How to get better cutting die from D2
How to get better cutting die from D2
(OP)
We do high speed punching, each run our dies has punched 250 000 times, but for reason that we couldn't found out yet, some die, make only 20 000 parts and others do 500 000 parts before taking them off for grinding.
We evaluate if or not the die need to be replaced by the quality of the cut on parts.
I suspect that our problems come from grinding. Each time we remove up to 0.010" by step of 0.002" and we do final step at 0.0002".
We use coolant, grinding wheel is sharpened each time we grind the die. It takes 20 minutes to get the die like new. Material is D2 at 62HRC.
We take care of not burning the surface of the die when we grind to keep the hardness high. Often, the first 2 or 3 grinding cycles, we do not have good results but further in the the life of the die, we obtain better results and for the 2 or 3 lasts grindings, we start again having the same problem.
I'll welcome any recommandations that can help us to get more parts between each grinding.
Is there any way, we can get D2 harder than 62HRC. Maybe an other matherial should be use instead of D2??
Thanks
petecul
We evaluate if or not the die need to be replaced by the quality of the cut on parts.
I suspect that our problems come from grinding. Each time we remove up to 0.010" by step of 0.002" and we do final step at 0.0002".
We use coolant, grinding wheel is sharpened each time we grind the die. It takes 20 minutes to get the die like new. Material is D2 at 62HRC.
We take care of not burning the surface of the die when we grind to keep the hardness high. Often, the first 2 or 3 grinding cycles, we do not have good results but further in the the life of the die, we obtain better results and for the 2 or 3 lasts grindings, we start again having the same problem.
I'll welcome any recommandations that can help us to get more parts between each grinding.
Is there any way, we can get D2 harder than 62HRC. Maybe an other matherial should be use instead of D2??
Thanks
petecul





RE: How to get better cutting die from D2
The die bores and the punch diameters are made within a tolerance and by natural selection a small bore and a big punch will be mated; likewise a big bore and small punch. As you can imagine the forces, friction and clearance will be different. In a critical operation, pairing might help.
If your application causes enough friction for a tool to get hot enough and temper back in hardness, the tool life will go down. D2 has a low tempering temperature. I am not sure if a micro-hardness tester would detect softening of a cutting edge, but if you have one, you might try it.
Without knowing your exact application I can only suggest that I have replaced D2 with M2 on pierce tooling resulting in better tool life.
D2 can be coated with TiN or Nitrided and regrinds need to remove enough material to clean up the striations. The only way to determine if this will help you is to test it.
If you have multiple piercings occurring on the same press stroke, differing placement on the press bed and different cutting heights will result in various localized forces in some cutting edges. Also the guiding of each tool pair and the perpendicularity of the punch to die face are factors.
Another factor effecting your quality of cut and tool life is the velocity at the moment of piercing. An eccentric press has a fast changing ram velocity towards TDC. If your pierce die cutting edge height changes (from re-grinds) on this type of press, it is possible to cut too fast or too slow resulting in poorer cutting. You can test re-registering the die height with shims after re-grinds.
The type of press and its gibbing and the total load can contribute as well. There are other things but this is good for now. If you can measure a group of tools and see if there is a correlation to quality and tool life, you will be on your way.
Oh, if your die grinding was the problem you should be able to measure a hardness change on the ground face. 20 minutes is slow enough, depending on how big the surface area is.
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RE: How to get better cutting die from D2
thanks
petecul
RE: How to get better cutting die from D2
This may or may not be applicable to the type of stamping that you're doing.
RE: How to get better cutting die from D2
Also make sure that the fluid is actually getting to the point of cut.plan an 1 to 1.5 GPM per HP used at the point of cut.
This link should get you to some more comprehensive inforation on this and other fluid related subjects
http:/
The cutting fluid is not all of this probem but I will bet it is part of it.
RE: How to get better cutting die from D2
The die is square foot big, we already thinked for carbide insert but the thing is maybe we gonna have more tool life but will have the get this more life to more more life, always more! Right know, it's faster, cheaper and easier for us to find out all details that affect tool life with D2, When we gonna be more in control, we will try to use some insert.
For coolant, I'll have a look, didn't thought that wcould affect our dies' hardness. I'll do some testing on that.
Thanks
petecul
RE: How to get better cutting die from D2