1、 Information from waste situation
Waste is essentially the reverse image of the forming hole. That is to say, the same position opposite to each other. By checking the scrap, you can judge whether the clearance between the upper and lower die is correct. If the gap is too large, the waste will appear rough, undulating fracture surface and a narrow bright zone area. The larger the gap, the larger the angle between the fracture surface and the bright zone. If the gap is too small, the waste will show a small angle fracture surface and a wide bright zone area.
The large gap forms a hole with large curling and edge tearing, which makes the profile slightly protrude with a thin edge. Too small gaps form a band with a slight curl and a large angle tear, resulting in a profile that is more or less perpendicular to the surface of the material.
An ideal waste material should have a reasonable collapse angle and a uniform bright band. In this way, the punching pressure can be kept to a minimum and a clean round hole with few burrs can be formed. From this point of view, increasing the gap to extend the life of the die is at the expense of the quality of the finished hole.
2、 Selection of die clearance
The clearance of the die is related to the type and thickness of the material being punched. Unreasonable clearances can cause the following problems:
(1) If the gap is too large, the burr of the stamping workpiece is relatively large, and the stamping quality is poor. If the gap is small, although the quality of punching is good, the wear of the die is serious, which greatly reduces the service life of the die, and it is easy to break the punch.
(2) If the gap is too large or too small, it is easy to produce adhesion on the punch material, resulting in the strip material during stamping. If the gap is too small, it is easy to form a vacuum between the bottom of the punch and the sheet metal, and the waste will rebound.
(3) Reasonable clearance can prolong the service life of the die, have good unloading effect, reduce burr and flanging, keep the plate clean, the hole diameter is the same and will not scratch the plate, reduce the grinding times, keep the plate straight and the punching positioning is accurate.
3、 How to improve the service life of mould
For users, increasing the service life of the die can greatly reduce the stamping cost. The factors affecting the service life of the mould are as follows:
1. Type and thickness of material;
2. Whether to choose a reasonable die clearance;
3. Mold structure;
4. Whether the material is well lubricated during stamping;
5. Whether the mold has undergone special surface treatment;
6. Such as titanium plating, titanium nitride;
7. Neutral of up and down rotating tower;
8. Reasonable use of adjusting gasket;
9. Whether the inclined edge die is properly used;
10. Whether the die seat of the machine tool has been worn;
4、 Problems in stamping special size holes
(1) Minimum diameter punch φ Zero point eight ——φ One point six Please use a special punch for range punching.
(2) When punching thick plates, please use a larger die relative to the machining hole diameter. Note: at this time, if the die of normal size is used, the thread of punch will be damaged.
(3) The ratio of minimum width to length of the cutting edge of punch shall not be less than 1:10 in general.
(4) The relationship between the minimum size of the cutting edge and the thickness of the plate. It is suggested that the minimum size of the cutting edge of the punch should be 2 times of the plate thickness.
5、 Grinding of die
1. The 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 the service life of the machine.
2. The specific characteristics of the tool need to be sharpened
There is not a strict number of blows to determine whether the edge grinding is needed. It mainly depends on the sharpness of the 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 (maximum r value shall not exceed zero point two five Mm).
(2) Check the punching quality. Is there any big burr?
(3) The need for grinding is judged by the noise of machine stamping. If the noise of the same die is abnormal, it means that the punch is blunt and needs to be sharpened.
Note: if the edge of the cutting edge becomes round or the back of the cutting edge is rough, the grinding of the cutting edge should also be considered.
3. Method of sharpening
There are many ways to grind the die, which can be realized by using special grinding machine or plane grinding machine. 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 greatly reduced number of blows per grinding.
(2) The benefits of the correct grinding method: regular grinding of the die, punching quality and accuracy can be maintained stable. The cutting edge of the die is damaged slowly and has a longer service life.
4. Sharpening rule
The following factors should be considered when grinding the die edge:
(1) The edge fillet is R0.1 - zero point two five The sharpness of the edge depends on the size of millimeter.
(2) The grinding wheel surface 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 zero point zero one three Mm, too much grinding will cause the die surface overheating, equivalent to annealing treatment, the die becomes soft, greatly reducing the 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 and fixture shall be used.
(7) The grinding amount of the die is certain. If it reaches this value, the punch will be scrapped. If continue to use, easy to cause mold and machine damage, the gain is not worth the loss.
(8) After grinding, the edge shall be treated with oilstone to remove the excessively sharp edges.
(9) Clean, demagnetize and oil the blade after grinding.
Note: the grinding amount of the die edge mainly depends on the thickness of the plate to be punched.
This article is provided by Jinan mould. The above is the introduction of mould processing knowledge. For more information, please click http://www.jnhjgs.cn