GRINDING-SUPPORTING DEVICE
In a method and apparatus for multiple-bearing grinding of workpieces, such as crankshafts, wherein a support element seat occurs at a bearing point at the same time as the grinding of the main bearing a grinding-supporting unit is used that contains a grinding spindle head having at least one grinding disk and support elements in the form of support jaws or support bodies that can be swiveled in. After the support point seat is ground, the support elements are brought into contact therewith and support the workpiece during the further machining. The simultaneous grinding of the support point seat and several bearing points results in a reduction in the machining time in the grinding of the workpiece compared to the prior art.
The invention relates to a method for the multiple-bearing grinding of workpieces, in which a plurality of bearing points are ground simultaneously by means of a grinding wheel set, wherein at least one bearing point is at least partly supported during the grinding for compensating for deformations of the workpiece caused by grinding forces, according to the preamble of claim 1. The invention also relates to a device for the multiple-bearing grinding of workpieces, in which a plurality of bearing points are ground simultaneously by means of a grinding wheel set which can be fed in at least in the radial X1 direction with respect to the workpiece on a common grinding spindle in a multiple-bearing grinding headstock, wherein at least one bearing point is at least partly supported during the grinding on a supporting element seat like a steady rest seat for compensating for deformations of the workpiece caused by grinding forces, and wherein the workpiece can be set in rotation about a rotation axis by means of a work headstock, for the use of the method according to the preamble of claim 8.
Such a method and an associated device is known from DE 101 44 644 B4. According to this document, the supporting element seat is initially ground using a grinding attachment and then the steady rest is set and the bearing seats are then ground on the crankshaft. This method has the disadvantage that no other machining can take place during the grinding of the supporting element. The machining time on the workpiece is therefore considerably increased.
The object of the invention is therefore to provide a method and a device of the type mentioned at the beginning in which the machining time for the workpiece is further reduced compared with the prior art.
This object is achieved with regard to the method according to the characterizing part of claim 1 in that a grinding wheel for grinding a supporting element seat like a steady rest seat is fed in to at least one bearing point and grinds the supporting element seat at least in an axial section of this bearing point, in that the grinding wheels of the grinding wheel set at least partly grind the side faces and/or the bearing surfaces of the bearing points during the grinding with the grinding wheel for grinding a supporting element seat, in that, after the finish grinding of the supporting element seat, the grinding wheel for grinding a supporting element seat is withdrawn by a small amount of lift or is set in a freely rotating manner, in that one or more force-absorbing elements are then brought to bear against the respectively finish-ground supporting element seat, and in that the bearing points are then finish-ground using the grinding wheel set.
The workpieces to be machined according to the method according to the invention are preferably crankshafts which are mass-produced and in which any reduction in the machine time is economically advantageous. However, the method can also be used with other workpieces if said workpieces can be machined by grinding and permit the use of supporting elements, such as steady rests, according to the prior art.
As a result of the procedure according to the invention, the bearing points and/or the flat sides of the bearing points of the crankshafts can already be machined during the grinding of the supporting element seat. The bearing points also no longer need to be produced to their final size in width by means of separate processing steps or operations, since this can be integrated into this operation without appreciably increasing the grinding times. As a result, the machining time can also be minimized in preceding operations. This is reflected in the costs of producing the workpiece since production can be more cost effective.
Thus at least some of the hitherto necessary preceding machining operations can be dispensed with, or increased tolerances can be used in the preceding machining sequences, which again has an effect in lower machining costs in the preceding machining sequences.
During the grinding of the supporting element seat, grinding can already be carried out at the flat sides of the bearing points by the grinding wheels at the bearing points. As a result, the machine is already fully in use during the grinding of the supporting element seat, and therefore very high cutting capacities and thus reduced machining times can be achieved.
The grinding of the flat sides having the bearing seats also has advantages with regard to the dimensional, geometrical and positional accuracy, since the flat shoulders at the bearing points are ground in the same setup as the bearing points themselves. Considerable advantages with regard to the production quality of the workpieces can be achieved here according to this method.
