geometry on the front side of the blank and/or the desired edge contour of the semi-finished product.

In other words, according to the invention, in the main step iii) of the method, processing of the contoured edge of the semi-finished product to be formed - be it in the sense of pre-edging or finished edging of the workpiece - is brought forward or brought forward in time, starting from the front side of the according to the main step ii) the blank recorded without blocking on the rear side, before the workpiece is surface-machined on its rear side after recording on its front side in the main step iv) according to the main step v). In any case, after the main step v), the generated semi-finished product is then completely separated from the excess, radially outer blank material, which falls off as a ring piece or in ring segments, as will be explained below.

This basically two-stage procedure - first workpiece pick-up on the back and machining on the front side of the workpiece near the edge of the blank, then pick-up on the front side and machining on the back of the workpiece also in the center - with the claimed sequence of the individual process steps offers in the machining particular advantages of spectacle lenses made of plastic. These advantages relate primarily to (1.) holding the workpiece during the actual edge (pre)machining, which is important for process reliability, and (2.) supporting the workpiece during the actual surface machining, which is relevant for the machining quality.

First of all (1.) the holding of the workpiece is concerned, there is no need in the prior art described above to record or block the blank on its front side in such a way that its edge region projects radially beyond the recording or the block piece in order to To allow the workpiece to be edged ahead without the tool colliding with the fixture or block piece. As a result, the processing forces in the prior art during edge pre-machining at the edge of the blank, i.e. which act maximally radially on the outside and are directed from the front to the rear (see the 17 ) that seek to "pry" the blank off its mount or piece of block should be avoided. In particular, in order to solve the problem, the edge pre-processing does not have to be dispensed with, which in the case of spectacle lenses would cause other problems, namely with the overall calculation of the surface geometry to be produced on the back of the lens, because the calculated rear surface of a spectacle lens to be processed does not exceed the calculated final diameter of the lens could be extrapolated.

Rather, according to the invention, in accordance with the predetermined edge thickness and edge contour of the semi-finished product to be formed, complete edge (pre-)machining of the workpiece, i.e. fundamentally unlimited in its machining depth and machining width, is possible. This is because the blank does not have to be clamped at the edge or held on its front side for this purpose, but after main step ii) - unlike in the prior art discussed at the beginning - is taken up on its rear side, while according to main step iii) the edge geometry or The contoured edge of the semi-finished product to be formed is produced in a casual manner by machining from the front side of the blank.

Here, the machining forces are rather moderate compared to the prior art described above, since in the main step iii) only a groove or a step or a recess is produced - for which only a small tool is required - but not all of the excess blank material has to be machined. This advantageously allows correspondingly lower holding forces through the receptacle and also leads to a comparatively reduced chip volume to be disposed of, which is also advantageous. In addition, the machining forces in the main step iii) are primarily directed radially and from the front side to the rear side, which is positive for a process-reliable holding of the blank, but not predominantly the other way around, away from the rear side recording, weakening the workpiece holding, e.g in the prior art (see 17 ). Overall, the "reduced" requirements of the main step iii) according to the invention compared to the previously known front edges also advantageously allow an uncomplicated "blockless" recording for the blank in the main step ii), eg with the technological operating principle vacuum by means of a vacuum sow gers, i.e. without a block piece on the blank, as described at the beginning of the conventional procedure.

With regard to (2.) the support of the workpiece during the actual surface machining, which is important for the required surface accuracy, it can be said about the invention that the staged procedure proposed here according to the main steps iii) and v) of the machining - in short: Edge from the front in front of the surface on the back - with the elimination of the need for an edge of the blank that projects radially beyond the receptacle according to the previously known concepts, opens up the possibility of supporting the workpiece not only centrally during surface machining, but also in the edge area. This can be done, for example, with the aid of suitably closely spaced pins or rods, similar to that in the reference US 9,969,051 B2 disclosed concept for a lens mount.

Ideally, in the main step iv), the workpiece is even picked up on the front side in such a way that the workpiece is held on the front side with full-surface support - i.e. not just several times locally - which is accordingly preferred. If, for example, the finished diameter of the lenses is in the range between 50 mm and 80 mm in today's prescription production of spectacle lenses, a holder with a diameter of at least 80 mm can be used for the main steps iv) and v) according to the invention, which means a support the entire front allows.

In addition - compared to the prior art discussed at the outset with a projecting workpiece edge (cf. again 17 ) - Advantageously the entire surface on the front side of the workpiece is available to hold the workpiece when machining the surface on the back. This also opens up the possibility of the process-reliable use of alternative holding concepts during surface processing, in which the holding takes place, for example, by creating a vacuum between the workpiece and the holding system. It is then also preferred if the workpiece is also picked up unblocked on the front side in the main step iv), because the method can then be carried out overall without blocking and unblocking and the associated (additional) effort. However, it is also conceivable, although less preferred for reasons of efficiency, to pick up the workpiece in the main step iv)—if possible over the entire surface—on the front side using a block piece, as is known in principle from the prior art.

The actual surface machining on the back of the workpiece can then be carried out as is known from the prior art, e.g. in the sequence (pre)milling, rough turning, fine turning or only by turning the back. The force components during machining are then in turn primarily directed radially and advantageously axially toward the mount on the front side of the workpiece.

As a result, the method according to the invention enables in particular the machining of lens blanks into semi-finished products for spectacle lenses, even if the holding system with which they are supported and held during machining of the back does not allow machining of the edge geometry. It thus also represents an essential part of a new, simplified process chain for the production of spectacle lenses made of plastic, which, in particular, does not require the use of the previously known block pieces.

In a first alternative of the method, it can be provided that in the main step iii) when forming the circumferential groove or step or the circumferential recess by means of the first tool, an edge contour is produced on the semi-finished product, which has a slight excess compared to an edge contour of the finished workpiece, the edge contour of the finished workpiece being produced only after the main step v) for machining the rear side of the workpiece, for example in the manner known from the prior art described at the outset, i.e. with the aid of an edger, if necessary after carrying out the usual coating steps . In other words, in this alternative of the method in the main step iii) the work piece is merely "cribbed" or pre-edged from the front side of the work piece.

In a second alternative of the method, on the other hand, it can be provided that in the main step iii) during or after formation of the circumferential groove or step or the circumferential recess using the first tool or a further tool, an edge contour is produced on the semi-finished product that already corresponds to an edge contour of the finished machined workpiece corresponds. With this process alternative, the workpiece already receives its final edge contour from its front side, which advantageously makes subsequent edging to produce the macro-geometry required for fitting into a spectacle frame unnecessary. Depending on the shape of the mount, the edge of the workpiece may then only need to be polished after the main step iii) before the spectacle lens is inserted into the spectacle frame after the remaining process steps have been carried out, such as coating if necessary. Of course, this alternative presupposes that the final edge shape of the spectacle lens is already known when the surface of the lens blank is machined.

