WO2011006816A1

WO2011006816A1 - Method for producing a shaped part having an inner contour and an outer contour

Info

Publication number: WO2011006816A1
Application number: PCT/EP2010/059772
Authority: WO
Inventors: Elmar Hock; Stefan Fecher; Lothar VÖLKL
Original assignee: Degudent Gmbh
Priority date: 2009-07-13
Filing date: 2010-07-08
Publication date: 2011-01-20
Also published as: DE102009026159A1; EP2453828A1

Abstract

The invention relates to a method for producing a shaped part having an inner contour and an outer contour, wherein the shaped part is machined from a blank and, in at least two successive processing steps, is roughed down and smoothed. To be able to produce a shaped part of the desired final geometry in the machining process with a high feed rate, it is proposed that, in a first processing step, the shaped part is roughed down in a first region, that, in a second processing step, the shaped part is roughed down in a second region, differing from the first region, that, in a third processing step, the second region is smoothed and that, in a fourth processing step, the first region is pre-smoothed and then, in a fifth processing step, is smoothed.

Description

Process for producing a molded part having an inner and outer contour

The invention relates to a method for producing a molding having an inner and an outer contour, in particular dental object such as coping, crown or bridge framework, wherein the molding is machined out of a blank and steps in at least two subsequent processing steps and is dressed and wherein at least after the second processing step, the molding with the remaining blank (blank) remains connected via a compound such as a circumferential ridge or a circumferential membrane-like compound preferably in the region of maximum extent (maximum circumferential line) of the molded part to be produced.

From WO-A-2005/051220 a method for producing a molded part such as dental object is known, which is machined from a blank by machining. Until the final contour of the molded part is reached, it is connected to the residual blank via a web or a membrane-like connection. To work out a milling strategy with a rough milling (roughing) from outside to inside and a subsequent fine milling (finishing) of the outer surface and the inner surface is provided.

A method for producing dentures according to EP-BI 443 869 proposes the use of a milling tool with a diameter between 0.5 mm and 5 mm. In order to produce molded ceramic parts, there is a processing of a green compact in several steps, in each of which certain areas are processed, already machined areas being surrounded by an embedding compound (DE-A-199 30 564).

For the production of a dental object, WO-A-02/45614 uses a blank consisting of at least one metal oxide, in particular Al ₂ O ₃ , TiO ₂ , MgO, Y ₂ O ₃ and / or zirconium oxide mixed crystal, which is machined becomes. The blank itself has the geometry of a cylinder.

In order to produce a dental prosthesis, a pre-sintered zirconia ceramic blank is first rough-worked with a tool at a speed of between 5,000 and 40,000 revolutions / min, and then at a rotational speed of between 5,000 revolutions per minute and 50,000, according to DE-B-01 071 Revolutions / min finely machined, with the feed rate between 20 mm / min and 5,000 mm / min. The milling tool has a diameter between 0.8 mm and 4 mm.

WO-A-99/47065 describes a material removal from a blank made of at least one of the metal oxide powders of the group consisting of Al ₂ O ₃ , TiO ₂ , MgO, Y ₂ O ₃ and zirconium oxide for producing a tooth replacement part such as tooth crown or bridge. Mixed crystal with milling tools at speeds in the range between 10,000 revolutions / min and 50,000 revolutions / min, a delivery between 1 mm and 15 mm and a feed rate between 3.5 cm / sec and 10 cm / sec.

With a milling / grinding machine according to EP-A-I 245 332, a dental workpiece such as a crown is first machined from its inside by roughing and finishing and then from its outside by roughing and finishing.

A method for material-removing machining of workpieces according to DE-A-IO 2005 001 600, the use of a cylindrical or frustoconical rotating tool, which is brought both the front side and the shell side with the workpiece in engagement.

In the known methods, in which the molding is first coarse and then finely processed, d. h., In the order roughing and finishing is processed, basically shows the disadvantage that at thin edges running out of z. B. crowns or bridge abutments Randausbrüche occur.

According to DE-B-101 56 156 an intermediate step is inserted for the preparation of a dental prosthesis between roughing and finishing step in order to reduce the stress of the milling tool used for the production of the dental prosthesis and / or the workpiece in the finishing step.

Another method for producing a dental restoration from a blank can be found in WO-A-2002/076328.

