The present invention concerns a dressing process and a dressing tool. In particular the invention concerns the dressing of a multi-start cylindrical grinding worm, preferably a grinding worm with vitrified bond, for the grinding of the tooth flanks of a gear, in particular of a small moduled gear, by the continuous generation process by means of a rotating disc shaped, abrasive coated dressing tool. The dressing embraces the functions of pre-profiling and finish profiling or calibration of the grinding worm threads, and preferably also the stripping of the grinding worm periphery.
For the dressing of cylindrical grinding worms for the continuous generation grinding of gears in the module range of 1 to 3 mm, gang rolls or full profile rolls are often employed which enclose the desired grinding worm profile over one or more threads. One such tool is known e.g. from CH 686 171 A5, which by a special construction permits the re-machining of the diamond coating of a composite diamond dressing tool for dressing both threads of a two-start cylindrical grinding worm.
Especially in the case of workpiece teeth with a module of less than 1 mm, however, so-called full profile rolls with 3 to 5 profile ribs are used which, in similar manner as a thread dressing roll, simultaneously enclose 3 to 5 adjacent threads of the total grinding worm profile. Such a profile roll is shown in
A disadvantage of these full profile rolls is that a re-machining of the abrasive coating to correct the flank geometry and to assure adequate surface quality of the ground gears is as yet technically unattainable, and that they must therefore be produced by the very expensive and time consuming negative or reversal process. This means that towards the end of the dressing process the grinding worm threads must be brought one after the other into mesh with several different profile ribs of the dressing tool without further dressing infeed, in order to reduce the effective roughness depth of the grinding worm flanks to the permissible value and to “calibrate” the profile.
For the continuous generation grinding of fine and ultra-fine teeth in the module range up to 1 mm, multi-start grinding worms with more than 5 starts are generally employed. For such grinding worms the well known above mentioned full profile rolls have an inadequate number of ribs available to profile all the grinding worm threads simultaneously, i.e. in the same dressing stroke. For this reason, to produce all the grinding worm threads of these grinding worms when pre-profiling, the profile roll must be put into action axially displaced several times.
Another disadvantage of the number of profile ribs being less than the number of grinding worm starts is that the ribs provided on the dressing tool must perform both the pre-profiling work and the finish profiling work. This means that the quality of the finish profiling, i.e. the calibration quality is impaired by the far greater wear of the abrasive coating during pre-profiling.
The disadvantages mentioned above make it apparent that the known full profile rolls with 3 to 5 profile ribs are unsuitable for the profiling of multi-start small moduled grinding worms.
Furthermore in the generation grinding of fine teeth as opposed to the grinding of large moduled workpieces it is usual, when changing over to a new workpiece, to remove the grinding worm profile no longer required, and to profile the grinding worm completely freshly. Since the abrasive profile of the known profile rolls is not suitable for the stripping or removal of the grinding worm profiles no longer required, a separate tool suitable for this expressed purpose must be provided on the machine, or the grinding worm must be removed from the machine to strip it, which makes breaking down and fresh setting up necessary.
One object of the present invention is to provide a process for dressing a multi-start cylindrical grinding worm for grinding the tooth flanks of a gear, in particular of a small moduled gear, by the continuous generation grinding process and a dressing tool, by and with which the grinding worm can be re-profiled with high precision or provided with a new grinding worm profile.
This object is achieved with a process and a dressing tool having the features stated in claims 1 and 6 respectively.
According to the invention the production of a new or freshly dressed grinding worm profile is performed by means of a dressing tool which is provided with a pre-profiling zone and a finish profiling or calibration zone. These are brought into engagement with the grinding worm in separate consecutive machining operations in a single set-up of the grinding worm and the dressing tool.
Preferably the pre-profiling zone at least is provided with a dressing profile which encloses the grinding worm profile over at least the entire lead of the grinding worm thread.
Another object of the invention is to provide a process and a dressing tool for the dressing of a multi-start cylindrical grinding worm for the grinding of the tooth flanks of a gear, in particular of a small moduled gear, by the continuous generation grinding process, by and with which a grinding worm profile no longer required can be replaced by a new one in the shortest possible time.
This object is achieved with a process and a dressing tool having the features stated in claim 2 and 8 respectively.
According to the invention the stripping of a grinding worm profile no longer needed is performed with the dressing tool mentioned above, which tool is additionally provided with a stripping zone. The stripping zone, pre-profiling zone and finish profiling or calibration zone are brought into engagement with the grinding worm consecutively.
