Backfilling engraved frontpanels

[MasonAtom]

[quote author="nrgrecording"]My calculator says 2mm/s feed for the X/Y axis with 6000 turns/min for a 0.2mm tool. (my feedrate is 12mm/s but with a highfrequency spindle)

For engravings you shoud use a Minimal Quantity Lubrication. Or at least put ethyl alcohol on the panel. Thats important. You'll get much better results. If that don't work try to engrave in two steps... 0,1mm and then another run with 0,1mm again to achieve 0,2mm.

If your engravings have a different width on the panel you either need a mechanical or an electronic device which regulates the z-height. If you're doing the cnc program manually with G-codes its probably not that easy to engrave some text deeper when they're not deep enough at the first run. A cad/cam program would make everything much easier. :wink:

Whats the type/name of your cnc machine?

Good luck!

Frank.[/quote]

Frank,

I am using a Hass Tool Room Mill. The max spindle speed is 4000 rpm. I'm using NCPlot to generate the g-code and I can vary the Z-depths easily to achieve different line widths.

I picked up a few new bits - one is 60 degrees, 1/4" down to 0.02" and the other is 30 degrees, 1/4" down to 0.01". I've tried the 60 degree bit and got pretty decent results. There are still some burrs left, but not nearly as many as before when I was using an old dull bit.

To de-burr I've gone through and scraped out the chaff with an exacto knife. This works OK, but is relatively labor intensive.

What kind of paint do you use to backfill the letters? I've tried a bunch of different things and my best results so far are with model airplane paint believe it or not. It flows pretty well out of a syringe and it is easy to dissolve the run-out if you make a mistake. How much does the vacuum-fitted syringe apparatus cost? It would be nice to do this without having to worry about the occasional paint bubble...

Thanks for your help thus far... it has been a lot of fun learning about engraving.

Mason

 

[nrgrecording]

Hi Mason.

Check some other bits. Try to get some tools which're made for aluminium not for steel or ply. Engraving bits have different back rake angles. For aluminum it is 35°. (astralon, celluloid or plexi is 45°).

The ToolRoom should work much better than cheap hobby mills and the engravings should be free of burrs.

The paint iam using isn't always the same. Iam using different brands and types of paint. They all work. You can buy special nitro-laquer from the engraving shops or just car paint. Both works. But your engraving depth should be at least 0,2mm if you're using a 0,2mm engraving bit and all other engravings should be at least 0,4mm. Airplane paint should work, too. If you need to use thinner for the paint... use the right one for that. If its nitro laquer.. use nitro thinner.

The dosage apparatus costs about 800€. Maybe you can buy a used one for cheap somewhere. They can be used for cyanacrylate glues, too.
But... iam sure it will not look 100% good as long as you don't have a surface free of burrs. Did you use engraving bits made from solid tungsten carbide?

Frank.