Shining the light on alignment

alignment

#1

I saw a picture of a Glowforge in front of a window, on a Facebook post today. Because mine too, sits in front of a window, I thought I would share a little hypothesis I have regarding alignment.

First off, I must state that my alignment has been remarkably, perfectly accurate - except for a couple of times. Literally only two times has it not been perfect.

So, here’s my hypothesis and my solution:
As with any camera, lighting is key, and I think it’s no different with the Glowforge cameras. Because lighting from external sources, such as sunlight throuh the window, or directional lighting within the room, can affect a camera’s image, it’s important to make sure such situations don’t exist.

The two times I had alignment issues, I simply turned my Glowforge off, covered the glass lid with a piece of cardboard, and then turned the machine back on, and allowed it to calibrate - Problem solved both times.

It worked for me, and it very well might work for you. Happy Glowforging.


#2

I never thought of that. Good idea. Thanks for the heads up.


#3

It’s funny, I have the opposite experience. I find that if I don’t have my overhead light on, I have trouble with alignment. Maybe it just needs uniform lighting? Anyway, yeah if you are having alignment issues, adjusting your lighting might be a good trick.


#4

Not having my forge yet – is there interior lighting inside the forge?


#5

There have been instances where bright room lights or sunlight have affected calibration.


#6

Yes. The unit is equipped with LED lighting.


#7

I’ve been using @cynd11’s A way to improve object placement and it definitely helps. And the room I’m in has no windows so its always the same lighting. But, as the compensation values change with each calibration, sometimes dramatically, it would be helpful to have some additional sanity checking.

@dan, When the Glowforge is “Scanning” the material, after clicking Print on the web interface but before pressing the Go button on the Glowforge itself, there is a red laser pointer used. Can the UI be updated to show that pointer? Then we could see where the laser lands both on screen and on the material and be sure we are positioned correctly.


#8

That’s odd. I have found the compensation values to be very consistent. I will go weeks or even months using the same values. I wonder if there is something else going on here.


#9

I’ve always been hesitant to say anything like that. First reaction is to get defensive.

All I can say is mine has almost never seemed to change with 11 months and three machines. There are those that talk about it constantly changing. Might be completely accurate. Wish there was a foolproof way of documenting these changes. Unfortunately unless each of us were looking over the other’s shoulders there would be little confidence that one of a dozen different setup things didn’t change.


#10

When I had the calibration issues with my machine, I was seeing slight variability in the positioning; but prior to that issue starting it was very reliable. When my replacement gets here I am hoping that I don’t see these issues. I think that @cynd11 is correct for the majority of cases, but I wouldn’t dismiss some of the problems being reported.

I believe @scott.wiederhold thinks that there is a bug in the calibration that can contribute to a compounding positioning error over time, but I don’t recall seeing any confirmation.


#11

It’s not actually in the calibration.

It’s in the “Scanning” routine.

The commanded motion to return home from the position where it scans the material height contains an extra step for both X and Y axis.

That part is confirmed. Whether or not there is a reason for it - the usual GF silence.


#12

Ah, I misunderstood that point. So based on what you’ve seen, the error increases with every job?


#13

Yes, but it is a minor amount of .01875 mm on both the X and Y.

It sends one extra step for each axes after each “Scanning” operation.

So, over time, the head winds up further and further “back and to the left” (I’m channeling my inner Oliver Stone).


#14

And that accounts for the “drift” Dan mentioned once. That’s why I power cycle the machine once a week. Time isn’t really a good metric to use (should be based on scanning cycles - like every 50 scans since the drift would be 1mm then) but it’s easy to remember to do it with the first job every Sunday.


#15

You leave your machine powered up 24/7? How come? I generally turn mine off post-cut, as I’m usually busy doing post-op steps (sanding, gluing, finishing, assembling) or designing for a while.

Just curious how you’re using the machine that keeping it up all the time is needed or otherwise beneficial. Educate me! :slight_smile:


#16

I think most days I only run up to maybe 10 jobs in any given cycle, so it seems like it would have been fairly minor impacts to me. But, I saw up to .2mm in between 2 jobs when the calibration problems started. Unfortunately, I don’t know what support found, and they seemed to want to do more testing with the machine in-house; which is why I had to ship it back.


#17

Because electronics suffer more from startup power surge and thermal shocking than continuous power. Most electronics will actually last longer if you leave them powered on. You have to decide if the electricity cost (or your sense of green) supports or contradicts doing this at your house :slight_smile:


#18

Electronics maybe (though I have never seen any data to support this idea – to be fair I’ve never gone looking one way or the other) … what about laser tubes? I wonder if the GF staff has an opinion on this? I’ve been turning it off to try to save wear and tear, maybe I’m doing it wrong?

Further when it is on, (at least in my pro) there’s a fan running all the time, at least that’s what it sounds like. That’s a mechanical part, for sure, and I’d say leaving it on 24/7 is drastically reducing your real MTBF on anything that spins or pumps or whatever it is that it’s doing. We need the GF peeps to tell us their theories here.


#19

Laser tubes are only energized when you’re burning something. At idle it’s just sitting there looking pretty.

You are correct about fans/pumps. But by and large those things have been engineered to phenomenal MTBFs and continuous run times.

It would be nice to know what GF thinks about this - Dan did mention not needing to turn it off except for the drift issue but I don’t recall him weighing in on lifespan impact of specific components.


#20

Electrolytic capacitors have finite lifetimes so you might wear out the PSU leaving it on for a long time.