DE3416441C2 - Plunge-cut grinding process - Google Patents

Abstract

To optimize the grinding time with a high and constant processing quality and accuracy, a plunge-cut grinding process is used in which the grinding wheel is approached at rapid speed until shortly before or until the grinding wheel comes into contact with the workpiece and then rough-ground until a small oversize is reached and then in a partial return In order to partially reduce the grinding pressure for a distance and then finish-ground with fine finishing feed speed until the finished dimension is reached, it is proposed to always choose the feed speed during rough grinding so that a constant removal speed is achieved and furthermore the partial return and the subsequent feed speed for finishing is selected in this way that a specified speed profile of the material removal is maintained during finishing.

Description

The invention relates to a plunge-cut grinding method in which the grinding wheel is up to shortly before or up to If the grinding wheel comes into contact with the workpiece, it is brought up to this at rapid speed and then with specified infeed speed is rough-ground until a specified small value is reached Oversize, then in a partial return by a distance the grinding pressure is partially reduced and then The workpiece is finish-ground until the finished dimension is reached at the fine finishing feed speed will.

One such plunge-cut grinding process is aur. the publication, »New process saves grinding time on cylindrical grinding machines«, technical journal for practical metalworking 1976, page 104, known. Through the empirically determined constant partial return very good grinding results are achieved under optimal conditions. But if the pane is blunt, di? occurs more or less always within a dressing cycle, a springback force, in particular be so large that the empirically determined return path is insufficient in the case of a large rearrangement Compensate for spring back force. Then the removal rate is too high in the finishing phase, see above that the roundness and the surface quality of the workpiece is unsatisfactory. Next is at freshly trained Grinding wheel with very good grip, the return travel too long. While this results in good workpieces, however to a very long finishing phase and thus to long machining times.

From the publication »Electronic measurement and Control devices for production grinding machines ", magazine Werkstatt und Betrieb, 1977, pages 749 bis 753, it is known that the actual change in the workpiece diameter over time (= removal rate) to determine and to use to control the grinding cycle and especially in the case of form inaccuracies of the workpiece an intermediate spark-out cycle between switching from roughing to finishing which is dependent on the elastic forces that are in the machining system during the roughing process have built. However, it is not possible to optimize the processing time.

The object of the present invention is to avoid the disadvantages described above Plunge-cut grinding process to be optimally designed so that while adapting to different grinding and Machining conditions optimal grinding times with high and consistent machining quality and accuracy is achieved.

To achieve this object, the invention provides that the change in the workpiece diameter over time is measured that the difference from the measured

such a temporal change in the workpiece diameter and a predetermined temporal change in the workpiece diameter as a manipulated variable for the infeed speed is used that the specified change over time during rough grinding of the workpiece diameter is constant, resulting in a constant change in the measured workpiece diameter over time is achieved, and that in the subsequent finish grinding the predetermined time Change in the workpiece diameter has a certain course.

This means that the infeed speed for both roughing and finishing depends on the desired Material removal set. The infeed process can vary within a dressing interval because with a sharp grinding wheel, the desired material removal is achieved with lower grinding pressure than with a blunt grinding wheel. Depending on the rigidity of the grinding system, the result is a great deal

different delivery routes. With a soft grinding system, the entire finish grinding process can be take place under the return movement of the grinding wheel, as the relative infeed movement for the material removal comes entirely from the spring back of the system. With a medium stiff grinding system it is conceivable that the finish grinding process can take place without an infeed movement of the grinding wheel, wherein then the relative Sewbewegung of the workpiece compared to the grinding wheel fully from the springback of the Grinding system takes place. The third possibility, with a relatively stiff system, is that after rough grinding the grinding wheel is greatly reduced to reduce the rearrangement and then to achieve the Material removal is delivered again during finishing, similar to that described above "Recon grinding process" is known, in which the grinding wheel after rough grinding by one reset a predetermined amount and then back against the workpiece at a constant feed speed is moved.

An optimization of the grinding time for a S <_iileif cycle can be achieved that the temporal change of the workpiece diameter with the approach reduced to the finished size. This enables the greatest material removal under optimal grinding conditions can be achieved in the shortest possible time.

To achieve a good surface quality with good dimensional accuracy, the change over time of the Workpiece diameter shortly before reaching until reaching the finished dimension a constant predetermined Have speed, with then - possibly with the exception of an intermediate firing in the case of worse Dimensional accuracy of the grinding blanks - this constant final finish removal speed is the lowest change in the workpiece diameter over time during the grinding process.

By taking the change in workpiece diameter over time as a basis for determining the infeed speed In an optimal way, a different rearing up of the workpieces is automatically achieved different dimensions and stiffnesses and further the blunting of the grinding wheel over the entire dressing interval is taken into account. There are also changes in dimensions due to the heating of the workpiece during roughing and the changes in the reference point of the measuring system due to thermal Influences are taken into account, so that optimal grinding results even in spite of strongly changing machining conditions can be achieved with optimally short grinding times.