If the flat shoulders at the bearing points can be ground at least partly to finished size during the grinding of the supporting element seat, the initial grinding of the supporting element seat can account for a considerable proportion of the grinding time. This reduction in the main time during the grinding by grinding the flat sides at the same time as the supporting element seat has an especially advantageous effect during the grinding of mass-produced crankshafts, since the cost pressure is very high here.
In this machining method, grinding is preferably carried out using grinding wheels having a grinding layer of ceramically bonded CBN. However, all other known grinding materials are also conceivable for the grinding tools.
The invention can be applied to grinding machine concepts having one or more grinding headstocks or grinding stations. Preferred fields of application are the grinding of crankshafts or camshafts or generally of workpieces having a plurality of spaced-apart regions which can be ground simultaneously with a grinding wheel set.
An advantageous configuration of the method can consist, as claimed in claim 2, in the fact that supporting element seats are ground at a plurality of bearing points by means of associated grinding wheels. For this purpose, these grinding wheels are preferably arranged on a common grinding spindle, and one or more supporting elements are advantageously assigned as force-absorbing elements to said grinding wheels. During the grinding of supporting element seats, however, a plurality of grinding-supporting arrangements can also be mounted on the machine, such that the supporting element seats can be ground independently of one another.
As claimed in claim 3, the supporting elements are brought into engagement with and disengaged from the associated supporting element seat by pivoting about a pivot axis or by a linear movement. The CNC control of the grinding machine is preferably used as computer control for the activation of the supporting elements, said CNC control controlling the infeed of all the grinding wheels and of the supporting elements and coordinating all the sequences of movement and the grinding operations.
In the configuration of the method as claimed in claim 5, the supporting element seat is ground only to a preliminary size of the bearing point close to the final size and the supporting element is set only to this preliminary size. In this case, this preliminary size close to the final size is only slightly larger than the desired size of the finish-ground bearing seat. The bearing seat is then finish-ground.
According to a further especially advantageous configuration as claimed in claim 6, the supporting element, according to the advance of the finish grinding using the grinding wheel set, follows the adjustment thereof in the X1 direction by an adjustment in the X2 direction coordinated therewith, that is to say in the opposite direction. As a result, the position of the supporting element follows the decreasing diameter of the ground bearing seat and can therefore always exert an optimum supporting effect. As a result, the precision of the grinding is markedly increased compared with the variant as claimed in claim 5.
To achieve the object already mentioned at the beginning, provision is made, with regard to the device in particular for carrying out the method as claimed in one of claims 1 to 7, in a device according to the preamble of claim 1, for there to be at a distance from the multiple-bearing grinding headstock at least one further grinding headstock as part of a grinding-supporting unit having a grinding wheel for grinding a supporting element seat, for the grinding-supporting unit to be capable of being fed in to the workpiece and removed therefrom in the radial X2 direction, and for the grinding-supporting unit to be arranged with at least one movable supporting element in the region of the grinding wheel for grinding a supporting element seat, which supporting element can be brought to bear against the supporting element seat.
In particular the method as claimed in claims 1 to 7 can be carried out using the device as claimed in claim 8. To this end, the grinding-supporting unit, which comprises as essential subassemblies a grinding headstock and movable supporting elements, is arranged on the same machine bed as the multiple-bearing grinding headstock. However, it preferably lies on the opposite side of the workpiece and can be fed in from there to the workpiece or removed from it. It is thereby possible to bring the grinding wheel and/or the supporting elements into engagement with a bearing point, to be ground, of the workpiece, while at the same time the grinding wheels of the multiple-bearing grinding headstock are already in grinding engagement on the opposite side of the workpiece.
With the device according to the invention, a supporting element seat, i.e. a ground bearing way for one or more supporting elements, can be ground, while at the same time the grinding of the bearing points using the grinding wheel set can already be started on the opposite side of the workpiece. As a result, the loss of time in the prior art due to the fact that a steady rest seat has to be ground first before a steady rest can be set and the actual grinding of the bearing points started does not occur.
