Engraving turret knobs (anodized/coated aluminum)

[Huckmeat]

I retrofitted a bridgeport and use autocad and bobcad to produce 3d drawings for parts I make. I'm debating adding a 4th axis, as I want to engrave marks and numbers (small) on the perimeter of custom knobs for my shooting optics - I'd be engraving/etching on small (1.2-2" diameter) aluminum cylinders, typically etching 100-105 lines along the outside perimeter, typically with a number at each line.

Is a laser etching machine the right tool for this, or should I work on getting a 4th axis for my bridgeport and trying to do it with small engravers (my spindle goes up to around 4500rpm is all).

If a laser machine will do this, what's a good machine for 'home' use? I'd probably only do 3-5 knobs per year, but it's a precise and specific enough thing that I'd have a hard time outsourcing it and being sure it was done right.

Is building a rotary axis to turn the part for one of the cheaper chinese lasers the way I should go?

Thanks in advance,
m

[bpoulin]

Anodized aluminum or bare aluminum? If it's anodized then the laser will work, if not then you'll need an etching cream or spray to etch the aluminum. And if you're only doing 3-4 units a year, you really would be better off outsourcing it. Because a unit large enough to have a rotary device would probably be in the $3k range. So unless you would have other uses for the laser I would outsource. Now that said, you can do tons of things with the laser, so maybe consider what other uses you could have for the laser, and it might justify the expense.

[Huckmeat]

Thanks for the reply!

The knobs are anodized or ceramic paint coated.

I was thinking I could machine my own rotary and manually operate it - turn the turret 3 degrees, engrave, repeat. The problem is that the pattern and markings are very specific to altitude, temperature, and a specific piece of equipement, so each knob ends up being 100% custom - I'm afraid trying to ourtsource it will just be full of headaches getting everything aligned up. In this case, a small desktop style machine might work, with my own rotary holding the component to be engraved.

If I was to outsource it, what type of format would communicate my markings and positions to a potential engraver efficiently? (cad?)

Thanks again.

[bpoulin]

If I were your engraver, I would prefer the image to be a vector image (.ai or .eps), this can be exported from a cad program. I can use cad files, but they take a bit of cleaning up before I can use them. The 2nd thing would be the image needs to be flat, confusing I know, but think of it as a wrap, you start off with a flat image that wraps around the work piece. Again I can work with a 3D cad file, but it will take time for me to transform it into a flat image my software can work with. As I'm sure you're aware, time=money when it comes to small projects. The reason it's difficult to find a low budget laser with a rotary is because of clearance issues. The smaller compact desktop lasers generally don't have room for rotary device between the table top and the laser head. The up/down clearance for the table is a few cm the slightly larger machines have more up/down clearance allowing for a rotary device.

[Huckmeat]

Thanks again! My input right now is a 300dpi .png file that is designed as a wrap - This file is generated by a perl script that parses hundreds of lines in a table and takes a few dimension of the knob and produces a flat image - Which I currently print and wrap around the knob with some scotch tape - It's not terribly durable, and because I need to leave room to see the marks on the knob already, I have to print everything smaller than I would like.