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Old Oct 30, 2012, 11:39 PM
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United States, CA, Santa Monica
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Delrin tips?

Hey all- I'm going to be machining 1/8'' black Delrin soon, does anyone have tips on feed rate and depth of cut?

I'll be using a 1/16 in 3 flute cutter or a 3/64 4 flute- which one should I pick?

Thanks
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Old Oct 31, 2012, 06:13 AM
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Denver, CO
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There are many different types of Delrin. Often Acetal is sold as Delrin. They all are similar in milling. Feed, and depth depends on many things, so is hard to answer directly.
A few tips:
- try to keep the depth of cut less than the mills diameter. Might be able to go a little deeper, but risk of breaking the end mill increases.
- Feed rate varies greatly with spindle rpm. You need to cut fast enough to keep the end mill cutting. So usually lower rpm, and high feed rates are used. The higher the rpm, the faster you need to keep it moving. Also the more flutes the faster you need to move. But then the higher count flutes have trouble clearing the chip, at those feed rates. So 2 flutes are often recomended for delrin. If the part is thin, or not well supported lower feeds may be needed.
-Coolant compatable with plastic, or air is used to clear the chips so they don't melt back into the part.
-I recomend to keep the mill moving when on the part.

If you tell me the rpm range of the machine I can calculate a reasonable starting feed rate. I usually start there, and adjust based on how the chips, and cut finish look.
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Old Oct 31, 2012, 08:58 PM
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It really is easy to mill. Difficulty comes in getting a really nice finish, and close tollerances.
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Old Oct 31, 2012, 09:08 PM
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Originally Posted by Roto Rob View Post
It really is easy to mill. Difficulty comes in getting a really nice finish, and close tollerances.
That depends on the machine. We do delrin all the time with .001 profile tolerances and quite good finish for plastic. Our cheaper machines are 140k though. 60-100 ipm full 3d is not out of the question on these machines with delrin.
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Old Oct 31, 2012, 10:09 PM
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Quote:
Originally Posted by Roto Rob View Post
There are many different types of Delrin. Often Acetal is sold as Delrin. They all are similar in milling. Feed, and depth depends on many things, so is hard to answer directly.
A few tips:
- try to keep the depth of cut less than the mills diameter. Might be able to go a little deeper, but risk of breaking the end mill increases.
- Feed rate varies greatly with spindle rpm. You need to cut fast enough to keep the end mill cutting. So usually lower rpm, and high feed rates are used. The higher the rpm, the faster you need to keep it moving. Also the more flutes the faster you need to move. But then the higher count flutes have trouble clearing the chip, at those feed rates. So 2 flutes are often recomended for delrin. If the part is thin, or not well supported lower feeds may be needed.
-Coolant compatable with plastic, or air is used to clear the chips so they don't melt back into the part.
-I recomend to keep the mill moving when on the part.

If you tell me the rpm range of the machine I can calculate a reasonable starting feed rate. I usually start there, and adjust based on how the chips, and cut finish look.
Thanks for the tips. My CNC router goes from 11k to 24k, I'll probably be cutting this with a 3/64'' 2 flute end mill then. Feed rate/depth of cut suggestions would be greatly appreciated. Also- is Delrin toxic? I've been looking around on different forums and some say it is, some say it isn't what is your experience with it?
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Old Nov 01, 2012, 06:57 AM
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Many calculators get funny results with small end mills. I used Gwizard, and the results I got where that its not practical. It would bend the end mill to much with most any depth, and cut width. The generic formula I have that does not consider end mill deforming, would put that diameter end mill at 36,672 rpm, and 220 ipm. That would most likely break the end mill.
So your not going to be at an ideal cut rate. I would just cut at the lowest rpm, and try about 11 ipm. See how the cut looks, and adjust from there. Hard to say how much stepover, needs to be enough to keep it cutting rather than rubbing. I'd try 0.020 inch and see how it looks.

Delrin can be toxic, like everything. Google the MSDS, it has a great deal of information. The differnet types of delrin have different hazzards. Some have glass fiber in it, or other materials.
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Old Nov 01, 2012, 11:50 PM
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Originally Posted by Roto Rob View Post
Many calculators get funny results with small end mills. I used Gwizard, and the results I got where that its not practical. It would bend the end mill to much with most any depth, and cut width. The generic formula I have that does not consider end mill deforming, would put that diameter end mill at 36,672 rpm, and 220 ipm. That would most likely break the end mill.
So your not going to be at an ideal cut rate. I would just cut at the lowest rpm, and try about 11 ipm. See how the cut looks, and adjust from there. Hard to say how much stepover, needs to be enough to keep it cutting rather than rubbing. I'd try 0.020 inch and see how it looks.

Delrin can be toxic, like everything. Google the MSDS, it has a great deal of information. The differnet types of delrin have different hazzards. Some have glass fiber in it, or other materials.
Thank you sir- I will try that tomorrow and report back how it works out.
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Old Nov 03, 2012, 04:36 AM
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The feed rate was near perfect, I pushed it up 40% and chaned depth of cut to 0.04 in and rpm to 15000 and get a nice finish. Thanks for the tips everyone.
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Old Nov 03, 2012, 08:20 PM
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This is the basic formula that I used for feed rate.
Feed rate in inches = RPM X Feed per tooth X number of Flutes X Diameter of end mill.
The Feed per tooth for Acetal is recomended at 0.003 to 0.010.
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