Coordination of the infeeds of multiple-bearing grinding headstock and grinding-supporting unit in the X1 direction and X2 direction, respectively, that is to say toward the workpiece and away therefrom, as claimed in claim 9 permits especially sensitive and flexible matching of the individual method steps. In particular, this measure opens up the possibility of using the grinding-supporting unit like a “following steady rest” in such a way that it follows a diameter, decreasing in the course of the grinding, of the workpiece at the engagement point.
An arrangement of the movable supporting elements on the grinding headstock as claimed in claim 10 simplifies the control and the complexity of the design, since both subassemblies can be mounted and fed in together on a common cross slide. In addition, a robust and compact arrangement of the functional subassemblies can thus be achieved.
As claimed in claim 11, the supporting elements used are preferably supporting jaws pivotable about a pivot axis or those which can be displaced on a straight path via a drive. The movement for engaging or disengaging the supporting elements is advantageously controlled by the CNC control of the grinding machine.
Each of the supporting elements has, in the intended region in contact with the workpiece, the supporting point, a wear- and friction-reducing coating which preferably consists of polycrystalline diamond (PCD) or of cubic boron nitride (CSN). The supporting element or elements, for favorable absorption of the grinding forces, have at least two supporting points, which can be realized, for example, by two supporting jaws having one supporting point each or by a compact supporting point having two supporting points arranged at a distance from one another.
The invention will subsequently be explained in more detail with reference to exemplary embodiments which are shown in the figures. In the drawing:
Here, the workpiece 10 is a crankshaft 20, the central main bearings 21 of which establish the center axis of the workpiece 10 and thus the rotation axis 22 thereof for the grinding. The rotation axis 22 is at the same time the rotation axis 22 of the work headstock 11 and the tailstock 16, which is indicated by the curved arrow C1. The work headstock 11 has a chuck 12 with chuck jaws 13 for rotationally driving the workpiece and a center 14 for centering the workpiece 10. A tailstock 16 having a center 17 is arranged at the other end of the crankshaft 20. It can be displaced in the Z direction, that is to say parallel to the rotation axis 22, for adaptation to the length of the workpiece 10. The workpiece 10 can also be moved in this Z direction, it being possible for the movement to be carried out by a cross slide (not shown here) under the multiple-bearing grinding headstock 8, as indicated by the arrow Z1. Said cross slide can then be displaced in the Z1 direction, that is to say parallel to the center axis of the workpiece 10. These infeed movements are preferably carried out in a CNC-controlled manner.
The grinding-supporting unit 30 according to the invention is located in the front region of the grinding machine 1, i.e. on the other side of the workpiece 10 with respect to the multiple-bearing grinding headstock 8, and is shown in a very simplified form. In a grinding headstock 24, the grinding-supporting unit 30 carries a rotationally drivable grinding spindle 31 having a grinding wheel 32 and the supporting jaws 35 or supporting bodies 40, which are not shown here but are shown in
The grinding-supporting unit 30 is arranged with respect to the workpiece 10 and the multiple-bearing grinding headstock 8 with the grinding wheel set 5 in such a way that the grinding wheel 32 thereof, when in use, comes into engagement at the same bearing point 27 of the workpiece as one of the grinding wheels 4 of the grinding wheel set 5. This is preferably one of the central grinding wheels 4, since a deflection of the workpiece 10 to be compensated is greatest in the central region. During simultaneous engagement of both the grinding wheel 32 and the grinding wheel set 5 on the workpiece 10, the opposite grinding wheels 4 and 32 in each case act as a support for the workpiece 10 in the manner of a steady rest, as explained in more detail with reference to
According to the invention, not only does the grinding wheel 32 of the grinding-supporting unit 30 serve as a support for the workpiece 10 during certain phases of the grinding, but further supporting elements 34 are also used, such as swing-in supporting jaws 35 or supporting bodies 41, which are shown in
With the device described, a plurality of pin bearings can of course be jointly ground in an advantageous manner, for which purpose the crankshaft 20 must be clamped eccentrically in such a way that the rotation axis 22 comes to lie in the center axis of the pin bearings 23. During the conventional grinding of in each case a pair of pin bearings 23, the grinding-supporting unit 30 is used at one of the two pin bearings 23, while the other pin bearing 23 is ground at the same time, but without support. Of course, support at a plurality of bearing points 27 is also possible here, as already explained with reference to the production of crankshafts.