In both of the aforementioned method alternatives, a chamfer at the transition between the edge and the rear side of the semi-finished product to be formed and/or a chamfer at the transition between the edge and the front side of the semi-finished product to be formed can already be applied in the main step iii). The formation of such a chamfer as a protective facet is particularly recommended if the workpiece is (also) to be moved or transported manually in further process steps in order to prevent injuries on a sharp edge of the workpiece. In the case of spectacle lenses, such a chamfer must be present on the back of the lens anyway, at the latest after edging, in order to avoid injuries to the spectacle wearer.

In a preferred embodiment of the aforementioned method development, it can also be provided that in the main step iii) the chamfer or chamfers is or are applied by means of the first tool at the same time as the circumferential groove or step or the circumferential recess. A suitably equipped combination tool with appropriately shaped cutting edges can be used for this purpose. This is conducive to rapid and efficient process management. However, it is also possible in the main step iii) in a sub-step to first form the main geometry (groove, step or recess with the peripheral surface of the semi-finished product to be produced) using the first tool and then in a subsequent sub-step to form the chamfer(s) using a further tool - or again by means of the first tool in a different position with respect to the workpiece, if this is possible with the existing machine kinematics - or vice versa in the chronological sequence.

In the case of the second alternative of the method described above (finished edges), it is also preferred if in the main step iii) a fastening geometry for the finished workpiece is also generated at the edge and/or on the front side of the semi-finished product to be formed. In particular, in the main step iii), the fastening geometry for the finished workpiece can be formed by means of the first tool at the same time as the circumferential groove or step or the circumferential recess, which is also conducive to rapid and efficient process management.

The fastening geometry generated in the main step iii) for the finished workpiece can be a pointed or roof facet or a circumferential groove or groove on the edge of the semi-finished product to be formed, depending on the fastening requirements of the respective socket for the workpiece. For this purpose, the first tool can in turn be designed as a combination tool with suitably shaped cutting edges. Alternatively or in addition to this, the fastening geometry generated in the main step iii) for the finished workpiece can include one or more bores or notches on the front side and/or the edge, again depending on the fastening requirements of the respective socket for the workpiece, for which a another tool is used if the aforementioned combination tool is not equipped accordingly.

In the concrete procedure, it is also preferred if, at the beginning of the main step iii), the first tool and/or the workpiece are moved relative to one another in such a way that the first tool for forming the circumferential groove or step or the circumferential recess starts from the front side of the workpiece dips into the workpiece at a front dip point. This supports the holding of the workpiece on its rear mount, because at least at the beginning of the machining a resulting force component points in the direction of the mount.

Alternatively, at the beginning of the main step iii), the first tool and/or the workpiece can also be moved relative to one another in such a way that the first tool to form the circumferential groove or step or the circumferential recess, starting from the edge of the workpiece at an edge-side immersion point in the workpiece is immersed. As a result, a first separation point is advantageously already produced on the radially outer remainder of the blank material, which falls away later in the main step v).

Furthermore, in the main step iii) after the first tool has been immersed in the workpiece, the first tool and/or the workpiece can preferably be moved relative to one another in such a way that the first tool cuts the groove or step or the recess in at least one revolution (i.e. if necessary also several revolutions) on the workpiece, wherein the first tool leaves the workpiece at an edge-side exit point at the edge of the workpiece that is remote from the front-side or edge-side immersion point. This also leads to a separation point at the radially outer remainder of the blank material that falls away later in the main step v).

During one or more revolutions on the workpiece, the tool in the main step iii) can also be radially extended out of the workpiece and retracted again several times, so that a number of separation points are created in the blank material, with the result that in the main step v) the , Radially outer remainder of the blank material falls off the semi-finished product produced in several ring segments. So about 2 or 3 or even more ring segments can occur as waste. A number of 4 to 8 separation points approximately leads to a corresponding number of correspondingly smaller ring segments as waste in the main step v), which can simplify, for example, the discharge and processing of a liquid cooling lubricant that may be used during machining.

Finally, as far as the first tool used in the main step iii) for machining the blank on the front side is concerned, this can preferably be an end milling cutter driven in rotation. Such an end mill, provided with a high-speed drive, is not only able to form a high-quality peripheral surface on the semi-finished product to be produced with comparatively low machining forces, but is also well suited, for example, for machining the aforementioned separation points in the remainder of the blank material to be removed, if in the main step iii ) a groove or recess is to be formed.

However, the use of other tools is also possible, for example if the production of the above separation points is not important and/or no more complex peripheral contours, in particular deviating from a circular or elliptical shape, are to be machined on the semi-finished product. For example, a disc milling cutter can be used to form the step in the main step iii). It is also fundamentally possible to use a non-rotatably held, narrow turning tool to form the groove, the step or the recess in the main step iii) if the machine kinematics of the machining device used for this purpose allow for this, i.e. the cutting speeds required for proper machining, in particular by means of a suitable one Rotary drive of the workpiece can be generated.

When using the last-mentioned tool examples, the possibility of forming the most varied of edge geometries on the semi-finished product is limited. However, such a tool can also be used for surface machining of the back of the workpiece in the main step v). Nevertheless, with regard to the greatest possible flexibility in the selection of the possible geometries on the edge and surface of the workpiece, it is preferred if the first tool used in the main step iii) for machining the blank on the front side is different from the one used in the main step v) for machining the workpiece the back used, at least one second tool is different.

