Engraving plastics

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eefits
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Re: Engraving plastics

Post by eefits » Tue Mar 31, 2015 2:14 pm

aarvidsson wrote:I agree completely. Trouble is, I'm trying to engrave a very thin line, so larger tools kind of defeat the purpose :)
If your are engraving, adding water while engraving will not get to the spoil board. Here is what I did. I use those winter sealing tape for the door. They are about 5mm thick. I tape around the edge of the board. That will contain the water. I tried a lot other method (feed rate/different bit) only added the water consistently giving me good result. By the way I am using single flute 2mm end mill running 200mm/min @8000rpm and it cut clean and does not melt.

aarvidsson
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Re: Engraving plastics

Post by aarvidsson » Tue Mar 31, 2015 4:14 pm

Apart from water droplets everywhere (to the great amusement of my cats, I might add), the result was unfortunately the same :(

I might simply have to bite the bullet and look at mounting an engraving tool instead. What is the difference, by the way?
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PAPPP
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Re: Engraving plastics

Post by PAPPP » Tue Mar 31, 2015 4:55 pm

Someone mentioned these earlier in the thread, but I'll voice support for the idea, I've had better luck engraving with spiral-ground engraving tools than simple V-bits, take a look at the Kyocera Tycom offerings for example, a while back I found a set of 10 of those, two each at five different angles from 30° to 120° (I've only destroyed two so far...), though I can't find anyone selling such a set right now. Definitely prefer carbide tooling. I'm usually not cutting quite as deeply as you are, but I've managed to do delicate things like putting patterns in the clear tops of cheap polystyrene CD jewel cases without cracking or melting.

I had a project doing fairly fine-tolerance cutouts in .060" HDPE sheet (To mount cherry keyswitches) I was working on a few weeks ago that I could _not_ get acceptable clean-edged cuts in until I gave up and got some single flute bits, after which it was easy, so I'm currently believing in blaming tooling ;).

My other thought: What are you using as a spindle? The things that might get you here are runout (the side whipping out will generate heat and a ragged edge, making the whole cut ugly), and that you want your spindle to be going stupid fast, IIRC the little commercial electric engraving tools tend to be spinning at 7000-7500RPM.

Hans
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Re: Engraving plastics

Post by Hans » Tue Mar 31, 2015 5:04 pm

I believe the other type of engraving tool mentioned is not rotary, but rather reciprocating/vibrating. They are for marking not cutting, but if your goal is just to draw lines they're a good solution.
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aarvidsson
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Re: Engraving plastics

Post by aarvidsson » Wed Apr 01, 2015 7:07 am

I've got some Kyocera unreasonably sharp engraving endmills on order from drillman1, I'll report back how those will work out. I'm using a quiet cut spindle equivalent, so I can run it from stationary to fairly high speed (20.000 RPM?) so I don't think that's the problem (or at least I hope it isn't :P)
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aarvidsson
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Re: Engraving plastics

Post by aarvidsson » Thu Apr 02, 2015 5:00 pm

Turns out that "painting" WD-40 on the surface that is to engraved helps enough that then using a piece of plastic or similar rigid thing to scrape off the plastic that gets stuck in the engraving lanes gives excellent results :D
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Brian Stone
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Re: Engraving plastics

Post by Brian Stone » Thu Apr 02, 2015 8:44 pm

aarvidsson wrote:Turns out that "painting" WD-40 on the surface that is to engraved helps enough that then using a piece of plastic or similar rigid thing to scrape off the plastic that gets stuck in the engraving lanes gives excellent results :D
Interesting find. I wounder if natural oil, just bare mineral oil, would work as well, since it's basically WD40 without solvents.
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Re: Engraving plastics

Post by PAPPP » Thu Apr 02, 2015 9:33 pm

It could be the mineral oil lubricating, it could be the light hydrocarbons (mineral spirits/naptha) vaporizing and carrying away heat, it could be a combination thereof, the penetrating spray/WD-40 type substances are sometimes dual-acting that way.

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