DE4409748C2 - Cut-off process and machine as well as cut-off wheel - Google Patents

Description

The invention relates to a cut-off process in which a cutting wheel rotating around its axis relatively against workpiece to be cut is fed and thereby an in oscillation running on the working plane of the cutting wheel moving movement of the cutting wheel relative to the workpiece is provided. The invention further relates to a separation grinding machine with at least one rotating cutting wheel, one infeed device with which the cutting wheel is relatively against workpiece to be cut is deliverable, and a movement supply device with which the cutting wheel in its ar working plane in an oscillating movement relative to the workpiece is relocatable. Finally, the invention relates to use end of the cutting process according to the invention and he cutting machine according to the invention as well as a corundum and a Diamond cutting wheel for performing the specified cutting grinding process.

A cut-off process is the complete one Cutting a workpiece through abrasive removal, d. H. by cutting with geometrically indefinite cutting edges, while one sees such devices as cutting machines, which are equipped with at least one cut-off tool, the  has abrasive abrasive grains on its surface, which under Press on an intended cutting line to penetrate moving object.

DE 40 06 668 A1 already describes one method and one Stone working machine as known in practice described in which a constantly rotating saw or Grinding wheel with constant vertical infeed repeated horizontally over a hard to be cut rock block is moved back and forth. The delivery takes place each in the end positions and is controlled so that the Saw or grinding wheel a certain maximum engagement in the stone block or a certain maximum work on Stone block has to perform. It always becomes a thin stone layer cut or sanded, with a depth of Intervention in the direction of delivery or via which of and from Grinding wheel diameter dependent length of engagement in Circumferential direction of the grinding wheel no further information be made. However, since the known arrangement on the cutting surface 1 m² / h, the contact length with the Gra nitblock engaging edge of the grinding wheel, d. H. that circumferential length of the grinding wheel on which the Rand has a negative effect at a given moment, at least 40 mm if one assumes that the grinding wheel diameter in the known device is about 1000 mm, so that Have granite blocks of less than 500 mm thickness cut, and that the device has a maximum feed rate of 200 mm / s.

In contrast, in the laboratory area for precise cutting of samples, in particular for the production of histological Preparations made from non-cut tissues and materials, such as tooth-bearing jaw sections with fillings, crowns and bridges ken, implant-bearing jaw or tubular bones or brittle hypermineralized bone parts, other heat-sensitive sensitive test specimens, test specimens of different hardness and / or tough composite materials and test specimens for one  Investigation as part of a material test, especially for Manufacture of grindings or thin sections, so far worldwide predominantly cut-off machines with endless diamondbe used abrasive belts. The reasons are firstly, that abrasive belts are less than separators grinding wheels tend to flutter, d. H. you can because of larger clamping forces not so easily due to lateral forces deflected from the cutting plane and ver if necessary in vibrations be set. Deflections or vibrations of the grinding mechanism Stuff is undesirable, mainly because it is next to a larger one Wear of the grinding tool also roughness of the cut surfaces and thus a subsequent grinding process result in greater effort. Also need straight forward moving abrasive belts compared to rotating separators grinding wheels to stabilize only relatively small movements speeds, which at comparable depths of engagement or contact lengths between the front edge of the abrasive cutter of or between the edge of the cutting wheel and the separating object less frictional heat is released, so that especially temperature-sensitive tissue samples very much can be cut more gently. With conventional separation grinding process using rotating abrasive cut slices tend to be cut because of the higher cutting speed tended to be even more tiny in the area of the procedure Tear fragments out of the cut surfaces, including the Cut quality suffers.

The disadvantages of cut-off machines with rotating Bands are in particular that such devices have a comparatively large space requirement and also none simultaneous cutting of a sample in several parallel Allow cutting planes. The behavior is also disadvantageous length of contact across the entire sample, the especially with test specimens made of different composite materials rialien, such as those made of heat-sensitive materials hand and tough and / or hard materials on the other hand, for. B. the implant-bearing bone tissue samples already mentioned,  very long cutting times required to heat the sample to temperatures above 40 ° C and thus undesirable Avoid changes in the bone tissue.