Further features, properties and advantages of the method according to the invention are apparent to the person skilled in the art from the following description of preferred exemplary embodiments.

character list

• 1 ein Ablaufdiagramm einer Prozesskette zur Herstellung von Brillenlinsen als Beispiel für optische Werkstücke, wobei die Prozesskette ohne die Notwendigkeit der Verwendung von Blockstücken bei der Herstellung auskommt und als einen einleitenden Prozess ein kurz als „Blocklos Generieren“ bezeichnetes Verfahren zur spanenden Bearbeitung von Brillenlinsen aus Kunststoff nach einem ersten Ausführungsbeispiel der Erfindung umfasst;
• 2 eine perspektivische Ansicht eines Aufnahmekopfs einer Bearbeitungsvorrichtung, an dem für den Hauptschritt „Randvorbearbeitung“ des Verfahrens „Blocklos Generieren“ in der Prozesskette gemäß 1 ein Brillenlinsenrohling mit seiner Rückseite blocklos aufgenommen und abgestützt gehalten wird;
• 3 eine Längsschnittansicht des Aufnahmekopfs gemäß 2 mit dem blocklos daran gehaltenen Brillenlinsenrohling vor dem Hauptschritt „Randvorbearbeitung“ in 1;
• 4 eine Längsschnittansicht des Aufnahmekopfs gemäß 2 mit dem blocklos daran gehaltenen Brillenlinsenrohling eingangs des Hauptschritts „Randvorbearbeitung“ in 1 während ein drehend angetriebener Fingerfräser als erstes Werkzeug ausgehend von dem Rand des Werkstücks an einer randseitigen Eintauchstelle in das Werkstück spanend eintaucht;
• 5 eine Längsschnittansicht des gegenüber der Darstellung in den 3 und 4 um 270° um seine Mittelachse verdrehten Aufnahmekopfs gemäß 2 mit dem blocklos daran gehaltenen Werkstück während des Hauptschritts „Randvorbearbeitung“ in 1, bei dem mittels des drehend angetriebenen Fingerfräsers von 4 eine umlaufende Nut in der Frontseite des Werkstücks ausgebildet wird;
• 6 eine perspektivische Ansicht des zur Vereinfachung der Darstellung von dem Aufnahmekopf gemäß 2 getrennt gezeigten Werkstücks nach dem Hauptschritt „Randvorbearbeitung“ in den 1, 4 und 5, mit Blick auf die als Ergebnis dieses Hauptschritts in der Frontseite des Werkstücks ausbildete umlaufende Nut, die bereits einen konturierten Rand des im erfindungsgemäßen Verfahren zu erzeugenden Halbzeugs definiert;
• 7 eine Längsschnittansicht des Aufnahmekopfs gemäß 2 entsprechend der Darstellungsweise in 5 mit dem blocklos daran gehaltenen Werkstück im Bearbeitungszustand der 6, das im Hauptschritt „Positionieren und Fixieren“ des Verfahrens „Blocklos Generieren“ in der Prozesskette gemäß 1 gerade mit seiner bearbeiteten Frontseite auf einer lediglich schematisch dargestellten Aufnahme zum abgestützten Halten positioniert wird;
• 8 eine schematische Längsschnittansicht der Aufnahme gemäß 7, an der das Werkstück nach dem Hauptschritt „Positionieren und Fixieren“ für den Hauptschritt „Flächenbearbeitung“ des Verfahrens „Blocklos Generieren“ in der Prozesskette gemäß 1 mit seiner bearbeiteten Frontseite flächig abgestützt gehalten wird;
• 9 eine schematische Längsschnittansicht der Aufnahme gemäß 7 mit dem daran über seine bearbeitete Frontseite flächig abgestützt gehaltenen Werkstück, das im Hauptschritt „Flächenbearbeitung“ in 1 gerade mittels eines zweiten Werkzeugs an seiner Rückseite bearbeitet wird, um dort eine vorbestimmte Flächengeometrie zu erhalten;
• 10 eine perspektivische Ansicht des zur Vereinfachung der Darstellung von der Aufnahme gemäß 7 getrennt gezeigten, im Hauptschritt „Flächenbearbeitung“ in 1 entsprechend der 9 generierten Halbzeugs, das danach vollständig vom überschüssigen, radial äußeren Rohlingsmaterial getrennt ist, welches in ebenfalls gezeigten Ringsegmenten abfällt;
• 11 eine Längsschnittansicht des Aufnahmekopfs gemäß 2 (hier ohne Stützstifte gezeigt), der nach dem Hauptschritt „Flächenbearbeitung“ in 1 das generierte Halbzeug von der Aufnahme der 7 für anschließende Prozesse in der Prozesskette gemäß 1 abholt;
• 12 eine Längsschnittansicht des Aufnahmekopfs gemäß 2 (hier wiederum ohne Stützstifte dargestellt), an dem das als Ergebnis des Verfahrens „Blocklos Generieren“ in der Prozesskette gemäß 1 generierte Halbzeug gehalten wird;
• 13 eine perspektivische Ansicht einer zur Vereinfachung der Darstellung von dem Aufnahmekopf gemäß 2 getrennt gezeigten Werkstückvariante nach dem Hauptschritt „Randvorbearbeitung“ in 1 im Bearbeitungsstand der 6, bei der anstelle der Nut eine umlaufende Stufe als Ergebnis dieses Hauptschritts an der Frontseite ausbildet wurde, die ebenfalls schon einen konturierten Rand des im erfindungsgemäßen Verfahren zu erzeugenden Halbzeugs definiert;
• 14 ein Ablaufdiagramm einer alternativen Prozesskette zur Herstellung von Brillenlinsen als Beispiel für optische Werkstücke, wobei die Prozesskette wiederum ohne die Notwendigkeit der Verwendung von Blockstücken bei der Herstellung auskommt und als einen einleitenden Prozess ein erneut kurz als „Blocklos Generieren“ bezeichnetes Verfahren zur spanenden Bearbeitung von Brillenlinsen aus Kunststoff nach einem zweiten Ausführungsbeispiel der Erfindung umfasst, bei dem das Werkstück vor der Flächenbearbeitung schon eine finale Bearbeitung seiner Randform erfährt, so dass ein Edgen am Ende der Prozesskette entfallen kann;
• 15 eine Längsschnittansicht des Aufnahmekopfs gemäß 2 mit einem blocklos daran gehaltenen Werkstück während des Hauptschritts „Randform final bearbeiten“ des Verfahrens „Blocklos Generieren“ in der Prozesskette gemäß 14 in einem Bearbeitungsstand entsprechend der 5, wobei mittels eines ersten Werkzeugs eine umlaufende Stufe an der Frontseite des Werkstücks ausgebildet wird (in 15 links gezeigt), worauf mittels eines zweiten Werkzeugs eine Randkontur am Werkstück erzeugt wird (in 15 rechts angedeutet), die schon der Randkontur des fertig bearbeiteten Werkstücks entspricht;
• 16 ein Ablaufdiagramm einer herkömmlichen Prozesskette zur Herstellung von Brillenlinsen, bei der während der Herstellung Blockstücke notwendigerweise Verwendung finden und die deshalb die Hilfsprozesse „Blocken“ und „Abblocken“ umfasst, welche den Wert der hergestellten Brillenlinsen nicht steigern; und
• 17 eine prinzipielle Darstellung zur Eingriffssituation eines Tellerfräsers als Werkzeug mit einem geblockten Brillenlinsenrohling als Werkstück während der „Randvorbearbeitung“ als Teilprozess des Prozesses „Generieren“ in der vorbekannten Prozesskette gemäß 16.

