Ramp-feature, Min Power, Weird behavior when making stamps

I found another old thread mentioning something similar to what I am experiencing, but it never came to a conclusion so I am making a new thread. (old one Ramp mode problem)

I recently aquired a China, RUIDA 6445 1000x600 white blue laser.

Since my wife is an avid Scrapbooking-addict i figured I would make her some stamps and started experimenting with the Ramp Mode. I started to notice something wierd when using Ramp mode that maybe someone can explain?

It seems that if i use a Min-power less than my laser Tube lower ignition power (it starts to ignite at 6.5%) it makes it seem almost that scanning offset is wrong.

Excuse the poor image and stamp quality, it was just quickly made to show the difference on the line finnish. The line on the left is scanned with 0% min power (55% max), and the one on the right with 10%, otherwise they are identical.

It is no real issue that i have to set the min power a bit higher, but I just want to understand why. Logic tells me that the ramp feature should be symmetric and even if the laser is not fired under 7% it should not be fired either way, wich would result a straight line anyway, but it seems it is just not fired on the one direction.
(Edit: Actually not direction, it must be either when the laser is turning on or when it is turning off since it shows on both sides…)

Attaching the lightburn testfile…
StampRampTest.lbrn (9.9 KB)

Try running that file with bi-directional fill disabled. That would tell you if the ‘fuzz’ is alternating or not. I suspect it might be firing late on the advancing side, and turning off late on the declining side, because the tube is already on - it might shut off later than the firing threshold, because ionization is easier to maintain than to initiate.

I redid the test with the bi-directional fill disabled, and sure enough the “fuzz” disappeared.

(This is with 0% min power)

So it seems that you are correct in that something, ionization or other, makes the tube fire slower (or faster) in one direction.

So I guess this is just something one has to take in to account when using the ramp feature? Or should this be something that could be configured deep in some hidden settings in the RUIDA controller or something?

Just out of curiosity i took a picture of the cross-section of the stamp, the leading edge to the left, and trailing to the right… It looks like it takes a bit longer for the laser to ramp upp overall since the edge is a bit wider with a lower angle. Is this to be expected or is this something specific to my setup somehow?

I think you just need to know what your firing threshold is, and keep Min Power at or above that, so the ramp is consistent. Glass tube CO2 systems have a few well known idiosyncrasies, and this is one of them. It takes more energy to fire the tube than it does to keep it firing. There’s a setting in the Machine Settings called “Engraving Mode”, and setting it to ‘Special Mode’, if I understand properly, gives the tube a little high-power kick at the beginning of each L-On transition, which allows higher wattage tubes to fire at lower power settings. Might be worth a shot for you, but I believe it also consumes the tube faster - worth looking into.

OK. I will give that a try.

Thanks so much for the great info, I atleast have a bit better understanding of how it works now :slightly_smiling_face:

And just a quick follow-up.

I tried changing the Engraving Mode to Special Mode, and atleast for me that did not make any noticable difference (I tried it with Min Power on 0% and got the same fuzz both with and without it active), so it seems keeping the Min Power above the firing threshold is key to nice crisp edges on the rubber stamp material.

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