So today I made my first attempt at both cutting plastic and cutting multiple parts from one sheet on the Pro 5. Think of it like an IT smoke test. I knew I didn’t have the best setup I wanted to see where it would fail, without being unsafe. Now I’m coming to the experienced folks to help me do it right next time.
I wanted to make custom cover plates for some of my guitars. These are made from 3/32" to 1/8" plastics - ABS, PVC. I’m not so well versed in plastics and suppliers don’t always say what your’e getting. I’ve always made these on a router table just as I’d cut woods with no problem. There with some basic safety workholding precautions, it’s pretty trivial to make an MDF template then bandsaw a piece a little oversize, attach with double side tape and machine it face down on the table with a flush trim bit.
So I tried cutting these 6 parts out from a 12" x 18" sheet using the #201 end mill. First attached an auxillary spoilboard to the table with two sided tape and cut this outline in it shallow. Then I attached the sheet with 1"x1" squares of ds tape at strategic points - corners of cuts, either side of the ramps in and out, and such The first two cut out perfectly at 70in/min 19000RPM default setting. On #3 the ramp out and retract pulled the sheet up and trashed that piece. I did some reading and decided 14000RPM was probably better. I managed two get two more cut out cleanly but two more were lost separately when the sheet pulled up midway through. It was impossible to realign it perfectly so they got misshapen.
I’m used to cutting large individual 7/8 to 2" thick boards weighing anywhere from 1 to 8 lbs which are no problem to hold down with double side tape and resist cutting forces. I don’t have a good strategy for workholding thin lightweight material short of buying or making a vacuum fixture.
For starters I know I should use an O flute bit so please give me any recommendations you have on tooling and workholding to do this better. Thanks!
By the way the ones that did cut out trouble free have crisp edges and I had no problem drilling narrow through holes and scribing a logo on them held down this way.
Use double sided tape under each piece to hold them when they are cut free. Screws in between the pieces holding the plastic sheet to the sacrificial auxillary spoilboard to help keep the plastic from lifting. I would clamp the auxillary spoilboard down.
If issues persisted, I would try clamping a thin piece of rigid wood over the entire piece of plastic and cut through the wood and plastic leaving tabs. For this approach, you would have to engrave the logo’s when the plastic was being held by double sided tape alone. Then add the wood over the plastic to cut the pieces free.
I have used a similar appoach to make stencils out of double sided tape by sandwiching double sided tape (stuck on wax paper) between two pieces of wood. Once cut, I removed the completed stencil from between the sacrificial wood, stuck it to metal, and painted.
Cheers.
Thanks that’s great advice! I’ve looked at screws for other holddowns. I tend to go down a sight rabbit hole. Ideally it would be machine screws and threaded inserts, therefore I’d need a program to drill those holes before starting without hitting an insert. I’m trying to make everything reusable (non-sacrificial) if possible. Next time I’ll try wood/metal screws directly to the MDF in those waste gaps and see how that goes.
The shield clamp layer is a very clever idea. I’ve clamped stuff that way but never thought to cut through it. I think its my cheapness again not wanting to sacrifice material lol, but if it saves a pricier sheet its worth it. The engraving worked with no issues that time so that sequence could work.
Thanks. I’m using a bunch of IDC bits with good results. I know folks here use the C3D O Flute bits for plastics and there are a few Amanas I’ve had my eye on to do some acrylic projects too.
An approach to holding thin stock is one I saw from the Woodsmith magazine folks Chris Fitch had a CNC base camp series (available on YouTube I think) where he cut thin brass and had a slick holding method. He took a sacrificial piece of mdf and used a thin coat f liquid hide glue to glue the thin brass stock down. He proceeded to cut the pieces. When done cutting dumped the parts in a bucket of water overnight which dissolve the liquid hide glue and released the thin parts with no prying
Thanks. That’s truly a novel approach. I haven’t used glues for workholding (or template holding) much because most of my projects are double sided wood. I’m always worried it will be impossible to separate without taking grain with it even if its masked. Some woods even the two sided tape pulls fibers off. But not a problem on plastic. I’ll look for those videos.
i cut a lot of thin plastic parts (between 2-3mm) out of resin and acrylic. Best method i’ve found is blue painters tape and ca glue. I tape off the entire bottom of the sheet not just in a few areas. Then tape off a surfaced flat piece of sacrificial MDF. 1 drop of glue every inch or so. Never had it pull up ever.
Thanks. Do you have a preference on the CA glue or will any hardware store brand do?
Surely I overthink this after working in a draconian shop that kept CA glue locked away after some mishaps. Picture someone pointing compressed air the wrong way near an open bottle and a $1000 custom order getting instant bonded to a workbench…
I’ve tried just about every major brand of water thin grades for crack repairs and inlays. Those are nearly instant bond. One shot to get it in the right position which is hard with big sheets