Since the set-up of the grinding worm and the dressing tool does not have to be changed either on change-over from stripping to pre-profiling or from pre-profiling to finish profiling, the grinding worm can be stripped and profiled in double quick time. Exchanging of the grinding worm when changing over to a new workpiece is no longer necessary. A grinding worm profile no longer needed can nevertheless be removed and a new one produced and calibrated for every workpiece.
The process according to the invention and the device according to the invention particularly are suitable for grinding worms with vitrified bond and/or for small moduled gears, i.e. below module 1 mm.
Further beneficial features of the invention are evident from the relevant claims.
In the following the invention is explained in detail by way of a few preferred embodiments which are illustrated in the annexed drawings. The drawings depict:
Depicted in
The basis for the solution according to the invention is presented by the known methods of profiling cylindrical grinding worms for continuous generation grinding, and by the special requirements in the manufacture of fine gear teeth in the module range of less than 1 mm by means of multi-start grinding worms.
The profile of the dressing tool 2 comprises at least two, here three, different profile zones 6, 7, 8 separated from each other by zones without profile ribs. These profile zones 6, 7, 8 can be brought individually into engagement with the grinding worm in any desired sequence without another zone colliding, in that the profile roll 2 is firstly swivelled about a swivel axis F at right angles to its axis of rotation 12, and then infed in the infeed direction X.
Two of the profile zones 7, 8 serve to consecutively pre-profile and finish profile the grinding worm threads. The other profile zone 6 is optional and serves to strip the grinding worm profile away. This stripping zone 6 has the shape of a truncated cone with familiar straight or crowned, i.e. cambered enveloping surface 10 and lead lands 11. The pre-profiling zone 7, likewise in the form of a truncated cone, and the preferably cylindrical finish profiling zone 8 are provided with the negative profile of the grinding worm 4. The number of profile ribs in the pre-profiling zone 7 corresponds with the number of starts on the grinding worm. The number of profile ribs in the finish profiling, i.e. calibration zone 8 can be less than the number of grinding worm starts. Preferably, however, it should be of equal number or of a larger number than this.
Finish profiling, i.e. calibration of the grinding worm threads is performed in the known manner, in that the profile ribs of the finish profiling zone 8 are allocated variously one after the other to the individual grinding worm threads without or with only minimum further dressing infeed, so that every grinding worm thread is finish dressed by several profile ribs. In order to minimize the necessary number of finish profiling strokes, the number of profile ribs in the finish profiling zone 8 is preferably a few calibration ribs more than the number of grinding worm starts. In every finish profiling, i.e. calibration dressing stroke all the grinding worm threads are always calibrated together, the desired effective roughness depth of the grinding worm 4 thereby being attained in the most effective manner.
The profiling zones 6, 7, 8 can be combined on a single tool or preferably composed of individual discs joined to form a gang tool, their abrasive coating differing, especially in the case of the composite design, with respect to at least one of the following features: type, grain size, coating pattern, density and bond. These features are adapted optimally to the relevant operative purpose.
In a second embodiment of the dressing tool according to the invention, i.e. the profile roll 2 depicted in
In a second variant the finish profiling zone 8 has a greater diameter than the pre-profiling zone 7. Preferably it is greater than the diameter of the pre-profiling zone 7 by at least twice the amount of a desired finish profiling infeed depth. In this case finish profiling takes place with an infeed depth corresponding to half the diameter difference between the profiling zones 7, 8. In both cases it must be ensured that when dressing the grinding worm 4 the pre-profiling zone 7 always runs ahead of the finish profiling zone 8. With these two variants of the profile roll 2, therefore, profiling can only be performed in one of the two dressing stroke directions Y. In a third variant of these two embodiments separate pre-profiling zones 7 are provided on both sides of the finish profiling zone 8. Profiling can thereby be performed in both dressing stroke directions Y.
In the embodiment according to
In all the embodiments described above, the pre-profiling zone 7 and the finish profiling zone 8 and, if provided, the stripping zone 6 are each at a conical angle and a spacing from one to the other, the angle and spacing being so dimensioned that each of these zones 6, 7, 8 can be brought into engagement with the grinding worm 4 without any other of these zones colliding.
Number | Date | Country | Kind |
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10 2004 020 947 | Apr 2004 | DE | national |
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2571293 | Ross et al. | Oct 1951 | A |
4993194 | Cadisch | Feb 1991 | A |
5339794 | Thyssen | Aug 1994 | A |
6234880 | Scacchi | May 2001 | B1 |
6491568 | Jankowski | Dec 2002 | B1 |
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686171 | Jan 1996 | CH |
7003805 | Jan 1970 | DE |
3235790 | Apr 1983 | DE |
0982881 | Dec 1982 | SU |
Number | Date | Country | |
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20050245176 A1 | Nov 2005 | US |