The invention is explained in more detail below using preferred exemplary embodiments with reference to the accompanying schematic drawings, in which identical or corresponding parts or sections are provided with the same reference symbols. In the drawings show:

• 1 a flow chart of a process chain for the production of spectacle lenses as an example for optical workpieces, whereby the process chain manages without the need to use block pieces during production and as an introductory process a method for the machining of spectacle lenses made of plastic, referred to as "blockless generation". a first embodiment of the invention;
• 2 a perspective view of a recording head of a processing device, on which for the main step “edge pre-processing” of the “blockless generation” method in the process chain according to FIG 1 an eyeglass lens blank is received with its back without blocking and is held in a supported manner;
• 3 a longitudinal sectional view of the recording head according to FIG 2 with the spectacle lens blank held on it without blocking before the main step "edge preparation" in 1 ;
• 4 a longitudinal sectional view of the recording head according to FIG 2 with the spectacle lens blank held on it without blocking at the beginning of the main step "edge preparation" in 1 while a rotationally driven end milling cutter as the first tool, starting from the edge of the workpiece, dips into the workpiece at an edge-side immersion point;
• 5 a longitudinal sectional view of the opposite of the representation in the 3 and 4 by 270 ° rotated about its central axis according to recording head 2 with the workpiece held without blocking it during the main step "edge preparation" in 1 , in which by means of the rotationally driven end mill from 4 a circumferential groove is formed in the face of the workpiece;
• 6 FIG. 14 is a perspective view of the pickup head shown in FIG 2 separately shown workpiece after the main step "edge preparation" in the 1 , 4 and 5 , with a view to the circumferential groove formed in the front side of the workpiece as a result of this main step, which already has a contoured edge of the semi-finished product to be produced in the method according to the invention;
• 7 a longitudinal sectional view of the recording head according to FIG 2 according to the representation in 5 with the blockless held workpiece in the processing state of the 6 , which is in accordance with the main step “positioning and fixing” of the “blockless generation” method in the process chain 1 is being positioned with its machined face on a cradle, shown only schematically, for support;
• 8th a schematic longitudinal sectional view of the recording according to FIG 7 , on which the workpiece after the main step "positioning and fixing" for the main step "surface processing" of the method "blockless generation" in the process chain according to 1 is held flat supported with its machined front side;
• 9 a schematic longitudinal sectional view of the recording according to FIG 7 with the workpiece held flat on its machined front side, which in the main step "surface machining" in 1 is being machined on its rear side by means of a second tool in order to obtain a predetermined surface geometry there;
• 10 a perspective view of the illustration to simplify the illustration according to FIG 7 shown separately, in the main step "Surface processing" in 1 according to the 9 generated semi-finished product, which is then completely separated from the excess, radially outer blank material, which falls off in ring segments that are also shown;
• 11 a longitudinal sectional view of the recording head according to FIG 2 (shown here without support pins), which follows the main "Surfacing" step in 1 the generated semi-finished product from recording the 7 for subsequent processes in the process chain 1 picks up
• 12 a longitudinal sectional view of the recording head according to FIG 2 (shown here again without support pins), on which the as a result of the “blockless generation” method in the process chain according to 1 generated semi-finished product is held;
• 13 FIG. 14 is a perspective view of the recording head of FIG 2 Workpiece variant shown separately after the main step "edge preparation" in 1 in the processing status of 6 , in which, instead of the groove, a circumferential step was formed as a result of this main step on the front side, which likewise already defines a contoured edge of the semi-finished product to be produced in the method according to the invention;
• 14 a flow chart of an alternative process chain for the production of spectacle lenses as an example for optical workpieces, whereby the process chain in turn does not require the use of block pieces during production and as an introductory process a method for machining spectacle lenses, again briefly referred to as "blockless generation". made of plastic according to a second exemplary embodiment of the invention, in which the workpiece already undergoes final processing of its edge shape before the surface processing, so that edging at the end of the process chain can be omitted;
• 15 a longitudinal sectional view of the recording head according to FIG 2 with a workpiece held to it without a block during the main step "Final processing of the edge shape" of the "Generate without blocks" method in the process chain 14 in a processing status according to the 5 , wherein a circumferential step is formed on the front side of the workpiece by means of a first tool (in 15 shown on the left), whereupon a second tool is used to create an edge contour on the workpiece (in 15 indicated on the right), which already corresponds to the edge contour of the finished workpiece;
• 16 a flow chart of a conventional process chain for the production of spectacle lenses, in which block pieces are necessarily used during production and which therefore includes the auxiliary processes "blocking" and "blocking" which do not increase the value of the spectacle lenses produced; and
• 17 a basic representation of the intervention situation of a disc milling cutter as a tool with a blocked spectacle lens blank as a workpiece during the "edge pre-processing" as a sub-process of the process "generate" in the previously known process chain according to 16 .

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The 1 shows a flowchart of a process chain for the production of spectacle lenses made of plastic as optical workpieces without the use of block pieces during production, which compared to the prior art according to FIG 16 First of all, the auxiliary processes “block” and “unblock” are omitted. As an inbound process, the process chain includes an in 1 “Generate Blockless” Said method for the machining of spectacle lenses made of plastic according to a first exemplary embodiment, in which, starting from an in 2 shown blank RL finally an in 12 illustrated semi-finished product HZ is formed. The 2 until 12 illustrate the main steps of this process.

The semi-finished product HZ produced as a result of this process (see 12 ) has predetermined surface geometries on a front side FS and a rear side RS facing away from it. It is also provided with a contoured edge RA of predetermined edge thickness D2 between the front face FS and the rear face RS. How about from a comparison of 3 , 7 , 9 and 12 As can be seen, the contoured edge RA of the semi-finished product HZ and then in particular the predetermined surface geometry on the rear side RS of the semi-finished product HZ result in the course of the method.

The final geometry of the semi-finished product HZ (see 12 ) is in the longitudinal sectional views according to the 3 until 5 , 7 until 9 , 11 , 12 and 15 always indicated with cross-hatching for illustration, although this geometry is actually only cut out of the blank material at the end of the process. Accordingly, for example, according to 3 Cross-hatching provided in the blank RL - quasi as a "placeholder" - only that part of the material of the blank RL from which the semi-finished product HZ is produced in the course of the process.