The present invention is based on the object, a method of the type mentioned for the production of a molded part, in particular a pre-sintered metal oxide such as zirconium oxide mixed crystal so that in the machining, especially in a CAM milling machine at high feed rate produced a molding desired final geometry can be without damage, especially in the edge area, such as breakouts occur.

To solve the problem, the invention essentially provides that the molded part in a first processing step in its inner contour area and between the connection and the interior (cavity) of the molding limiting edge extending outer contour area is scrubbed that the molded part in a second processing step in his outer contour region is scrubbed above the compound, that in a third processing step, the outer contour region above the compound is finished, that the inner contour region in a fourth Machining step is vorgelichtet and that the inner contour area is finished step in a fifth processing step.

In this case, in particular if the outer contour region between the connection and the lower edge has residual material, that is to say material which protrudes beyond a desired allowance, can be removed by pre-finishing. The finishing of this outer contour area succeeds after the finishing of the inner contour area.

According to the invention, a milling strategy is proposed, in which, in departure from the method specified by the prior art blank for working out of the molding is not successively processed from coarse to fine decreasing diameter with cutting tools, but between the roughing and finishing a process step is interposed, at the blank is processed coarser than when finishing. This pre-sizing step means that residual material milling occurs to remove material that protrudes above the predetermined allowance after roughing. The coarse-fine-coarse machining surprisingly results in the advantage that a defect-free molded part can be produced without causing damage, especially in the edge region.

In other words, it has surprisingly been found that defects do not occur when, in contrast to the procedure usually selected by the person skilled in the art, which consists of a first coarse milling operation with a large diameter milling cutter and in the following milling operations, the tool diameter continuously to reduce already after the first rough milling a machining with a cutter with the smallest diameter einschiebt before continuing the further processing with a larger diameter tool in the usual way with decreasing tool diameters and leads to the end.

By fiction, contemporary milling strategy, a particular pre-sintered ceramic body can be processed faster and thus more economical, wherein At the same time the surface quality, edge quality and accuracy of fit compared to known methods maintained or improved.

In the first and second processing step, a roughing out of the molding from a blank, wherein at least one allowance is maintained with respect to the final contour to be achieved. The allowance can be in the range between 0.1 mm to 1 mm. The rough machining is done with the same milling tool, the z. B. has a diameter between 2 mm and 4 mm, in particular in the range of 3 mm. The feed rate can be between 2 m / min and 6 m / min, in particular between 2.5 m / min and 4 m / min.

A working out of the molding from the blank is further carried out such that after the rough machining of the inner and outer contour of the molding remains connected via a circumferential ridge or a circumferential membrane-like connection with the rest blank. The thickness of the web amounts to between 0.4 mm to 2 mm, in particular to 0.8 mm. Then there is a sizing of the outer contour, wherein at the same time the circumferential web or the membrane-like compound is severed sections. In particular, it is provided that the peripheral web is severed at a distance between 5 mm and 30 mm and over a length of between 1 mm and 5 mm.

Regardless of this, a milling tool with a diameter between 0.5 mm and 1.5 mm, in particular about 1 mm should be used in the third processing step. The feed rate should be between 1 m / min and 6 m / min, in particular between 2 m / min and 6 m / min.

Then, for machining the inner contour, a milling tool of larger diameter, in particular between 1.5 mm and 3 mm, preferably approximately 2 mm, is used to mill out residual material of the inner contour, with residual material being the one projecting beyond the desired allowance. The feed rate should be between 2 m / min and 6 m / min, preferably between 2.5 m / min and 4 m / min in this processing step.

Finally, the finishing of the inner contour takes place on Endkonturmaß, d. h. that the allowance is removed. Here, a milling tool with a diameter between 0.5 mm and 1.5 mm, in particular with a diameter of 1 mm and a feed rate between 1 m / min and 6 m / min, in particular between 2 m / min and 4 m / be used min.

At the indicated diameters, of course, the constraint is observed that the diameter of the milling tools used in the first and second processing step are greater than the fourth processing step and that the corresponding tool has a larger diameter than that in the third and fifth processing step.

Furthermore, it is provided according to the invention that the outer contour region extending between the circumferential web or the circumferential membrane-like connection and the interior of the molded part is machined in the first processing step after the roughing of the inner contour, d. H. is scrubbed.

