OmTech MF-2028 80W Max Speed Limiter

Yipyioh · January 6, 2025, 11:23pm

Afternoon all! Doing some initial project work now that I’ve got my Omtech MF2028-80W set up with mirrors aligned and focus height determined. Using Lightburn, I’m cutting out some small-ish geometric tokens (about an inch wide with some funky cut-in corners) with some text outlines being cut lightly on them using some medium weight chipboard (think cereal box material). Previously, I had been doing this using a 10W Xtool D1 Pro diode laser, and my settings were:

Text Lines: 75mm/s 60% Power
Cut Lines: 12mm/s, 100% Power, 2 passes

This would cut out a sheet of these in roughly 45 minutes. On the MF2028, I did some material tests and decided to go with

Text Lines: 400mm/s 10% Power
Cut Lines: 300mm/s, 40% Power, 1 pass

These settings, despite being drastically faster and using only one cut pass, result in a predicted and real-world time of about 35 minutes.

From paying attention to the laser, looking through Lightburn options, reading through the user manual, etc, I suspected last week something between Lightburn and my laser may have something like a speed cap of less than 300mm/s. Since then, I have done some research through the forums here and found information pointing me to the Machine Settings>Vendor Settings section, where the x/y max speeds were set to 400/300mms respectively. As some posts here indicated those may need to be higher to actually hit 400/300 etc, I bumped both up to 700mm/s which brought my estimate down to 25 minutes, but now that I’ve sat down and toyed with the settings it seems like the preview is estimating no difference in project time with any speeds above 100mm/s.

So, to the actual question; is there a speed governor somewhere else in the laser’s settings or firmware, and if so can it be turned off/raised and/or is it safe to do so when using it to do lots of small squiggly text? Or, is there something else I’m missing like Lightburn or having some sort of control limitation based on the actual shape being cut out? Watching how much extra space the head needs when it’s whipping back and forth to do high speed fill projects, I understand there has to be some realistic limitation to line speed when it comes to tiny intricate details so the laser doesn’t way overshoot corners, I just expected the laser/software would let me make my mistakes and ruin a project before they’d have that level of idiot proofing, so I was prepped to just up the speed up by degrees until I saw problems, but it looks like instead I’m cranking the speed to get no difference past a certain point and I’d like to find out where/why that is.

If it really is Lightburn or the laser just saying “bro, slow down, you’ll overshoot these particular lines if you go any faster than 80mm/s” that’s totally fine, I’d just like to know. Seeing how much more power and how much tighter the control is on this thing than my diode laser, I’d be surprised if it really can’t do much faster realistic movement for line cutting than the diode. I’m clearly having no issues cutting through this material in one pass at a maxxed speed even down below 16%, so I was hoping to find a way to try doing some designs with it ripping along at 300 or 400mm/s at 30-40%

Attached are pictures of the Machine Settings menu, because I honestly don’t know what most of this actually entails, I’m trying to learn all this new C02/Ruida controller info as fast as possible but the materials I have don’t cover much of this.

ednisley · January 7, 2025, 12:01am

Basically, you just raised the cap on the possible maximum speed, but as you’ve just seen, that can have little effect on the actual speed.

The limiting factor is the ability of the motors to accelerate the (huge) mass of the gantry and (large) mass of the laser head. The Max acceleration values in the X and Y axis settings determine how hard it will accelerate; those values look typical.

The acceleration value in Cut Parameters limits the maximum acceleration in any direction during vector motions, so the larger value in the X axis will never happen.

The acceleration values in Engraving Parameters apply during engraving passes, which will affect the overscan distance.

The RepRap Acceleration calculator will show you how much short distances limit the maximum speed for a given acceleration. The 2000 mm/s² limit imposed in the Cut Parameters means that the machine will reach just over 200 mm/s halfway through a 25 mm vector:

Raising the acceleration to 5000 mm/² hits 300 mm/s.

Motor torque limits the maximum acceleration, because that’s “how hard the motor can shove” the mass of the gantry or laser head. You can try increasing the acceleration up to the point where the motors lose sync and the machine makes horrible gnashing sounds, then back off by a factor of two.

The machine is also much heavier, so the speed increase isn’t as large as you might imagine. What it will do it cut pretty nearly anything organic without regard to color, which may come as a pleasant surprise.

Note that LightBurn sets only the target speed for the vector: say 700 mm/s. The controller then determines the motor speed based on the desired speed, the vector length, and maximum speeds & accelerations along each axis. As that graph shows, the top speed may hit only 350 mm/s before slowing down again.

Also, the controller settings are not free variables you can change at will, because they’re determined by the hardware in the machine. The original settings will be conservative, but drastic increases will cause the motors to lose sync when you least expect it.

Make a backup of the original settings so you can return to a known-good configuration. It’s easy to change this, that, and the other value, then lose track of what you’ve done and be stuck with a dysfunctional machine.

soniclab · January 7, 2025, 12:03am

you may also improve your estimated preview times : https://youtu.be/s1jCqB233N0?si=G4iBK2Drnp8zYpH2

Yipyioh · January 7, 2025, 12:24am

This information is outstandingly helpful, thank you for pointing me in the right direction! I’ll see what I can do with working this out and check back later.

jkwilborn · January 7, 2025, 1:28am

I would have expected these to be set properly. If I’m reading it correctly it’s maximum X speed 5mm/s? Even if I used it as a comma, 5000mm/s would be too fast…

I’d start with the maximum value of about 700mm/s, likely it will go faster, but there isn’t a great reason for going that fast anyway.

I’d also expect the acceleration values more in the lines of 2,000 to 5,000mm/s^2

Save the current setting before modifying anything… a backup or factory settings is always a good idea.

You can modify both the maximum speed and acceleration values.

When it fails it make a big racket, but for short time, it won’t hurt anything. The magnetic fields are moving faster than the mechanical parts of the motor can respond.

Good luck

ednisley · January 7, 2025, 2:26pm

If that’s in Engraving Parameters, it’s the X axis acceleration in mm/s² and seems reasonable-ish.

One of these days I must follow your lead to find just how fast the stock hardware can run and how much acceleration it can tolerage. The usual test pattern should come in handy to knock the motors out of sync around corners.