• i) dem Bereitstellen des Rohlings RL, der eine Rohlingsdicke D1 (vgl. die 2 und 3) besitzt, an der Frontseite FS bereits die vorbestimmte Flächengeometrie aufweisen kann, wie hier gezeigt, und wenigstens an seiner Rückseite RS sowie seinem Rand RA zu bearbeiten ist,
  • - noch die folgenden vier, in der angegebenen Reihenfolge ablaufenden Hauptschritte ii) bis v):
• ii) Blockloses Aufnehmen des Rohlings RL an der Rückseite RS zum abgestützten Halten des Werkstücks, wie in 2 und 3 gezeigt - in 1 unter „Position feststellen“ enthalten.
• iii) Bearbeiten des Rohlings RL an der Frontseite FS mittels eines ersten Werkzeugs WZ1 (siehe die 4 und 5), zur Ausbildung einer umlaufenden Nut NU (vgl. z.B. 6) oder Stufe ST (siehe 13) mit einer Tiefe TI, welche größer oder gleich der Randdicke D2 des auszubildenden Halbzeugs HZ und kleiner als die Rohlingsdicke D1 ist, und zwar so - in 1 als „Randvorbearbeitung“ bezeichnet - dass am Werkstück eine Umfangsfläche UF verbleibt, die schon den konturierten Rand RA des auszubildenden Halbzeugs HZ definiert. Wie weiter oben bereits erwähnt, kann neben den geometrischen (Grund)Formen Nut NU und Stufe ST - ggf. auch in einer Kombination damit - ein umlaufender Einstich erzeugt werden (in den Figuren nicht dargestellt), der wenigstens teilweise eine Tiefe gleich der Rohlingsdicke D1 besitzt und damit den Rohling RL zumindest örtlich „durchsticht“.
• iv) Aufnehmen des Werkstücks an der Frontseite FS zum abgestützten Halten des Werkstücks, wie in 7 und 8 gezeigt - in 1 als „Positionieren und Fixieren“ bezeichnet.
• v) Bearbeiten des Werkstücks an der Rückseite RS mittels wenigstens eines zweiten Werkzeugs WZ2 (siehe die 9), zur Ausbildung des Halbzeugs HZ (vgl. die 10 bis 12) mit der vorbestimmten Flächengeometrie an der Rückseite RS - kurz „Flächenbearbeitung“ in 1 genannt. Infolge dieser Bearbeitung wird zwingend auch das Halbzeug HZ vom radial äußeren Rest des Rohlingsmaterials (in den 8, 9 und 11 mit einer kleineren Kreuzschraffur gekennzeichnet) getrennt. Letzterer Rest fällt im dargestellten Ausführungsbeispiel in Ringsegmenten RG ab (vgl. 10), wie nachfolgend noch erläutert wird.

In general, the method "blockless generation" of 1 - after the beginning of course:

• i) the provision of the blank RL, which has a blank thickness D1 (cf 2 and 3 ) has, can already have the predetermined surface geometry on the front side FS, as shown here, and is to be processed at least on its rear side RS and its edge RA,
  • - the following four main steps ii) to v), which take place in the order given:
• ii) Non-blocking picking up of the blank RL on the rear side RS for supporting the workpiece, as in 2 and 3 shown - in 1 included under “Locate Position”.
• iii) Machining of the blank RL on the front side FS using a first tool WZ1 (see Fig 4 and 5 ), to form a circumferential groove NU (cf. e.g 6 ) or level ST (see 13 ) with a depth TI, which is greater than or equal to the edge thickness D2 of the semi-finished product to be formed HZ and smaller than the blank thickness D1, namely as - in 1 referred to as "edge pre-machining" - that a peripheral surface UF remains on the workpiece, which already defines the contoured edge RA of the semi-finished product HZ to be formed. As already mentioned above, in addition to the (basic) geometric shapes of groove NU and step ST - possibly also in combination with them - a circumferential recess can be produced (not shown in the figures) which at least partially has a depth equal to the thickness of the blank D1 owns and thus "pierces" the blank RL at least locally.
• iv) picking up the workpiece at the front FS to support the workpiece, as in 7 and 8th shown - in 1 referred to as "positioning and fixing".
• v) Machining of the workpiece on the rear RS using at least one second tool WZ2 (see 9 ), for the formation of the semi-finished product HZ (cf. the 10 until 12 ) with the predetermined surface geometry on the rear RS - in short "surface processing" in 1 called. As a result of this processing, the semi-finished product HZ is also forced to be separated from the radially outer remainder of the blank material (in the 8th , 9 and 11 marked with a smaller cross hatch) separately. In the exemplary embodiment shown, the latter remainder falls off in ring segments RG (cf. 10 ), as explained below.

This separation of the semi-finished product HZ from the ring segments RG is inevitable because the depth TI of the groove NU previously made on the front side FS of the blank RL or the step ST (or recess, not shown) is greater than or equal to the edge thickness D2 of the semi-finished product HZ produced is, which results from the rear side RS as a result of the surface machining of the workpiece. In other words, the cutting action of the second tool WZ2 when generating the geometry on the rear side RS of the workpiece "cuts" the geometry (groove NU, step ST, recess) previously formed on the front side FS of the workpiece using the first tool WZ1, so that the excess raw material is completely removed from the semi-finished product HZ produced.

In the embodiment shown here, in the above main step iii) in the formation of the circumferential groove NU or step ST (or the circumferential recess) using the first tool WZ1 according to 6 and 10 an edge contour RK1 is produced on the semi-finished product HZ, which has a slight oversize with respect to an edge contour RK2 (indicated by a dashed line in the figures mentioned) of the finished workpiece. Edit the edge contour RK2 of the finish th workpiece is then only generated after the above main step v) for processing the rear side RS of the workpiece, namely in the final process "Edges" in the process chain according to 1 .

In this respect, it can be seen that the “blockless generation” method in 1 is basically based on a two-stage procedure: In the first method stage, the edge RA is pre-machined on the workpiece held on its rear side RS by machining the front side FS of the workpiece. In the second stage of the process, the surface machining takes place on the rear RS of the workpiece, which is held on its front side FS, with the final geometry on the edge and surfaces of the semi-finished product HZ produced at the end of this method only being completed by the tool being used during surface machining the rear side RS machines the workpiece down to the geometry formed on its front side FS (groove NU, step ST or recess).

