CNC Waterjet cutting instrument holes

On Thursday, February 26, 2015 at 1:09:53 PM UTC-8, wrote:
Thanks Darryl, this is a fiberglass panel, not carbon. So not quite as stiff or strong and any delamination damage is quite a bit more obvious.
I did a layup of approximately the same thickness as the panel blank from Schempp Hirth. It's made out of about 6 plys of Rutan 7725 bid cloth that I had lying around (a decent cloth, but surely not what Schempp Hirth used) and US Composites laminating epoxy which is quite a bit lower grade than the MGS epoxy the factory used. I'm sure also mine has more air bubbles than what the factory made.
One of the shops suggested I bring that and do a trial cut and see how it turns out. My guess is if it would cleanly cut a laminate with weaker epoxy and worse craftsmanship, it'll probably cut the real thing well.


Sorry I was just taking about CF with soembdy else and got my wires crossed..

Yes try a test cut, but this is something that I'd hope whoever you go to either water jet or laser has some experience with this. Laser will likely scorch up fairly badly on the edges, but you can usually sand this back with wet and dry and get a nice smooth (if darkened) edge... that is what we are doing with G10 at the moment, a little sanding with 600 grit wet and the edges are great. We could probably tune down some of the scorching by playing with laser pulse settings etc., but it's not worth the time. Smaller shops/those not set up for it may not want to cut fiberglass composite sheets becasue of fumes from the epoxy.

A "low-tech" option is to laser cut a template (e.g. 1/4" clear acrylic sheet) and then use that as a router template with solid carbide router bits intended for fiberglass (Whiteside make some nice ones).

Again, my first choice would be waterjet company with some experience with this. Although I love laser cutters as it's so easy to cut quick cheap tests, e.g. in corrugated cardboard.

If you use a hole saw (Lowes or Home depot variety) you can get really nice results if you do a couple things.

1. Buy a hole saw holder with the replaceable center drill bit. Remove the center drill bit and replace it with a (seems like 3/16 or 1/4") smooth rod. This helps avoid the center drill from oversizing the guide hole as you go.

2. Drill the center hole with the appropriate sized drill bit first.

2a. Make a template for the 4 screw holes that centers off the center guide hole. Drill the screw holes before you cut the 2 1/4" or 3 1/8" instrument hole.

3. Once you switch to the hole saw with the smooth rod center guide, place the panel on something like a 2 x 4 with a matching 1/4" hole to keep the hole saw from torquing out of position as the cut starts to make it's way through the last bit of the panel thickness. You may need different shapes of 2 x 4 if you are cutting holes in a corner of the panel.