JPS6161753A - Grinding method for work with highly hardened surface - Google Patents

Abstract

PURPOSE:To perform highly accurate grinding, by stopping the infeed of a grinding wheel when load of a wheel spindle motor becomes more than the setting value in case of grinding for a place high in hardness, while sparking out first rough grind, removing a large forward stock amount and, after second rough grind and wheel dressing, performing file grind and the spark-out. CONSTITUTION:A work being subjected to surface nitriding is attached to a chuck 1 and a table situated in a backward end B is fed to a grinding position G, thus first rough grind infeed takes place. When load of a wheel spindle driving motor grows large due to an increase in grinding resistance because of work surface hardness with a grinding wheel 4 going forward and it reaches the setting point of a watt-hour meter, the infeed of the table is stopped, making a spark-out timer act thereon, and a forward stock amount to be produced by flection of grinding force is ground. And, the table is situated at a wheel dressing position D whereby the grinding wheel 4 is dressed by a diamond tool 7, then again the table is fed to the grinding position G and fine infeed is started, therefore the infeed is stopped with a signal out of a sizing device, thus the slight forward stock amount is ground, stopping the infeed with a sizing signal so that any grinding of more than the sizing infeed is not performed at all.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a grinding method suitable for grinding a workpiece with a high hardness, such as a nitrided workpiece, where a small amount of grinding stock and high precision grinding is required.

When a prior art product is required to have abrasion resistance, its surface needs to be hard, and the surface is often nitrided. Since the grinding allowance of this nitrided workpiece is as small as about □□□5 mm, it is difficult to obtain a high precision deformation in the grinding process of the workpiece. The nitrided workpiece is about 0.01 to 0.02 from the black skin surface.
It is sufficiently nitrided to about 1000 yen.

Therefore, the hardest part has an AV of 1000 or more and is so hard that the grinding resistance is the highest and grinding is impossible unless high-speed cutting is performed. When the grinding resistance increases above a certain value, the grinding marks at this point become noticeable and the surface roughness remains on the product.

Decrease flatness (in case of end face grinding). And about 0.0 from the black skin surface? ``If high-speed cutting is performed even after grinding about 0.02 mm, the sharp decrease in grinding resistance will cause a biting phenomenon, and the grinding will proceed beyond the specified size at once, resulting in excessive grinding, making it impossible to obtain the specified size and ensuring accuracy. Something is happening that becomes impossible.

The invention is about to be decided! jJ vanishing point Therefore, the present invention aims to solve the problem that, if high-speed cutting continues even after a sharp decrease in grinding resistance during grinding of a highly hard surface, it becomes impossible to secure dimensions by biting.

Means to Solve the Problem Perform the first rough cut grinding, detect that the load on the grindstone shaft motor during grinding has exceeded the set value, and stop the first rough cut based on the detection signal to spark out. After that, a second rough cut grinding is performed, and when the coarse cut depth is reached, spark out is performed, and after the grinding wheel returns to the cutting depth, the grinding wheel is corrected, and then a middle cut grinding is performed to set the fine cut size. This is to cause the spark out to occur afterwards.

Example Embodiments of the present invention will be described below based on the drawings.

The grinding machine is an end face grinding machine with a well-known structure, and a headstock 3 rotatably supporting a main shaft 2 having a chuck 1 fitted at its tip is fixed on a bed (not shown). A grindstone head rotatably supporting a grindstone shaft 5 on which a cup grindstone 4 is fitted is mounted on a table (not shown) which can move forward and backward and whose positioning is controlled so as to face the main spindle 3.

The control circuit includes a wattmeter that outputs a signal when the load on the drive motor of the grindstone @5 rises above a set value. The table is driven by a hydraulic cylinder, and by switching the hydraulic circuit and selectively controlling the solenoid valve, it is positioned at a correction position advanced from the retreat end position B, and further advanced to the grinding position G, from which automatic cutting is performed. An end face grindstone correction device 6 having a diamond tool 7 is provided so as to be movable forward and backward by a hydraulic cylinder controlled by a switching solenoid valve so as to dress the grindstone 4 when the table is in the correction position. The switching solenoid valve is operated by a limit switch signal indicating each position of the table, end face grinding wheel correction device, etc., a timer signal determining the spark-out time when the wattmeter is activated, etc.