Furthermore, the circumferential web or the membrane-like compound from the blank is worked out in such a way that the web or the membrane-like compound in the region of greatest circumference, d. H. maximum circumferential line of the outer contour extends, viewed in the longitudinal axis direction of the blank, or, if this is a dental object, in the insertion direction of this.

Regardless, the roughing in the first and / or second processing step should step with a milling tool with a speed between 10,000 revolutions / min and 25,000 revolutions / min or pre-finishing in the fourth processing step at a speed between 20,000 revolutions / min and 40,000 revolutions / min and the finishing in the third and / or fifth processing step be carried out at a speed between 25,000 revolutions / min and 50,000 revolutions / min.

The delivery of each used milling tool should be between 1 mm and 9 mm in the first and second processing step, in which the inner or outer contour are coarsely machined from the blank, wherein the delivery by the desired allowance of the final contour of the molding is limited. This allowance should be between 0.1 mm and 1 mm, preferably in the range of 0.4 mm.

The pre-finishing delivery corresponds to a height equal to the amount of residual material above the allowance from the final contour; during pre-finishing, the areas not removed during roughing are milled off, which protrude above the allowance.

During sizing, infeed takes place over a height corresponding to the oversize over the final contour.

The tool is in particular a single or double-edged radius cutter.

As a blank in particular a disc with a diameter between 80 mm and 120 mm and a height of 15 mm to 40 mm is used. In this dimensioning, there is the advantage that z. B. 20 dental objects usual size can be worked out.

In rough milling, ie roughing, a Z constant milling is carried out with the Z axis running in the direction of the axis of the blank. The milling tool is moved by the CAM milling machine software in planes of equal Z coordinates to remove material from the blank. The milling tool almost jumps from place to place. In the pre-finishing and finishing according to the method, a circular processing takes place. Further details, advantages and features of the invention will become apparent not only from the claims, the features to be taken from them-alone and / or in combination-but also from the following description of a preferred embodiment to be taken from the drawing.

Show it:

1 shows a detail of a blank with a molded part with allowance,

2 a of FIG. 1 corresponding representation with the molding,

whose outer contour corresponds in sections to the final contour,

Fig. 3 shows the molding with residual blank of FIG. 2 in plan view and

Fig. 4, the molding in the final contour.

The method according to the invention will be explained on the basis of the production of a dental object in the form of a crown 10, without the teaching according to the invention being limited thereby.

According to the invention, the crown 10 is machined out of a preform sintered, that is to say not yet sintered through, which consists of a metal oxide, in particular zirconium oxide mixed crystal. In this case, the crown to be produced 10 has, in accordance with the shrinkage occurring during sintering dimensionally on this compensating magnification compared to the finished dentures.

The blank preferably has a disk shape with a diameter of 100 mm and a thickness of 20 mm, so that at the same time several objects in a CAM milling machine can be worked out of the blank. Basic procedural measures for controlling a corresponding CAM milling machine are z. As the WO-A-90/15376, so that reference is made to the relevant disclosure.

In order to work out the molding or the crown 10 from the blank, the milling strategy according to the invention described below is carried out.

Thus, in a first step, the inside 12 of the crown 10 is milled out of the blank with a desired allowance by roughing. The allowance is shown in Fig. 1 by the dotted area 14, wherein the Fräsaufmaß a thickness of z. B. may have 0.4 mm.

After roughing the inner side 12, the outer side 16 is also machined by roughing, using the same cutter used for inner contour machining. The roughing of the outer side 16 is performed in accordance with that of the inner contour 12, so that there is an oversize compared to the final contour, which is symbolized by the area 18. When roughing the inner or outer side 12, 16, the object remains connected to the remaining part of the blank, that is to say to the remaining blank 20 via a circumferential web 22, wherein the web 22 extends in the region of maximum circumferential line of the restoration to be produced, ie the crown 10, considered in the direction of insertion of the dental object. The web-like connection can also be referred to as a flat or corrugated disc, which should have a thickness of about 0.8 mm, in order to ensure a secure support of the molding.