Proceeding from this, the invention is based on the object Cutting wheel working with rotating cutting discs process and a cutting wheel and machine for performing the cutting Provide grinding process, especially in the laboratory rich with a clear reduction of the previously required Allow cutting times to cut objects precisely and with which a much more economical and cost cheaper cut-off than previously possible.

This object is achieved by the characterizing Part of claims 1 for the method and 12 and 13 for the cut-off wheel and 14 for the Features specified resolved. Then draws the inventive method is characterized in that the order traverse speed of the cut-off wheel a maximum of about 1000 m / min is and the delivery is controlled so that the Length of engagement between the cutting disc and the factory piece is a maximum of about 5 mm.

Preferred embodiments of the method are in claims 2 to 11 and preferred embodiments of the partition Grinding machine described in claims 15 to 18. Claims 19 to 21 relate to preferred uses of the Procedure and / or the machine.

Such small engagement lengths are in themselves already Cut-off process for cutting less hard and known heat-sensitive objects of small thickness for example from very thin plates or bars with a thickness of less than 5 mm, but instead of a com binary feed and feed movement between the separator  a grinding wheel and the object to be cut thrust movement "in full", d. H. the cutting disc and the Objects only move in one direction relative to each other and not oscillating back and forth.

In contrast, the present invention is in the field grinding of extremely hard and / or tough Materials, preferably in combination with much softer ones and mostly also heat-sensitive materials that the subject So far, there have been major technical and economic problems has made a host previously thought impossible Efficiency with excellent cut quality and clearer Reduction of the cutting times achieved by the selected control of the infeed depth of engagement and thus also the length of engagement and the contact area of the with cutting object in the engaged cutting loop disc edge depending on the hardness and / or toughness of the cutting material and, if necessary, its heat sensitivity should be kept as small as possible. In this way succeeds in making workpieces from very hard materials such as Oxide ceramics, e.g. B. corundum, relatively quickly and with one amazingly low wear of the cutting wheels cut through and also a very good cut quality achieve.

A preferred embodiment of the invention provides that the Length of engagement when cutting very hard and / or tough work pieces, for example of implants made of CoCrMo or polycri stalliner Al₂O₃ ceramics with a Mohs hardness of 9.0, depending is set by the material of the workpiece and in particular less than 2.5 mm, with the best cutting results when cutting such materials with engagement lengths preferably in the range of 1.5 mm and could be achieved below. Separation tests on in plastic embedded implants made of CoCrMo, for example, have shown results ben that with engagement lengths of about 0.4 to 0.5 mm in the range  of the implant and from 4 to 5 mm in the area of the plastic very precise separation with extremely little heating and therefore without softening and smearing the plastic. For cutting monocrystalline Al₂O₃ ceramics with a Mohs hardness of 9.9, on the other hand, recommend even smaller interventions lengths that can go down to 0.25 mm. In principle a point-like contact is sought, so that to only a few grains at a given time the cutting wheel with the counter to be cut was engaged. When cutting softer materia lien or softer components of composite materials different hardness and / or toughness, for example Cut through the surrounding an implant with plastic in the impregnated fabric or an embedding compound made of polymethyl methacrylate or from another plastic material however, advantageously the engagement lengths up to the claimed upper limit of 5 mm can be increased, for example wise by increasing the depth of engagement to thereby Increase cutting speed.

Surprisingly, in addition to the slight warming and the desired precise cut two more serious advantages over abrasive belts that are used for one is that when using equivalent, z. B. on an electrolytic path with grinding mechanism set with diamond dust witness the cutting times considerably, d. H. by double to Could be reduced threefold, and that to the other has shown that not for cutting implant materials necessarily diamond-tipped tools are required, but that the use of reworked commercial corundum Cutting wheels is possible, the cost of which is inclusive the post-processing from about 20 to 30 DM many times are smaller than those previously used for this purpose used abrasive belts from about 900 to 1000 DM The service life is not only comparable, but for corundum because of their self-sharpening properties a little bigger. The not particularly complex post-processing of the  Corundum cut-off wheels only involve unscrewing the Bearing hole for the output shaft with simultaneous Ver reduction of the tolerances of the inner diameter, as well as a Grind their peripheral edge for an exact concentricity and to ensure constant depth of engagement.