Furthermore, a sizing device is provided on the bed that comes into contact with the grinding end surface of the workpiece and outputs each signal at sizing positions iP, 2P, 3F, and 4F due to dimensional changes due to grinding.

When a workpiece whose surface has been nitrided is attached to the chuck 1 based on the working cutting cycle diagram shown in Fig. 1, the direction of the pressure oil is switched and the table, which was at the retreat end B, moves forward and reaches the grinding position G. A first coarse depth of cut feed is provided. When the grindstone 4 comes into contact with the surface of the workpiece during the forward movement of the cut, the grinding resistance gradually increases due to the high surface hardness, increasing the load on the grindstone drive motor. The wattmeter that measures this load in terms of electric power has a detection point set at a value corresponding to the load when the grinding allowance reaches approximately 0.02 mm, so the grinding wheel 4
When the machine grinds to a predetermined depth and the load reaches a set value, a detection signal is outputted and sent to the control device to stop the first rough cut of the table and activate a spark-out timer.

When the grindstone stops cutting and sparks out, the amount of wear caused by deflection due to high grinding force is removed. When the spark-out timer times up, the table is given a second coarse feed. On the other hand, the sizing device is moved forward and comes into contact with the grinding end surface of the workpiece, and when it reaches the 1P sizing, it outputs a signal, stops the cutting of the table, performs spark out, and grinds the amount of indentation caused by the deflection of the grinding force. When the sizing device outputs a 2P sizing signal, the notch of the table is returned and the table is positioned at the retracted corrected position. Pressure oil is sent to the hydraulic cylinder of the grindstone end face correction device B, and the diamond tool 7 moves forward to obliquely dress the end face of the cup grindstone 4. When the dressing is finished, the table is moved forward again and positioned at the grinding position G. Gap feed equivalent to coarse cut feed is performed on the table, and fine cut feed is started at the fine cut start position. The grindstone 4 on the table reaches the 2P sizing position in the middle of making a close cut at a slow speed and then begins actual grinding, and when the sizing device outputs a 3P sizing signal, the close cut is stopped and spark-out begins. During this time, a very small amount of indentation is ground, and the sizing device outputs a 4P sizing signal, so that cutting of the table is stopped and the table is returned by the amount of cutting, and the table is positioned at the corrected position. The grindstone end face correction device 6 moves forward again, and the diamond tool 7 corrects the end face of the grindstone 4 obliquely. When the correction is completed, the table retreats and is located at the retreat end B, completing the grinding of one workpiece.
When the load on the grinding wheel shaft motor exceeds the set value, the cutting of the grinding wheel is stopped using No. 3 of the wattmeter, and the first rough grinding is sparked out to remove a large gap, and then the second rough grinding is performed and the grinding wheel is corrected. This allows for close grinding and straight out grinding, so even on highly hard nitrided workpieces, the sharp reduction in grinding resistance allows for grinding beyond the specified size at once with a small grinding allowance of 38'rf. This has the effect of making it possible to grind D-loe with high precision in flatness.

[Brief explanation of the drawing]

FIG. 1 is a grinding cycle diagram, FIG. 2 is a diagram showing the affr relationship between the grindstone and the workpiece, and FIG. 3 is a watt-make output diagram. 1... Chuck 4... Grinding wheel 6... Grinding wheel end face modification coating B... Table retreat end grinding

Claims (1)

[Claims] (1) When grinding a workpiece with high surface hardness, it is detected that the load on the grindstone shaft motor during grinding has exceeded a set value after performing the first rough cut, and the first rough cut is performed based on the detection signal. After stopping and performing spark-out, perform the second rough cut grinding, and when the coarse depth of cut reaches the fixed size, spark-out is performed, once the grinding wheel is returned to the cut, the grinding wheel is corrected, and then fine-cut grinding is performed. A method for grinding a workpiece with a high hardness surface, characterized by performing spark-out after making a close cut and determining the size.