DE102007050470A1 - Lens-polishing method for producing optically active surfaces by polishing rough-ground lenses uses large-surface polishing tools and 5-axle computerized numerically controlled polishing machines with work-piece/tool spindles - Google Patents

Abstract

A cap tool (26) is used under pressure with its flexible polishing membrane kept before an actual polishing process in contact with the surface of a lens (10) to be polished with its roughly pre-shaped polishing surface and a polishing foil. A polishing surface is molded as a negative shape with a polishing foil after applying pressure on the lens. During polishing movements, the negative shape is renewed again and again at each new position in the polishing surface. An independent claim is also included for a device for carrying out the method of the present invention.

Description

The The invention relates to a method for producing optically active Surfaces by polishing pre-ground lenses and a device for carrying out the method accordingly those mentioned in the preambles of claim 1 and claim 16 Features.

aim The invention is the economy and quality when polishing optically active surfaces. The quality improvement relates both to the accuracy, as well as the roughness depth of the generated areas. These tasks be solved with the features of claims 1 and 16. The disadvantages of the prior art methods become so avoided.

The said optically active surfaces may be both on lenses, and on mirrors with spatially curved Surfaces are located. To the linguistic simplification becomes below only spoken by lenses, since the proposed Process should relate primarily to the production of lenses. It is envisaged with the procedure lenses from all areas to edit the optics. This can z. B. lenses of fine optics, but also be spectacle lenses. But are always synonymous mirror.

method for polishing lenses with devices for implementation the methods are known per se. These have in comparison with However, the method proposed here has several disadvantages.

at All polishing procedures must try to find the optimum between economical production and the highest possible quality to find the generated optical surfaces. This is working for technical reasons always on a compromise, since Both claims are only partially in the same procedure let fulfill.

polishing process with high material removal and thus good economy, are suitable procedurally less for generating complicated and high quality finishes. Conversely allow Polishing methods that make complicated surfaces good Quality can be produced only a small amount Material removal and thus only a low cost.

These Connections can be clarified when looking at the procedures for polishing lenses, according to the prior art, with the associated devices for carrying out the A closer look at the method.

optical Lenses are made from blanks in several steps. First, the desired geometries of the Lens surfaces by means of various grinding operations produced, followed by the polishing of these surfaces, whereby they obtain their optically active properties.

To the Polishing lenses are used on polishing machines have at least two spindles. At one becomes the polishing tool tightened (tool spindle) while at the other the workpiece (lens) by means of a corresponding receiving device is attached (workpiece spindle). The two spindles are arranged one above the other and have vertical axes of rotation with drives.

In order to the relative movements required for polishing by means of molds generated between lens and polishing tool as small circular movements can be one of the two spindles, including its rotary drive, from the vertical position into an oblique Panning position.

At the Polishing spherical lenses becomes the swivel angle chosen so that the axes of the vertical and the pivoted spindle in the center of curvature of the machined cut spherical lens surface. For lenses with multiple radii of curvature needs for the swivel angle a corresponding mean value can be formed.

This leads to further inaccuracies on the workpiece surface and thus to a loss of quality. At the compromise in particular between quality and economy play also the high tool costs a big role.

When Polishing tools come mainly because of the good economy Forming tools used. These have a large polishing surface and accordingly a great polishing performance. Smears at the lens quality are accepted as the surface shape the active polishing surface for cost reasons the Lens geometry adjusted only approximate or graded can be.

Less common are polishing processes where tools with small polishing surface (Polishing pins) are used. They are used for making very exact special lenses. Because of the small polishing surface is However, the polishing performance only low and therefore the cost-effectiveness.

The polishing tool and the lens are then brought into contact with each other for polishing by moving one of the spindles in the Z-axis and pressed against each other during the polishing process with a predetermined working pressure. Tool and lens are driven by the two spindles rotationally and in the same direction of rotation. Usually, the speed and the phase angle of the two spindles match.

Of the Polishing process then runs with the addition of polishing suspension due to their composition (polishing body and chemically active substances) for the desired material removal ensures and at the same time serves as a coolant. Polishing suspension is used in all polishing processes and therefore not always mentioned in the following text.

As mentioned, it comes in the development of modern polishing processes This is the compromise between economic efficiency and to find quality. Let the problem areas occur to further clarify, if one from the multiplicity of the well-known become the two possible extreme cases pick out and look at.

• 1. Polierverfahren, bei denen Formwerkzeuge zur Anwendung kommen (Nachteil: Die Polierfläche ist groß und damit die Poliergenauigkeit klein. Außerdem ist eine Vielzahl von unterschiedlichen Polierwerkzeugen erforderlich. Diese Werkzeugart eigenet sich nur für sphärische und torische Flächen).
• 2. Polierverfahren, bei denen sogenannte Polierstifte benutzt werden (Nachteil: Die Polierfläche ist klein und damit auch die Polierleistung).

These are:

• 1. Polishing method using molding tools (Disadvantage: The polishing surface is large and thus the polishing accuracy is small, and a variety of different polishing tools are required.) This tool is only suitable for spherical and toric surfaces).
• 2. Polishing method, in which so-called polishing pins are used (Disadvantage: The polishing surface is small and thus the polishing performance).

To 1.:

at This method is used for polishing molding tools, the be used on CNC polishing machines. These polishing devices feature at its one end via a pin for attachment the tool spindle, while at the other end of the polishing surface located. This has the form of a negative imprint of the to be polished Lens surface and is covered with a polishing film.

The Lens is by means of a fastening device on the other spindle (Workpiece spindle) attached. So that the necessary Relative movements (small circular movements) take place between the lens and the tool, one of the two spindles is tilted by pivoting. This is usually the tool spindle arranged above. The swivel angle is chosen so that the intersection the two spindle axes in the center of curvature (mean value) the lens surface is located. After the collapse of Lens and tool is the large-scale polishing with the addition of polishing suspension.

