machining Delrin

[Bob W.]

I am doing a project with Delrin and the part is flat and thin. The first piece warped like a potato chip. Is there a way to stress relieve Delrin so warpage is not as much of an issue?

 

Thanks,

Bob

[Colin Gilchrist]

Hey Bob,

 

Can you cut it from both sides? Sometimes it helps to get the skin off of both sides. What kind of dimensions, machining parameters, and cutting tools?

[MACHINEMASTERG]

how thin ??.25 we have delrin double disc ground to thickness then do machining and weve been having good results when you buy your delrin ask for a copolymer acetal its beter and no part line in the center ...hth

[#Rekd™]

Hi,

 

How thin? How big? Mill? How many parts?

 

John

[Bob W.]

The part is 15" x 10" x .225" and I am milling it. I would like to hit a flatness value of <.01" if possible.

[Bruce Caulley]

Use vacuum if you can and alternate cuts on each side.

 

Bruce

[Jim at Gentex]

Here's my method for machining Delrin parts:

 

-Start with a block of material large enough to encapsulate the whole part with 0.5" or more extra material all around. (The more extra material, the more rigidity, and thus a better the result.)

 

-Fly cut the top surface, then mill a pocket at least 0.1" deep to establish the top surface of the part.

 

-Machine the outside perhipery, including all contours, holes, slots, etc. possible to reach from the top cplane. You now have a block with one big pocket with your part nested in the center, recessed at Z-0.1 deep.

 

-Apply wax or mold release inside the pocket and on all machined surfaces, then fill the entire void with a 2 part casting material. (We use BCC Lik-Wood)

 

-After the casting material hardens, fly cut the top surface of the block again to remove excess casting material and provide a smooth surface to locate from for the next operation.

 

-Flip the block over (top to bottom) and machine the bottom contours, surfaces, or any other features that were unreachable from the top cplane. The casting material holds the part in place while the bottom cplane features are machined.

 

-After all machining is finished, bandsaw through the block and casting material all around the outside of the part, and discard the 4 strips of material that formed the outside perimeter of your original block. You now have a slug of casting material with the bottom of your part visible. Simply cut away the excess casting material with a knife or cutting pliers, and there's your finished part with no warping!

 

I've used this method literally hundreds of times and it almost never fails! The only time I've had problems were when the part didn't have too many features for the casting material to really lock it into place, or if a large volume of material needs to be removed when doing the bottom machining operation. When that happens, I just leave a few thin webs of material which keep the part connected to the inside of the block, then just remove those webs later.

 

 

HTH

[CAM-mando]

Yes it can be, I believe around 325°F you can probably find something on the DuPont website.

[Bruce Kanzelmeyer]

You can try annealing, post machining data available at www.boedeker.com/anneal.htm

 

Heat up to 320 degree F over 4 hr

Hold at 320 for 30 min for each 1/4" thickness

Cool down 50 degrees per hr.

 

I've had good luck using their parameters for polycarbonate.