Due to the fact that costs are lower by a factor of 100, Im plantology series cuts for the first time with a small distance above the entire length of a prosthesis affordable, making statements about the state and, if necessary, about changes in the interfaces between prosthesis and bone over the entire length of the prosthesis can be taken and not as previously for cost reasons only in a few selected places, with the risk that essential findings are not recorded.

The reason for the lower warming and for the higher Cutting performance in the method according to the invention is therein seen that the cut-off wheel in one wheel knife of 120 mm, as used to cut test specimens is usually used, and a slice thickness of 100 µm for very thin diamond cut-off wheels or of 2 mm with corundum disks on a circumferential surface, which not with a preferred engagement length of less than 1 mm is more than 0.01 or 2 mm². On the one hand, this means that only on a very small, essentially punctiform surface Frictional heat is generated, which is also due to the good access the abrasive peripheral surface of the abrasive cut slice with the help of the supplied, preferably in front of the area of the engagement approximately tangential to the edge of the cut-off loop sprayed coolant can be easily removed can. On the other hand, you get a very small one Feed force a sufficiently high specific cutting force, see above that ratio of the abrasive diamond or corundum grains remove moderately thick chips of a hard and / or tough material gene, but at the same time the reaction forces the cutting tool can be kept relatively small NEN, so that a "flutter" of the cutting wheel prevents  becomes. Rotating diamond cutting around such a flutter grinding wheels with a small grinding wheel thickness of 100 µm to 200 µm when cutting with a large engagement length So far, it has been necessary to use the cut-off wheels to be clamped between two support plates so that the support plate cover most of the cut-off wheel and only freely read a narrow outer edge area of the cutting wheel sen, with the result that the depth of cut to a maximum of 10% of Grinding wheel diameter is limited. Due to the Lich smaller axial forces with small engagement lengths, like them the method according to the invention provides, in contrast, at same diameter and same thickness of the cutting disc now the support disc diameter is reduced as far be that depths of cut of at least 20 to 25%, in gün other cases, namely for materials with low hardness, even up to 30 to 35% of the cutting wheel diameter possible are.

In addition, due to the short length of the erosive Circumferential surface ensures a very good chip removal. Thereby can in particular when severing in the bone or in Implants used in the jaw can be prevented from Cutting wheel carried chips of the implant material to one embedded in the surrounding tissue or the other Tear fragments out of the fabric and do it this way greatly change that an investigation without a previous one heavy material removal by grinding cannot be used Results.

A defined, optimal for the respective application To ensure the handle length, the cut-off is fed disc controlled, preferably step by step in the area the end points of the oscillating movement of the cutting wheel, so that there are defined depths of engagement let set. A path-controlled delivery, the intervention lengths between 0.06 and 5 mm, is advantageous with the help of a  Delivery device that acts on a threaded spindle kenden stepper motor, wherein rotation of the stepper mo tors in the range between 0.36 and 5 degrees in combination with a Pitch of the threaded spindle in the range between 2 and 6 mm an infeed of the cutting wheel between 2 and 170 µm causes what corresponds to the aforementioned contact lengths.

It is used to deliver the Cut-off wheel whose drive motor is parallel to the working level the cutting wheel in the vertical direction opposite one in the vertical direction, fixed support table for the cut severing object. The drive motor is preferably with the cutting disc from the thread spindle carried, the weight of the drive motor the grinding process in the vertical direction disc reaction forces significantly exceeded. Before is preferably the one which interacts with the threaded spindle of the delivery device Mother rigid with the one guided in the vertical direction Drive motor of the cutting wheel connected, the Ge weight is absorbed by the threaded spindle. The To position and the oscillating movement of the cutting wheel expediently take place by suitable measures known per se free of play. By using a self-locking threaded spin del can also be ensured that a lowering of the An drive motor only while driving the thread spindle can be done.

