V-carving clear plastic

[Chuck Keysor]

Hello Shopbot friends:

I tried to V-carve a simple sign on some clear plastic someone had given me. I don't know what type of plastic it was, as the cover paper had been removed, and I have never cut clear plastic. (My guess is that it was something that would be purchased at a local hardware store for storm window replacements.) The plastic was 1/4" thick. I used a 60 degree "laser" bit, at 1.5IPS, and 12krpm.

The first letter turned out OK, but after that, most, if not all were ruined as follows: Plastic re-melted and stuck onto the point of the bit, forming a disk, that scrubbed and melted the surface of the plastic on both sides of the carved text.

When the bit would lift to make a move, I used a thin piece of wood to knock off the disk from the tip, but in a few seconds, a new plastic disk had formed on the tip, and it resumed scrubbing/melting the surface on each side of the V-groove. When I was done, I had maybe 20 little plastic disks laying on my machine bed, some as large as a quarter of an inch in diameter.

My first guess is that if the original protective sheet of paper had been in place, that none of this would have happened. But that is just my guess. Are there other issues here that would have condemned this experiment to failure?

I'll upload pictures later, but I hope my description is sufficient for some basic feedback.

Thanks, Chuck

[jerry_stanek]

If you spray it with some dish detergent before you cut that will help a lot

[Chuck Keysor]

Thanks Jerry! But what I forgot to mention,,,,, duh,,,, is that I have a second piece of this exact same material, so I don't want to mess THAT one up. And, it is exactly the same as the piece that I wrecked yesterday. Thanks, Chuck

[tlempicke]

There are lots of different kinds of plastic. Some cut pretty well and some not so good. Plexiglas can be either cast or extruded, and that makes a difference.
Don't be chicken with the cutting speeds. You have to be taking chips and moving right along to keep the bit cool.
One of the guys who shows up regularly at the Spring get together in Columbia SC has done some beautiful 3D carvings in plexi and edge lighted it with LED's. Really stunning work!

[Burkhardt]

Make sure you blow the chips off while cutting. If they accumulate in the grooves they are being re-cut while still warm and just melt on. The air stream may also cool the bit but I am not sure if that is substantial.
Maybe you can try some speed settings with the part that you already ruined. And make sure the v-bit is REALLY sharp.

[Chuck Keysor]

Thank you for your added input. I did move slowly, and did get small chips, which you can kind of see in the blurry photo (sorry, $40 digital cameras don't seem to work very well.......) But when originally experimenting with V-Carving, and reading posts, 1.5IPS is about as fast as I can go.

The blurry picture with the tape measure also shows some of the little disks which I kept flicking off of the tip of the V-bit.

The second picture shows the over-all sign, and ignoring all the chips and dust on the plastic, it shows how the disks scrubbed/melted the plastic on each side of the V-carving....

As I'm giving the sign away, I don't want to go buy the right material for this job........ However, what type of plastic SHOULD I be using?

Also note, I reverse cut this, IE, I cut it on the back side with reversed text.

Thanks, Chuck

[Chuck Keysor]

This is what I wanted the plaque to look like after painting. (Reverse carved on the back side, letters infilled, then the entire back side painted white.

Years ago, I had used a hand router to reverse carve letters on the back side of a piece of plexiglass (or something,,,, it too was free), and it carved well, and looked fantastic when viewed from the front side.

Chuck

[cnc_works]

I fairly confident that your issue is what tlempicke mentioned. You are describing classic problems with trying to cut extruded acrylic. I ran into this early on and learned fast to only cut cast acrylic. Good Luck!

[Tim Lucas]

Hello Shopbot friends:

I tried to V-carve a simple sign on some clear plastic someone had given me. I don't know what type of plastic it was, as the cover paper had been removed, and I have never cut clear plastic. (My guess is that it was something that would be purchased at a local hardware store for storm window replacements.) The plastic was 1/4" thick. I used a 60 degree "laser" bit, at 1.5IPS, and 12krpm.

The first letter turned out OK, but after that, most, if not all were ruined as follows: Plastic re-melted and stuck onto the point of the bit, forming a disk, that scrubbed and melted the surface of the plastic on both sides of the carved text.

When the bit would lift to make a move, I used a thin piece of wood to knock off the disk from the tip, but in a few seconds, a new plastic disk had formed on the tip, and it resumed scrubbing/melting the surface on each side of the V-groove. When I was done, I had maybe 20 little plastic disks laying on my machine bed, some as large as a quarter of an inch in diameter.

My first guess is that if the original protective sheet of paper had been in place, that none of this would have happened. But that is just my guess. Are there other issues here that would have condemned this experiment to failure?

I'll upload pictures later, but I hope my description is sufficient for some basic feedback.

Thanks, Chuck

Hello Chuck

I am not familiar with a laser bit - is it for cutting plastic? I have not cut much plastic but I did purchase a good quality bit just for plastic and that made all the difference.


Tim

[steve_g]

http://www.ebay.com/itm/like/1221517...&ul_noapp=true

CMT makes a 3 flute 60° bit that comes to a true point and market it as a laser point bit. IMHO, it’s the best V-Carving bit made!
On the down side, however, I haven’t found anyone who can sharpen them to original glory…
SG