UV (JPT Galvo) Parameter Selection (QPulse vs Freq with Inversion)

I recently purchased a 5W JPT UV Laser from Finnlaser. It’s a really nice unit, the company provides quick and effective tech support, and the price was only 70% of what other vendors were asking.

I’ve spent about a week now working with Finnlaser Tech support and searching the net for more information on configuring the parameters on these beasties. I think I’ve gotten to the point where I have exhausted all online info I could find and that which Finnlaser could provide. I’ve run lots and lots of Lightburn test panels, but one significant question remains for me.

Here we go (a little background first)…

I understand that UV lasers do not allow a power factor to be directly specified. The way to adjust a UV lasers effective power is to adjust the QPulse and the Freq. %Power is not an adjustable parameter.

So, here is the Power/Freq/QPulse chart for my 5W JPT UV Laser:

JPT 5W UV Freq, Pulse, Power

The way I read that chart is as follows… Pick your desired FREQ, pair it with the associated “optimum” QPULSE (Red Line → Red Data), and then you can also ref (at the same Freq) the resulting power output (Blue Line → Blue Data) for that pair. (I think that is how that chart is supposed to be used) The red line indicates the optimum QPulse for any specific Freq, and then the blue line (at the same freq) indicates what the rersulting output would be for that pair. For example, according to my chart, max power (6.5W) of my laser can be generated at 40Khz with an optimum QPulse of about 11.5ns:

JPT 5W UV Freq, Pulse, Power (Max)

  • If I am not reading/interpreting the power chart properly, can someone please clarify further?

Anyway, although 40Khz provides the max output of my laser, certain materials (glass, metal) may respond better to higher (or lower) frequencies. So, I’m thinking we pick the freq going in and then note the optimum QPulse for that specific freq…

If anyone is interpreting these charts differently, now would be a good time to discuss this. :slight_smile:

So moving forward, assuming I’m reading this correctly, for Max power I would want a freq of 40Khz and a QPulse of 11.5ns. But here is the issue, based on my test panels, and comparing them what other folks have posted, having the deepest effect at the low end (QPulse) of the chart is indicative of an “inverted” Pulse setting.

I think I understand what that means, but the specifics escape me…

Inverted from what, how? Yes, I’m getting more effective power at lower pulse settings, but how do I manually invert a DESIRED setting (i.e. 11.5ns) to something I can specify? IOW: what is the calculation that can be used to Invert/Uninvert a specific Pulse setting?

The effective range on my laser (JPT SEAL 355-5) is Freq = 20-150Khz, QPulse = 1-20ns:

So, if I want an actual freq of 11.5ns, do I need to specify 9.5ns (20-11.5)?

If Lightburn is indeed “inverting” my QPulse, what is the calculation I need to perform to get the specific value I want?

Is there a setting in Lightburn such that I can turn off this inversion?

If that were the case why would the materials test print it?

I saw this graph before, but it was unclear to me what P/W actually means… The manual you posted

Don’t know about your UV, but my fiber has good variance just varying the speed/interval…

I really doubt that Lightburn is inverting anything… but I think I see what you mean…


UV lasers are completely different animals than Fiber lasers (I have both).

You need to ask the Lightburn software developers about that… Its completely meaningless.

UV lasers simply don’t support a Power Setting. They generally run at the same input power all the time and QPulse and Freq can be used to optimize or calculate their effective power output. Thats what that table is all about…

Yes, the Lightburn “Material Test” page will show (and pretends to allow you to select) a power setting - but it has absolutely no effect. Even if Lightburn did submit a power request, its likely the UV laser would simply discard the associated parameter as it has no purpose with UV lasers. However, the fact that Lightburn (with recent UV support) now greys out all power settings would seem to indicate that they likely don’t even pass the parameter to begin with.

From the editor, the power setting is actually greyed out and unchangeable if you try to set it for a “line” or “fill”. It basically contains whatever setting is left over from the “color pallete” on the bottom of the window. You can’t change it and it doesn’t matter. Anyone who runs a UV laser should know this (or needs to). It’s unfortunate that the Lightburn software developers simply don’t leave the box empty (instead of leaving some meaningless unchangeable value in there).

I even ran a manual test with several boxes each with a different entity color. I.E Black, Red, Blue, etc. Each showed a different power setting (greyed out) in the user dialog (100, 80, 60), but they all etched EXACTLY the same (as I had set identical Freq and QPulse parameters for them)

It’s a shame the Lightburn Software developers haven’t caught up but the UV lasers only recently got support (which is good). Hopefully they will get the erroneous stuff eliminated from the GUI at some point. Right now it works fine as long as you understand whats important, whats not, and what is completely meaningless…

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Thanks for the explanation…

Don’t have a uv, just a few other types…


Full disclosure…

I’m trying to locate the original thread(s) in this forum where it was suggested that the “UV Pulse was Inverted” if the highest power was seen at the lowest Pulse levels in the Material test page. I’m coming up empty. I know I saw it somewhere (I didn’t make up the term) but now I’m at a loss to find it. I tried many search variations…

If anyone following along knows where that original posting is, it would be good to include the link in this thread for context.

Otherwise it appears my dementia may be onset faster than I expected… :wink:

OK Found it: https://forum.lightburnsoftware.com/t/anyone-got-uv-galvo-running-in-lightburn-supposed-to-work-in-1-3/84442

I’m not sure if the “QPulse Inversion” is an actual thing or just speculation from the above posting.

Perhaps someone could clarify if UV Pulse is actually being inverted in some way?

Feedback I received directly from Oz:

LightBurn is not inverting anything… EZCad provides the option to invert the pulse, if I remember right, but I haven’t played with that or added support for it.

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