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Bob Davis
11-30-2009, 11:36 PM
I use the LMM-600 paste occasionally and have always had good results.
Unfortunately I have run into a problem using it with a rotary fixture to engrave large wine-coolers.
The problem that occurs is that the coating separates from the stainless during the job, and the airflow blows it away from the surface in flakes. I would suppose that this results from heat from the laser causing expansion of the metal and breaking the bond. The problem still exists after increasing the speed from the Epilog recommendation.
The stainless has been cleaned with acetone and then water with detergent, so I don't think I can get it much cleaner.
It appears to me that the problem is either the LMM-600 or the substrate, or perhaps the application method. I used my usual application method which is with a soft fine brush, and the paste is quite thin after being diluted with methylated spirits (which is called denatured alcohol in the U.S.)
I haven't used the LMM-600 on a curved surface for quite some time, but it's been fine on flat pieces. This particular batch of LMM-600 must be at least 5 years old, but has never given problems in the past. Maybe it has a finite shelf life?
The wine coolers are marked as "finest stainless steel" and are made in India. And I have 49 of them to engrave. There were 50, but I don't think I can charge for this one...
Can anybody pinpoint what is going wrong with this little project?

Gary Hair
12-01-2009, 1:20 AM
Bob,
Even though you have had success before, I am sure it is your application method. From your picture, it looks to me like you have way more Cermark than you should have on the piece. I spray it with an airbrush and you can still see the metal glistening through the Cermark. It's also possible that the stainless is coated, is it stuck in the places it appears to be black? If so then it may not be coated and simply needs to be thinner. I use a cheapo Harbor Freight airbrush and thin to the consistency of milk - very thin! I spray a very light coat, as I mentioned above.

Gary

Rodne Gold
12-01-2009, 2:48 AM
I do what gary does and add in a few drops of cheap dishwasher liquid in the mix as a wetting agent and to promote adhesion..also I use no air assist at all when doing cermark

Tony Lenkic
12-01-2009, 11:09 AM
Bob,

For polished metal finish Ferro recommends their LM6038 product.
Visit their web site or call them for more info.

www dot ferro dot com

Sergio Arze
12-01-2009, 12:23 PM
it is probably due to the metal surface, from the picture looks like a polished metal. Try using less air to avoid blowing off the Cermark product.

Mark Winlund
12-01-2009, 1:33 PM
The wine coolers are marked as "finest stainless steel" and are made in India.


The words "finest stainless steel" and "made in India" do not belong in the same sentence together. Many are not aware that "stainless steel" has no meaning. There are literally hundreds of types of stainless. Many products are marked "stainless" when only coated or plated. Often you will see brushed steel with an organic coating marked "stainless". This is likely the cause of many of the failures in laser work.

Mark

Dan Hintz
12-01-2009, 6:38 PM
"Stainless" or not, I'm willing to bet there's a coating on that thing that shoudl be lasered off first.

Frank Corker
12-01-2009, 6:58 PM
Hey Bob, sorry to hear that you are encountering problems, but a lot of what has been said already is right. The thinner the mix, the better, spraying it on is better than brushing and I also find that dabbing it on with a fine sponge is better than brush.

I have cermark that is over four years old and I don't have any problems with it. I would suggest that you do the same again but give the mix in the pot a good stir even before you add the meths. I too use meths and have had no problems with it. I suspect your problem is the power/speed ratio. The recommended speed at 300 dpi is 20 speed to 100 power 25/100 at 400dpi and 30/100 at 600. On the Epilog if you are reading from the manual, it is very easy to get these speeds the wrong way around, sending your power at 20 and speed at 100. You will get same result as you have.

These settings in the manual are recommendations, they are not laws, reduce your speed but keep your power at maximum. In the past I have reduced my speed to as low at 4 to get a good result, quite often two subject pieces for lasering will vary. However I believe that this last paragraph will sort your issues out.

It is simply a process of illimination, if you have doubts about your cermark, try it on another piece of metal/scrap, if it works on that, it has to be the wine coolers. It also means that you will have to try reducing the speed in order to keep the beam on the wine coolers for longer. One word of warning, watch for distortion, the piece will get hot if you reduce the speed.

Bob Davis
12-01-2009, 9:37 PM
Thank you gentlemen for your kind assistance.
I have now picked up a suitable spray gun, diluted the mix even more and trialled the piece, and the results are much better.
The "stickier" variety would be my first choice but it is not quickly available where I am. The standard LMM-600 still flakes off in some areas, such as the inside of letters, but that doesn't seem to happen until the laser has gone past that area.
By the way, I am not using air-assist; the flaking happens simply from exhaust flow. I could actually see the coating distort and delaminate from the stainless as a flake and then fall off.
Power and speed settings are definitely in the right ballpark.
I think the major problem with these pieces has been the semi-polished surface which doesn't allow much grab from the coating.