Hi everyone,
See attached picture. I was routing a PCB today and this happened. Two areas didn’t route, a larger area on the left and small area on the right. You can see the tool passed over it but didn’t cut.
The blacked areas left and right are where I had it clamped. The board was sitting in a pocket I milled onto MDF with the XCarve, so it should be parallel/true to the XCarve itself. The board is FR-1 purchased from Inventables.
I have the 31"x31" XCarve. I’m running the large .0100" tapered PCB bit from precisebits.com (http://www.precisebits.com/products/carbidebits/tapered_stub_125.asp). Cut depth is .010", 10 in/min travel rate. PCB designed in FreeCAD, CAM’ed in FlatCAM, sent to the XCarve through UGCS.
Any ideas? Thanks in advance!
Dustin
Seems clear that wasn’t the case. The clamp lowered that part of the copper clad by at least 10 mils. You’ll probably find that the traces which did cut in that area are shallower than the areas where it was completely cut.
Try using two sided tape to hold the copper clad so you’re not putting too much pressure on it.
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I didn’t think two sided tape would be strong enough, but applied liberally it seems to be working well. Routing now, I’ll report back when it’s done.
Thanks!
Aaaaaand I spoke too soon, it detached itself about half way through.
Any other ideas? More clamps with less pressure on each?
Some people here use carpet tape as a hold down. It’s an excellent double sided tape.
Yes, a square (wooden corners or a carpenter’s square) to hold around the edges for lateral movement and light clamping to hold it down could work.
Did it seem to work in the affected areas before it crapped out?
Bill,
Yes, looked a lot better. Overclamping and warping was definitely the root cause. Thanks for the direction!
Dustin
Totally borked my bit, oops. Only had the one in .01", so need to redo the CAM work with a smaller stepover and will try again with the .0071" bit I have.
You should create a flat wasteboard by using aluminum or worst case, MDF. Screw it down, route it flat, put your board on that, screw it down and you will not have a problem. It is flexing on you. For a big board, put screws in the middle to keep it flat. Using tape is crazy in my opinion.
cut out a frame to fit to edges of pcb then clamp frame it will apply more even pressure. Or like i use temporary spray adhesive thats what i use to hold sheet metal down on the xcarve. Also the double sided tape needs a clean surface remove surface oxidation with scotchbrite pad wipe clean with alcohol or acetone. These are things that have worked for me.
Thanks for the feedback everyone! Current plan is to buy a couple of square feet of plastic of some sort (probably Delrin). screw one piece down to the xcarve bed, route it flat with a pocket, and then put a cover/window of delrin over it.
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I mill my PCB’s on the X-Carve using PCB-GCode for Eagle and the best solution i’ve found so far… Hot glue 
Seriously…
I take a 6"x6" piece of MDF, and clamp it to the waste board, then i face it off to make sure it’s parallel with the machine’s axis, then i place my board, and tack the 4 corners with a small dab of hot glue… it really doesn’t take much, just enough to touch the edge where the PCB meets the MDF…
For larget boards, i would suggest 1 dab every 2 inches…
When you’re done, you cut the glue away from the edge of the PCB with an exacto knife and pick the PCB up… You can now scrape the excess glue off, and face the board again to do another… i usually face 0.25mm off the top and look for low spots, if there’s a spot that wasn’t hit, i’ll take another 0.25mm until no more low spots are there.
