Plexi Engraving Basics

[M2@ASI]

I need to experiment with engraving edge-lit plexi but have little knowledge about
it. I have run a few basic tests already using a conical engraving bit with feedrates
ranging from 60 to 180 ipm. I continue to run into problems with chips welding into
the grooves. Can anyone give me some basics about how to approach this particular
substrate, or point me to any online resources? Is some form of cutting fluid helpful
for this application? I don't have a mister or automatic lubricator, can I spray or
wipe the substrate with something before I begin, or manually mist it during cutting?

Any tool, feed rate, spindle rpm or other recommendation that I can base my efforts on
would be much appreciated.

Mike

[bebob1]

what rpm, depth of cut, feed are you using? vertical machining CNC?

the idea is to make the cutting edge take big bites into the plastic to make bigger chips than say cutting aluminum. this is relative depending on rpm and feed. so a suitable low rpm and high feed is a good start. Some spindles can only spin fast, which means your feed needs to be very high. High feeds can suffer accuracy issues for small features with sudden change of direction (like right angle motions become rounded) if motion acceleration cant match g-code without enough dwell time. An obvious tradeoff can be understood here. Sharp tools should be used that are dedicated for plastic (dont worry if you dont mess up the tools will likely last a very long time). Some say zero helix cutters are good. Ive seen some amazing plastic roughing cutters that can do depth of cut 2X the diameter of the tool and still come out ok.

Good old fashioned water maybe with some detergent in it (dish soap) under full flood cooling conditions is best. Often this may mean you cant use your flood coolant system if it was rigged to use some oil based coolant. For vertical machinig you can often just pour some water on a large flat stock if you are just cutting 2.5D stuff. Stuff held on a vice may require flood coolant with a nozzle and coolant flow.

Ensure good chip evacuation to prevent chip rubbing (!) and recutting that generates a lot of heat. Maybe play around with your depth of cut. Lower it for better results.

[shearder]

I think what would be REALLY awesome is IF the people asking for assistance or advice actually came back and said it what was told actually worked or it didn't.

So M2@ASI--- did it work? OR did you find a better solution??

[tommylight]

I think what would be REALLY awesome is IF the people asking for assistance or advice actually came back and said it what was told actually worked or it didn't.

So M2@ASI--- did it work? OR did you find a better solution??

#M2@ASI is MIA ????

I do agree with you, i read his post and thought of putting my 2 cents in since i did a lot of edge lit plexi lately and i had no problem at all( i honestly had much more problems cutting the damn thing with a circular saw ).
A bit of patience and experimenting with different settings can make life sooooo much easier.

Regards,
Tom

[shearder]

#M2@ASI is MIA ????

I do agree with you, i read his post and thought of putting my 2 cents in since i did a lot of edge lit plexi lately and i had no problem at all( i honestly had much more problems cutting the damn thing with a circular saw ).
A bit of patience and experimenting with different settings can make life sooooo much easier.

Regards,
Tom

Hey Tom

What settings do yuo find work best with perspex/plexi/acrylic? I would assume al 3 have different properties? Do yuo mist or wet while cutting? I just heard to cut on a slow speed so that it doesn't heat up - but that would seem normal as there is friction at any speed but i guess it should be slow enough to not melt...

[tommylight]

Hey Tom

What settings do yuo find work best with perspex/plexi/acrylic? I would assume al 3 have different properties? Do yuo mist or wet while cutting? I just heard to cut on a slow speed so that it doesn't heat up - but that would seem normal as there is friction at any speed but i guess it should be slow enough to not melt...

Hi shearder,
For backlit plexi i use a speed of 1450 rpm and a feed rate of 600mm/min (24 ipm) with a home made end mill ground on a tip of an M8 screw!!! On 10mm thick plexi i do about 1mm deep cuts, on thinner material i do normally only 0.5-0.7mm.
I do not use any lube or water, nothing just slow and easy.
Regards,
Tom

[fixtureman1]

First off make sure you have cast acrylic and not extruded. Extruded will reweld and will not give as good a cut as cast.

[shearder]

Hey guys, thanks for the responses and tips. Much appreciated.
When I cut this stuff I'll make a note to use this info

[shearder]

Just some feedback - I cut some Perspex this weekend. I used a 3mm - 1/8" carbide 2 flute end mill @ 8000RPM and feed @ 200mm/min or 7.9IPM. It was nice clean cuts.

I cut two ways i ran it in 2 passes on 3mm Perspex to a depth of 3.8 and alsop a single pass at the same speed. Both gave good results but I am leaning toward doing 2 passes to ease the strain on the tool and it LOOKS slightly better.

i used NO coolant or lubricant.