Missing steps or something else?

I'm wondering if anyone has come across this before.

In axis the drawing looks right, and when I run it through my laser cutter it comes out right too. But when I run my design on my probotix setup it messes up in a few spots, the same spots, every time...

A few are highlighted in the photo:
1. The "W" gets shifted over when the cutter goes around for the second pass (using a serif font in cambam seems to make it double pass each line to get it done)
2. The "S" tale gets misaligned.
3. The "O" doesn't finish in the same spot.

The "I" "L" and "N" all come out fine, and this mess up is repeatable..


Has anyone encountered such a thing?

Using CamBam 0.9.8 and LinuxCNC 2.5

Until the forums cooperate without throwing errors every 10 seconds heres the picture on imgur lol
imgur.com/YcEOAOf

the spindle has some flex but its pretty tight... well as best as it can be with the construction of the frame.

Another thing I just tried today was replaying the job but setting the feed override to about 60%. That almost fixed the "W" but it gave the "O" an even bigger tale :/


Could it be a mathematical problem? like the steps and velocities aren't quite right?

As Andy said reduce your velocity and acceleration and perhaps try taking lighter cuts.

Set X and Y at a known location, after running a part does the machine return to the exact same position? That will show if you are losing steps.

Rick G

I have not done the 10x thing to the velocities and steps yet. I do have tests that show there are hiccups in the cut when I'm doing diagonal moves (both axises moving) ((which oddly enough with the "W" balance out letting the position remain correct 0_0))

It really looks like the Y axis is taking off first when I would think both should move at the same exact time.
(my moves were: X0, Y0; X4, Y4; X0, Y0)

I have two pictures that show the actual cuts, then i drew in blue ink what it looks like to me.

imgur.com/YdEUmDs
imgur.com/l3zYKC3

there are hiccups in the cut when I'm doing diagonal moves (both axises moving)

That might also indicate a too small a power supply problem.

Again reduce acceleration and velocity and see if problem still occurs, try a lighter cut or even mount a pen in the spindle and try the same move.

Rick G

Reduced the velocity and acceleration and still has the little hiccups. They appear to be in the same place for that particular move.

For example going from 0,0 to 4,4 the hiccup happens about 1.5,1.5.
going from 4,4 to 0,0 the hiccup happens about 4,4.

Same thing when doing a different diagonal (say 4,0 to 0,4)

This is with the tool in the air not making any cut, I can see the tiny hiccup as it moves and feel it if I hold my hand on the tool as it moves.

The power supply is a 40v part of this kit www.probotix.com/3_axis_stepper_motor_dr...er_motor_driver_kit/

If you go to x0y0 and mark that spot then make a bunch of diagonal moves then return to x0y0 is the machine in the correct spot or has it drifted?

Rick G

It mostly comes back to the same position. There was maybe one or two times when it wasn't exactly at the same place.
I figure the random jerks end up canceling each other out.

I would attempt to video it moving like this but I'm not sure how visible it would be on camera