There the polishing tool most of the lens surface covers, this is on many individual surface elements polished at the same time. Accordingly, the polishing performance is good and thus the economy. Such methods are therefore preferred used when larger quantities be polished by lenses with the same surface geometry should, since then the tool costs do not occur multiple times.

The However, polishing with molds also has several disadvantages, in particular if very different lenses (eg, lenses) to be polished.

• – Wenn die Kontur der zu polierenden Linse auch im Feinbereich erhalten werden soll, muss das Formwerkzeug ein exakter Negativabdruck der Linsenoberfläche sein. Dies führt wegen der verschiedenen Linsenformen zu einer Vielzahl von verschieden geformten Werkzeugen. Dementsprechend hoch sind die Fertigungs- und Lagerkosten für die Werkzeuge. Hinzu kommt, dass das Werkzeug praktisch bei jeder neu zu polierenden Linse ausgewechselt werden muss. Für die Herstellung von a-sphärischen und a-torischen Flächen sowie von Freiformflächen kann diese Werkzeugart nicht genutzt werden. Die Linse muss beim Einlegen in die Halterung der Werkstückspindel außerdem genau auf das Formwerkzeug ausgerichtet werden, da sie sich ja genau in den dort vorhandenen Negativabdruck (nicht rotationssymmetrisch!) ihrer Kontur einfügen muss. Auch die hier genannten Besonderheiten erhöhen die Kosten
• – Eine andere Möglichkeit mit Formwerkzeugen zu arbeiten besteht darin, dass man aus Gründen der Kostenersparnis nicht für jede Linsenform und jeden Radius ein solches Polierwerkzeug anfertigt, sondern die Werkzeuge mit abgestuften Krümmungsradien an der Bearbeitungsfläche herstellt. Da aber bereits torische Linsen zwei unterschiedliche Radien haben, muss hier für jeden ersten Radius (R₁) eine abgestufte Reihe von zweiten Radien (R₂) vorgesehen werden.

These disadvantages are as follows:

• - If the contour of the lens to be polished is also to be obtained in the fine range, the mold must be an exact negative impression of the lens surface. This leads to a variety of different shaped tools because of the different lens shapes. Accordingly high are the manufacturing and storage costs for the tools. In addition, the tool needs to be replaced with virtually every new lens to be polished. For the production of a-spherical and a-toric surfaces as well as free-form surfaces, this type of tool can not be used. The lens must also be precisely aligned with the mold when inserting into the holder of the workpiece spindle, since it must fit exactly into the existing negative impression (not rotationally symmetrical!) Of its contour. The special features mentioned here increase the costs
• - Another way to work with molds is that for reasons of cost savings not for each lens shape and each radius makes such a polishing tool, but produces the tools with graded radii of curvature on the processing surface. However, since toric lenses already have two different radii, a graduated series of second radii (R ₂ ) must be provided here for each first radius (R ₁ ).

To 2 .:

The polishing tool used in this process are polishing pegs used on multi-axis CNC polishing machines. These polishing pins are substantially cylindrical bodies which are fastened with their one end to the tool spindle (usually the upper one), while at the other end is the polishing surface with the polishing foil. This is a soft film which is in contact with the surface to be polished is brought and performs the polishing work with the addition of polishing suspension.

The The lens to be polished is located on the other spindle (workpiece spindle). Their surface is point by the rotating polish pen Departed for point and thereby polished. The smaller the Polishing pen is, so the finer contours can be on the Lens surface are polished without it for leveling of fine structures that may occur during sanding were generated.

It is understandable that with a polish pin no high Profitability can be generated as its benefits only then come into play when its diameter, measured on the lens diameter, is small. But with a small polishing surface can be do not achieve high polishing performance in terms of time unit. In practice, therefore, many compromises are made, as far as the diameter of the polishing pin and its shape are concerned.

at Consideration of the two aforementioned extreme examples becomes visible that considerable problems arise when the polishing performance (economy) and the surface quality of the polished lens to be optimized.

Therefore, another method has been known which is intended to partially avoid the disadvantages of working with molds. This procedure is used in the DE 101 06 007 A1 described.

To reduce the high tooling costs and limit the large number of mold tools needed in the DE 101 06 007 A1 proposed a polishing method, which is carried out with a variable mold.

Also In this method, the finished ground lens is present provided. The variable mold is constructed so that it in the workspace over a yielding, soft structure (Work surface), which presses against the lens surface on this forms and so the shape assumes a negative impression of the lens. After that, the work surface becomes fixed in this form.

These fixed working surface of the variable mold retains the shape of the negative impression of the lens, for the duration of the Polishing process, at. The polishing process is then on a suitable CNC polishing machine, as usual with molds performed. After that, the fixation of the working surface of the variable Mold tool again lifted and as previously described the new Shape of the next lens to be formed.

at the implementation of the method using the variable Form tool results over the method with simple Molds a saving in tooling costs.

