Speeds and feeds come from the chip load specified by the tooling manufacturer, if you get generic stuff, see if you can find the chip load for a similar tool elsewhere and use that.
I definitely need to do some work on the tooling and speeds and feeds. I broke the tips on my engraving bits, Iām thinking I need to be way more conservative on the feed rate. The engraving bits I used do seem kind of delicate, reading around maybe using a spot drill bit might be a more robust option.
Either way, it cleaned up nicely with a bit of filing, wet sanding and buffing.
I coloured the letters with some spay paint and then sanding off the paint that wasnāt in the grooves.
Those cuts didnt go as well, ie the very tip of the bit broke of almost immediately. At that point I changed the āflat diameterā to roughly approximate the new/broken tip and re-ran the cut, which went ok although it didnt seem to do a very clean a job of cutting the letters.
I guess I kind of makes sense, the v-bit cutting surface is basically 90 degrees to the surface being cut so probably doesnt cut as well as the end mill.
None of this seemed to be stressing the machine out at all.
Potentially a naive question on my part here with regard to the way you added spray paint to the brass.
I have seen videos for wood projects where a āmaskā has been applied to the wood with the design cut through that surface into the wood. Paints/ epoxy fill used to colour the design that has been cut, then the mask is removed so only limited (if any) sanding is required to tidy up the design.
Would that process work on brass too ? I have a long term project in mind where I will make a memorial trophy shield/ plaque where it has a brass plaque like the one you have make in your project giving the pertinent details of the trophy and why it exists so I was interested to read of your process and the outcome. Wondering whether the mask process would work, while I contemplate the multitude of other projects I have on the go before I become a member and get anywhere near this !!
It might be worth a try. The brass stock a got did come with a plastic film on it. Whether that would be cut cleanly enough by the cnc machine to work as a mask Im not sure.
If you could avoid sanding all together you might be able to use polished brass stock and you could avoid the polishing step altogether, which would be a bonus.
Although this might be a bit optimistic as, for me, the CNC machine did leave burs around the cuts it made, these needed to be sanded off too. This is hopefully something that can be improved upon by tweaking the feeds, speeds and tooling.
Like I say definitely worth a try, you can always go down the sanding and polishing route if it doesnāt work
This time I used epoxy rather than paint to fill the engraving which looks pretty good.
For fixturing I super glued the brass stock to a bit of sacrificial perspex, I was able to remove it using an iron to heat up the brass and soften the glue. That really worked well!
