Cermarking chrome

[Andy Joe]

So i have a job etching chrome derby covers for a MC. Problem is i have never used cermark on chrome. I talked to cermark and they gave me a peramiter test instruction pdf. but in order to use is i have to have a sample peice of chrome large enough and same quality as the stuff i will be using. I have done a couple spares they had and i can get the cermark to stick but it turns a bronze color is places and its not consitent on where it does. Do any of you out there in forum land have experince with this and could lend me a hand on settings or any advice i should know before i start in on this job. My laser is a Kern 150 HSE with a 50x52 table. max power is 59 and max speed is 60. dpi from 150 to 600. Dont think there is anything im leaving out.

Thanks
Andrew

[Dan Hintz]

Try something in the area of 50S/100P/600dpi. A low resolution is going to work against you as the area will cool too quickly, but you have quite a bit of power to work with, so you'll be moving a lot faster than most of us here.

[Andy Joe]

so if my max num for power is 59 ans speed is 50 you want me to run at 25 speed and 59 power? what does changing the dpi do for me? Sorry im not a laser guy, im a painter and sandblaster.

[Dan Hintz]

Ah, didn't realize those numbers you were running at were not percentages (most here use machines that run at 70-75ips, so 100S = 75ips, and 100P would be 100% power). Unless you're running with a couple hundred Watts, you'll be running at 100% power (for you, that's 59) and <100% speed. If your max speed is 60ips, expect to decrease most people's power measurements by 20%.

On my 70W (true power) machine, I run around 15S/100P/500dpi. You'll want to adjust your numbers appropriately, and even then they'll be ballpark figures.

The 500 dpi assures there some overlap between pulses, leading to more heat at any one location... too much, however, and you'll warp thin metals and/or burn the Cermark. At 150W, you may get away with a lower dpi, but your speed will have to be slowed down, as well.

[Rodne Gold]

Is the mark you are making turning a bronze colour or is the cermark turning a bronze colour?

Overpowering the mark is as bad as underpower - if the mark is turning brown , try turn down the wick a bit ,ie less power or more speed. I have max 30w machines and go quite quick when using cermark
If the cermark is turning brown - there might be a coating on the chrome
First thing to do is to clean the chrome with a degreaser , benziene , spirits , thinners etc.

Chrome is often a bear to mark with the metal marking pastes for various reasons - we often add a drop or 2 of dishwashing liquid to it that acts as a wetting agent so it really has an even coverage and doesnt get those teeny micro holes where the cermark doesnt stick.
If you do get a black mark , you also need to do a scotchpad test , ie give the mark a few rubs with a dry scotchpad ,often the mark looks good but is not at all resistant to scuffing or cleaning etc and can easily come off.
Be careful about coating and then leaving the stuff on a long time before and after lasering , the chrome can stain where the cermark is applied.
Part of the secret of success with the metal marking compounds is even and thin coating , best is to airbrush on , normal brushing or foam pads dont work that well.

[Andy Joe]

the max speed i can use is 50, and the max power i can use is 59. So far i tried 18,22,25 for speed and 59 for power. Im getting a ring of brown or bronze color around the marking, its not in the middle and its not on the outside which is weird. When i tried giving it more speed it didnt stick and came up on me. So im going to try to go faster with a higher dpi like was suggested and see if it will stick then. I really just wish i had a peice of scrap to run tests on instead of just the good peices they want.

[Dan Hintz]

50 what? Is the speed in terms of ips? Is it some arbitrary value Kern has chosen? Same question for power... is it in terms of average power in Watts, is it a percentage of the max power, etc.

[Andy Joe]

they call the power setting laser modulation, and yes the speed is ips. I can set the speed at 60 for max but if i go over 50 the machine jumps and skips in the engraving. 59 is max for laser modulation, it was 60 but they had me go in an adjust the numbers making it 59 to persever laser life. I was told by people who purchased the machine that the kern hse was one of the fastest machines out there so i dont know how 50 on speed relates to you being able to run at 100. Are they eqivilant?

[Dan Hintz]

the speed is ips... I can set the speed at 60 for max but if i go over 50 the machine jumps and skips in the engraving. I was told by people who purchased the machine that the kern hse was one of the fastest machines out there so i dont know how 50 on speed relates to you being able to run at 100. Are they eqivilant?
Considering most Epilog and ULS machines run at 70-75ips, a max speed of 50 ips on your machine would not make it faster... either your "people" were incorrect or the 50 value is not an ips value. I know too little about the Kern machines to say either way, so you'll have to make that decision.

In the end, I think you'll have to make a test power grid (or several). you can either make one now and get it over with, wasting one or two items, or you can continue to make sub-par guesses and make mstakes on significantly more items.