• – Das Polierwerkzeug hat nur eine geringe Lebensdauer, da insbesondere seine aktive Polierfläche (inkl. Polierfolie) einem starken Verschleiß unterworfen ist. Dies hängt damit zusammen, dass die Arbeitsfläche einen starr fixierten Abdruck der Linsenoberfläche darstellt und nicht beweglich ist. So entstehen starke Zwängungen zwischen Werkzeug und Linse, wenn die Polierbewegungen stattfinden.
• – Wegen der starr fixierten Arbeitsfläche des Polierwerkzeugs entspricht die erzeugte Oberflächenqualität nicht dem gewünschten Optimum. Es besteht die Gefahr, das feinere Konturen wegpoliert werden.
• – Mit Rücksicht auf den vorgenannten Verschleiß und die Linsenqualität können die Relativbewegungen zwischen Werkzeug und Linse nicht so groß gewählt werden, wie dies unter wirtschaftlichen Gesichtspunkten wünschenswert wäre. Die Folge ist, dass die Polierleistung nicht optimal eingestellt werden kann.
• – Das variable Formwerkzeug ist wegen seines komplizierten Aufbaus deutlich teurer als die üblichen, einfachen Formwerkzeuge, was sich ebenfalls nachteilig auf die Wirtschaftlichkeit des entsprechenden Verfahrens auswirkt.

The method according to DE 101 06 007 A1 but also has some disadvantages as follows:

• - The polishing tool has only a short life, since in particular its active polishing surface (including polishing foil) is subject to heavy wear. This is related to the fact that the work surface is a rigidly fixed impression of the lens surface and is not movable. This creates strong constraints between the tool and the lens when the polishing movements take place.
• Because of the rigidly fixed working surface of the polishing tool, the surface quality produced does not correspond to the desired optimum. There is a risk that the finer contours are polished away.
• - With regard to the aforementioned wear and the lens quality, the relative movements between the tool and lens can not be chosen as large as would be desirable from an economic point of view. The result is that the polishing performance can not be optimally adjusted.
• - The variable mold is significantly more expensive than the usual, simple molds because of its complicated structure, which also has a detrimental effect on the economics of the corresponding method.

at the method according to the invention proposed here become the disadvantages in terms of economy and quality avoided, as in the polishing methods of the prior art given are. The method can be used for polishing of lens surfaces of any kind. Among other things also a-spherical and a-toric as well as free-form surfaces getting produced.

at the proposed method results in minimal tool and Processing costs, with very good quality of the produced Lenses.

• 1. Es wird ein besonderes Polierwerkzeug (Kappenwerkzeug) mit elastischer Polierkappe benutzt, das über eine grob vorgeformte Polierfläche und zwei Rutschkupplungen verfügt. Dabei wird die Polierfläche mit der daran befestigten Polierfolie von einem Druckmedium gegen die zu polierende Linsenoberfläche gedrückt und an dieser abgeformt, jedoch nicht fixiert.
• 2. Es wird eine Vorrichtung zum dynamischen Längenausgleich (Ausgleichsvorrichtung) zwischen der Werkstückspindel und dem Linsenhalter mit der Linse angeordnet. Auch bei dieser Ausgleichsvorrichtung werden die beweglichen Teile, welche die Linse tragen, mit einem Druckmedium beaufschlagt, wodurch u. a. der zum Polieren benötigte Anpressdruck erzeugt wird.
• 3. Es wird eine besondere Anordnung von Polierwerkzeug und Linse an der CNC-Poliermaschine vorgesehen. Dabei steht die Linse mit der oberen, vertikalen Werkstückspindel in Verbindung, während sich das Kappenwerkzeug an der unteren schräggestellten Werkzeugspindel befindet. Die Linse stützt sich dabei auf das im Durchmesser größere Werkzeug ab. Nach dem Stand der Technik wird üblicherweise die umgekehrte Anordnung gewählt.

This is achieved by the following three peculiarities of the procedure:

• 1. It uses a special polishing tool (cap tool) with elastic polishing cap, which has a rough pre-shaped polishing surface and two slip clutches. In this case, the polishing surface is pressed with the polishing film attached thereto by a pressure medium against the lens surface to be polished and molded on this, but not fixed.
• 2. A device for dynamic length compensation (balancing device) between the workpiece spindle and the lens holder is arranged with the lens. Even with this off Gleichsvorrichtung the moving parts, which carry the lens, acted upon by a pressure medium, whereby, inter alia, the contact pressure required for polishing is generated.
• 3. A special arrangement of polishing tool and lens is provided on the CNC polishing machine. In this case, the lens is in communication with the upper, vertical workpiece spindle while the cap tool is located on the lower inclined tool spindle. The lens is based on the larger diameter tool. In the prior art, usually the reverse arrangement is chosen.

With the proposed method can be polished lenses of any kind be, d. h., the scope does not just cover simple spherical lenses but also and in particular lenses with a-spherical, toric and a-toric surfaces but also lenses with even more complicated surfaces.

All The proposed method for polishing is particularly well suited of lenses with individual freeform surfaces (eg Spectacle lenses), which are produced as unique items. Here especially great advantages arise.

The Cap tool can be used on the well-known CNC polishing machines, as already described, are used. Because lenses with the aforementioned complicated surfaces (eg multiple radii of curvature) should be polished, the CNC polishing machine for These works have 5 machine axes. Both spindles (tool and workpiece spindle) must over Have facilities that allow the supply of print media.

The 5 machine axes have one common control and are thus linked. The controller is programmed with a mathematical model, which corresponds in each case to the lens to be polished. The workflow takes place fully automatically with these CNC-controlled polishing machines.

• – Eine X-Achse für das Querverfahren der oben angeordneten Werkstückspindel mit der daran befestigten Linse.
• – Eine Z-Achse für das vertikale Verfahren der Werkstückspindel.
• – Eine C₁-Achse als gesteuerte Drehachse der Werkstückspindel.
• – Eine B-Achse für das Schwenken (Schrägstellen) der unten angeordneten Werkzeugspindel.
• – Eine C₂-Achse als gesteuerte Drehachse der Werkzeugspindel.