The roughing is z. B performed with a 2-edged radius cutter with a diameter of 3 mm and a feed rate of preferably 3 m / min to 5 m / min. The infeed, ie the depth at which the milling tool dips into the blank, should be between 1 mm and 9 mm. According to FIG. 1, the peripheral web 22 extends at a distance from the preparation border, ie lower edge 24 of the crown 10. Therefore, the outer contour region 26, between the circumferential web 22 and the rim 28 delimiting the cavity 28 of the crown 10 after roughing of the inner contour region 12 coarsely machined (roughed) before a rough milling of the remaining outer contour region 16 takes place.

In other words, in the first processing step by rough milling (roughing), the "lower half" of the crown 10 is coarsely machined, which consists of the complete inner side 12 and the region 26 of the outer side 16, between the provided for holding the crown 10 circumferential connection 22 and the lower edge 24 extends.

After the above-explained first and second processing steps, ie the roughing of the inner contour region including the lower outer contour region and the upper outer contour region, the outer contour region is finished to the final outer contour 30 of the crown 10 in a subsequent milling operation, namely the region which extends above the circumferential web 22 , The sizing can also be done with a 2-edged radius cutter using RPM's between 25,000 and 50,000. The delivery corresponds to the amount of the allowance.

During the third processing step, furthermore, the circumferential web 22 is severed in certain regions, specifically apertures 32, 34, 36 are worked out over a length of 1 mm to 5 mm at a distance of 5 mm to 30 mm. This is evident from FIG. 3. Thus, web-like connections 38, 40, 42 remain between the molded part to be produced and the residual blank 20.

It is therefore in the third processing step, ie the actual second milling cycle, not worked with a tool of the next smaller size - as is customary in the prior art - but with the tool usually provided for the finishing. In particular, a cutter with a diameter of in about 1 mm and a feed of up to 4 m / min worked. In the third processing step, so the second milling cycle, the outer contour above the disc-shaped connection (web 22) is processed to gauge and also the disc-shaped connection perforated so that evenly, distributed over the entire circumference, several web-like compounds remain, the may have a width of 1 mm to 5 mm.

Then, for further processing of the inner contour region 12, a milling tool is used, which has a larger diameter than that for finishing the outer contour 30, in order to carry out a pre-finishing of the inner contour region 12, in which regions of the inner contour are milled which protrude beyond the desired allowance. A corresponding area is indicated purely by way of example in FIG. 1 by reference numeral 44. The pre-finishing, ie the residual material milling in the inner contour region 12, can be carried out with a 2-edged radius cutter of a diameter of 2 mm. The feed rate should be in the range of 4 m / min.

After pre-finishing, the inner contour region 12 is finished to the final dimension of the inner contour 46. The web-like connections 38, 40, 42 remain. The sizing to final dimension of the inner contour 46 is carried out with a preferably 2-edged radius cutter with a diameter of 1 mm, with a feed of 3 m / min and rotational speeds of 25,000 revolutions / min to 50,000 revolutions / min are to be preferred.

After finishing the inner contour 46 and the area between edge 24 and the web-like connections 38, 40, 42, these are severed. This can possibly be done only after the Durchsintern.

Due to the teaching according to the invention, the machine dynamics of a milling machine can be optimally utilized, so that economical processing times can be achieved. A high accuracy of fit despite shortened processing time is achievable. In particular, there is a very good quality of the edge 24, without rework is required.

Claims

A method for producing a molded part having an inner and outer contour

1. A method for producing an inner and an outer contour having molding, in particular dental object such as copings, crown or bridge framework, wherein the molded part of a blank machined and steps in at least two consecutive processing steps and is dressed and at least after the second processing step, the molded part remains connected to the remaining blank (residual blank) via a connection such as peripheral web or circumferential membrane-like connection, preferably in the region of greatest circumference (maximum circumferential line) of the molded part to be produced,

characterized,

in a first processing step, the molding is roughed in its inner contour region and in the outer contour region extending between the connection and the inner space (cavity) of the molded part, that the molding is roughed in its outer contour region above the connection in a second processing step a third processing step, the outer contour region is finished above the connection, that the inner contour region is pre-exposed in a fourth processing step and that the inner contour region is finished step in a fifth processing step.

2. The method according to claim 1,

characterized,

that the inner and the outer contour area are machined coarsely in the first and second processing step.

3. The method according to claim 1,

characterized,

in that the outer contour region extending between the connection and the edge is pre-classified after the pre-finishing of the inner contour region when at least one region of the outer contour region projects beyond an allowance predetermined by the roughing.