[Andy Joe]

well thanks for the advice, i broke down and called the local platers and bribed them into giving up some chromed panles for me to run tests on. The value of 50 on my interface screen says ips next to it. Im surprised that 50 is max speed on what kerns claims is a high speed engraver version of the normal machine. Thanks again for your sugestions and help

[Rodne Gold]

Try reducing your power - lets say 20-30 power and 20 speed.
The only way you can determine what machine is faster is time the same image at the same dpi on them , the one that finishes first is the winner , it's actual thruput that counts. (assuming both engraved images are acceptable quality wise)
Your car can have a faster top speed than another yet you might well be beaten in a drag race by a car with a slower top speed. I would be very happy to have a 50 x52 machine with 150 w , even if it was slower than a smaller table in max ips

[Peck Sidara]

Some suggestions with a slight reiteration of what has already been said.

I think you're overpowering it.

Clean the surface
Slower speed settings maybe 5-15% (of your values)
Moderate power of maybe 20-30% (of your values)
600DPI
Try 1-3 clicks (.005-.020") "out of focus" up or down.

From there, adjust either only the power or speed, not both at the same time.

HTH,

[Andy Joe]

I am very happy with my machine, i was just surprised because the machine is advertised as a high speed engraver. Im not looking to have the highest isp machine around to brag about, just shocked at the number diference. so i tried 30 power and 20 speed and nothing stuck too the chrome. I should be getting a test panle today and that will make things alot easier for me. I wish they would just stick with aluminum

[Dan Hintz]

Also be aware that chrome from one company is not going to act exactly like that form another. Hopefully they'll be close enough not to matter, but it's something to be aware of...

[Andy Joe]

Well im sure your getting tired of hearing about this but i turned down power and speed. I cleaned the part real well, and i used a setting i got to work on a test peice and still didnt get good results. The cermark got really hard and britle and flaked away. Im thinking its still too much power. My setting was 10 speed, 11 power and 600 dpi and still i had bad results. i was going to try 20 speed and 25 power but im not sure how much diference there is in power there. Maybe im going the wrong way with numbers. Im not much of a laser guy

[Andy Joe]

So has anyone here used molybdenum compound on the chrome before etching it? This was apart of the processes several companies i found on line where useing. They claim they wash down the part, then coat it in molybdenum compound then spray it with cermark then laser it and then wash the whole thing down and tada!!! it sticks.

[Dan Hintz]

The cermark got really hard and britle and flaked away.
Sounds like you're cooking it...

Stop changing several parameters at once. You have test pieces to play with, so make a speed/power grid. Guessing at these parameters with no prior projects to base it upon is a complete crap shoot.

[Mike Null]

Andy

Just curious--is the derby cover flat or convex? If it's not flat you will have an issue trying to focus the laser and will not be able to do the job.

[James Stokes]

I have done the derby covers before. I think they are more trouble than they are worth.

[David Hartstone]

I run a Kern 150 HSE and use 40% power and 50" / sec when using Cermark; this produces excellant results

[Andy Joe]

Ok im going to have to agree, too much trouble. I ran 3 test panles and found the same settings worked on all 3 peices. I then used that setting on the derby cover(which is domed) and boo hooo it didnt work again. Im not sure how these companies on line are doing it so well. All i can think is that the curve is giving me and issue and that there is soo much diference between the chrome on product a and the chrome on product b. I think im going to have to tell this customer that i cant do what he is asking but i feel like i have failed and i hate that. I just wish i could see how these other companies are doing this and making so much money at it. Well thanks for all the advice

[Dan Hintz]

If the money is so good, purchase a few of the covers and do your testing on them.

[Andy Joe]

i have ran testing on 4 diferent covers so far, every cover runs diferent for me. The only thing that runs good is flat peices i get platted by the local platter in town. I used a mill gauge and it appears that they dont have as much chrome(and whatever else is in it) on the store bought halrey parts as the parts i get chromed.

[Mike Null]

Andy

Depending on the size of the image this may work--find out where the optimum focal point is for each part of the image and re-focus the laser to run each part of the image separately.

[Thomas Baranowski]

There are additional issues you will need to address once you get the machine set up to etch a nice mark. Derby covers are domed and you will need to check your focus from center to outer edge of the graphic you are etching. You will end up having to split your focal point to get a balance and somewhat even etch. Depending on your lens you might not have a issue ( 2" focus=issues with size, 4" focus= less issues). If graphic is pushing focus more than 1/2" spread from high to low point, etching failure is likely!
I do custom work for a bike builder and have done derby covers, the best solution I have is the following:
wash parts with dawn dish detergent, dry and wipe with denatured alcohol,
airbrush on Thermark ( my setting is 3 light passes) getting aprx 2-3mil thickness ( do not get too thick or it will blister or peel off)
put in oven to preheat part to 80-100 degrees ( the derby will cool fast and with evac system fighting the laser heat to keep constant temp) heat is needed to get a good Thermark bond.
If derby cover is not a Harley made part, issues with poor plating and metal adhesion often results ( H-D chroming is some of the best in world) I have had cheap plating lift off the metal when etched.

If you have practice panels make sure to compare the thickness of the metal from them to the actual piece you need to etch, if they are thinner you will need to adjust your speed to be lower with the thicker piece. I hope this helps you complete the work, derby covers are very frustrating work and can be a hit or miss job and not for the faint of heart. I have ruined many in finding what can work ( thank goodness they were damaged practice covers).