In contrast to the delivery device, the movement acts direction of the workpiece to be cut, d. H. so on the support table, so that this under the Cutting wheel is oscillating back and forth.  

The oscillating movement of the support table in a horizontal Direction can be force or path controlled, in particular Step-by-step control, especially for smaller laboratory devices the feed path is preferred because it enables identical construction Components for the delivery device and the oscillating Use moving device. An An control of the two stepper motors for the infeed of the Cutting wheel or for the oscillating movement of the Support table done together, so that with a single Setting both the step size of the delivery and the the oscillating movement can be changed, e.g. B. about them changed material properties of the material to be cut  Adapt workpiece. In contrast, with gear DC motors achieve a more uniform feed what recommend their use especially for larger devices lenswert makes.

While one cooperating with the threaded spindle of the movement device, with the Support table rigidly connected feed nut in a first of the two opposite oscillating directions of movement by the of the cutting disc on the workpiece and thus on the Support table exercised against the first direction of oscillation acting thrust is made free of play, it is provided that Play in the feed nut in the other, second oscillation to eliminate direction by means of a weight body, the one attached to the support table and deflected by a roller ten band is attached and in one of the second direction of oscillation attacks in the opposite direction on the support table.

To prevent unwanted movements of the cutting disc perpendicular to Preventing the working plane of the cut-off wheel is another useful one Embodiment of the invention that the output shaft of the Drive motor is mounted free of play in the axial direction. A Thermal expansion of the output shaft is used according to another purpose moderate design of the invention as small as held possible to pass through the output shaft one between the drive motor and the cutting disc arranged, the interior of the drive motor from the wet, abrasi the milieu of the support table and the cutting disc end of the bearing cover is a labyrinth surrounding the output shaft seal is provided.

To cut a workpiece to be examined into individual slices cut or to remove a disc from the workpiece can separate, the support table or the drive motor of the Cutting disc slidable perpendicular to the oscillating direction orderly and lockable in defined displacement positions his. A single disc or two parallel and parallel Alternatively, adjacent panes can also be used together  cut out of the workpiece when on the output shaft two or three cut-off wheels at an axial distance from each other are attached.

As already mentioned, there is a very advantageous effect of the inventive method in the low heating of the workpiece to be cut due to the extremely small Area of engagement between the cutting wheel and the through separating workpiece, which in connection with the already mentioned extremely smooth, flat and undamaged cut areas of application for the production of histological Preparations opened, in particular an insert for cutting of implant-carrying tissue samples for examination purposes, for example for the production of tissue or bone thin grind at which the temperature during cut-off in Cutting area should preferably be below 40 ° C to tissue exclude changes.

Methods and devices of the type described with very Small engagement lengths can be due to the small space may use the machine especially in the laboratory. In addition to the already mentioned field of application in manufacturing histological specimens become the method according to the invention and the machine according to the invention preferably for separating hard and / or tough workpieces made of metal or ceramic Materials used to make these metallurgically, with regard to their structure, based on boundary conditions or the like search. By reducing the engagement length to a value in A range of less than 1 mm can also be used with very hard and / - or tough, previously only with the help of diamond cutters workpieces machined not only Cut cutting times significantly, but at the same time Instead of diamond cutting discs much cheaper right, cut-off wheels with corundum or impregnated use so that the cost per cut is many times are lower. You also get such after cutting Workpieces already so smooth and flat cut surfaces that  a subsequent grinding process is shortened and in individual Cases can even become superfluous.

