Melting Acrylic during engraving

[deezee]

So I'm just having a play with the stock machine until some other parts turn up (chinese quiet spindle etc) so I'm using the generic dremal that comes with the kit. I have a V Bit I'd like to engrave with on acrylic, but during a little test it just leaves melted material is the cut groove (400mm/min speed, 75mm/min plunge, dremal thing on speed 4). Anyone got any tips?

[bharbour]

On ABS plastic with the stock 1/8" 2 flute bit that came with the unit I used 3 in/min with a .01 inch plunge depth. Any faster than 5 in/min and deeper than 0.05" plunge I got melting. That's super slow, but it worked great. Let us know how it goes...

Oh...and I slowed the spindle down to the slowest speed.

[Improbable Construct]

Acrylic is tricky. Its easy to crack it and its easy to melt it. What you have to do is find the "just right speed" If you are going too slow the bit is just rubbing on the acrylic and creating heat and melting. If you are going too fast, the material will jam in the bit and then rub and create heat. So its really about finding what works for your machine, spindle, and bit. Acrylic also comes in two flavors cast and extruded. The cast acrylic is usually covered in a paper backing and the extruded is usually covered in a clear or blue plastic. The extruded stuff is a nightmare to work with.

[deezee]

Thanks guys. I've slowed it down a little and put in 2 passes. That seems to have cleared a lot of the build up. Its all experience hey!

[Nigel K Tolley]

The issue with exuded is it wants to cut properly at a different speed along the extrusion axis, than the other.

Whatever speed you pick won't work well to cut a circle!

[eefits]

I was having the same kind of problems until i squid a puddle of water covered the design. Engraving is just one pass it should work good. I have good experience with this method cutting profile up to 10 pass. With that you kind of need to siphon off the water with the chipping and put fresh water until it is done.

[HPGreyling]

[https://www.dropbox.com/s/z7w9ezlv5vd5n ... 4.jpg?dl=0][/img]

I did the above on extruded. 2straight flute, 400mm/ min feed and 100mm Plunge. 0.5mm depth. Speed was fastest on the quiet spindle

Must admit I had to play around a lot before I got it right.