Alignment issue?


#1

Hello All,
Long time lurker, first time poster. The issue of alignment has appeared multiple times on the ‘problems and support’, but a comprehensive explanation of the problem is lacking (please correct me if I’m wrong and a link to the relevant discussion would be great). Would those of you fortunate enough to have received your GF (and maybe someone from Glowforge?) be willing to answer the following questions:

  • what is the alignment issue exactly?

  • Is the issue universal? Are all GFs experiencing the exact same issue or is it different from one unit to the next?

  • Does the 1/4 inch tolerance apply across the working area or just at the extremes near edges of the working area?

  • Are cuts/engraves being distorted or just the position of the cut/engrave within the working area off different from expected?

  • A software fix has been mentioned, is any time frame for release of this fix?

Thank you all so much for your time!


#2

It is primarily an image interpretation and positioning thing. The farther you get from the center of the bed, the greater the chance of the image being shifted.

It is pretty universal, as it is a software interpreting the image. There may be some slight variances due to the individual nature of each machine, but they are taking many measurements from each machine to allow the update(s) that fix this to work with each machine.

It most significantly effects at the extreme edges. There tends to be little or no variance directly under the camera.

It does not distort cuts or engraves. It is only positioning that is affected. My own experience has been that relational positioning is consistent until the material is moved, meaning that you could have a cut/engrave template, cut a hole for holding the actual material (such as from cardboard), then ignore the cut and do the engrave on the material placed into that template (so long as the template has not been moved). If you fill the area with engraves and cuts, they keep position to each other very well. If you do the 12X20 workspace in your source file, all positionings should be exact.

No clue on actual fix timeline. They are working on and have a plan that includes taking individual machine measurements into account (per the last update).


#3

I can’t answer all of your questions, but I can tell you what I’ve seen on my GF. In the middle of the bed the alignment is off by about 1/16" in both x and y directions. At the far corners of the bed it’s off by about 1/4" in one direction and slightly less than that in the other direction. I’ve had issues with cuts at the far corners not cutting all the way through, but I haven’t noticed any issues with engraves.

Just to give an example, I tried to cut 9 copies of the keychain design that Glowforge just released using Proofgrade cherry plywood. I placed them in the bottom-left corner and only two cut out.


#4

From unit to unit, and material to material the :glowforge: is not cutting or engraving exactly where it is supposed to. This alignment is controlled by a camera in the lid. Huge potential good stuff, just not quite there yet.

It is universal in that most every one experience it to some small degree but not universal in how bad it is.

The closer to directly under the camera the piece is the less problem it has. What :glowforge: is saying is that if you are out by more than a 1/4 in. at the edge of your working area, you have a problem that needs addressing now. If it is less, take a deep breath and wait for the fix.

Just the position. For this reson, if you submit an artboard full of work it will print fine and you will never know that this exists. On the other hand, if you are trying to add some art to an existing plack or such it can be a real problem.

No, :glowforge: never anounces these things until a day or two out.


#5

Jason and Mark beat me to it…it is mainly a positioning/placement problem on the material. Distortion of cuts and engraves is non-existent.

No idea when they plan to roll out the fix, but it will soon start going out with the machines, so if you haven’t gotten yours yet, you might not ever see it.


#6

To compound this, the system has no idea if the gantry/head have gone out of alignment since the calibration. If you bump the gantry back half an inch when you’re removing your material but don’t realize it, the next print will be off by half an inch. The gantry and head are known to have some wander without being bumped as well, so it’s best to home often.

This problem could be solved by future iterations of the bed having a homing fiducial on the bed itself to which the head could home after every job. Sit it right under the head camera resting location


#7

All Glowforges do not have exact, 0.000" correspondence from lid camera bed image to design placement to resulting cut/engrave/score on the material over 100% of the honeycomb area of the crumb tray.

There are variations experienced among many Glowforge production units, variations through time from the first PRUs almost a year ago, and variations according to use cases in individual Glowforges. @Tom_A got a unit swapped because it was found that his variations were not within acceptable (according to Glowforge) limits. Several others have too.