The 5 machine axes are as follows:

• - An X-axis for the transverse process of the overhead workpiece spindle with the attached lens.
• - A Z-axis for the vertical movement of the workpiece spindle.
• - A C ₁ -axis as a controlled axis of rotation of the workpiece spindle.
• - A B axis for pivoting (tilting) the lower tool spindle.
• - A C ₂ axis as a controlled axis of rotation of the tool spindle.

An essential feature of the present invention proposed polishing method is the use of the novel capping tool. This adapts with its active polishing surface of the lens geometry, as already in the DE 101 06 007 A1 has been described.

in the Contrary to the polishing device provided there, the polishing surface However, in the capping tool according to the invention not fixed after molding.

For this, the cap tool is structured as follows:
A base tool has a hollow-bored mounting pin, with which it can be attached to the likewise hollow tool spindle of the CNC polishing machine. The interior of the base tool is also hollow and connected to an inner cap of an elastic material (eg rubber). This inner cap has an inverted cup shape and accordingly consists of a cylindrical part and on its upper side via a round membrane (inner membrane), which is slightly curved and facing the lens.

With the lower, widened edge of its cylindrical part is the Inner cap connected to the base tool. For this purpose, a fastening ring is provided, in a groove at the bottom of the cylindrical part of the inner cap engaging. The mounting ring is made by an outer cylinder held in turn by means of screw connection with the base tool connected is.

This Outer cylinder is open at both ends and in the diameters (inside and outside) repeatedly deducted. This forms an annular surface which, as mentioned, communicates with the mounting ring. The outer cylinder largely covers the inner cap on its cylindrical part, whereby it is stabilized.

The Polishing cap was named so because it has a cap shape (cup shape) has, d. H. It consists of a cylinder part (hollow cylinder) and a flat, round part (polishing membrane) on the upper front side.

she is with its cylinder part over the outer cylinder slipped and is there only by frictional forces, but not held by fasteners. Your polishing membrane is lying on the inner membrane of the inner cap.

Since the polishing cap is held in position only by frictional forces, it can be replaced very quickly and without tools. The associated time savings is a great advantage and improves cost-effectiveness. All the more so As the capping tool is specifically designed for polishing very different lens shapes and thus the polishing caps must be changed very often with their preformed polishing surfaces.

The Connection between the cylindrical part of the polishing cap and the outer cylinder forms a 1st slip clutch, the meaning of which will be described later becomes. To reinforce the frictional forces is the wall thickness enlarged in the lower part of the cylinder part.

There the inner membrane of the also elastic polishing membrane of Polishing cap is covered gap-free, also occur between the outside the inner membrane and the inside of the polishing membrane friction forces on. This 2nd slip clutch can be an additional Torque transmitted and the effect of the aforementioned 1st slip clutch support.

The polishing cap including the polishing membrane is homogeneously made of an elastic material (eg rubber). On the outside of the polishing membrane is the polishing surface, which carries the polishing film. The polishing surface and thus the polishing foil have z. B. for polishing spectacle lenses a toric surface with two different radii R ₁ and R ₂ , wherein the two radii differ by about 2 to 3 dpt.

Radii between 120 mm and 50 mm have proven to be advantageous. A particularly advantageous combination of radii is given if the following radii are selected: R ₁ = 100 mm and R ₂ = 70 mm.

It However, they are also other than toric geometries on the polishing surface intended. Likewise, other radii and radii combinations are planned.

There most lenses (eg, eyeglass lenses) usually toric or approximate toric surfaces have cylinders (usually between 0.5 dpt and 6 dpt), The preformed polishing membrane adapts to its polishing surface Already almost form-fitting to the surface to the lens. If the cap tool then applied to a pressure medium the polishing membrane lays down with its polishing surface completely and accurately to the lens.

This is one of the reasons for the very good polishing results in terms of quality and polishing performance. These will achieved without the polishing surface of the capping tool even before the pressurization an accurate negative impression must represent the lens geometry. It is enough if the Polishing surfaces in relatively coarse gradations accordingly the lens geometries are preformed.

There an exact fitting of the tool to the lens geometry is not required, the number of tools needed be greatly reduced, resulting in further, significant cost savings result.

The Cap tool according to the invention in the attached lower part of the polishing machine arranged tool spindle. This can be used to generate the polishing movement by pivoting in the B-axis be tilted and rotated with a controlled Rotational movement in the C2 axis.

There both the spindle and the associated capping tool hollow, the inner cap can be inclusive their inner membrane are acted upon by said pressure medium. By this pressurization, the inner membrane bulges to the outside and thereby takes the applied to her polishing membrane the polishing cap with.

By this deformation becomes the elastic polishing membrane with its polishing surface and the polishing film to the lens surface to be polished pressed, taking their geometry. If during the polishing process then due to the inclined tool spindle between the cap tool and the lens mentioned Relative movements (small circular movements) occur, results the big advantage that the cap tool with his Polishing surface always exactly the same at any time Lens contour adapts.

Also when the touching surface elements of Moving the lens and tool against each other as a result of the polishing movements, The lens contour on the tool can be repeated over and over again be imaged.

from that results in a very good surface quality, because there is no constraint between the lens and the tool surface, which is constantly changing from new to the lens geometry adapts. In addition, the high polishing performance, as usual for molds is reached. Small discontinuities in the two spindle speeds and in the phase angle of the two mentioned slip clutches balanced. This will also improve the lens quality improved.

By the avoidance of constraint between the preformed polishing surface and the finish-ground lens surface, that will Tool less stressed. This results in a longer Lifetime for the tool and thus a more economical Advantage.

Very It is also advantageous that the lens and the active polishing surface the cap tool when setting the polishing machine not to each other must be aligned in the correct phase, even if the Polishing surface according to the lens geometry coarse is preformed.