Because of the low level of heating that occurs when cutting off with of the device according to the invention on the workpiece to be cut occurs and in combination with the large cut This can happen with hard and / or tough materials The method according to the invention is also very advantageous when passing through separating composite materials are used, for example of composite materials in addition to hard and / or tough metals or poorly heat-conducting hard ceramic materials too Contain plastics. In the known methods and Vorrich cuts occur when cutting such composite materials often difficulties because the plastics on the one hand more heating tend to smear or decompose and on the other hand in the known methods as a result of Hardness or toughness of the metals or the hardness of the ceramic mat rialien low feed speeds federela dodge, which results in uneven cut surfaces. There considerably lower heating in the process according to the invention If the material to be cut occurs, a Ver lubricate or decompose the plastic with certainty avoided, and chip evacuation is not reduced by melted Plastic material that covers the spaces between the abrasive, engaged with the object to be cut Diamond or corundum grains clogged, so that with Shorter cutting times also produce smoother cutting surfaces can be.

The high quality of the cut surface can also, for example when cutting semiconductor materials of greater thickness from Be an advantage to minimize subsequent grinding losses and Reduce cutting times.

In the following the invention with reference to one in the drawing in schematically illustrated embodiment explained. It shows  

Figure 1 is a front view of a laboratory cutting machine according to the invention with a rotating cutting wheel.

Fig. 2 is a top view of the machine of Fig. 1;

Fig. 3 is a schematic representation of the engagement of the cutting wheel in a workpiece during the cutting process.

The cutting machine 1 shown in the drawing essentially consists of a trough-shaped machine lower part designed as a coolant collecting trough 2 , a projecting part protruding upwards above the collecting trough 2 , the lower part into a partition 4 dividing in front of it and a rear part, two towards the rear towards the partition 4 subsequent stiffening walls 6 , 8 , in the front part above the drip pan 2 slidably mounted in the horizontal direction support table 20 for a workpiece 12 to be cut, a movement device 14 to the support table 20 with the workpiece 12 in oscillating directions of movement V in the area of the end points the oscillating movement back and forth to move a vertically displaceably mounted drive motor 16 , on the output shaft 18 above the support table 20 a cutting wheel 22 is releasably attached, an infeed device 24 to the drive motor 16 and the separator grinding wheel, is controlled to the Auflagertisch 20 and lower the fixed thereon workpiece 12, as well as one above the catch basin 2 detachably BEFE stigte splash guard hood and a cooling device (both not shown) in a feeding direction Z corresponding to the working plane of the cutting wheel 22 22 to cool the Workpiece 12 during a cutting with the cutting wheel 22 .

The partition 4 has an elongated in the vertical direction te, rounded at the upper and lower ends of the passage opening 26 , through which the output shaft 18 of the drive motor 16 arranged behind the partition 4 is passed. From the drive shaft 18 is forward over the partition 4 , so that the cutting wheel attached to its free end be 22 is located approximately in the middle above the support table 20 .

The delivery device 24 for the drive motor 16 comprises a stepper motor 28 flanged above the drive motor 16 at the rear of the partition 4 for the stepwise rotation of a vertical threaded spindle 30 designed as a trapezoidal spindle, which interacts with a nut 32 rigidly attached to the drive motor 16 in order to ensure the gradual rotary movement of the Threaded spindle 30 in a vertical translational feed movement of the drive motor 16 and the cutting wheel 22 to implement. On both sides of the drive motor 16 , a vertical cylindrical guide rod 36 is rigidly attached to the drive motor 16 by means of two clamping connections 34 arranged one below the other, which is guided above and below the passage opening 26 in a linear bearing, not shown, so that the drive motor 16 is only in can move in the vertical direction, while opposing forces are absorbed by the guide.

The weight of the drive motor 16 , which exceeds the reaction forces in the vertical direction on the cutting wheel 22 by several times during the cutting process, is introduced via the nut 32 into the threaded spindle 30 , so that the nut 32 down against the engaged gears Threaded spindle 30 pulled and thus a backlash-free delivery is ensured.

Precise guidance of the cutting wheel 22 in its working level is achieved in that, on the one hand, the output shaft 18 of the drive motor 16 is free of play by suitable measures and that, on the other hand, heating of the output shaft 18 due to the required encapsulation of the drive motor 16 is minimized by the output shaft 18 is led out of the housing 38 of the drive motor 16 through a labyrinth seal, not shown.