The first grinding of the supporting element seat 28 using the grinding wheel 32 of the grinding-supporting unit 30 is shown in a detailed view in
In this procedure, in which grinding wheels 4 and 32 are simultaneously fed in from opposite sides to the same bearing point 27 of the workpiece 10, each of the grinding wheels 4, 32 acts as a supporting means for the workpiece 10 against bending transversely to its longitudinal axis—the rotation axis 22. An effect as produced by a steady rest is therefore obtained. This effect is also transmitted to the other bearing points 27, which are simultaneously ground by the other grinding wheels 4 of the grinding wheel set 5.
It goes without saying that, at a more advanced stage of the machining than that shown in
The design of the supporting elements 34 and the swinging-in thereof or otherwise bringing them into engagement with the workpiece 10 must of course be such that the supporting parts 39 of the respective supporting element 34, 35, 40 on the one hand make contact with the supporting element seat 28 produced beforehand with the grinding wheel 32 and on the other hand do not collide with the grinding wheel 32 or parts of the workpiece 10. The supporting jaws 35 according to
The supporting jaws 35 can preferably be swung in hydraulically onto a fixed stop (not shown here). However, other drive variants, such as, for instance, a linear infeed, can also be realized. The supporting jaws 35 are swung out (shown by broken lines) during the grinding of the supporting element seat 28. When the supporting element seat 28 is finish-ground, the supporting jaws 35 are swung in and the bearing points 27 on the workpiece 10 can also be ground to finished size.
In order to be able to realize a high degree of stiffness and short pivoting distances of the supporting jaws 35 for the support, said supporting jaws 35 are preferably arranged on the grinding wheel guard 43 (cf.
It is also possible to grind the supporting element seat virtually to finished size, such that the grinding-supporting unit 30 has to be fed in to a predetermined value of the X2 axis and does not have to perform a follow-up movement according to the X1 axis.
In the front region, the supporting jaws 35 have a friction- and wear-reducing layer 38, which preferably consists of PCD (polycrystalline diamond) or CBN (carbon boron nitride).
Shown in
Between the two spaced-apart supporting points 39, the supporting body 40, due to its design, is further away from the workpiece 10 than the supporting points 39, which here are formed symmetrically on the supporting body 40, as can also be seen in
To swing in the supporting bodies 40 according to
An arrangement with a supporting body 40 is shown in
A further embodiment of a supporting body 41 is shown in
A partial view of
- 1 Grinding machine
- 2 Infeed slide
- 3 Grinding spindle
- 4 Grinding wheel
- 5 Grinding wheel set
- 6 Grinding layer
- 7 Rotary drive
- 8 Multiple-bearing grinding headstock
- 10 Workpiece
- 11 Work headstock
- 12 Chuck
- 13 Chuck jaw
- 14 Center
- 15 Rotary drive
- 16 Tailstock
- 17 Center
- 20 Crankshaft
- 21 Central main bearing
- 22 Rotation axis
- 23 Pin bearing
- 24 Grinding headstock
- 25 Flat sides
- 26 Flat shoulder
- 27 Bearing point
- 28 Supporting element seat
- 29 Unmachined region
- 30 Grinding-supporting unit
- 31 Grinding spindle
- 31a Rotation axis
- 32 Grinding wheel
- 33 Grinding layer
- 34 Supporting element
- 35 Supporting jaw
- 36 Pivot axis
- 37 Stop
- 38 Layer
- 39 Supporting point
- 40 Supporting body
- 41 Parent body
- 42 Adjustable extension
- 43 Cooling tubes
- 44 Bearing arrangement with drive for supporting jaws
- 45 Machine bed
- 46 Housing
- 47 Infeed slide
- 48 Grinding wheel guard
Claims
1. A method for multiple-bearing grinding of a workpiece, comprising grinding, with a grinding wheel set, a plurality of bearing points simultaneously, wherein
- at least one of the bearing points is at least partly supported during the grinding for compensating for deformations of the workpiece caused by grinding forces,
- a grinding wheel for grinding a supporting element seat is fed in to at least one of the bearing points and grinds the supporting element seat at least in an axial section of said at least one of the bearing points,
- grinding wheels of the grinding wheel set at least partly grind flat sides and/or bearing surfaces of the bearing points during the grinding with the grinding wheel for grinding a supporting element seat,
- after finish grinding of the supporting element seat, the grinding wheel for grinding a supporting element seat is withdrawn by a small amount of lift or is set in a freely rotating manner,
- one or more supporting elements are then infed to bear as force-absorbing elements against the finish-ground supporting element seat, and
- the bearing points are then finish-ground using the grinding wheel set.
