Low Power Laser No Matter What I Do

[Novus]

Connected the tube like this:

Red cable from laser driver to back of tube, meaning opposite the end where the beam comes out. Twisted wire around the post and sealed it with silicone and tubing.
Blue cable from amp meter (and white wire from laser driver) to front of tube where the laser comes out. Twisted wire around the post and sealed it with silicone and tubing.

[Tech_Marco]

Remember that the Concave side of the lens is facing down, while the convex side is facing up (to the incoming light beam)
The focus point can be found easily by firing at a piece of paper with low output, say 8%. The finest dot it burn is the focus point

Marco

[DonL]

The common focal lengths are
38.1mm 1 1/2"
50.8mm 2"
63.5mm 2 1/4"

This is measured from the bottom of the lense, not the lense holder, to the surface of your material, The longer the focal length, the longer the the focus remains in the max power zone so a longer focal length has a larger diamiter spot but it cuts deeper. For cutting thick material, use the 63.5 lense, the 38.1 lense is nice for fine engraving and rubber stamp making but the power deminishes quickly beyond the 38.1mm point so it is very weak at 39 or 40mm so it will have a hard time cutting through 3 or 4mm material without raising the material and recutting where as the 63.5mm lense has a larger dot and less initial power, by slowing down the speed to compensate for the power loss or cranking up the current, you can easily cut through 4 or 5mm+ material in one pass... Air assist really helps when cutting thick material. Lows away the smoke and carcon plus aids by providing more oxygen to the focal point, almost like a cutting torch doesn't cut worth nothin' without oxygen. Now we don't use pure oxygen but air has some oxygen in it and that helps provide a deeper, cleaner cut.

There is a nice template for a gauge here in the forum you can cut from 1/8 clear Plastic, I used 1/16 Lexan,

focus.JPG (48.29 KiB) Viewed 3350 times

[Novus]

Big thanks to the folks who don't work for LightObject for the help they've offered! I really appreciate it! Any further suggestions or things to try would be much appreciated.

That said... I'm still having problems.

The focal length looks correct.
The settings look correct.
The air assist is working properly.
Cooling is working correctly.
The mirrors are aligned well and cleaned thoroughly. But, I have a mirror that isn't great so I changed that out for one of my spares which is only marginally better. I just ordered a new mirror and lens, too.
The amp-meter is calibrated so I know that is correct.
The wiring is correct.
The lens is in correctly (now).
It's a new laser power supply (LightObject)
It's a new tube (LightObject)

PWM used to be 25000 so 42% max power at the machine was 16.2mA. Changed PWM to 15000 (middle of manual recommendations) and 26% max power is 16.4mA throughput.

The tube is about 6 weeks old (but it's only been in use for about 2 weeks) and I can't return it (or even have it checked, apparently) because there is only a 10 day window for that.

And It still takes 4 passes with a 40W tube to cut through 1/8" MDF.

I'm getting super frustrated and I'm way beyond my budget.

[Tech_Marco]

Hello Novus:

Don't let the frustration beat you. We all learning and we don't know everything. There is always a learning curve here or there.
I don't mind if you ship the machine to me for diagnostic if you're willing to pay for the shipping cost.
I don't mind if you send the tube back to me for checking. If it is under rated, I'll send you a new tube.

I DO mind if you give up so early and really not trying hard to learn. I gained my knowledge from "hands on" and believe or not, I didn't get much help from other folks.

So, wake up have Marco's 'fighting spirit'


Marco

[Novus]

Definitely not giving up. Not my style.

I'm in the Bay Area and wouldn't be averse to bringing the machine to you for diagnostics. What would I need to bring, just the machine itself? Not sure when I can, though. My day job and an upcoming funeral will keep me from bringing it out to you during the week. It's likely something I missed, but it's really hard to tell because EVERYTHING looks correct (now that I have the lens in right). I've even put the settings archive from the guy I got it from into the machine and no change. The only thing I can think of is that the tube is damaged and I've been super careful with it.

It's very strange: I'm drawing 16mA but only getting about 25% of the power, it seems.

[Novus]

OK, so the new mirror seemed to improve things, a bit. Now it only takes 3 passes to cut through. Might take only two but I haven't tested that yet. I'll do the lens switch on Monday. Here's hoping it was only messed up optics!

[Novus]

The new lens and focal length (longer) helped, too. But not much. Can I bring the machine in to you next week sometime, Marco?

[Tech_Marco]

I may have time on 26th Friday next week.


Marco

[Novus]

Ok! I'll remind you again on Wednesday. Thanks for your help!

[Novus]

Marco, will you be available tomorrow for me to come by with my cutter? What should I bring along with me/it?

[DonL]

There must be something being overlooked.... The photo you show is a FL: 50.8 lens, so from the work surface to the lens is 50.8mm ? You need to have this measurement spot on for best performance... You can't see the lens so you need to figure it is in the bottom of the laser head below the above the cone and the cap is 3mm thick so 3mm up from the bottom to the surface is 50.8mm right?

Try this... Set the max power to 12% put a piece of paper in the path of the beam as though you were aligning it, and hit the fire button very quickly... it should just darken the paper, now set it to 60% and do the same thing and it should pop a hole in the paper

[Novus]

Hi again, DonL! I've a new lens, which is in perfect condition, with a 68.3mm FL. My lens bracket is 7mm thick (about) and I cut (multiple passes) a 61mm focus tool. I'm confident the focus is good. That said, with the new FL I'm able to get 80-90% through 0.125" MDF on one pass @ 16.3mA with a speed of 3mm/sec.

I'm really thinking it's either the tube or something I'm not understanding about setting up the software.

[Tech_Marco]

I have time on Friday morning from 10am to 12pm. Stop by and left me take a look.
Hopefully it is just tuning issue but not a bad tube. Or...

Marco

[Novus]

Marco,

Couldn't make it today. Is there time next week?