Some CNC Router Machining Failures

Lest you think that everything always goes correctly in my garage when using a CNC router, here’s a couple parts that I spectacularly ruined recently. Although I was disappointed with these cuts, they really don’t compare with smoking a brand new Dremel 4000!  So here are my latest epic CNC failures:

Routing (Melting) Delrin:

Delrin is a great material for industrial applications.  Although it’s not hard at all, it’s wear resistance is extremely high.  Unfortunately, I didn’t realize that it melts quite easily when machining.  This was undoubtedly compounded by the fact that I was cutting deep into the material, and the chips weren’t cleared, so there wasn’t much in the way of convective cooling.  After close to an hour of fairly cautious cutting, everything on the bottom was melted, and the piece was pretty useless.

I’d recommend making sure the chips don’t stay on the bottom to be melted, and using some sort of coolant would probably help as well.  Here’s a thread on practicalmachinist with some advice on this subject.

Multiple CD Ninja-Stars:

CD melted together when machiningIf one CD cut into a ninja star is good, certainly three would be even better.  Keyence, which makes excellent scanners that I use at work, seems to be sending me their program CD with every sensor I buy, reminiscent of early 90’s AOL.  As with AOL, I decided to “recycle” these disks into something useful.  Sure I can’t put a copy of Scorched Earth on a written CD like with 3 1/2 inch floppies, but I do have a CNC router now and a ninja-star model…

My idea was to fixture three CDs one on top of another and use a mill instead of the engraving bit that I had used before.  As with the Delrin experiment, apparently cooling was an issue.  The top CD melted onto the second one creating something pretty nasty.  If that hadn’t messed up my routing, the screw that held everything in place started coming undone.  Not my finest work.

CD melted when CNC machining pulled apartIf I tried this multi-level CD setup again, I’d be less aggressive with my mill and probably use a lock-nut to keep everything fixtured correctly.  Additionally, I might put a piece of paper between each layer to keep everything from melting together.  As with anything here, if you have a better idea of how to machine CDs or the Delrin above, be sure to say so in the comments!


It may be time to get a better system (if you call randomly using a Shop Vac to clear the chips out a system) for sucking the chips out of whatever I’m working on.  The Zen Toolworks forum has some really neat designs, for this so I’ll have to do some research and see what I can come up with!

Also, On a related subject, be sure to check out this post if you have a lot of extra engineering catalogs that you need a use for.

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