The stepper motor 28 used makes it possible to take 1000 steps per revolution, which corresponds to a step size of 0.36 degrees. In connection with a pitch of the threaded spindle 30 of 3 mm, an infeed of the drive motor 16 and the cut-off wheel 22 in steps of 3 μm is possible, which corresponds to a depth of engagement of this size and, with a cut-off wheel diameter of 120 mm, an engagement length of 90 μm. This smallest engagement length can if necessary be reduced even further without structural changes by controlling the stepper motor in half steps and / or by using a cutting disc with a smaller diameter. By increasing the respective pulse number of the stepping motor 28 to integer multiples of 1, larger step sizes of 6 µm, 9 µm can be achieved. . . etc. adjust.

Apart from an initial manually controlled lowering of the cutting wheel 22 to the surface of the workpiece 12 or in the vicinity thereof, the infeed takes place whenever the support table 20 is in one of the two end points of the oscillating movement. To control the stepper motor 28 , a proximity switch (not shown) is used, which, when the support table 20 approaches the respective end point, on the one hand causes a reversal of the direction of movement of the support table 20 and on the other hand an infeed of the drive motor 16 by a predetermined or set increment. The proximity switch are each slidably mounted in a receiving bore so that the end positions of the support table 20 can be adjusted accordingly the size of the workpiece 12 to be cut. Another, in the vertical direction ver adjustable and triggering when the drive motor 16 approaches triggering switch (also not shown) ensures after the end of the separation process, ie when falling below a preset height, for a shutdown of the entire machine 1st

The support table 20 is rigidly connected by means of four clamping connections 40 arranged in pairs on its front or rear side to two mutually parallel cylindrical guide rods 42 which pass through openings 44 in the somewhat raised side walls of the collecting trough 2 and in each case on opposite sides in Linear bearings 46 are mounted horizontally. The moving means 14 for oscillating displacement of the Auflagertischs 20 includes a fixed on one of the side walls of the drip tray 2 stepping motor 48, from step 48 driven, guided through a passage opening 50 in the side wall of collecting well 2 and supported in the opposed side wall motor-threaded spindle 52, as well as a nut (not shown) rigidly attached to the support table 20 and cooperating with the threaded spindle 52 . The stepper motor 48 , the threaded spindle 52 and the nut of the movement device 14 are identical to the stepper motor 28 , the threaded spindle 30 and the nut 32 of the delivery device 24 , so that the feed also in steps of 3 microns, 6 microns, 9 microns, etc. and if necessary from less than 3 microns, the Oszillationsge speed can be increased or decreased with an optimal step size determined by increasing or decreasing the number of pulses.

During the support table 20 and thus the mother of the movement device 14 in a first, the circumferential direction of the cutting wheel 22 in the region of the engagement (arrow A in Fig. 1) opposite direction of movement (arrow B in Fig. 1) by the grinding wheel 22 from the cutting the workpiece 12 exerted thrust forces is held free of play on the threaded spindle 52 , a play-free feed of the support table 20 in the other, second feed direction (arrow C in Fig. 1) is ensured with the help of a weight body (not shown) suspended on a cord, the Cord is guided over a stationary order to the steering roller and attacks against this second feed direction on the support table 20 .

The choice of the optimal step size of the movement device 14 and the delivery device 24 is expediently determined in each case by experiments, the step size of the step motor 48 of the movement device 14 not only corresponding to that of the step motor 28 of the delivery device 24 , but also being able to differ therefrom.

The workpiece 12 can be fastened on the support table 20 , for example, with the aid of a vise arranged on the support table 20 or by means of a vacuum plate against which the workpiece 12 is sucked.

