Thermark tape occasional "pinholes" or drop-outs

[Amy Shelton]

I've been using LMM6018 tape. I have found the spray hasn't been making as black a mark on these particular items. (But it could be that the spray is old, I wish they'd put a date on the can.) I'm engraving 302 stainless steel, polished, and it's round. I'm not using a rotary, just finding a good average focus.

Some will engrave perfectly, absolutely dark and solid.

But some will have a few pinholes or tiny dots that aren't engraved. This is a very shiny substrate, so even little ones show up. Sometimes they occur in the center (highest) area, and sometimes they occur on the edge (lowest) area, and sometimes both. That makes me think it's not the focus. Sometimes there's just one, sometimes a few, and sometimes none.

I noticed the lens needs cleaning more often using the tape. Even after cleaning, it still does it.

I've decreased the speed. I'm not sure if I should keep decreasing, but since some are engraving perfectly fine, I think I have the speed ok.

I am engraving 76 power, 4.7 speed, 1000 ppi on my 50 watt ULS. Thermark said to use the speed they recommend (76 in my case) then vary the speed.

If you have any suggestions, let me know. Also, if you think it's worth it to change my set-up and use a new can of Cermark LMM6000, I can try that again. I was having trouble with it peeling off the items even before it got to the laser. I scrubbed with denatured alcohol, but I think the surface is highly polished which was causing the Cermark not to stick; water was beading off as if it had wax, but it had none.

It's a company's logo, so I'd rather not post a pic.

Thanks,
Amy

[Tony Lenkic]

Amy, suggestions are to engrave full power 100% and speed of power of your laser in your case 50% than lower the speed if needed.
You used 1000 PPI, what is the DPI setting? You may have to adjust that as well.

I have never used tape version so don't have suggestion there.
For spray version if peeling is the only problem try LM6038. That is the one Ferro lists for polished finish.
See it here on their site........
http://www.ferro.com/Our+Products/ColorGlassPM/Glass/Products+and+Markets/CerMark/Materials/Laser+Marking+on+Metal.htm

[Amy Shelton]

Thanks, Tony... my laser driver uses PPI terminology, and I am using Image Density of 5. The image is a logo that is rastered solid black, it's not a bitmap.

I didn't know they made the 6038.

[Tony Lenkic]

Amy image density of 5 means 500 DPI for ULS systems.

[Mike Null]

Amy

I think Cermark has an unlimited shelf life. Another engraver gave me their bottle several years ago and I just started using it. It works fine (after thinning with dna and mixing very well). My last purchase was at least two years ago and it's still working fine.