In the embodiment shown, the blank RL according to the 2 until 5 held on the back RS by a vacuum suction cup VS during the processing of the front side FS. Due to the fact that only a relatively small geometry (groove NU, step ST or recess) is machined on the front side FS of the workpiece and not all of the excess blank material is machined, only small forces arise on the holding mechanism. This allows, for example, the use of a conventional vacuum suction cup VS, which according to the more basic representation in the 2 until 5 and 7 comprises, in a manner known per se, a central suction cup SN for holding the workpiece, which is surrounded by a plurality of support pins SS for supporting the held workpiece. Such vacuum suction cups are available on the market, for example, from J. Schmalz GmbH, 72293 Glatten, Germany.

To generate the required relative movements between the workpiece and the tool, i.e. to position the blank RL in all six degrees of freedom, such a vacuum suction cup VS can be moved by means of 6-axis kinematics (not shown), the three translational axes and three rotational axes around the Has translation axes. As an alternative, the use of a 6-axis articulated arm robot is conceivable (also not shown), which carries such a vacuum suction cup VS at its free end. In this case, the tool can then be arranged at a fixed point, while the spatial movement is carried out on the workpiece side in order to generate the relative movement between the tool and the workpiece required for the formation of the geometry. Such movement mechanisms, as well as mechanisms that are possible in principle, which work with a kinematic reversal - i.e. the tool is moved while the workpiece is arranged in a fixed position - as well as conceivable mixed forms of the movement distribution between tool and workpiece are well known to the person skilled in the art, so that they do not require any further explanation at this point.

As for the tool WZ1 for editing the blank RL on the front side FS in the main step iii) above, is in the 4 , 5 and 15 a rotationally driven end mill is shown as an example. In the simplest form, this can, for example, have milling cutters on the end face and on the circumference, which form a cylindrical envelope as a result of the tool rotation.

In the exemplary embodiment shown, the end mill used as the first tool WZ1 is provided with angled milling cutter edges around its circumference—viewed in a projection, as shown—for example as a two- or three-cutter cutter. More precisely, the respective cutter blade of the illustrated end mill has a cutting section parallel to the axis of rotation and a cutting section at the free end of the end mill that is angled radially outward by about 45° with respect to the axis of rotation. This results in a kind of combination of T-slot and finger cutters or dovetail cutters.

With such a cutting edge formation on the first tool WZ1, a chamfer FA1 (see the 4 and 5 ) at the transition between the edge RA and the rear RS of the semi-finished product HZ to be formed, at the same time as the circumferential groove NU (or step or recess), as shown in the figures mentioned. This chamfer FA1 can be applied to the finished semi-finished product HZ (cf. 12 ) then serve as a protective facet, as mentioned above.

However, it is also possible to process such geometries, e.g. using a simple milling cutter with a cylindrical envelope of the milling cutter cutting edge(s) on the workpiece, by cutting such a tool in the main step iii) with two (or more) cuts around the semi-finished product HZ to be produced (or vice versa). the workpiece is (are) guided around such a tool or both around each other), the cuts then being executed sequentially taking place at different angles of the tool axis relative to the workpiece axis MA (e.g. initially 0°, then 45°).

It is obvious to the person skilled in the art that in this way or in another cutting edge design on the first tool WZ1 in the main step iii) a chamfer can also be applied at the transition between the edge RA and the front side FS of the semi-finished product HZ to be formed (not shown in the figures). In addition, although an end milling cutter is shown and described at this point as the first tool WZ1 for the main step iii), other tool types are also conceivable, as already mentioned at the outset.

As far as the first cut of the blank RL is concerned at the beginning of the main step iii), it is possible to move the first tool WZ1 and/or the workpiece relative to one another in such a way that the first tool WZ1 is used to form the circumferential groove NU (or step or the circumferential recess ) starting from the front side FS of the blank RL, dips into the workpiece at a front-side immersion point. The 4 however, illustrates a procedure in which, at the beginning of the main step iii), the first tool WZ1 and/or the workpiece are moved relative to one another in such a way that the first tool WZ1 is used to form the circumferential groove NU (or step or the circumferential recess) starting from the edge RA of the blank RL dips into the workpiece at an edge-side immersion point ES.

After the first tool WZ1 has been immersed in the workpiece, the first tool WZ1 and/or the workpiece can then be moved relative to one another in such a way that the first tool WZ1 in the main step iii) cuts the groove NU (or step ST or the recess) in at least one Circulation is generated on the workpiece, with the first tool WZ1 leaving the workpiece at an edge-side exit point AS at the edge RA of the workpiece that is remote from the front-side or edge-side immersion point ES. The geometry created in this way on the workpiece is in 6 illustrated for the case that the first tool WZ1 plunges once into the workpiece (radial plunge point ES) and leaves the workpiece once (radial exit point AS).

During one revolution, however, the first tool WZ1 can also leave the workpiece several times at exit points AS angularly spaced about the central axis MA and dip back into the workpiece at immersion points ES angularly spaced about the central axis MA. This leads to a subdivision of the material of the blank RL that is present radially outside of the semi-finished product HZ to be produced. This excess blank material ultimately falls off the semi-finished product HZ in ring segments RG corresponding to the number of tool entries and exits as a result of the main step v), as already mentioned above, and therefore advantageously does not have to be machined separately.

To the 7 and 8th (as well as 9 and 11) it should first be noted that the workpiece in the above main step iv) is also recorded without a block on the front side FS in order to achieve the main purpose of the method in this exemplary embodiment or application example 1 shown "blockless" process chain. In particular, in the illustrated embodiment, in the main step iv), the workpiece is picked up on the front side FS in such a way that the workpiece, more precisely the semi-finished product HZ to be produced, is held with full-surface support on the front side FS, as best shown in 8th can be seen.

One is used for this in the 7 until 9 and 11 workpiece holder WA shown only schematically, which can basically work with the technological operating principle vacuum as described above for the prior art. However, other systems such as those currently used in spectacle lens production can also be used.

Such a workpiece holder WA can be attached, for example, to the free end of a workpiece spindle of a generator, such as that described in the document already mentioned at the outset EP 2 011 603 A1 is known, to which reference is expressly made at this point with regard to the structure and function of a suitable generator. The generator kinematics are also described in detail there, ie how a workpiece held rotatably on the workpiece spindle can be moved relative to various tools.

In the second method stage, ie the main step v) above, the rear side RS of the workpiece is then machined down to the prefabricated groove NU (or stage ST or recess) in the course of surface machining in the generator. In the schematic 9 a plate milling cutter is indicated as the second tool WZ2. In this exemplary embodiment, the first tool WZ1 used in the main step iii) for machining the blank RL on the front side FS is different from the at least one second tool WZ2 used in the main step v) for machining the workpiece on the rear side RS, which is also fundamentally different can be.