In a particularly advantageous manner, when it is established Dimensional inaccuracy during and especially in the final phase of roughing the part return in Depending on the size of the deviation, initiated at a greater oversize and before Finishing grinding a spark-out phase can be provided until a given shape accuracy is reached, only to then initiate the finishing phase. As a result, the processing quality can be increased significantly so that the reject rate is significantly reduced when processing. It can also In the spark-out phase, a grinding wheel infeed is carried out to reduce the machining time Reduced speed compared to ski grinding. In further development it can be particularly advantageous to further improve the work accuracy the infeed speed for finish grinding as a function of the determined shape inaccuracy be adjustable, the infeed speed being smaller, the greater the inaccuracy of the shape is. The range of variation of the delivery speed in the firing phase can be between zero and the infeed speed for finishing. So there is also a steady transition to finishing at Achieving the desired shape accuracy is possible. For a more detailed explanation of the prior art and

ίο of the present invention are diagram curves as an attachment attached. It shows

F i g. 1 the material removal and the infeed movement under optimal conditions according to the status of Technology according to the publication "New process saves grinding time on cylindrical grinding machines",

2 shows the corresponding processing with a blunt grinding wheel,

F i g. 3 the same machining with a sharp grinding wheel,

4 shows the material ^{removal and J} : e infeed movement according to the method of the present invention with little rearing, that is to say with a relatively rigid grinding system and

5 shows the material removal and the infeed movement in the inventive grinding process with a large rearrangement, i.e. a relatively soft grinding system.

In the diagrams of FIG. 1 to 3 show plunge-cut grinding with the »Recon control« for a workpiece under different grinding conditions. The infeed movement takes place at constant speed during roughing. Shortly before reaching the final dimension, there is a rapid partial return by the amount a and then the

j5 finishing infeed also with constant material reduced infeed speed until the finished dimension is reached. The infeed movement and the material removal in Fig. 1 are shown for optimal grinding conditions. In the diagrams of FIG. 2 is the same grinding process when grinding with a silent disc. The delivery is at Reaching the dimension slightly larger before finishing in order to achieve the necessary removal. But with that even when finishing with a relatively higher grinding

J5 pressure worked because the reset dimension α is not sufficient to compensate for the spring back force sufficiently. As a result, the change in the workpiece diameter over time in the final phase of finishing becomes too high, so that the roundness and the surface quality of the workpiece are unsatisfactory.

In the diagrams of FIG. 3, the grinding process is shown with a freshly dressed sharp grinding wheel "- · !!». The default a is here after a lower grinding pressure is required, too great, so that a very long slaughter phase is required. by never however, a good grinding quality is achieved.

In Fig. 4 is the grinding process according to the invention Method shown for a relatively rigid grinding system with a small rear up. When sliding

bo start, the delivery speed is relatively high in order to get the Compensate for workpiece evasions when rearing up and to achieve the required change in the workpiece diameter over time. Thereafter decreased the delivery speed and runs practically parallel with the vVerkstC / ffabtragung. After reaching the dimension with finishing oversize, the temporal change in the tool diameter is greatly reduced on fine finishing infeed. A

Backward movement of the target movement that rises to the front the optimal removal rate is reversed again into a positive target movement, as shown in Fig. 4 lower diagram can be seen. The change The point between roughing and finishing is shown in dashed lines in all figures.

In the embodiment of FIG. 5 is the one according to the invention Grinding method shown in a grinding system with a large rearrangement, i.e. a relatively large one Deflection of the workpiece during grinding. In this embodiment, the speed is the material removal between roughing and finishing practically continuously during the Finishing process as shown in Fig. 5, lower diagram is. opposite to the query direction ιϊ made, the grinding wheel thus withdrawn during the entire finishing process, with the return speed is reduced until the finished size is reached and then put back in the entrance. In this way, optimally short grinding times with high form accuracy and surface quality can be achieved

Here / u 2 sheets of drawings

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Claims (6)

Patent claims: 1. Plunge-cut grinding process in which the grinding wheel is held until shortly before or until it comes into contact with the The grinding wheel with the workpiece is brought up to it at rapid speed and then at the specified The infeed speed is rough-ground until it reaches a predetermined small value Oversize, then partially reduced and in a partial return by a distance of the grinding pressure then the workpiece at fine finishing feed speed until the finished dimension is reached is finish-ground, characterized in that that the change in the workpiece diameter with time is measured, that the difference from the measured temporal change in the reverse diameter and a predetermined one temporal change of the workpiece diameter is used as a manipulated variable for the infeed speed becomes that during the roughing grinder the predetermined temporal change of the workpiece diameter is constant, whereby a constant temporal change in the measured workpiece diameter is achieved, and that in the subsequent Finish grinding the specified change in the workpiece diameter a certain Has course. 2. Plunge-cut grinding method according to claim 1, characterized in that the change over time the workpiece diameter during finish grinding decreased with the approach to the finished size. 3. Einechschleifverfahrep according to claim 1 or 2, characterized in that bum finishing grinding the change in the workpiece diameter over time shortly before reaching the finished dimension has a constant predetermined value which is the smallest change in the workpiece diameter over time represents within the grinding process. 4. Plunge-cut grinding method according to one of the claims 1 to 3, characterized in that if the shape inaccuracy is detected during and in particular in the final phase of roughing the partial return depending on the size of the Deviation is initiated in the event of a larger oversize and, if necessary, before finish grinding a spark-out phase is provided until the specified shape accuracy is achieved. 5. Plunge-cut grinding method according to one of claims 1 to 4, characterized in that the Infeed speed for finish grinding depending on the determined shape accuracy is regulated. 6. Plunge-cut grinding method according to one of claims 1 to 5, characterized in that the Temporal change in the workpiece diameter during finishing initially larger and with the approach is reduced to the finished size (Fig. 4).