To cut workpieces in the laboratory area, depending on the dimensions of the workpiece, either corundum cut-off wheels or diamond-coated cut-off wheels 22 with a diameter between 100 and 150 mm are used, with the latter usually the diamond dust electrolytically on the edge of a metal disk with a normal thickness between 0.1 mm and 1 mm is applied so that the abrasive diamond grains protrude over the circumference of the disc. Such diamond cutting wheels 22 are considerably more expensive than the corundum cutting wheels, which have a thickness of about 2 mm, but lower cutting losses can be achieved, which is particularly necessary when very many par allele cuts are made on a small workpiece length should be.

To carry out the cutting process, the drive motor 16 is lowered in a manually controlled manner with the feed device 24 until the lower edge of the cutting wheel 22 is near the surface of the workpiece 12 or is just touching it. Then the drive motor 16 is switched on and the support table 20 with the workpiece 12 is moved in a horizontal direction from the direction of movement 14 until it reaches the previously set first end point. When the first end point is reached, the proximity switch arranged there controls the stepper motor 48 of the movement device 14 in such a way that its direction of rotation is reversed, while at the same time the stepper motor 28 of the delivery device 24 rotates the threaded spindle 30 by one or more steps, depending on the set number of pulses, and thereby the drive motor 16 and the cutting disc 22 lowered by the desired depth of engagement. Then he follows a gradual feed of the support table 20 until the support table 20 reaches the other end point, where the direction of rotation of the threaded spindle 52 is reversed again and the drive motor 16 is lowered again by the set increment.

When cutting an implant made of CoCrMo with a diameter of about 16 mm embedded in a polymethyl methacrylate block with a side length of about 30 mm with the aid of a diamond or corundum cutting-off wheel 22 , for example with a step size of 150 μm in the area of the embedding material, correspondingly an engagement length of a little less than 5 mm, and of 15 µm in the area of the implant, corresponding to an engagement length of a little less than 1.5 mm, produce very smooth and flat cut surfaces, whereby even when using a corundum cutting disc, a considerable reduction in the Cutting time to about 2 hours (compared to a cutting time of 8 to 10 hours with a conventional diamond-cut belt cutting machine) can be achieved. As a result of the considerably lower costs of the corundum cutting discs with a somewhat longer service life, this leads to a multiple reduction in cutting costs.

At a suitable rotational speed of the drive motor 16 of approximately 1000 rpm, circumferential speeds of approximately 400 m / min result in the case mentioned with a diameter of the cut-off wheel of 120 mm, this value being considerably below the normally selected circumferential speeds of diamond or corundum Cut-off wheels 22 is located. The Oscillationsgeschwindig speed is approximately 10 to 40 mm / min when cutting the implant material in both oscillation directions and is correspondingly higher in the area of the plastic material above and below the implant because of the larger step size.

The engagement of the cutting wheel 22 in the workpiece 12 is shown exaggerated in FIG. 3. At a radius R of the grinding wheel of 60 mm and an engagement depth T in the direction of delivery of 15 microns, the removal of the workpiece 12 takes place on a circular arc section (engagement length X) of the grinding wheel edge of about 1.5 mm in length with a center angle α of 1.42 degrees, which corresponds to a contact area of 0.75 mm² or 3 mm² with a thickness of the cutting wheel 22 of 0.5 mm (diamond wheel) or 2 mm (corundum wheel) (contact area = engagement length x thickness of the cutting wheel) .

The relationship between the engagement length X of the cutting edge benrandes, the engagement depth T, the center angle α (in degrees) and the radius R of the cutting wheel 22 is as follows:

Claims (21)