2. The method as claimed in claim 1, wherein the supporting element seats are ground at a plurality of the bearing points by a plurality of the grinding wheels for grinding a supporting element seat.
3. The method as claimed in claim 1, wherein the supporting elements are brought into engagement with and disengaged from the supporting element seat by pivoting about a pivot axis or by linear movement.
4. The method as claimed in claim 1, wherein the infeeds of all the grinding wheels and of the supporting elements are coordinated via an electronic computer.
5. The method as claimed claim 1, wherein the supporting elements are set to a preliminary size of the supporting element seat or of the bearing point close to a final size and remain in this position.
6. The method as claimed in claim 1 wherein the supporting elements follow the actual size of the associated bearing point according to adjustment of the grinding wheel set in an X1 direction by adjustment in an X2 direction.
7. An apparatus for the multiple-bearing grinding of workpieces, comprising a grinding wheel set for grinding a plurality of bearing points simultaneously, the grinding wheel set being arranged on a common grinding spindle in a multiple-bearing grinding headstock arranged for infeeding of the grinding wheel set in at least a radial X1 direction with respect to the workpiece, a supporting element seat for at least partly supporting during the grinding at least one bearing point thereby to compensate for deformations of the workpiece caused by grinding forces, and a work headstock for supporting the workpiece and rotating the workpiece about a rotation axis, spaced from the multiple-bearing grinding headstock at least one further grinding headstock as part of a grinding-supporting unit having a grinding wheel for grinding a supporting element seat, the grinding wheel for grinding a supporting element seat and the supporting element seat being located on opposite sides of the workpiece, the grinding-supporting unit being arranged for being fed in to the workpiece and removed therefrom in a radial X2 direction, and being provided with at least one movable supporting element proximate the grinding wheel for grinding a supporting element seat, the supporting elements being arranged for infeeding to bear against the supporting element seat.
8. The apparatus as claimed in claim 7, wherein the infeed of the multiple-bearing grinding headstock in the X1 direction and the infeed of the grinding-supporting unit with the further headstock in the X2 direction are controllable independently of one another.
9. The apparatus as claimed in claim 7, wherein the at least one supporting element of the grinding-supporting unit is arranged on the further grinding headstock for movement together with the latter further grinding headstock.
10. The apparatus as claimed in claim 7, wherein the grinding-supporting unit comprises at least one supporting jaw or supporting body which is pivotable about a pivot axis or linearly movable.
11. The apparatus as claimed in claim 7, wherein the supporting elements have, at surfaces in contact with the workpiece, a friction- and wear-reducing layer.
12. The method as claimed in claim 1, wherein the supporting element seat comprises a steady rest seat.
13. The apparatus as claimed in claim 7, wherein the supporting element seat comprises a steady rest seat.
14. The apparatus as claimed in claim 7, wherein the layer is of polycrystalline diamond or cubic boron nitride.
Type: Application
Filed: Jun 8, 2010
Publication Date: Jun 28, 2012
Inventor: Georg Himmelsbach (Haslach)
Application Number: 13/376,953