If Lens and tool are moved together, so the twisted Polishing cap of the tool until both surfaces (lens surface and polishing surface) exactly in phase and form-fitting on top of each other lie. In this twisting finds the required slip the two mentioned slip clutches instead, which is another advantage this construction is.

In the method according to the invention, it is provided that the workpiece spindle has an X and Z axis, with which it can be moved linearly in the horizontal and vertical directions. The rotational movement of the spindle is controlled by the C ₁ axis.

It has also proved to be advantageous, a device for dynamic Provide length compensation (balancing device) on the workpiece spindle. This balancing device is preferably between the above lying, vertical workpiece spindle and the receiving device for The lens is arranged and has the task of small path differences in the Z direction and to compensate for the required polishing pressure produce. For this purpose, it is charged with a pressure medium.

The Compensating device consists of a hollow-drilled base part, for attachment to the likewise hollow-bored workpiece spindle via a Flange or a spigot has. In the central Bore of the base part is the guide cylinder of the him connected adapter parts easily movable out.

Thereby can the adapter part with guide cylinder and the lens holder connected to it (eg block piece) perform small axial movements. Since it is provided pressurize the equalizer also with a pressure medium which produces the required polishing pressure becomes a seal between base and adapter part a cuff made of elastic Material (eg rubber) provided. The cuff transfers also the torque required for polishing of the base part on the adapter part

Of the Guide cylinder has holes, which allow the print medium to pass over the workpiece spindle is fed to lead to the top of the adapter part. By this pressurization, the adapter part with lens holder and Lens uniformly pressed towards the polishing surface.

The Lens settles without constraint (no static overdetermination) on the polishing surface. This increases the quality the generated lens surface and protects the tool, which thereby achieves a significantly longer life. This also results in economic benefits.

at The method according to the invention is also a special arrangement of tool and lens on the spindles of the CNC polishing machine intended. The lens is under the interposition of said Compensation device with the upper, vertical workpiece spindle while the cap tool slanted at the bottom Tool spindle is located.

A Special feature is also that the tool in the proposed Method is larger than the lens. However, it is also provided that the lens is larger than that Tool or the same size.

The Lens rests during the polishing process the larger diameter tool from. Thereby the lens is guided very safely and it can even very small workpieces can be polished. These are too advantageous properties of the proposed method.

at Process variants, however, is also provided that the lens is larger as the tool, if it results in individual cases advantages.

at the previously known polishing method is the arrangement lens and tool usually just the opposite, d. H. the upper tool is supported on the arranged below larger lens.

If the lens is very small, the tool must be very small, because it is smaller than the lens. This will be in the process according to the prior art, in addition, the number of needed tools enlarged and thus Costs incurred in the proposed method here.

In the proposed method, it has proved to be advantageous to choose the diameter ratios between tool and lens as follows:
Tool diameter to lens diameter = 1.1 to 1.5. (In the case of the previously known methods, the ratio is about 0.6). However, other diameter ratios are also provided.

The method according to the invention then proceeds as follows:
The balancer with the associated lens (workpiece) is attached to the upper, vertical workpiece spindle of a 5-axis CNC polishing machine. At the lower also vertical tool spindle, the cap tool is attached and the tool spindle then tilted by pivoting in the B axis.

Of the Swivel angle is chosen so that the intercept point the two machine spindles with the center of curvature the lens surface can be made to coincide and there is a sufficient overlap of lens and tool results.

The Align the axis intersection to the center of curvature is done by moving the workpiece spindle in the X-axis. If the lens geometry at the surface to be polished several Has radii of curvature, so an average is formed and the center of curvature is selected thereafter.

Thereafter, the controlled rotation of the spindles in the C ₁ and C ₂ axes is started. The C ₁ -axis of the workpiece spindle and the C ₂ -axis of the tool spindle is assigned. The rotation of the two axis-controlled spindles takes place in the same direction and with the same angular velocity (ω ₁ = ω ₂ ). The phase position of the two spindles is arbitrary at the start of the spindle rotation, since the polishing cap aligns with its polishing surface by turning on the lens geometry. This is made possible by the two slip clutches. However, the phase alignment of the two spindles remains after the start.

To switching on the means for supplying the polishing suspension is achieved by moving the workpiece spindle in the Z-axis then the lens surface to be processed up to a short distance to the polishing surface of the capping tool moved up. The polishing surface is covered with a polishing foil busy.

Subsequently the balancing device is subjected to a slight pre-pressure, whereby their moving parts with the attached lens after drive down and this comes in contact with the cap tool.

The Cap tool is then also subjected to a pressure medium, whereby the polishing surface of the polishing membrane on the Geometry of the lens molds after the polishing cap so far twisted (made possible by slip clutch) that their preformed contour brought to coincide with the lens geometry is.

Of the Polishing process begins when then the compensation device was subjected to the full pressure and thereby the required Contact pressure (polishing pressure) between lens and cap tool available is.

While of polishing, the polishing surface is constantly forming new from the lens geometry. Small inaccuracies in speed and phase angle of the spindles are from the two slip clutches balanced while constraining on the workpiece spindle and the lens in the axial direction by means of the balancing device is avoided.

By This polishing with very accurate tool geometry (molded polishing surface) and the avoidance of constraints of all kinds arises very good result both in terms of surface geometry the generated lens, as well as with respect to the generated roughness. Even the tool wear is low, since no constraint between lens and tool occurs.

There it is the cap tool to the further development of a mold their high polishing performance is achieved. Ie. not only the quality but also the economy are significantly better than in the previously known polishing process.

The method according to the invention and the devices for carrying out the method will be described below by means of an example and the 1 to 3 described. However, other variants and embodiments of these devices are provided.

