Someone asked me today. He said that the thimble barrel he used is easy to burn, and the material is made of domestic SKD61. What is the reason?
This is how I answered:
thimble barrels are generally used in high-temperature plastic molds, and metals have their own melting points. If the temperature is too high, the metals will burn out or even melt. If the SKD61 cylinder is subjected to vacuum nitriding heat treatment, the heat resistance effect will be more significant
These will also have an impact
1.The quality of the cylinder is not good, and the gap between the core hole and the cylinder is too small.
2. The water transportation design of the mold is unreasonable, and the ordinary cylinders work under high temperature. If it is a die-casting mold, a high-temperature resistant cylinder should be used.
3. Abnormal friction between the outer tube of the cylinder and the inner needle. It is very likely that a plate of the movable mold fixes the inner needle hole and the thimble plate. When assembling, check whether the inner needle is smooth, and then lock the screw. And it should not be locked too tightly.
4. The material of the movable mold core is related. According to the teacher in the workshop, there is a kind of 136 steel material that is not suitable for the back mold, and it is easy to burn the thimble.
design standards
1. If the thimble is smaller than 3mm, use two thimble.
2. The top block that is ejected with a rod must be inserted into the top block by 8 mm. The top block must have a guide sleeve, and the guide sleeve must be fixed.
3. If the small top block cannot be fixed with screws, please design with pins for positioning.
4. The R angle of the top piece must be designed.
5. In the case that the mold can use either the top sheet or the ejector pin, the ejector pin will be given priority.
6. The thimble's penetrating knife is 20-25mm.
7. The left and right gap of the thimble plate penetrates 0.5 mm.
8. The thimble board must have a lower guide post and trash nails.
9. Try to give priority to ejector accessories when resetting the thimble board. (Except the spring required by the customer)
10. Try to use a larger thimble for ejection (force and life).
11. On the premise that the product can be automatically taken off with the inclined top, try to avoid using the gas top.
12. The core and cavity valves should be designed to be concentric (especially transparent products).
13. The mold design carefully calculates the ejection distance to avoid insufficient ejection stroke.
14. For products that do not have the original shape, carefully consider the ejection position and ejection method.
15. Place the oil cylinder on the ejector plate for the mold ejected from the oil cylinder.
16. The valve installation should be disassembled from bottom to top.
17. The core in the push tube should not be fixed with screws as much as possible, it must be fixed with a pressure plate.
18. The thimble on the inclined surface and the thimble step are designed to be long and bar-shaped to avoid the inconvenience of D-shaped processing.
19. The board under the fixed screw of the inclined top sliding foot is designed to be worn and easy to disassemble.
20. The opposite position of the reset lever should be designed with a cushion insert. (Easy to process, resistant to bumps)
21. The ejector hole design of the mold below 300mm is ￠45mm; the design of the mold larger than 300mm is ￠60mm (large mold depends on the situation).
22. There should be more than 5 ejector holes for molds over 400mm.
23. The air cap is D-shaped air cap on the inclined plane.
24. The 4 corners of the inclined top and the square small straight top block should form an R angle (to reduce friction).
25. The stripper can be designed as a top ring type as far as possible.