Grinding of die
1. The Importance of Die Grinding
Regular sharpening of the die is the guarantee of consistent punching quality. Regular grinding of the die can not only improve the service life of the die but also increase the service life of the machine. It is necessary to grasp the correct grinding time.
2. Specific features of the die requiring grinding
For die grinding, there is no strict strike number to determine whether grinding is required. 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 R0.1mm (the maximum R value shall not exceed 0.25mm), it needs to be sharpened.
(2) Check the punching quality. Is there any big burr?
(3) Judge whether grinding is required by the noise of machine punching. If the noise of the same die is abnormal during stamping, it indicates that the punch is blunt and needs to be sharpened.
Note: If the edge of the cutting edge becomes rounded or the back of the cutting edge is rough, grinding should also be considered.
3. Grinding method
There are many methods for die grinding, which can be realized by using a special grinding machine or a surface grinder. The frequency of punch and lower die grinding 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 greatly reduced number of blows per grinding.
(2) Benefits of correct grinding method: regularly grind the die, and the quality and accuracy of punching can be kept 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 when grinding the die:
(1) The sharpness of the cutting edge shall be considered when the fillet of the cutting edge is R0.1-0.25mm.
(2) The surface of the grinding wheel shall be cleaned.
(3) A loose, coarse grain, soft grinding wheel is recommended. E.g. WA46KV
(4) Each grinding amount (cutting amount) shall not exceed 0.013mm. Excessive grinding amount will cause overheating of the mold surface, which is equivalent to annealing treatment, and the mold will become soft, greatly reducing the life of the mold.
(5) Sufficient 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 it is used continuously, it is easy to cause damage to the mold and the machine, and the gain is not worth the loss.
(8) After grinding, the edges shall be treated with an oilstone to remove excessively sharp edges.
(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 punched sheet.
Attention shall be paid to the punch before use
1. Storage
(1) Clean the inside and outside of the upper mold sleeve with a clean rag.
(2) Be careful not to scratch or dent the surface when storing.
(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 for installing the punch on the 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. Do not use nylon hammers. During installation, the punch cannot be fixed by tightening the bolts on the upper die sleeve. The bolts can only be tightened after the punch is correctly positioned.
4. Install the upper formwork assembly into the turret
If you want to extend the service life of the mold, the clearance between the outer diameter of the upper mold sleeve and the turret hole should be as small as possible. So please execute the following procedure carefully.
(1) Clean and oil the keyway and inner diameter of the turret hole.
(2) Adjust the keyway of the upper die guide sleeve to fit the key of the turret hole.
(3) Insert the upper die sleeve into the tower hole straightly and carefully without any inclination. The upper die guide sleeve should slide into the turret hole by its own weight.
(4) If the upper mold sleeve is inclined to one side, gently knock it with soft material tools such as nylon hammer. Repeat the tapping until the upper die guide sleeve slides into the correct position with its own weight.
Note: Do not force on the outer diameter of the upper die guide sleeve, 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.
Maintenance of moulds
If the punch is stuck by the material and cannot be taken out, please check according to the following items.
1. Re sharpening of punch and lower die. The die with sharp edge can process beautiful cutting section. If the edge is blunt, additional punching force is required. Moreover, the workpiece section is rough, resulting in great resistance, causing the punch to be bitten by the material.
2. Die clearance. If the clearance of the die is not suitable for the thickness of the plate, the punch needs a large demoulding force when it is separated from the material. If the punch is bitten by the material for this reason, please replace the lower die with a reasonable clearance.
3. Status of processing materials. When the material is dirty or there is dirt, the dirt will attach to the mold, making the punch bit by the material and unable to process.
4. Material with deformation. After punching the hole, the warped material will clamp the punch so that the punch is bitten. For materials with warpage, please smooth them before processing.
5. Excessive use of springs. It will fatigue the spring. 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 material being processed. For cold rolled steel plate, corrosion resistant steel plate and other rust free and scale free materials, oil shall be injected into the mold. The oil injection points are the guide sleeve, the oil injection port, the contact surface between the tool body and the guide sleeve, and the lower mold. Light engine oil for oil.
For materials with rust and scale, rust powder will be sucked into the space between the punch and the guide sleeve during processing, resulting in dirt, which will prevent the punch from sliding freely in the guide sleeve. In this case, if oil is applied, the rust will be more easily stained. Therefore, instead of cleaning the oil when flushing this material, it should be disassembled once a month, and the dirt on the punch and the lower mold should be removed with gasoline (diesel) oil, and then cleaned before reassembly. In this way, good lubrication performance of the die can be guaranteed.