Some units have been improved remotely by whatever tweaking is possible from the mother ship.

The 1/4" tolerance is not a standard that can be applied equally to everyone’s experience. some experience much better position accuracy and some don’t. I am unaware of any consistent research available to indicate the different kinds of variations among different users. Once way back when we were trying to figure out whether or not our lid camera images were sharp or blurry and what to expect as a standard, many of us exchanged lid camera images to help. It was discovered that there were improvements to be made in both lid camera fixture and software issues. I do not remember if anyone had to get a new unit because the lid camera image could not be clarified remotely and was just too blurry to use.

I will post my real world example today of cutting a circular object that is 2.5" x 2.65"

The location on the acrylic, non-proofgrade Chemcast .215" thick and entering material thickness as that in the GFUI is a narrow band that is 2.55 inches wide at its narrowest but with the cutouts, I can fit this object into the spot. I expect that the Glowforge should cut this out. That means that I can count on close to kerf width accuracy in placement.

Kind of hard to see the light teal circle at this zoom level, but it’s visible.

I’m writing this as I perform this operation. Let’s see what happens.

And iPad shot after.


#8

Here’s a grid showing the alignment on my unit (Basic). The major grid lines are 1", the minor are 1/8".

As other’s have stated, the problem is with the “Preview”, not the actual cut. The actual crosshatches you see in the picture are cut pretty much exactly where they should be. I did an experiment on this, and measured that they within better than ±.003 of where they were supposed to be across the sheet. Pretty accurate for a “hobby grade” machine.

The correction is done in the cloud, not on the machine, and the amount of correction required is very machine specific. The data needed for this correction is reportedly recorded at the factory as part of the final checkout. In his October update, @dan stated that “[w]hen it’s ready, it will roll out with new machines off the assembly line - but then we’ll wave a magic wand and start applying it retroactively to all the machines in the field, reprocessing their current photos and original calibration images to bring them to exactly the same precision as new units.”

No date announced, which is SOP for Glowforge.

But, hey, in other news, they are apparently allocating resources to develop an app unrelated to pre-promised features. So, you know, priorities.


#9

Had not seen that about the app! Ugh this company


#10

To be honest, it’s a toss up for me using optical, so I generally try not to use it. Occasionally I’ll use it for placement on scrap, but outside of that I just run my outer cut line over a piece of tape so I know exactly where the cut is gonna go, then I put my material down


#11

That’s by far the best use. Not ‘every’ cut can be from a fresh piece of material.


#12

Ah, thank you Scott for making the “preview” distinction. So if I understand you right the offset is only between the overlay and the cut, but the cut is fairly accurate. So if I cut a bunch of pieces that have to fit together, even though they won’t align with the preview, the actual cut pieces will align/fit. correct?

Seems they could create another type of alignment mode (manual) that wouldn’t rely on the cameras if you needed to get your cut to land precisely on your material.


#13

They’ve had iOS, and I believe Android developer(s), on staff for quite a while.

So while it’s easy to say, oh look at what they are allocating resources towards, the reality is that the mobile development employees probably have very little to do with machine vision. Just like marketing has very little to do with MV. And every other job in the company that is not a MV position.


#14

You got it. For instance, I just cut this (following @dmi’s very excellent tutorial):

Scary on the GUI:

Looks like this on the actual cut:

They came out perfect.

Yeppers. The fitting is spot on (used .010" kerf setting). They actually ‘snapped’ together:


#15

Failure to cut through doesn’t have anything to do with alignment. Usually that happens because the material isn’t flat against the tray. If that’s not the case, please post to Problems & Support.

We actually have multiple waves of work to improve alignment, as there are many factors that affect it.

One that people often don’t realize is thickness. If you enter the thickness incorrectly, your alignment will be off. More subtlely, if there’s something under one of the feet of the grate, or the material isn’t dead flat against it, or anything else that raises or lowers the surface, then it’s the same as entering the wrong thickness - the preview will be different than the cut.

There are other factors too - all of them will eventually be accounted for, and then the preview will be as accurate as the cuts already are.


#16

Thank you all so much for your replies!