View Full Version : Help needed on small curved steel caps with cermark

Patrick McCoy Arkansas
01-26-2017, 2:23 PM
Ok, so I've tried searching posts but unable to find a decent solution.

I have an order of laser marking hundreds of 1.5" diameter, stainless caps, on the side. The rotary attachment is not much of an option as 1. the size of the cap is really too small to use the rotary and 2. if I could rig it, the time would be insane.

I took the time to build a jig to line up a number of the caps and had the hopes of finding a happy medium of my focal point to get the highs and lows of the curve. The design is .80 of an inch in width across the curve. I cannot be positive to the depth difference for the high and low points, I believe I'm about 3mm from the center high to the edge lows. Is this depth difference too much to get good results from the highs and lows? or is there any other way I can give myself a larger sweet spot on my depth?

Mike Null
01-26-2017, 2:56 PM
As I understand you the job would be similar to engraving on the edge of a silver dollar. If that is correct, I would attempt to rig a jig on the cone of the rotary device that would hold the caps. On mine I would probably use a laser cut disc of wood mounted with engravers tape. With a little luck your cap will be magnetic and you can fasten a magnet to the wood which will rotate with the rotary cone.

The diameter of the coin must be carefully measured and entered into your software and maybe your machine depending on what you have.

If this doesn't sound like something you want to try then focus your laser at the halfway point of the arc and give it a try. (1.5mm)

Gary Hair
01-26-2017, 3:00 PM
3mm each way, 6mm total, is probably too much for you to get good results unless you have a long focal length lens - 4" might work. Even then I think you would have trouble at the extents of the focus. How about making a fixture to hold them for the rotary? I'm envisioning a piece of pvc pipe with a channel cut out that fits the size of the engraved area. If you could gang up enough of them at once it might work out pretty well.

Kev Williams
01-26-2017, 3:01 PM
first of all, if your rotary is a chuck style, then use it. If you have to Macguiver up some way to hold the caps, it'll be worth it in the long run--

If not, then working flat--

You say you're engraving spans .8" across a curve of a 1.5" diameter. With Corel you can easily caluculate the depth drop-

first, 1.5 x pi = is 4.71", you're using .8" of that.... .8" / 4.71" = 17% of the available space. 17% of 360 means you'll use approx. 61 of rotation...

Now we go to Corel and draw a 1.5" circle. Then we figure out how much of it 61 is, so I draw a line from the center of the circle to the top-
then I rotate both 61- then I draw another line up- then rotate it all back 30.5...

this is the graphic--

EDIT---I was measuring the wrong size of circle, not sure how that happened!? Below has been edited too...

Now we know exactly how far around your engraving will be. I put a guideline at lowest points, at the edges of the engraving area.
The top of the circle is 0"-Y, the Y guideline position is shown in the coordinate box, which is .104"
--which is a bit beyond the focus range of a 2" lens.

The engraving area is okay, it's not so far around as to cause any noticeable distorting to the text or graphics being engraved...

I do this quite often, mostly on bracelets. My LS900 makes it easy, as it will automatically raise the table using different colored text. Your Epi may do that? If so, it'll be easy--
This particular part will need at least THREE different focus settings, but FOUR would be better- one for the extreme outsides, one for the middle, then 2 more between the outside and 1" inside.
I've drawn in the sections and some guidelines...the guidelines are roughly .026" apart. This is probably a little tighter than necessary to stay in focus, but not much... note that the farther
around you go, the shorter each section becomes....

You CAN do this manually but it would be a royal pain. Rotary if you can! :)