Harley Derby Cover Thermark Problems

[Kevin Humphrey]

I've read all the forums I can find on thermark and chrome, and I've made a power grid and pre heated the derby cover. The best I can get is about 25% of the graphic to stick. The rest wipes off. I am using an Artcut 40 watt CO2 laser, and the best results seem to be around 80% power and 5% speed. The Harley derby cover is domed and my laser does not have an auto focus. Could the curvature of the dome be too much for a set focal length? Does anyone know if the Harley parts are coated?

[James Jaragosky]

I've read all the forums I can find on thermark and chrome, and I've made a power grid and pre heated the derby cover. The best I can get is about 25% of the graphic to stick. The rest wipes off. I am using an Artcut 40 watt CO2 laser, and the best results seem to be around 80% power and 5% speed. The Harley derby cover is domed and my laser does not have an auto focus. Could the curvature of the dome be too much for a set focal length? Does anyone know if the Harley parts are coated?

Yes the curvature is most likely causing your problem.
Small amounts of variance can be overcome by using a longer focal length lens; like a 2in, and setting your focus point slightly deeper into the material.
Auto focus does not adjust the focal point as the machine is cutting, it is used at setup. Although there may be some 200k machine that has the option to adjust focus while cutting.

[James Rambo]

This is one i did. It took 3 runs at different focuses for me to get the cermark to 'stick'.
Sorry it's not a very good photo it came out very good (not missing in places like the picture shows)

[Mike Christen]

Im having same problem, trying to do it at one focal distance may not work. I ordered a 4 inch lens for something else and will try it on a cover and see what happens. From what i understand it has a longer focal distance and keeps the beam tighter over a longer distance. I will let you know if it works.

[Kevin Humphrey]

I have a 2 1/8" lens. When you say you did it a 3 focal lengths, did you do that all on the same coat of thermark, and re-laser 3 times at different focus settings? From your responses I'm guessing no one thinks the Harley chrome is coated?
Thanks
Kevin

[Steve C Wallace]

The problem is the cover being domed. I have done a couple and here is how I resolved the issue with 2 passes. First I ran my 35watt laser at 100% power 5% speed. My artwork (I'll use approximate numbers because I don't remember the exact ones but you'll get the idea.) is within a 6" diameter circle. I drew another 3" diameter circle, centered over the 6" artwork. Then I did a fill of white between the 3" and 6" circles (hairline on the circle so it does not engrave during raster). This leaves just the 3" inch diameter exposed art work in the center of the derby cover. Focus your beam at the 1.5" mark away from the center of the cover. Engrave. Now fill the circle white for the inside circle and expose the outside ring. Focus at 4.5" from the center of the cover and engrave.

Key notes: Make certain of the orientation of the cover on the bike matches the orientation in your machine. (mark the top on the bike to top in your machine) Do not at any time during this process move the cover, only the very lucky will ever get it lined up correctly if you move it. Remember to only raster, NO VECTOR. You do not want to scribe a line in the chrome.

Hope this helps.

[Joe Hayes]

Like everyone else has said going out of focus do to the dome is your problem. CerMark is sensitive to the power and needs to be kept in focus to get adequate power to stick. I have done several of these covers and you will need to have multiple set ups to cover the different heights of the dome.

I might also not that true Harley chrome engraves very well but some to the foreign knock offs do not engrave well at all no matter what power or focal length you use. It has something to do with the makeup of the chrome. Voice of experience speaking on this one.

[Kevin Humphrey]

Great advise on the circles, I'll give that a try tonight. I think the covers are Harley (they are used from ebay), I have a new one coming from Harley this week, so I can compare the markings when it gets here. The new one is about $70 with shipping, so I don't want it to be my test piece.

[Gary Hair]

40 watt CO2 laser, and the best results seem to be around 80% power and 5% speed

Use 100% power, always! There is no benefit to less than 100% and you may be able to run a little bit faster.

Gary

[Kevin Humphrey]

Ran some focus test blocks, engraves best at 2 1/8 (factory recommended) and 2 1/4. 100% power, still parts of the test blocks washed away. What's left looks black in some light, but in most light is looks gray and scratches off with fingernail. I was testing with 5% speed and a .2 line gap. Will a smaller (tighter) line gap help? Also, scan delay is 1ms - not sure what that does.
The scan mode is on MONO, I have choices of GRAY RELIEF, SCREEN 1, SCREEN 2, and SCREEN 3. I don't recall anything about the scan mode in the Newlydraw 1.5 instructions. I also pre heated the cover to very warm to the touch before a light coat of LMM14, used heat gun to dry fast and lasered right away. Any Ideas?