1 shows the essential components of a schematically illustrated CNC polishing machine, which carries on its upper workpiece spindle, the compensation device with lens, while on the lower, skewed tool spindle, the capping tool is attached.

2 shows the capping tool in an enlarged view.

3 also shows the compensation device in an enlarged view.

To 1

1 shows the schematic representation of a 5-axis CNC polishing machine ( 1 ), on which the method according to the invention is carried out. It has in the upper machine part ( 2 ) via a workpiece spindle ( 3 ) and in the lower machine part ( 4 ) via a tool spindle ( 5 ). Both spindles rotate clockwise when seen from above with the same angular velocity (ω ₁ = ω ₂ ) and in the same direction Phasing. The workpiece spindle ( 3 ) associated with the axis of rotation C ₁ (C ₁ axis), while the tool spindle ( 5 ) has the rotation axis C ₂ (C ₂ axis).

The workpiece spindle ( 3 ) is so with the CNC polishing machine ( 1 ) that it can be moved by means of linear guides (not shown) in the horizontal X-axis and the vertical Z-axis controlled.

The tool spindle ( 5 ), however, has a pivoting device (not shown), with which it can be tilted from the vertical position by 30 ° degrees to both sides. The pivoting movement is also controlled and in the B axis.

All movements in the axes of the CNC polishing machine ( 1 ) are controlled and according to a mathematical model that is tuned to the lens geometry. The machine axes are thus interconnected and perform their movements simultaneously or in succession.

The workpiece spindle ( 3 ) carries at its lower end the balancing device ( 6 ), which by means of a screw connection ( 7 ) on the flange ( 8th ) of the workpiece spindle ( 3 ) is attached. At the lower end of the balancing device ( 6 ) is the lens mount ( 9 ) on which the lens to be processed ( 10 ) is attached.

The tool spindle ( 5 ) carries at its upper end the cap tool ( 26 ), which by means of a fastening pin ( 27 ) with the tool spindle ( 5 ) connected is. The fixing pin ( 27 ) is part of the basic tool ( 28 ), to which all other functional parts are attached.

The mentioned pressure medium is the central bore ( 19 ) in the workpiece spindle ( 3 ) via a supply line ( 22 ) and a rotary feedthrough ( 23 ). In the tool spindle ( 5 ) the pressure medium of the central bore ( 41 ) via the rotary feedthrough ( 42 ), which in turn is connected to the supply line ( 43 ) connected is. The pressure of the print medium can be adjusted to give an optimal polishing result in terms of quality and economy.

To 2

(The Lens ( 10 ) is in 2 not shown. For details see 1 )

The cap tool ( 26 ) is by means of a fastening pin ( 27 ) on the tool spindle ( 5 ) attached. This mounting pin ( 27 ) is fixed with a basic tool ( 28 ) connected.

On the upper flange surface ( 29 ) of the basic tool ( 28 ) is the inner cap ( 30 ) with its lower edge. It has the shape of an inverted cup and consists of an elastic material (eg rubber). The inner cap ( 30 ) has on its upper side a circular inner membrane ( 45 ) on.

When exposed to a pressure medium, this inner membrane ( 45 ) the task, the actual polishing membrane ( 39 ) of the cap tool ( 26 ) with its polishing surface ( 35 ) against the surface of the lens to be processed ( 10 ).

The inner cap ( 30 ) is placed on the upper flange surface ( 29 ) of the basic tool ( 28 ) of a fastening ring ( 31 ), which enters the groove ( 32 ) of the inner cap ( 30 ) is inserted. The fastening ring ( 31 ) is itself from an annular surface ( 44 ) of the outer cylinder ( 33 ) held by a screw connection ( 34 ) with the upper flange surface ( 29 ) of the basic tool ( 28 ) connected is.

To the inside of the outer cylinder ( 33 ) settles upon pressurization of the cylindrical part ( 36 ) of the elastic inner cap ( 30 ) at. Over the outside of the outer cylinder ( 33 ) the polishing cap ( 37 ) with its cylinder part ( 46 ) pushed. This cylinder part ( 46 ) has a wall thickening at its lower part ( 38 ). This is necessary in order to obtain a sufficient contact force between the polishing cap ( 37 ) and the outer cylinder ( 33 ), since both components form a slip clutch in this area.

A second slip clutch is formed between the outside of the inner membrane ( 45 ) and the inside of the polishing membrane ( 39 ). This second slip clutch also transmits a torque and thus supports the effect of the first slip clutch.

Because the polishing cap ( 37 ) without all fasteners over the outer cylinder ( 33 ), it can be replaced very easily if another lens mold is to be polished, which has a polishing cap ( 37 ) with differently preformed polishing membrane ( 39 ) requires.

The upper end of the polishing cap ( 37 ) is removed from the polishing membrane ( 39 ) educated. This is on her polishing surface ( 35 ) with a polishing foil ( 40 ).

The polishing membrane ( 39 ) when polishing as a result of the pressurization of the capping tool ( 26 ) with its polishing surface ( 35 ) and the polisher foil ( 40 ) against the lens ( 10 ) and molded on this. Due to the rotational movements of the inclined tool spindle ( 5 ) and the vertical workpiece spindle ( 3 ) results in the polishing movement in the form of small circles between the lens ( 10 ) and the polishing membrane ( 39 ) with the polishing foil ( 40 ).

During the polishing process, the polishing foil ( 40 ) Supplied polishing slurry, which ensures the desired material removal and also dissipates the frictional heat generated. The device for the supply of the polishing suspension is not shown, since not the subject of this invention.