4. The method according to claim 1,

characterized,

in that after finishing the inner contour area, the outer contour area is finished between the connection and the edge.

5. The method according to claim 1,

characterized,

in that the molding is processed to its final contour by the finishing taking place in the third and fifth processing steps.

6. The method according to claim 1,

characterized,

that the peripheral web or the circumferential membrane-like compound is severed in sections in the third processing step.

7. The method according to at least claim 1,

characterized,

during the first and second processing steps, the peripheral web or the surrounding membrane-like compound having a thickness d of 0.4 mm <d <2 mm, in particular approximately 0.8 mm, is machined out.

8. The method according to at least claim 1,

characterized,

that the circumferential ridge or the circumferential membrane-like compound in the third processing step is severed at a distance between 5 mm and 30 mm over a length of 1 mm to 5 mm.

9. The method according to at least claim 1,

characterized,

in that the roughing is carried out in the first and / or second processing step with a milling tool at a speed between 10,000 revolutions / min and 25,000 revolutions / min.

10. The method according to at least claim 1,

characterized,

that the pre-finishing in the fourth processing step at a speed between 20,000 revolutions / min and 40,000 revolutions / min is performed.

11. The method according to at least claim 1,

characterized,

that the finishing in the third and / or fifth processing step is performed with a milling tool at a speed between 25,000 revolutions / min and 50,000 revolutions / min.

12. The method according to at least claim 1,

characterized,

that the milling tool in the first and / or second processing step is delivered between 1 mm and 9 mm, wherein the delivery is limited by an allowance over the final contour of the molding.

13. The method according to at least claim 1,

characterized,

that the milling tool is delivered during pre-finishing over a height that corresponds to height of residual material above the allowance above the final contour.

14. The method according to at least claim 1,

characterized,

during milling, the milling tool is delivered over a height corresponding to the oversize over the final contour.

15. The method according to at least claim 10,

characterized,

that 0.1 mm to 1 mm, preferably 0.4 mm, is defined as an allowance over the final contour.

16. The method according to at least claim 1,

characterized,

that the milling tool in the first and / or second processing step with a feed rate between 2 m / min and 6 m / min, in particular between 2.5 m / min and 4 m / min is operated.

17. The method according to at least claim 1,

characterized,

the milling tool is operated in the third processing step at a feed rate of between 1 m / min and 6 m / min, in particular between 2 m / min and 6 m / min.

18. The method according to at least claim 1,

characterized,

that the milling tool in the fourth processing step with a feed rate between 2 m / min and 6 m / min, preferably between 2.5 m / min and 4 m / min is operated.

19. The method according to at least claim 1,

characterized,

that the milling tool is operated in the fifth processing step at a feed rate between 1 m / min and 6 m / min, in particular between 2 m / min and 4 m / min.

20. The method according to at least claim 1,

characterized,

that in the first processing step and / or in the second processing step Z-constant milling is performed.

21. The method according to at least claim 1,

characterized,

in that a circular processing takes place in the third and / or fourth and / or fifth processing step.

22. The method according to at least claim 1,

characterized,

in that a pre-sintered ceramic body or pressed ceramic material is used as the blank.

23. The method according to at least claim 1,

characterized,

in that for the first and / or second processing step a milling tool having a diameter D ₁₂ with 2 mm <D ₁₂ <4 mm, in particular D ₁₂ = 3 mm is used.

24. The method according to at least claim 1,

characterized,

that in the third and / or fifth processing step, a milling tool having a diameter D ₃₅ with 0.5 mm <D ₃₅ <1.5 mm, in particular D ₃₅ = 1 mm is used.

25. The method according to at least claim 1,

characterized,

that in the fourth processing step a milling tool with a diameter D ₄ with 1.5 mm <D ₄ <3 mm, in particular D ₄ = 2 mm is used.

26. The method according to at least claim 1,

characterized,

that milling tools with the diameters D ₁ , D ₂ , D ₃ , D ₄ and D ₅ are used, wherein D ₃₅ <D ₄ <D ₁₂ .

27. The method according to at least claim 1,

characterized,

that a single or double-edged radius cutter is used as the milling tool.

28. The method according to at least claim 1,

characterized,

that a disc with a diameter D _s with 80 mm <D _s <120 mm and / or a height H with 15 mm <H <40 mm is used as the blank.