Engraving on irregular shape objects

[smgvbest (Sandra E Carroll)]

I have the need to engrave on Knobs (top and down side)
I am using a 60W MOPA Laser from Cloudray

The knob tops are flat and do not present a issue.
Going down the side does,
First thing is the transition from top to side is rounded, This seen to cause a deeper engrave on that corner.
once on that flat of the knob I’m ok until the next transition in the knob and same issue of over graving due to the transition

about the knobs.
this are 3D printed knobs in a transparent white resin
they are painted 4 layer of black followed by 4 layers of grey then sealed with a top coat
I engrave the grey away in areas to expose the black.
then the black is engraved away to expose the white

the knobs are illuminated when used.

I use a jig to hold the knobs, they have a typical 5 degree draft angle on the sides so then job positions them to be flat to the laser.

what I’m looking for is there any feature in lightburn to help reduce the over engraving of the transition from top to side, side to bottom?

this is an example of what some should look like when done

[jkwilborn (Jack Wilborn)]

Do you have a long lens.?

A longer lens will get you more depth of field, but you might have to re-orient the know to get it around the knob.

[smgvbest (Sandra E Carroll)]

This is on a 175mm lens, I do have a 250mm and 300mm lens

One thought I have but I don’t know if lightburn or any laser software can do is using a rotary could lightburn make adjustments for the curve on the rotary?

[jkwilborn (Jack Wilborn)]

The 300mm (mine is F420 to cover 300mmX300mm) but it has something like a 4 or 5mm depth of field…

I assume from the photo you are doing the pointer line on the knob… ?

[smgvbest (Sandra E Carroll)]

Hi Yes, its a F420 covering 300mmx300m still getting used to terms
and yes, engraving the pointer line, both the black and white parts

[jkwilborn (Jack Wilborn)]

These look like they are larger than what you can expect, depth of field wise, to be able to use a reasonable focal length…

I think you’ll have to make some kind of jig to hole them… the top one might be doable, but I doubt you can make it work on the bottom one…

Let us know what you come up with… we’re all interested…

[smgvbest (Sandra E Carroll)]

Here’s some tries at the knobs.

the left 2 as I did the face of the knob you can see it blew out the top. the right knob I’ve only done the top face and so far its near perfect.

these were done in a clear resin then painted white, then black then grey

[jkwilborn (Jack Wilborn)]

I guess you need some way to rotate them…

Lightburn will rotate a able, maybe you could make a jig and rotate it the required amount so you can get complete coverage?

The right one looks good.

[smgvbest (Sandra E Carroll)]

I have a jig that puts each surface at the same focal distance.
Generally the tops are flat,
sides have a 5 degree draft
so I rotate then in a jig to be 85 degrees which puts the side at the correct angle.

my issue is i keep blowing thru the layers of paint as I go around the curves.
do you think going to the longer focal length lens will help with that?

These the engrave pattern(s) I use currently

[jkwilborn (Jack Wilborn)]

Fiber lasers are pulse lasers, unlike your cw (continuous wave) co2.

You can modify how many pules/mm with the frequency and applied power with q-pulse width.

Both of these can dramatically change the damage on the material…

You’re dealing with pulse widths, I think we have the same basic fiber… I’m still learning, from the manual

These are how much power you are putting into the material for a specified pulse width…

Here is a spread sheet that will tell you the pulses/mm for a given frequency.

I’d like to help… If these are 3d printed, maybe a flat sheet to determine the values that will mark but not damage…