1. abrasive cutting method in which a rotating about its axis the cutting wheel (22) is delivered relative to a cut through the workpiece (12) and in the working of the grinding wheel plane (22) extending oscillating motion of the cutting wheel (22) relative to the workpiece ( 12 ) is provided, characterized in that the peripheral speed of the cut-off wheel ( 22 ) is a maximum of about 1000 m / min and the infeed is controlled such that the engagement length (X) between the cut-off wheel ( 22 ) and the workpiece ( 12 ) is a maximum of about 5 mm. 2. Cut-off method according to claim 1, characterized in that the engagement length (X) is set depending on the material of the workpiece ( 12 ). 3. Cut-off method according to claim 1 or 2, characterized ge indicates that the engagement length (X) is less than 2.5 mm is. 4. Cut-off method according to claim 1 or 2, characterized ge indicates that the engagement length (X) is less than 1.5 mm is. 5. Cut-off method according to one of claims 1 to 4, characterized in that the contact area between the peripheral edge of the grinding wheel ( 22 ) and the workpiece ( 12 ) to be cut is a maximum of about 15 mm². 6. Cut-off method according to one of claims 1 to 4, characterized in that the contact area between the peripheral edge of the cutting wheel ( 22 ) and the workpiece ( 12 ) to be cut is less than 7.5 mm². 7. Cut-off process according to one of claims 1 to 6, characterized in that the peripheral speed of the cut-off wheel ( 22 ) is less than 500 m / min. 8. abrasive cutting method according to any one of claims 1 to 7, as step in the region of the end points of the oscillating movement of the cutting wheel (22) is effected by in that the delivery of the cutting wheel (22). 9. Cut-off process according to one of claims 1 to 8, characterized in that the oscillating movement of the cut-off wheel ( 22 ) takes place step by step. 10. Cut-off method according to claim 9, characterized in that the oscillating movement of the cut-off wheel ( 22 ) takes place with step lengths of at most about 250 µm. 11. Cut-off method according to claim 9, characterized in that the oscillating movement of the cut-off wheel ( 22 ) takes place with step lengths of at most about 100 µm. 12. Corundum cutting disc for performing the cut Grinding method according to one of claims 1 to 11, characterized characterized in that they have a disk diameter between 100 and 150 mm and a pane thickness of 2 mm.   13. Diamond cutting disc for performing the cut Grinding method according to one of claims 1 to 11, characterized characterized in that they have a disk diameter between 100 and 150 mm and a slice thickness of 100 to 200 µm having. 14. Cut-off machine for performing the cut-off process according to claims 1 to 11 with at least one rotating cut-off wheel ( 22 ), a delivery device ( 24 ) with which the cut-off wheel ( 22 ) can be advanced relative to a workpiece ( 12 ) to be cut, and a movement device ( 14 ) with which the cutting wheel ( 22 ) in its working plane in an oscillating movement relative to the workpiece ( 12 ) can be set, characterized in that the delivery device ( 24 ) and the movement device ( 14 ) each one of one Stepper motor ( 28 ; 48 ) has a driven threaded spindle ( 30 ; 52 ). 15. Cut-off machine according to claim 14, characterized in that on the stepper motors ( 28 ; 48 ) a step size of less than 1 degree is adjustable. 16. Cut-off machine according to claim 14, characterized in that a step size of less than 0.5 degrees can be set on the stepper motors ( 28 ; 48 ). 17. Cut-off machine according to one of claims 14 to 16, characterized in that with the threaded spindle ( 30 ) of the feed device ( 24 ) cooperating nut ( 32 ) rigidly connected to the drive motor ( 16 ) of the cut-off wheel ( 22 ) guided in the vertical direction is whose Ge weight force is absorbed by the threaded spindle ( 30 ). 18. Cut-off device according to one of claims 14 to 17, characterized in that the movement device ( 14 ) acts on the workpiece to be cut ( 12 ). 19. Use of the cut-off process according to claims 1 to 12 and / or the cut-off machine according to An Proverbs 14 to 18 for severing heat sensitive Workpieces, such as tissue samples carrying implants. 20. Use of the cut-off method according to claims 1 to 12 and / or the cut-off machine according to An pronouncements 14 to 18 for cutting objects Composite materials of different hardness and toughness and of semiconductor materials. 21. Use of the cut-off method according to claims 1 to 12 and / or the cut-off machine according to claims 14 to 18 for cutting out a thin disc from the workpiece ( 12 ) by means of two grinding discs ( 22 ) arranged parallel to one another at a distance ne.