Mask releasing with heat

With regards to my question this is related to CNC but I thought it may be better suited for the sign forum..

We have been running a bit of work cutting through various masks but a good bit of 813. Some of this has been shallow v-groove over maple, walnut, poplar, and other raw woods (no clear applied, mask straight on the raw wood). I notice when watching the cut that you can see small blisters appear beside the tool from the heat causing the mask adhesive to release. At times we are also not getting a nice sharp cut through the mask. It will tend to be slightly jagged at the edge.

We have been applying the mask, burnishing it down with a squeegee, and tried running various feeds and speeds (pretty fast is our default as the slower you go the more the blister/jagged seems to be). I havent tried an air jet which I thought may keep the whole process (mask and work piece) cooler..

Not a critical issue. We are getting along with the work, but trying to refine.

Thanks

What's your feed rate? RPM? Bit type?

I've never used 813. I've used Avery and Gerber. My guess is one of two things are happening.

1. You're not laying down the masking as smoothly as you think you are. There's air trapped and that's what the bubbles are from.

2. You're not letting the mask sit long enough before going to the router. After some early failures, I've found giving everything more time is the solution to most of my problems. Laying the mask and going right to the router didn't work well for me. Putting the mask on and letting it sit for an hour or so and then going to the router ultimately benefited me. Just like painting and waiting 24-48 hours after the last coat made a huge difference between just waiting 12-18 hours.

I'm surprised that the mask sticks at all to raw wood. I would put on at least one coat of whatever & sand it smooth enough to get good adhesion,
I would also agree with everything Ross said.

Thanks guys. Never dawned on me to let it sit a bit and I will check to make sure Im getting it as tight as I can. We do run it over finish quite a bit and tend to see the same issues. This is usually when running a Vbit, typically 22-24k RPM doing very shallow v-carving with only a bit of the tip engaged. When you watch the carving closely you can see the mask release right around the cut where the heat is generated. Undoubtedly chips/dust are getting under there as well. The cut is not super sharp either even with a brand new insert. Of course down there at the tip there is less and less cutting action.

Mark, what about running at a slower RPM to potentially reduce heat?

Is it a certainty that heat is the problem?

I use Oracal 813 directly on unfinished wood as a standard practice. I have cut hundreds of pieces that way. It works just fine under most circumstances. The level of detail I can achieve using this technique on fine engravings still surprises me sometimes. The real problem is getting it off without using abrasives. Weeding can be time consuming.

Quote:

---

Originally Posted by Rodger MacMunn

I'm surprised that the mask sticks at all to raw wood. I would put on at least one coat of whatever & sand it smooth enough to get good adhesion,
I would also agree with everything Ross said.

---

Will give some slower RPMS a shot. The releasing is not in large areas but you can see the mask lifting immediately adjacent to the cut in real time.

I don't have a cnc but have run into a similar situation with the laser. My solution is to use a small wall paper roller to apply more pressure to the engraved area. It helps.