Jittery motion


#1

I was doing a score operation on cardboard with speed relatively high and power of about 4. The operation worked fine but when doing small letters, specifically a letter “c” which appeared 9 times in the design, the motion got very jittery almost like there was a resonance in the commands sent by the stepper motor and the gantry itself. The noise made by the laser head moving around also didn’t sound normal. Sounded almost like the head was hitting an obstacle.

It didn’t seem to affect the accuracy of the scores, but the motion and noise was kind of alarming. I tried to take a video but it’s not really that visible in the video. Maybe need to try a lower speed for this sort of fine detail?


#2

I’ve noticed the same thing. It really wants to bang its way around corners. If it were a 3D printer we’d just adjust the acceleration limits to let it decelerate more smoothly so maybe we’ll get improvements in this regard in the future, but maybe not depending on how smoothly they can attenuate laser power.

I also found that there was a little overshoot in the vertical direction. The tube on the gantry is a lot of moving mass.

Since you’re not at the lowest power, you can work around this by reducing power and speed.


#3

Unfortunately, I don’t have any guidance on materials provided by other vendors. It’s very common for materials to perform inconsistently in a laser. However, Proofgrade materials should print perfectly every time. Should you find a problem when printing on them, please let us know right away.

I’m moving this post to Beyond the Manual in case you want see if the community has suggestions about materials and/or material settings. Note however that advice in this section is unsupported and is not reviewed by Glowforge.


#4

@dan @rita : This is part of what we complain about. While what is said here is true, it doesn’t address what the actual topic is: Hardware.
If a device is making noises or odd movements or doing anything else unexpected, should what one is trying to cut be the first thing you look at? It sounds like a hardware interpretation of, or directly a software waveform question of “is this normal?” as they say the print turned out okay.
Could that be addressed instead of skimming, seeing cardboard, and “dismiss it, get the quota filled, it’s non-proofgrade, we don’t care.”

That’s the impression it leaves anyway.


#5

When I first received a unit about 8 months ago I tried a large vector drawing of a tree with all of it’s intricate branches. I had the speed set very high because at the time 10 months ago the laser did not have low power capabilities. So faster was my only option. The head was bouncing around very quickly and occasionally would make a big clunk sound as the head/gantry would change direction abruptly. Thought the machine was going to shake itself loose. Yet everything cut normally.

I have not had to use those types of high speed vector cuts or scores since the low power options were enabled. Engraves are always just back and forth with built in motion controls at the end of a line so even at the highest speeds don’t have the same abrupt direction changes.

Sounds like the condition is created by a little too much speed. I don’t think there is anything wrong with your machine.


#6

I agree - I don’t think the software/hardware issue that I experienced - shaking/vibration of the gantry, weird sounds - had anything to do with the fact that it was a cardboard, other than that I chose the speed/power combination myself instead of using the pre-programmed settings. I could just as easily put in a piece of proofgrade material and set the same parameters manually and I imagine the problem would be there.

I think the issue was due to the speed being too high for intricate score operations that involved lots of back and forth motion (rates of acceleration/deceleration too high) in a small distance, and maybe some resonance between the mass and inertia of the gantry and the commands from the stepper motor.

The artwork that caused the problem was scoring the outline of the letter “c” in the word “Since” (see below). The letter was about 0.15" tall. The other letters and numbers in that line printed OK, it was only on the “c” that it made the weird jumpy motion. I had 9 instances of this text on the same print, and each time, the “c” is when the problem occurred. They were spaced out in different X and Y coordinates, so I don’t think it was something mechanical related to a particular position on the print bed.

image