By pressurizing the inner cap ( 30 ) and thus indirectly also the polishing membrane ( 39 ) with the polishing foil ( 40 ) attach these two components very precisely to the surface of the lens ( 10 ) at. The polishing surface ( 35 ) of the polishing membrane ( 39 ) as well as the polishing foil ( 40 ) take, as desired, the shape of a negative impression of the surface geometry of the lens ( 10 ) at.

It is very advantageous that this negative impression is formed again and again when the cap tool ( 26 ) due to the polishing movements relative to the lens ( 10 ) emotional. At any point in the polishing process, therefore, the polishing surface ( 35 ) and with it the polishing foil ( 40 ) the ideal shape (negative impression) for very accurate polishing of the lens ( 10 ).

As the polishing membrane ( 39 ) due to the pressurization of the capping tool ( 26 ) but with the required polishing pressure elastically to the surface of the lens ( 10 ) creates no constraint between the two components.

As a result, not only the quality of the lens surface produced is significantly improved, but also the tool wear is significantly smaller than is the case with polishing tools with a rigid (fixed) contour. This effect is supported by the in 2 not shown balancing device ( 6 ). This ensures that no restriction arises in the axial direction.

To 3

The workpiece spindle ( 3 ) with its central bore ( 19 ) and its flange ( 8th ) are in 3 not shown, see details 1 ) The balancing device ( 6 ) is with its base part ( 14 ) by means of a screw connection ( 7 ) with a flange ( 8th ) of the workpiece spindle ( 3 ) connected. The lens holder ( 9 ) with the lens to be processed ( 10 ) is at the lower end of the balancing device ( 6 ) attached.

At the bottom of the balancing device ( 6 ) is an adapter part ( 11 ) arranged that by means of a guide cylinder ( 12 ) in a central bore ( 13 ) of the base part ( 14 ) is guided axially displaceable. On the adapter part ( 11 ) is an intermediate piece ( 15 ) by means of screw connection ( 16 ) attached. The intermediate piece ( 15 ) carries the lens mount ( 9 ) with the lens ( 10 ) and is used to quickly change the lens mount ( 9 ) with lens ( 10 ).

The guide cylinder ( 12 ) has an axial bore ( 17 ) and a horizontal hole ( 18 ). Both holes are aligned with the central hole ( 19 ) of the workpiece spindle ( 3 ), via which the compensating device ( 6 ) A printing medium can be supplied. This passes through the holes in the interior ( 20 ) of the balancing device ( 6 ), of a cuff ( 21 ) of elastic material (eg rubber) is enclosed. This allows axial movements by deformation and is with the base part ( 14 ) and the adapter part ( 11 ) connected pressure-tight.

The cuff ( 21 ) also transmits the torque required for polishing from the base part ( 14 ) on the adapter part ( 11 ), without interfering with the axial mobility of the components connected to its lower part.

The pressure medium exerts its pressure among other things on the upper end face ( 24 ) of the guide cylinder ( 12 ) and on the ring surface ( 25 ) of the adapter part ( 11 ) out. The force generated thereby moves the adapter part ( 11 ) with the associated components and the lens ( 10 ) in the axial direction down until the lens ( 10 ) on the cap tool ( 26 ) (The cap tool is in 3 not shown, see details 1 ). The contact force generated between the lens ( 10 ) and the cap tool ( 26 ) is required in the subsequent polishing process to produce the polishing pressure.

1

CNC polishing machine

2

upper machinery

3

Workpiece spindle

4

lower machinery

5

tool spindle

6

balancer

7

screw connection

8th

flange

9

lens holder

10

lens

11

adapter part

12

guide cylinder

13

central drilling

14

base

15

connecting piece

16

screw connection

17

axial drilling

18

horizontal drilling

19

central drilling

20

inner space

21

cuff

22

supply

23

Rotary union

24

face

25

ring surface

26

cap tool

27

fastening pins

28

basic tool

29

upper flange

30

inner cap

31

fixing ring

32

groove

33

outer cylinder

34

screw connection

35

polishing surface

36

cylindrical part

37

polishing cap

38

wall thickening

39

polishing membrane

40

polishing film

41

central drilling

42

Rotary union

43

supply

44

ring surface

45

inner membrane

46

cylinder part

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10106007 A1 [0028, 0029, 0033, 0042]

Claims (25)

