All you want about stamping die is here (II)

5、 Die grinding

1. Importance of die grinding

Regular grinding of die is the guarantee of punching quality consistency. Regular grinding of the die can not only improve the service life of the die, but also improve the service life of the machine. It is necessary to grasp the correct grinding time.

2. The specific characteristics of the die need to be sharpened

For the grinding of the die, there is no strict number of blows to determine whether the grinding is needed. It mainly depends on the sharpness of the cutting edge. It is mainly determined by the following three factors:

 (1) Check the fillet of the cutting edge, if the fillet radius reaches R0 1 mm (the maximum r value shall not exceed 0.25 mm) requires grinding.

 (2) Check the punching quality and whether there are large burrs?

 (3) Determine whether grinding is required by the noise of machine stamping. If the noise of the same die is abnormal during stamping, it indicates that the punch has been blunt and needs grinding.

Note: if the edge of the cutting edge becomes round or the rear of the cutting edge is rough, grinding should also be considered.

3. Grinding method

There are many ways to grind the die, which can be realized by special grinding machine or surface grinder. The grinding frequency of punch and lower die is generally 4:1. Please adjust the die height after grinding.

 (1) Harm of incorrect grinding method: incorrect grinding will aggravate the rapid damage of the die edge, resulting in a significant reduction in the number of blows per grinding.

 (2) Benefits of correct grinding method: regularly grinding the die, and the quality and accuracy of punching can remain stable. The cutting edge of the die is damaged slowly and has a longer service life.

4. Grinding rules

The following factors shall be considered during die grinding:

 (1) The rounded edge is R0 The sharpness of the edge depends on the size of 1-0.25mm.

 (2) The surface of grinding wheel shall be cleaned.

 (3) A loose, coarse and soft grinding wheel is recommended. Such as wa46kv

 (4) The grinding amount (cutting amount) of each time shall not exceed 0.013mm. Excessive grinding amount will cause overheating of the die surface, which is equivalent to annealing treatment, softening the die and greatly reducing the service life of the die.

 (5) Enough coolant must be added during grinding.

 (6) During grinding, the punch and lower die shall be fixed stably, and special tooling fixtures shall be used.

 (7) The grinding amount of the die is certain. If it reaches this value, the punch will be scrapped. If you continue to use, it is easy to cause damage to the mold and machine, and the gain is not worth the loss.

 (8) After grinding, the edge shall be treated with oilstone to remove excessively sharp edges and lines.

 (9) After grinding, the blade shall be cleaned, demagnetized and oiled.

Note: the grinding amount of the die mainly depends on the thickness of the stamped plate.

6、 Attention shall be paid to the punch before use

1. Store

 (1) Wipe the inside and outside of the upper mold sleeve with a clean rag.

 (2) When storing, be careful not to scratch or dent the surface.

 (3) Apply oil to prevent rust.

2. Preparation before use

 (1) Clean the upper die sleeve thoroughly before use.

 (2) Check the surface for scratches and dents. If any, remove it with an oilstone.

 (3) Oil inside and outside.

3. Precautions when installing punch on upper die sleeve

 (1) Clean the punch and oil its long handle.

 (2) Insert the punch into the bottom of the upper die sleeve on the large station die without force. Nylon hammer cannot be used. During installation, the punch cannot be fixed by tightening the bolts on the upper die sleeve. The bolts can be tightened only after the punch is correctly positioned.

4. Install the upper mold assembly into the turret

If you want to prolong the service life of the die, the gap between the outer diameter of the upper die sleeve and the turret hole should be as small as possible. Therefore, please carefully perform the following procedures.

 (1) Clean and oil the keyway and inner diameter of the turret hole.

 (2) Adjust the keyway of the upper die guide sleeve to match the key of the turret hole.

 (3) Insert the upper mold sleeve straight into the tower hole, and be careful not to tilt. The upper die guide sleeve should slide into the turret hole by its own weight.

 (4) If the upper die sleeve tilts to one side, it can be gently knocked right with soft material tools such as nylon hammer. Repeat the knocking until the upper die guide sleeve slides into the correct position by its own weight.

Note: do not apply force to the outer diameter of the guide sleeve of the upper die, but only on the top of the punch. Do not knock the top of the upper die sleeve to avoid damaging the turret hole and shortening the service life of individual stations.

7、 Overhauled mold

If the punch cannot be taken out because it is bitten by the material, please check according to the following items.

1. Regrinding of punch and lower die. The die with sharp edge can process beautiful cutting section. If the edge is blunt, additional punching pressure is required. Moreover, the section of the workpiece is rough, which produces great resistance, causing the punch to be bitten by the material.

2. Die clearance. If the clearance of the die is not properly selected relative to the plate thickness, the punch needs a large demoulding force when it is separated from the material. If the punch is caught by the material for this reason, please replace the lower die with reasonable clearance.

3. Status of processed materials. When the material is dirty or has dirt, the dirt adheres to the die, so that the punch is bitten by the material and cannot be processed.

4. Deformed material. After punching the hole, the warped material will clamp the punch and make the punch bite. Warped materials should be leveled before processing.

5. Excessive use of springs. Will cause spring fatigue. Please always check the performance of the spring.

8、 Oiling

The amount of oil and the number of oil injections depend on the conditions of the processing materials. For materials without rust and scale such as cold-rolled steel plate and corrosion-resistant steel plate, oil shall be injected into the die. The oil injection points are guide sleeve, oil injection port, contact surface between knife body and guide sleeve, lower die, etc. Use light engine oil for oil.

For materials with rust and scale, the rust powder will be sucked between the punch and the guide sleeve during processing, resulting in dirt, so that the punch can not slide freely in the guide sleeve. In this case, if you apply oil, it will make the rust scale easier to stick to. Therefore, when flushing this material, on the contrary, wipe the oil, decompose it once a month, remove the dirt of the punch and lower die with steam (firewood) oil, and then wipe it clean before reassembly. This can ensure that the mold has good lubrication performance.