So I just removed the router and permanently switched my mpcnc over to a dedicated laser. I installed a neje a40640 and am starting to work the bugs out. I would like to increase the velocity and acceleration settings in order to run the laser faster and at a higher power.
Has anyone increased these settings successfully or found the threshold where you started skipping steps? For reference, this is a stainless tube build with all parts purchased from V1. Rambo 1.4 board 24"x36" work area
Looks like the default settings are acceleration-180 and velocity-50
Those settings are pretty conservative. My advice is to adjust the speed up first and then back away from the whatever speed you skip steps. Once you find your max speed, you can raise the acceleration. I don’t think increasing the Z speeds will pay off.
I wouldn’t be surprised if you doubled the limits.
Awesome, thank you Jeffe! that’s what I was hoping to hear. I should be getting out to the garage tonight to start messing with the settings. I figured with no cutting loads I should be able to up the ante on this thing. I am assuming I can just make the changes using the lcd instead of changing the firmware correct?
You don’t have to change the firmware. In my memory, it is very slow to change on the LCD, and you want to send some large moves to reach top speed. I would use gcode from a computer, personally.
M203 changes the speed:
M201 for acceleration:
If you get settings you like, M500 will save them for the next reboot.
As a recent laser module purchaser, I’ve also considered the issue of speed. With respect to your settings, I have no idea and I’m watching for any instructive comments on this topic, or your feedback if you run tests of the settings. I have however considered other ways that might improve speed, including 1) upping the voltage to 24V, and 2) reducing the weight of the Z axis. If you remove the Z axis and mount the laser directly to the core, you will save around 2+ pounds being pushed around by the steppers. I purchased a 24V power supply, and created a lighter Z axis assembly, but I won’t get around to testing them until sometime in February.
When I set my first home-built CNC up under LinuxCNC, the recommendation that worked well for me was as follows:
Choose a slow but bulletproof speed (velocity) to begin with.
Tune the acceleration by starting low and working up until you lose steps, then back it off 5-10% for a safety margin.
Tune the velocity by working up until you lose steps, then back that off by 5-10% for safety margin.
I guess the idea is that if you tune velocity first, you may have to tune it again after dialing in the acceleration. You’re also sure it’s an acceleration issue when you first lose steps, whereas if you start with velocity it could be either setting that triggers the loss.
I never lost steps on that machine, and got reasonable speeds out of it. Especially considering that it was a hobby machine built out of MDF, hardware store zinc plated rods, and PEX tubing for “linear” guides.
For more speed, you can also use 20 teeth pulleys instead of the default 16 teeth ones.
I had placed a wrong order on pulleys and decided to keep them(20teeth), you will have to adapt step/mm, in my case 80 steps/mm.
Well I played around with the velocity and accelleration. I moved the accelleration to the max that the lcd would let me (From 180 up to 300) and also increased the velocity to 300mm/s without skipping steps. The limiting factor in the speed seems to be the accelleration. At the max acceleration, it is still taking too much time to get up to speed at even 200mm/s. Overall I am happy though. Even making it to a reasonable 100mm/s with the max acceleration is much better for the work I am doing