JPH0635100B2 - Grinding method for high hardness surface work - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding method suitable for a case where a surface having high hardness, such as a nitrided work, requires high-precision grinding with a small grinding allowance.

Prior art When the wear resistance of a product is required, the hardness of the surface is required and the surface is often subjected to a nitriding treatment. Since the grinding allowance of the nitrided work is as small as about 0.05 mm, it is difficult to obtain high precision in the grinding of the work. The nitrided work is fully nitrided about 0.01 to 0.02 mm from the surface of the black skin.

Therefore, the hardest part reaches Hv1000 or more and is extremely hard, so the grinding resistance is the highest and grinding is impossible unless high-speed cutting is performed. Then, when the grinding resistance rises above a certain value, the grinds at this point remarkably appear and the surface roughness and flatness (in the case of end surface grinding) of the product deteriorate. When high-speed cutting is performed even after grinding about 0.01 to 0.02 mm from the surface of the black skin, the biting phenomenon occurs due to the sharp decrease in grinding resistance, and the grinding progresses more than a certain size all at once, resulting in excessive grinding. It has been impossible to obtain a predetermined size and it is impossible to ensure accuracy.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Accordingly, the present invention solves the problem that the dimension cannot be secured by biting if high-speed cutting is continued even after a sharp reduction in grinding resistance during grinding of a hard surface. To aim.

Means for Solving the Problems In grinding a workpiece having a high surface hardness such as a nitrided workpiece with a small machining allowance, the first rough cut grinding is performed on the hardest part of the surface, and the load of the wheel spindle motor during the grinding. Detected that the load at the time of reaching a predetermined grinding allowance was greater than or equal to the set value, and the detection signal stopped the first rough cut to cause sparkout, and then the second rough cut. A method of performing spark-out when the depth of cut reaches to a certain level by performing cut-in grinding, temporarily returning the grindstone to correct the grindstone after re-cutting, and then performing fine-cut grinding to perform spark-out after constant-dimension cut. Is.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. The grinding machine is an end surface grinding machine having a well-known structure. A headstock 3 for rotatably supporting a spindle 2 fitted with a chuck 1 at its tip is fixed to a bed (not shown). On a table (not shown) which can be moved forward and backward and whose position is controlled, a grindstone base rotatably bearing a grindstone shaft 5 fitted with a cup grindstone 4 is mounted so as to face the spindle 3. The control circuit incorporates a Wattometer which outputs a signal when the load of the drive motor for the grindstone shaft 5 rises above a set value. The table is driven by a hydraulic cylinder, and the hydraulic circuit is positioned at the corrected position D advanced from the backward end position B by the selective control by the switching solenoid valve, further advanced to the grinding position G, and automatic cutting is performed from this. An end face grindstone correction device 6 having a diamond tool 7 is provided so as to be able to advance and retreat 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 actuated by a signal of a limit switch showing each position of the table, the end surface grindstone correcting device, etc., a signal of a timer which determines a spark-out time when the water meter operates. Furthermore, a sizing device is provided on the bed, which outputs each signal at a sizing position of 1P, 2P, 3P, 4P in contact with the ground end surface of the workpiece and dimensional change due to grinding.

Action Based on FIG. 1 showing the cutting cycle diagram, when a workpiece whose surface is nitrided is attached to the chuck 1, the direction of pressure oil is switched and the table corresponding to the retreat end B is advanced to reach the grinding position G. A first rough cut feed is provided. When the grinding wheel 4 comes into contact with the surface of the workpiece during the cutting advance, the grinding resistance gradually increases due to the high surface hardness, and the load on the grinding wheel drive motor increases. The Wattometer that measures this load with the power value has the detection point set to the value corresponding to the load when the grinding allowance reaches about 0.02 mm, so the grindstone 4 grinds to the specified depth and the load reaches the set value. When it reaches, a detection signal is output and sent to the control device to stop the first rough cut of the table, and at the same time, the spark-out timer operates. The amount of inflection caused by the bending due to the high grinding force is ground by the cutout spark out of the grindstone. The time-up of the spark-out timer gives the table a second coarse feed. On the other hand, the sizing device is moved forward and is in contact with the grinding end surface of the workpiece, and when the 1P sizing is reached, a signal is output to stop the table cutting and spark out to grind the amount of bending due to the bending of the grinding force. Then, when the sizing device outputs a 2P sizing signal, the notch of the table is restored and the table is positioned at the corrected position D retracted. Pressure oil is sent to the hydraulic cylinder of the whetstone end face correcting device 6 and moves forward, and the diamond tool 7 obliquely dresses the end face of the cup whetstone 4. When dressing is completed, the table is advanced again and positioned at the grinding position G. The gear feed corresponding to the rough cut feed is performed on the table, and the fine cut feed is started at the fine cut start position. The grindstone 4 on the table starts the actual grinding after reaching the 2P sizing position in the middle of the low-speed dense cutting, and when the sizing device outputs the 3P sizing signal, the fine cutting is stopped and the sparking out is started. In the meantime, the incision of the extremely small amount is ground and the sizing device outputs a 4P sizing signal to stop the cutting of the table. The table is returned by the cutting and the table is positioned at the correction position D. The whetstone end face correcting device 6 moves forward again, and the diamond tool 7 obliquely corrects the whetstone 4 end face. When the correction is finished, the table is moved back to the retreat end B and the grinding of one workpiece is completed.

Effect As described in detail above, according to the present invention, when the load of the grindstone shaft motor becomes equal to or more than the set value in grinding in a place of high hardness, the cutting of the grindstone is stopped by the signal of the Wattmeter to perform the spark-out of the first rough grinding. After removing a large amount of grinding, second rough grinding, grindstone modification to perform fine grinding and spark out, so even with a high grinding hardness of a nitrided work with a small grinding allowance Due to the decrease, the grinding does not progress more than a certain size at a stretch, and it has an effect that high-precision grinding can be performed with good flatness.

[Brief description of drawings]

FIG. 1 is a grinding cycle diagram, FIG. 2 is a diagram showing a positional relationship between a grindstone and a workpiece, and FIG. 3 is an output diagram of a Wattometer. 1 ... Check, 4 ... Whetstone 6 ... Whetstone end face correction device B ... Table retreat end position D ... Whetstone correction position, G ... Grinding position

Claims (1)

[Claims] 1. In the grinding of a workpiece having a high surface hardness such as a nitrided workpiece with a small machining allowance, the first rough cut grinding is performed on the hardest part of the surface, and the load of the wheel spindle motor during the grinding is predetermined. It is detected that the load at the time of reaching the grinding allowance is equal to or greater than the set value, and the first rough cut is stopped by the detection signal to perform sparkout, and then the second rough cut grinding is performed. It is characterized by performing spark out when reaching the rough cutting fixed size, temporarily correcting the grindstone after cutting back the grindstone, and then performing fine cut grinding and performing spark out after the fine cut constant size. Method for grinding high hardness surface workpieces.