I know I have seen people mention this issue in other threads but I didn’t pay attention because I didn’t think it would ever affect me. And now I am trying to find those threads with little luck.
After adding a laser I am finding that I need to use faster Feedrates (speeds). However on a straight path X or Y my machine will begin to stutter at speeds higher than 150 mm/s. Same G code will cause the problem in the same spots every time. Curves are fine. And the same g code running with the flow rate set down to 30% (aka running slower) it doesn’t stutter. So I know it isn’t hardware. I believe I have seen something mentioned even recently about steps per second and the board having trouble keeping up at high speeds. So can someone please point me to a thread to read or give me the high level of what my options are?
Thanks in advance! Oh and for those who don’t get offended at a genuine wish of merriment. Merry Christmas Eve!
You are capped at 120 in the firmware. Honestly at that speed you have very little power in the steppers. If you want fast, you need to change to larger pulleys. We are configured for power not speed.
If you don’t lose steps at that speed then probably it’s firmware issue. And 150 mm/s is pretty high even for 3d printer.
I guess that with marlin you will not able to get higher. May be if cut features - i mean as example LCD.
Or you have to search luck with another firmware - repetier, grbl or klipper (if you have raspberry - why not?). As i know klipper provide best perfomance (about 100000-150000 steps/sec) on the 8 bit avr, but it primary targeted for 3d printer usage
yes, as Ryan said you can use 20 pulley. You can try to reduce microsteps. And if you will get losing steps it would be nice to use 24v power supply for stepper drivers
Cool thanks. Looks like I may want to make a second machine then. One for Router and one for laser. In the meantime I’ll run at slower speeds and just power down the laser. I have a 5.6 watt on order from Endurance lasers but a cheap 15 watt on the machine right now. It is too hot even at half power. For the Kaizen foam I am trying to cut.
Ill just dial it down some more and max out my speed at 115 for now.
That helps with the maximum step rate, but the steppers themselves have a very steep power curve rated by RPM. You can do some math to find out the ideal power to speed gear ratio vs. pulley diameter.
200mm/s is 10rps or 600rpm for 20 teeth pulley. That is 2000 full steps/s for 1,8 stepper, or 4000 half steps or 32000 of 1/16 microsteps (by the way this means that 1/32 of dvr8825 is pretty hard for 8bit marlin at high feedrates).
For 300mm/s all numbers *1,5
I also has a few interesting articles in the pocket )
Here guys made a lot of interesting experiments. But honestly their stepper has to low nominal current and to high inductance.
This article (sorry, it’s in russian)
Explains that typical nema17 became down torque at 300rpm at 24v and at from 600-700rpm at 48v. So he made own drivers based on tbb6600hg chip for run at higher voltage.
Are you sure your trying to move your axis at 9meters / Min or 150mm/sec?
that seems extremely fast to me even for a laser. I have just added a laser and only use a max 1200mm/min or 20mm/sec. i think you need to rethink your measurements
Thank you everyone for the help and advice. I have managed to get it working now I just need to see if I can get it to cut deep enough. I have 30 mm thick Kaizen foam. I am lowering the laser 1 mm every pass and now doing 30 passes at 70 mm/s. Granted it rarely gets up to full speed because of all the curves and the firmware acceleration settings. The laser is set to 120 of the 255 for power.
Just to show what I was running into at slow speeds and full power. I was able to cut the same material in 3 passes at 10 mm/s But it melted huge grooves into the material on each pass. Not sure if they will show in this pic but here are the grooves.
[attachment file=80730]
As I said before I am now running 70 mm/s at 120 power. This picture I only made 15 passes. I had to rip the foam the rest of the way. But the part that was cut is clean.
[attachment file=80731]
So I am excited. 30 passes may be overkill but I need a good prototype soon to test at the office.
Hmmm, I am not sure but you might be able to get a laser with a different focal length, that might give you a narrow enough beam to do it in less passes? Or just mill it out.
Yeah. I have learned that moving the laser down doesn’t help. It will only burn about 18 mm down and that’s it. I assume it is because the beam gets spread out onto the sides of the walls. So I am now getting clean cuts with 15 passes at 70 mm then a couple slower passes to make sure it cut through.
Ryan, Your idea of milling it out made me rethink the laser. In the near future I may need to cut some 60 mm kaizen foam. I am not sure if I can do it with the laser or not. I also can’t find a router bit that long. But I found this hot foam cutter pen that might work. It’s like a soldering iron with a long tip. I will test it manually first and see how it works. If I like it I’ll make a tool mount for it.
