V-carving clear plastic

[steve_g]

Chuck...
The swirls on the bottom of the cut are exactly what you should expect with this bit… it’s not a bottom cutting bit! A better finish can be had with a “FEM” style bit, flat across the bottom… at least in wood, not sure about plastic.
SG

[Chuck Keysor]

Thanks Steve! It is good to know that the cutting marks I got are not from some defect in my machine.

I used that bit because I had purchased it after seeing that it was recommended for cutting aluminum. But I hadn't gotten around to cutting the aluminum yet, so I knew the bit was sharp.

The bad news is that the on the aluminum that I plan to cut, I need to have a clean bottom cut! (Not to digress from my own thread, but should I plan to cut my aluminum with the Amana O-flute bit, and then clean it up with a different bit OR cut the aluminum with a different bit that will leave a smooth cut on the bottom?)

Thanks again, Chuck

[Chuck Keysor]

Hello Shopbot friends. I finally installed the carved plastic sign which I had discussed earlier in this thread. I tried to get some up-close pictures, but this camera's macro function is shot/junk.

Even though there were lots of machine marks on the bottoms of the grooves, (cut with a fish-tail end-mill, doing a profile cut "on-the-line"), as soon as I filled the grooves with black oil based paint, the machine marks disappeared! I got lucky for once. But there are machining irregularities on the sidewalls of the cuts, which in places make it so that all of the straight lines of the letters, are not as straight as they should be......

After filling in the grooves with black paint, and then letting that dry, I painted the back with white paint. When I held it up to the light to inspect the final work, I was chagrinned to see light shining through. So to fix that, I put on two heavy coats of grey paint on top of the white paint. It actually turned out OK, considering it was made from plastic I got out of the dumpster. But by the time I was done, I think I spent about 5 hours in total.... which is a bit disappointing.

Chuck

[Xray]

Hey you spelled Property wrong !

No just kidding, looks nice.
I learned early on that light will shine through in spots that the eyeballs cannot detect so I always overcoat, usually once one way, when dry another coat cross wise, then a 3rd coat for good measure.

Choppy lines, outside of whacked nodes, can be caused by either a dull cutter, too high feed speeds or both.
Improper holddown and machine flex can also be factors.

[Chuck Keysor]

Yikes! You really had me fooled there on the property spelling! I am one of the worst spellers, so I could have easily spelled something wrong. But my reflexes instantly passed the buck, as I sent the text to the fire fighter's union steward to get his OK before I cut anything. Then I read the next line, and saw your just kidding line.

Thank you Doug for your kind words, and the good laugh!

I may have had some hold down issues, as I don't have a vacuum hold-down, and the plastic, though held down securely on the perimeter by mechanical clamps, had some crowning in the middle, and I was too lazy to take the part out and flip it over, figuring it would just give me varying depths of my on-line profile cut. But since I couldn't get a good close-up, I have forgotten exactly what the cutting irregularities actually looked like.

It was funny, as just the other day on the Aspire forum, someone complained that when he tried V-carving plastic, he got little plastic globs. Someone else had already replied that an on-line profile cut with an endmill would provide more satisfactory results.

Thanks, Chuck

[8Ball]

For a sign like that, i probably would have used color core since there isn't any painting required or as suggested, Corian. Corian is inexpensive for smaller pieces and is very easy to work with. I make plaques and signs similar to yours and it only takes an hour at most, total time for the sign using Corian.

[Chuck Keysor]

Thanks 8Ball. Other than wood, I do my experimenting with junk/scrap free stuff.

I do however, have some nice white Corian. But it has a glue-up to double the thickness on the edge for a big bullnose, and a lot of particle board glued onto the bottom. It seemed like a lot to clean it up to use for a free sign, so I chose the clear plastic figuring it would be more direct......... I guess I was wrong!

But there is something nice about the clear plastic with the engraving on the back side. The smooth exposed front looks good, and the fact that the letters seem to float inside the plastic is also appealing.

And I learned that V-carving low-grade clear plastic is not likely to work. Also, this was my first time doing on-the-line profile cutting for lettering, as I had always just done V-carving for lettering before. So I learned something there too.

Thanks, Chuck