The milling process as the first sub-step of the main step v) the surface processing on the rear RS takes place as described in the prior art and separates the resulting shape of the semi-finished product HZ completely from the surrounding blank material, as in 10 can be seen. As a result of the previous segmentation, the two (or more) ring segments RG in the exemplary embodiment shown fall off the semi-finished product HZ and can be removed and disposed of with the chips that are produced anyway.

A turning process as a second substep of the main step v) of surface machining on the rear side RS can now also be carried out as described in the prior art, specifically only on the rear side geometry of the semi-finished product to be produced HZ resulting from the previous milling process. The semi-finished product HZ machined in this way can now be lifted off the workpiece holder WA (see 11 ) and has final ( 12 ) the same geometric properties as would result after processing using methods according to the prior art (see the introduction to the description).

The HZ semi-finished product removed from the generator can then be polished (see the second process "blockless polishing" in the process chain according to 1 ). In principle, the same polishing processes can be used for this purpose as described in the prior art. The semi-finished product HZ can be fixed with the flat holding system mentioned above, or with a vacuum suction device, as is already used in various places for handling tasks.

The optional marking (process "blockless marking" in 1 ) of the polished semi-finished products HZ can now in turn be done using the same methods as described in the prior art. Because in the process chain according to 1 However, if the position of the semi-finished product HZ is not defined by a block piece, an additional metrological step is required to determine the location and position of the semi-finished product HZ in advance.

The polished and, if necessary, marked semi-finished products are then HZ coated (process “coating” in 1 ), as known from the state of the art, before the adjustment or fitting of the semi-finished product HZ to the frame shape can be tackled ("Edgen" process in 1 ), which is also done as known in the prior art. Here, the edge of the workpiece is given its final edge contour, as indicated by the reference sign RK2 in FIGS 6 and 10 already indicated. In addition, the fastening geometries required for fastening the spectacle lens produced as the end product in the socket (spectacle frame), such as pointed and roof facets, bores, etc., are formed here.

With 13 The illustrated variant of the method, in which no groove is milled, but the blank material is machined in the main step iii) according to the depth of the calculated groove up to the edge of the semi-finished product HZ to be produced, so that a step ST is created on the workpiece, has already been addressed above. Such a stage ST would also result automatically in the main step iii) if the finished diameter of the workpiece deviates from the raw diameter of the blank RL by less than twice the cutter diameter. However, in cases where this difference in diameter is larger, such processing is also possible.

The 14 shows a flow chart according to one of the process chain 1 different process chain for the production of spectacle lenses made of plastic as optical workpieces without the use of block pieces in the production, which compared to the prior art according to 16 first of all, the auxiliary processes "blocking" and "unblocking" are omitted. In addition, the process chain according to 14 also compared to the process chain according to 1 the “Edgen” process as the final process in the process chain. This is made possible by another ingress process, namely an in 14 Again, a method called “blockless generation” for the machining of spectacle lenses made of plastic according to a second exemplary embodiment. This alternative method is based on the 15 described only insofar as it differs significantly from the method explained above according to the first exemplary embodiment.

From a comparison of 1 and 14 It is obvious here that instead of the main step "edge preparation" in 1 in 14 the main step "Final edit edge shape" occurs, which ultimately results in the "Edges" process 1 in the process chain according to 14 makes dispensable. More precisely, in the method according to the second exemplary embodiment, in the main step iii) during or after formation of the circumferential groove NU or step ST (or the circumferential recess) using the first tool WZ1 or a further tool WZ1' (see 15 ) generates an edge contour RK2 on the semi-finished product HZ, which already corresponds to an edge contour RK2 on the finished workpiece.

For this purpose, at the in 15 On the left, in the main step iii), the end mill described above is used as the first tool WZ1, which produces a peripheral surface UF on the workpiece that already defines the edge contour RK2 of the finished workpiece. The aforementioned chamfer FA1 between the edge RA and the rear side RS of the semi-finished product HZ to be produced can - but does not have to - also be formed according to the milling cutter shape shown here as an example, as in 15 shown on the left.

At the in 15 In the process design illustrated on the right, in the main step iii) there is even a fastening geometry for the finished workpiece - here as an example at the transition from Edge RA and front FS of the semi-finished product to be trained HZ shown - generated. In the exemplary embodiment shown, the fastening geometry is a pointed bevel SF which, in the case of a spectacle lens, usually interacts with a complementary groove in a spectacle frame in order to fasten the spectacle lens in the spectacle frame. The formation of this fastening geometry for the finished workpiece takes place here in the main step iii) using the in 15 tool WZ1' shown on the right together with the circumferential groove NU (or step ST or recess), for which purpose the tool WZ1' is provided with a suitable shape of the cutting edge(s).

Finally, it is obvious to the person skilled in the art that in the main step iii) by choosing a suitable tool instead of the in 15 pointed bevel SF shown on the right, other fastening geometries can also be formed on the semi-finished product HZ. The fastening geometry generated in the main step iii) for the finished workpiece can be a roof facet or a circumferential groove or slot on the edge RA of the semi-finished product HZ to be formed (not shown here). Alternatively or in addition to this, the fastening geometry generated in the main step iii) for the finished workpiece can also include one or more bores or notches on the front side FS and/or the edge RA, depending on the respective fastening requirements of the socket and corresponding to the tooling used processing machine.

Regarding the remaining main steps of the process "blockless generation" in 14 as well as the further processes of 14 otherwise refer to the above statements on the 1 until 13 referred.

A method for machining optical workpieces, in which a semi-finished product with predetermined surface geometries on the front side and rear side and a contoured edge of predetermined edge thickness in between is formed from a blank, comprises the following main steps: i) Providing the material to be machined at least on the rear side and edge blank with a blank thickness; ii) non-blocking picking up of the blank for supported holding at the rear; iii) machining the blank on the front side using a first tool to form a circumferential geometric shape with a depth greater than or equal to the edge thickness of the semi-finished product to be formed, leaving a peripheral surface on the workpiece which defines the contoured edge of the semi-finished product to be formed; iv) picking up the workpiece for support at the front; and v) machining the workpiece on the back using at least one second tool to form the semi-finished product with the predetermined surface geometry on the back.

