Breaking Bits

I'm new to working in the manufacturing world, and some things at my place of work do not seem to be agreeing. I have a design engineer who blames the operators for bits constantly being broken. As I have worked on our routers when I was first hired I do not agree. I feel like we are running something incorrectly.

We are machining UHMW, HDPE plastics from 1/4" - 1 1/2" thicknesses. The thinner stuff cuts no problem but the 1" and 1 1/2" keeps snapping bits in half. At first, I thought they were buying cheap bits, but we source from multiple in the area. One place they bought them out.

They run the routers the same regardless same feed rate and 18k rpm for 1/4" as they do for the big stuff. Some stuff I am seeing online says slow feed rate increase rpm others say the opposite. The cut quality is fine right now, I figure I can fix issues that arise later. I just need to stop snapping six $80+ bits in two days.

Something for you to think about is what is happening to the chips/swarf when cutting in the thicker plastics. If they are not getting removed quickly enough they may be getting recut and heated more, causing problems. See this thread: https://www.cnczone.com/forums/cnc-t...65610-cnc.html

Do you have a way to provide an air blast to the cutting face to remove swarf and cool the cut?

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Something for you to think about is what is happening to the chips/swarf when cutting in the thicker plastics. If they are not getting removed quickly enough they may be getting recut and heated more, causing problems. See this thread: https://www.cnczone.com/forums/cnc-tooling/465610-cnc.html

Do you have a way to provide an air blast to the cutting face to remove swarf and cool the cut?

It sounds like a problem with the depth of cut at that feedrate. If a 1/4" cut works fine, but your bits all snap when you cut thicker stuff just as fast, either change the toolpath to only cut 1/4" at a time, or slow it down accordingly. You could also try increasing the RPMs, but there's a limit to that, and you might risk melting the plastic onto your cutters.