PDA

View Full Version : Lasers powers and lens questions



Martin Boekers
09-30-2015, 12:12 PM
Recently I purchased an Epilog Fusion M2 120 watt laser, I already have 2 - Epilog Legend 75 watt ones.

My questions are;

The Fusion M2 has a 3" lens, the Legends have 2" lenses. I have notice that with the 120 watt that the burn is much
darker on Alder wood than with the 75 watt ones, even after adjusting settings to get a similar depth. Is this because
of the different focal length lens? The more powerful tube, better quality optics on the new machine or something else?

Granted the 75 watt machines are about 10 years old, but both have had new tubes in the last 3 years and new lenses
in the last 2 years. Even when they were new they didn't have the quality of burn the Fusion has. The older lasers have
served me fine and I expect quite a few more years from both. My dilemma is, I'd like to be consistent on my jobs and
their end result. I find myself having to designate which laser gets which job a little more closely than anticipated.

Any thoughts or ideas? Should I try a 3" lens on one of the older machines?

I'm sure if I asked Epilog they would say "We can set you up with a couple of new Fusions".... :D

Ross Moshinsky
09-30-2015, 12:44 PM
It's probably a combination of the power and beam size. Wider beam = better burn. More power = better burn.

If you want consistency, it might just mean using less power. Try running the 120W machine at 75W. That would be a good place to start.

Gary Hair
09-30-2015, 12:45 PM
My guess would be that it's because the 3" lens has a larger spot size and the power density is lower than the 2" lens. Using the same settings you are effectively spreading the power over a larger area and it is burning more than ablating. I found similar results with powder coating - a longer lens and slightly out of focus tended to melt the power instead of vaporizing it, even with the same settings.

Martin Boekers
09-30-2015, 1:45 PM
Thanks Gary, I may just get a3 3" lens and see what that does...

Martin Boekers
09-30-2015, 1:48 PM
It's probably a combination of the power and beam size. Wider beam = better burn. More power = better burn.

If you want consistency, it might just mean using less power. Try running the 120W machine at 75W. That would be a good place to start.

Ross, I'm not sure how to set it to 75 Watts, I adjusted the power settings until I got a similar depth.... It would be interesting though if they had an option like that in the driver...

Gary Hair
09-30-2015, 1:57 PM
Ross, I'm not sure how to set it to 75 Watts, I adjusted the power settings until I got a similar depth.... It would be interesting though if they had an option like that in the driver...

Even though it's not exact, use the percentage of power to tell you the wattage. Ie. if you use 75% power on the 75 watt laser that should be close to 56.25 watts (75*75%). To get the same wattage on your 120 watt machine you would use 47% power (56.25/120). Same thing with speed - use the max speed of each machine and the percentage you are using / needing and calculate it accordingly. If you don't feel like doing the math every time it would be very easy to setup a spreadsheet with the proper formula to give you the settings.

Dave Sheldrake
09-30-2015, 2:39 PM
The bigger tubes usually have a larger diameter incident beam (the beam coming out of the tube) the bigger the beam hitting the final lens the smaller and thus higher power density the spot will be.

A longer focal length lens works the opposite way, longer focal length = bigger spot = lower power density

Keith Winter
09-30-2015, 3:48 PM
Your bigger lens has more overlap so it creates more of a burned look.


Recently I purchased an Epilog Fusion M2 120 watt laser, I already have 2 - Epilog Legend 75 watt ones.

My questions are;

The Fusion M2 has a 3" lens, the Legends have 2" lenses. I have notice that with the 120 watt that the burn is much
darker on Alder wood than with the 75 watt ones, even after adjusting settings to get a similar depth. Is this because
of the different focal length lens? The more powerful tube, better quality optics on the new machine or something else?

Granted the 75 watt machines are about 10 years old, but both have had new tubes in the last 3 years and new lenses
in the last 2 years. Even when they were new they didn't have the quality of burn the Fusion has. The older lasers have
served me fine and I expect quite a few more years from both. My dilemma is, I'd like to be consistent on my jobs and
their end result. I find myself having to designate which laser gets which job a little more closely than anticipated.

Any thoughts or ideas? Should I try a 3" lens on one of the older machines?

I'm sure if I asked Epilog they would say "We can set you up with a couple of new Fusions".... :D

Ross Moshinsky
09-30-2015, 3:54 PM
Ross, I'm not sure how to set it to 75 Watts, I adjusted the power settings until I got a similar depth.... It would be interesting though if they had an option like that in the driver...

75W / 120W * 100 = 62.5% power. That's how I've done it in the past and it's gotten me close. It's not exact, but it's a good place to start.

For example, tweaking my settings on crystal the other day to my 60W tube, I ended up basically using the same settings I use on my 30W machine. It was something like 60% power and 70% speed. On my 30w I run at 100% power and 30ish speed. The 30W is a faster machine so the power and dwell time is pretty similar between the two machines. The end result was the engraving between the two machines was very similar.

Kev Williams
09-30-2015, 4:54 PM
As you suggested, I would try a 3" lens on the 75w machines- and vice versa, try a 2" on the new machine..

Question: Can your lens be easily removed from its holder/mount, and turned upside down? If not don't bother, but if yes, try it. I've found with my Triumph that I can cut thru 1/16" Rowmark with quite a bit less power with the lens turned upside down (curved side facing the work). Also when upside down, I've been able to fully burn away *certain* black anodizing right down to bare metal, whereas it won't with the lens in the right way...

I know it's not kosher to do this, but there IS a distinct difference, at least that I've noticed, and I've noticed nothing 'detrimental' about it. And engraving quality (the few times I've done it) looks just fine... NOTE that the focus distance will likely be different, a 'ramp test' can tell you the best focus distance.

Always fun to experiment! :)

Jack Clague
09-30-2015, 5:41 PM
If your keen in the maths and specifics of it I was given this link by i believe someone on here: http://www.parallax-tech.com/faq.htm

Martin Boekers
10-01-2015, 9:25 AM
Thanks all, on the Fusion M2 I purchased the optical camera with it, I was told you need a 3" lens for that to work. I guess I could get a2" lens
for it if I'm not using the camera.