Reference List

AS

exit point

BS

block piece

D1

blank thickness

D2

edge thickness

IT

immersion point

FA1

chamfer

FS

front

HZ

Workpiece

MA

central axis

NOW

groove

RA

edge

RG

ring segments

RK1

Edge contour of the semi-finished product

RK2

Edge contour of the finished workpiece

RL

blank

RS

back

SF

pointed facet

SN

suction cup

ss

support pin

ST

Step

tf

disc milling cutter

ti

depth

UF

peripheral surface

vs

vacuum cup

WA

workpiece holder

WZ1

first tool

WZ2

second tool

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 1593458 A2 [0004]
• DE 102007007161 A1 [0004]
• EP 2011604 A1 [0004]
• WO 2009135689 A1 [0004]
• EP 1719585 A2 [0005]
• EP 2011603 A1 [0005, 0072]
• EP 1203626 B1 [0006]
• EP 0758571 B1 [0007]
• EP 1779967 A2 [0008]
• EP 1473116 A1 [0010]
• EP 1698432 A2 [0010]
• EP 2308644 A2 [0010]
• WO 2016058661 A1 [0010]
• EP 1916060 B1 [0011]
• WO 2011042091 A1 [0012]
• WO 2011107227 A1 [0012]
• EP 1243380 A2 [0014]
• WO 2015059007 A1 [0015, 0016, 0017]
• US 9969051 B2 [0015, 0018, 0033]
• DE 102016112999 A1 [0015, 0020]
• EP 1037727 B1 [0022]

Claims (15)

Process for the machining of optical workpieces, in particular spectacle lenses made of plastic, in which, starting from a blank (RL), a semi-finished product (HZ) with predetermined surface geometries on a front side (FS) and a rear side (RS) facing away from it and with a contoured edge ( RA) of predetermined edge thickness (D2) is formed between the front face (FS) and the back face (RS) with the following main steps occurring in the order given: i) providing the blank (RL), which has a blank thickness (D1), can already have the predetermined surface geometry on the front side (FS) and is to be machined at least on the rear side (RS) and the edge (RA); ii) non-blocking picking up of the blank (RL) at the rear side (RS) to support the workpiece; iii) Processing the blank (RL) on the front side (FS) using a first tool (WZ1) to form a circumferential groove (NU) or step (ST) with a depth (TI) which is greater than or equal to the edge thickness (D2 ) of the semi-finished product (HZ) to be formed and is smaller than the thickness of the blank (D1), or a circumferential groove, which at least partially has a depth equal to the thickness of the blank (D1), so that a peripheral surface (UF) remains on the workpiece, which defines the contoured edge (RA) of the semi-finished product to be trained (HZ) defined; iv) picking up the workpiece at the front (FS) to support the workpiece; and v) Processing the workpiece on the back (RS) using at least one second tool (WZ2) to form the semi-finished product (HZ) with the predetermined surface geometry on the back (RS). procedure after claim 1 , wherein in the main step iii) when the circumferential groove (NU) or step (ST) or the circumferential recess is formed by means of the first tool (WZ1), an edge contour (RK1) is produced on the semi-finished product (HZ) which, with respect to an edge contour (RK2) of the finished workpiece has a slight oversize, and the edge contour (RK2) of the finished workpiece is produced only after the main step v) for machining the rear side (RS) of the workpiece. procedure after claim 1 , wherein in the main step iii) during or after the formation of the circumferential groove (NU) or step (ST) or the circumferential recess using the first tool (WZ1) or another tool, an edge contour (RK2) is produced on the semi-finished product (HZ), which already corresponds to an edge contour (RK2) of the finished workpiece. procedure after claim 2 or 3 , wherein in the main step iii) a chamfer (FA1) at the transition between the edge (RA) and the back (RS) of the semi-finished product to be formed (HZ) and/or a chamfer at the transition between the edge (RA) and the front (FS) of the semi-finished product (HZ) to be trained is or will be attached. procedure after claim 4 , wherein in the main step iii) the chamfer or chamfers (FA1) is or are attached by means of the first tool (WZ1) at the same time as the circumferential groove (NU) or step (ST) or the circumferential recess. Procedure according to one of claims 3 until 5 , wherein in the main step iii) a fastening geometry for the finished workpiece on the edge (RA) and / or on the front side (FS) of the semi-finished product to be formed (HZ) is generated. procedure after claim 6 , wherein in the main step iii) the fastening geometry for the finished workpiece is formed by means of the first tool (WZ1') at the same time as the circumferential groove (NU) or step (ST) or the circumferential recess. procedure after claim 6 or 7 , whereby the fastening geometry generated in the main step iii) for the finished workpiece is a pointed or roof facet (SF) or a circumferential groove or groove on the edge (RA) of the semi-finished product (HZ) to be formed and/or the im Main step iii) generated mounting geometry for the finished workpiece includes one or more holes or notches on the front side (FS) and / or the edge (RA). Method according to one of the preceding claims, wherein at the start of the main step iii) the first tool (WZ1) and/or the workpiece are moved relative to one another in such a way that the first tool (WZ1) for forming the circumferential groove (NU) or step (ST) or the circumferential puncture, starting from the front side (FS) of the workpiece, dips into the workpiece at a front-side plunge point. Procedure according to one of Claims 1 until 8th , wherein at the beginning of the main step iii) the first tool (WZ1) and/or the workpiece are moved relative to one another in such a way that the first tool (WZ1) to form the circumferential groove (NU) or step (ST) or the circumferential recess starting from the edge (RA) of the workpiece at a peripheral immersion point (ES) in the workpiece. procedure after claim 9 or 10 , wherein in the main step iii) after immersion of the first tool (WZ1) in the workpiece, the first tool (WZ1) and/or the workpiece are moved relative to one another in such a way that the first tool (WZ1) makes the groove (NU) or step (ST) or the recess in at least one revolution on the workpiece is generated, and wherein the first tool (WZ1) leaves the workpiece at an edge-side exit point (AS) at the edge (RA) of the workpiece that is remote from the front-side or edge-side immersion point (ES). Method according to one of the preceding claims, wherein in the main step iii) a rotationally driven end milling cutter is used as the first tool (WZ1) for machining the blank (RL) on the front side (FS). Method according to one of the preceding claims, wherein the first tool (WZ1) used in the main step iii) for machining the blank (RL) on the front side (FS) differs from that used in the main step v) for machining the workpiece on the rear side (RS), at least one second tool (WZ2) is different. Method according to one of the preceding claims, in which the workpiece in the main step iv) is received without a block on the front side (FS). Method according to one of the preceding claims, wherein in the main step iv) the workpiece is picked up on the front side (FS) in such a way that the workpiece is held with full-area support on the front side (FS).

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