Unfortunately, we’ve had this discussion many times before, and usually it results in a lot of wasted time and a lot of bad feeling. I believe Tom and Mark are just trying to forestall that happening again.
I’m going to preface all of this by stating that this is my understanding of what’s going on. I might be off base somewhere, but I have no desire to get deeper into the weeds on anything or continue discussions about it, or argue whether it’s a good idea to add something or not. Already been through that.
The time to have this discussion was back while they were creating the software for the machines, about a year and a half ago, and we did. Several times. Also unfortunately, it’s not a trivial thing to implement, because their rendering software, (not the interface), is using a relative location method to create the code for the head movement.
They made the decision not to go with limit switches on this machine long before they ever built it. I know that because of an explanation Dan gave to a potential customer at a talk he gave once. (And I can’t even begin to remember which one, so i can’t find it again now.) In it, he described the potential for limit switches to fail rapidly with repeated banging of the head into them, requiring replacement and downtime that were unacceptable, expensive and requiring people have to take the machines apart and reassemble them correctly. (Which might have also caused the need for realigning the beam path on the laser, which is apparently a very precise thing.) In other words, they wanted to make the machine easy for people to use without having to be able to take the machine apart and put it back together. Or ship it back for repair.
So…no limit switch. There’s a reason for it, and now everyone knows what it is. I’m pretty sure they aren’t going to add one, no matter how many people think it’s a good idea.
Without a limit switch, the camera uses the Glowforge bug on the laser head to orient itself. It takes pictures, squares itself up, and then takes a few pictures of the bed and positions the design in relation to that. The problems with misplacement of designs on objects on the bed has to do with the curvature of the lens necessary to see a bed that large…the farther out you get from the camera in the center of the lid, the more fisheye distortion is introduced. They have an algorithm that compensates for that based on the metrics that they have captured for each machine. These early units might not have completely captured metrics yet so the compensation for the fisheye effect might not yet be implemented. When they ask you if you understood that the placement on objects on the bed could be off by up to 1/4", this is what they meant.
They can go back and adjust that remotely to a certain extent using their software, if they have the metrics for your machine. Dan has said in a recent status update that improvements to that process will start going out with machines being built going forward soon, and then applied retroactively to those machines that are currently already out there. So the 1/4" offset is going to improve for everyone, including the machines already out. (For those of you who haven’t received your units yet, if you don’t want to have to mess with it, delay receipt of your unit until they start rolling out with the improved metrics tracking. They give us a choice about receiving it now or waiting, although we don’t know when that will be and they’re probably not going to prognosticate.)
My pre-release unit has been in operation for seven months and it’s visual object placement is accurate to within a fraction of a mm. It didn’t start out that way, it started out being off by about a quarter of an inch, and during the times that they make updates to their firmware, it can get out of whack again. Unfortunately other mechanical issues can apparently also cause that to be off. The only ones who can determine what is causing the problem is Support. They have access to the metrics for individual machines and get feedback on what is causing problems that we don’t see here. If trying to reboot the machine doesn’t fix an alignment problem for you, which is about all that we as customers can recommend that you try, then you need to wait to hear back from Support.
Back to the original issue at hand - that of how to align objects accurately…you can do that very easily in outside design software (Illustrator, Inkscape, AD, CD) and save that as an SVG file that captures all of the information in perfectly aligned, perfectly scaled, perfect engraves and cuts. The secret to using it is relative addressing. The rendering software looks for one object, either a cut or an engrave in the file and then it moves the head relative to that object in order to perfectly place the other design elements. The advantage to doing it this way is that you can drag the artwork anywhere on your material to use up the leftovers without having to cut it up into a specific size to place the piece of wood up against an endstop where the artwork needs to happen. In addition, they have added a workaround for those who want to do numerical placement. If you make your artboard 12" x 20" in your design software, then where you place your artwork on the artboard is exactly where the item appears on your screen when you save the SVG file. Scaling is correct, and relationships between elements are maintained.
The use of jigs is a technical version of just adding a weeding box around your artwork in the SVG file. You can engrave one side of a double sided design, cut the weeding box, flip it over, engrave the other side of the object, and finally cut out the shape inside the weeding box. It’s a perfectly precise method. The placement of the weeding box around the artwork acts as the anchor here, you can place the artwork anywhere on the artboard, or move it anywhere and get perfectly accurate results with the build. I prefer to use jigs (ie: just add a weeding box to the design) but I only need to make one or two at a time. If you are engraving on thousands of precut items and you need repeat ability, you can use the artboard sized correctly for numerical placement.
A lot of people want answers to why Glowforge doesn’t jump on their wonderful suggestions and just make it happen. This is why. If you managed to make it through all of that, you now have a pretty good idea of why I think it ain’t gonna happen any time soon. You also might have a better idea of how to proceed to get excellent results using the tool you have at hand. Just use outside design software to work with the tool’s parameters. There are reasons it was created this way. Once you get a little comfortable with it, you’ll get an idea of the true power of this machine. It’s astounding.
Changes down the road are likely a long way out. They will capture the interest now, but I don’t expect to see anything major implemented any time soon. We should still give the suggestions so they can gauge interest, but keep in mind that it’s for the future.
TLDR : Quote “Thanks for the suggestion, we’ll let the team know.”