Method for producing optically active surfaces by polishing pre-ground lenses using large-area polishing tools and 5-axis CNC polishing machines having a workpiece spindle and a tool spindle, characterized in that a pressurized cap tool ( 26 ) whose elastic polishing membrane ( 39 ) before the actual polishing process with its roughly preformed polishing surface ( 35 ) and the polishing foil ( 40 ) with the surface of the lens to be polished ( 10 ) and that the polishing surface ( 35 ) with the polishing foil ( 40 ) due to the pressurization of the lens ( 10 ) is formed as a negative impression, wherein this negative impression during the polishing movements at each new position of the polishing surface ( 35 ) is generated again and again and that inaccuracies in the angular velocities and phase angles of the axes of rotation C ₁ and C ₂ are compensated by means of two slip clutches and that constraints in the axial direction by a likewise pressurized compensating device ( 6 ), which allows a length compensation by axially displaceable components and generates the adjustable polishing pressure on the printing medium. A method according to claim 1, characterized in that as a capping tool ( 26 ) trained polishing tool in the lower machine part ( 4 ) on the tool spindle ( 5 ) while the compensating device ( 6 ) with the lens ( 10 ) in the upper machine part ( 2 ) on the vertical workpiece spindle ( 3 ) is attached. Method according to claim 1 and 2, characterized in that the tool spindle ( 5 ) is pivoted in the B axis and rotated in the C2 axis. A method according to claim 1 to 3, characterized in that the workpiece spindle ( 3 ) is moved in the X and Z axes and rotated in the C ₁ axis. Method according to claims 1 to 4, characterized that the 5 machine axes of a CNC device accordingly be controlled by a mathematical model, the mathematical Model is created according to the lens geometry. A method according to claim 1 to 5, characterized in that the two machine spindles in the axes C ₁ and C ₂ rotate in the same sense and at the same angular velocity without shifting the phase angle. Method according to claims 1 to 6, characterized in that the capping tool ( 26 ) via the central bore ( 41 ) of the tool spindle ( 5 ) a printing medium is supplied. Method according to claims 1 to 7, characterized in that the compensating device ( 6 ) via the central bore ( 13 ) of the workpiece spindle ( 3 ) a printing medium is supplied. A method according to claim 1 to 8, characterized in that the pressure levels of the two print media on the capping tool ( 26 ) on the one hand and the compensating device ( 6 On the other hand, are set independently during the polishing process so as to give optimum lens quality with maximum efficiency. A method according to claim 1 to 9, characterized in that a polishing surface ( 35 ) whose diameter is greater than that of the lens ( 10 ). A method according to claim 1 to 10, characterized in that the lens ( 10 ) during the polishing process on the polishing membrane ( 39 ) of the cap tool ( 26 ), wherein the polishing membrane ( 39 ) with a polishing foil ( 40 ) is occupied. A method according to claim 1 to 11, characterized in that the diameter of the polishing surface ( 35 ) on the polishing membrane ( 39 ) is selected so that the diameter ratio of diameter of the polishing surface ( 35 ) to diameter of the lens ( 10 ) is in the range of 1.1 to 1.5. A method according to claim 1 to 12, characterized in that for polishing toric spectacle lenses cap tools ( 26 ) whose toric surface has two radii differing by 2 to 3 dpt. A method according to claim 1 to 13, characterized in that for polishing toric spectacle lenses cap tools ( 26 ) are used, whose two radii are between 50 mm and 120 mm. A method according to claim 1 to 14, characterized in that for polishing toric spectacle lenses cap tools ( 26 ), where one radius is 70 mm and the other radius is 100 mm. Device for carrying out the method according to claim 1, characterized in that in the lower machine part ( 4 ) of a CNC polishing machine ( 1 ) a pivotable about the B-axis tool spindle ( 5 ) is present, with which as a capping tool ( 26 ) performed polishing tool, while in the upper machine part ( 2 ) one vertical workpiece spindle ( 3 ) provided with the compensating device ( 6 ), which the lens ( 10 ) wearing, Apparatus according to claim 16, characterized in that the CNC polishing machine ( 1 ) has 5-machine axes connected to a CNC device programmed with a mathematical model and that the tool spindle ( 5 ) and the workpiece spindle ( 3 ) are each connected to an electric drive. Apparatus according to claim 16 and 17, characterized in that the tool spindle ( 5 ) is connected to the B and C ₂ axes. Apparatus according to claim 16 to 18, characterized in that the workpiece spindle ( 3 ) is connected to the X and Z axes as well as to the C1 axis. Apparatus according to claim 16 to 19, characterized in that on the tool spindle ( 5 ) a central bore ( 41 ), which is connected to the rotary union ( 42 ), which in turn is connected to the supply line ( 43 ) connected is. Apparatus according to claim 16 to 20 characterized in that on the workpiece spindle ( 3 ) a central bore ( 19 ), which is connected to the rotary union ( 23 ), which in turn is connected to the supply line ( 22 ) connected is. Apparatus according to claim 16 to 21, characterized in that the capping tool ( 26 ) by means of a fastening pin ( 27 ) with the tool spindle ( 5 ) and this part of the basic tool ( 28 ) and that the basic tool ( 28 ) with its upper flange surface ( 29 ) on the one hand with the inner cap ( 30 ) and on the other hand by means of a screw connection ( 34 ) with the outer cylinder ( 33 ) and that the inner cap ( 30 ) with a fastening ring ( 31 ) and in turn connected to the outer cylinder ( 33 ) and that the polishing cap ( 37 ) with its cylinder part ( 46 ) with the outside of the outer cylinder ( 33 ) and in this area a slip clutch is present, including the wall thickening ( 38 ) and that the polishing membrane ( 39 ) of the polishing cap ( 37 ) with the inner membrane ( 45 ) of the inner cap ( 30 ) and in this area a slip clutch is present and that the polishing surface ( 35 ) of the polishing membrane ( 39 ) with a polishing foil ( 40 ) connected is. Apparatus according to claim 16 to 22, characterized in that the compensating device ( 6 ) by means of its base part ( 14 ) and the screw connection ( 7 ) with a flange ( 8th ) of the workpiece spindle ( 3 ) and that in the base part ( 14 ) a central bore ( 13 ) is present, in which an axially displaceable guide cylinder ( 12 ) is arranged, which at its lower end with an adapter part ( 11 ), which in turn is connected via a screw connection ( 16 ) with the intermediate piece ( 15 ), in turn connected to the lens mount ( 9 ) and the lens ( 10 ) and that between the base part ( 14 ) and the adapter part ( 11 ) a cuff ( 21 ) is present, which the interior ( 20 ) and that in the guide cylinder ( 12 ) an axial bore ( 17 ) and a horizontal hole ( 18 ) available. Apparatus according to claim 16 to 23, characterized in that in the supply line ( 43 ), the rotary feedthrough ( 42 ) and the central bore ( 41 ) and inside the inner cap ( 30 ) a pressure medium is present Apparatus according to claim 16 to 24, characterized in that in the supply line ( 22 ), the rotary feedthrough ( 23 ) and the central bore ( 19 ) and in the axial bore ( 17 ), the horizontal hole ( 18 ) and the interior ( 20 ) a pressure medium is present.