Recalibration button missing


#1

I just learned that if you move the head manually while putting your material on the bed, the Glowforge has NO IDEA that you did this. It proceeds to cut on the assumption the head is starting where it had been parked.

I sent a job where it should cut a circle in the middle of the bed, and fortunately my accidental offset was JUST barely not enough to drive me out of the cutting area (I wound up charring my rubber flap for the passthrough, don’t think I actually cut through it)

You can see here the red circle where the glowforge THOUGHT it was going to cut, and the char outlined circle far below where it actually did cut.

I can turn the machine off and on to force a calibration (what I did after this job), but having a button somewhere in the App to force a calibration (maybe even a shorter one for just re-home) would be desired.


#2

Yikes! I thought there were warnings in the manual about not moving the head manually while the machine was turned on…did they take that out or was it an accidental bump? :frowning:


#3

Warranty-level warning: You should never ever ever move the Glowforge head when it’s turned on. In fact, even powered off, I would refrain from quickly moving the head.

When you move stepper motors manually, they become electric power generators. And although there is circuitry to prevent feedback of this power that causes damage, doing so when the Glowforge already has power could limit this protection… frying circuitry in the process.


#4

It is a bad habit from using my home built laser. And yes… manual warns not to do so, but there are other things which can lead to the head moving while powered on (Like an accidental coffee cup…).


#5

I’m fairly sure I’ve shifted it on occasion while picking up cuts. (Hopefully there wasn’t enough to damage circuits.)


#6

We should be able to designate a “parking space” for the head to ease material removal


#7

Doesn’t the head park at rear left corner at the end of a build?

@Tom_A said the motors are energised permanently which would make it hard to move, is that not the case?


#8

Yeah, it’s strange that the gantry was able to move while it was powered on. How much holding force do lil’ steppers have?

There could be a hack in here. Anyone compare the physical limits of their machine to the limits set by the software? Maybe some purposeful pre-print movement could be employed to get some extra work-area.

PS; With a dial indicator and a proper rig/clamp/jig that you could attach to the rails, you could even do precise pre-print adjustment.


#9

If the head was movable with little resistance while the power was on, then that just means the Glowforge firmware doesn’t keep the stepper motor coils energized when there’s no jobs running. Which is typical. Keeping the coils energized when not in use both wastes energy and generates heat inside the case.


#10

Ah, I thought it was typical to keep them energized. A quick Google search points to the idea of reducing the current when the motors are idle, allowing them to stay stationary while generating less heat than they would if they were fully powered.


#11

Yes if you reduce the current you reduce the holding torque by the same proportion but the power dissipation falls by the square and so does the temperature rise above ambient.


#12

I wish I could tell you if it did or not, from my own experience, on my own unit! Someone mentioned moving the head to pull a print earlier.


#13

Yup, that’s where it goes.


#14

If they are steppers I’m kind of surprised they don’t “brake” them when it is stopped with power on. (Or at least when the lid is opened.) I know on my home built CNC that the steppers can not be turned by hand when they are set up to “brake”. Although… they are super torquey steppers, well beyond what I would assume the GF has. So… maybe they do but you can still push them around.


#15

Ha… never mind I see other comments about this. I should read the whole thread before commenting :wink:


#16

Typically a power cycle will cause the machine to rehome. In the early PRU days, they did hold the enable pin high when the machine was idle. Didn’t even noticed that was disabled. As for any CNC, I try to avoid gantry when the machine is active or a multi-op is in progress. This mental rule even applies to my other machines and they are closed looped. You only need to be burned by that once.


#17

And jacobturner has nicely illustrated why in the medical device world you are not allowed to mitigate risk with a statement in the manual.


#18

Doesn’t clicking the gear icon force a calibration when it rescans? I don’t pay much attention to that anymore but I thought (at least at some point) it did.


#19

Nope. It just scans. And you’re better off that way. If it had to re-calibrate every single time it took a picture you’d get real sick of that real quick.


#20

Huh. The re-scan already seems to take forever :slight_smile: