Feature request: Absolute positioning - CNC Mill style

I utilize a similar function on the current laser I am using. I built a jig to hold the paddles I engrave. I then took a picture of the jig, pulled the phot of the jig into Inkscape and made an outline of it in SVG format and set it to the same dimension as the actual jig. I load it up in the laser program so that I can position what ever art I am using and it comes out perfect without having to figure out if I have it straight on the bed. It saves a lot of time and worry if I have it lined up correctly. Here is an image of the jig it is very simple:


And the paddle that goes in it:

And since the laser I work with initialized from the upper left corner of the bed all I have to do is place the jig in that corner place the paddles in it and no more worrying about grinding and sanding an engraving out of the wood to make it usable again!!

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Can something like this be used for positional alignment?

http://m.ebay.com/itm/131808967789

Those are ok, but I hesitate to even use those, as the spot size on red lasers generally tend to be rather large. They’re great when you don’t need a lot of accuracy, ya know making sure it’s actually on the object and not off to the side, but for anything with precision, math/numeric placement is your best friend.

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I bet having one of those would be helpful, if it was setup right. One exactly like that, a crosshair, would need to be mounted directly above the 0,0 point since shining at an angle would cause the intersection to move depending on the thickness of the material it’s shining on. Of course, having the laser emitter mounted directly above the 0,0 point would obscure the cutting laser in that area. Two line emitters could draw a crosshair on the 0,0 point, and they’d only have to be mounted in such a way that the planes created are vertical and cross on the origin.

But even then, they have the problem mentioned above (large spot size). Though, even with a 2mm wide line, you could probably get down to ±1mm, which is… decent (IMO).

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Right. Not much different than lining something up with the GF lid camera. No added value. Then you have the issue of trying to line up the red dot laser with the actual laser target on the material - they get out of alignment on the ones I’ve used.

The closest thing to CNC Mill that I have used is my Silhouette. Which uses registration marks. But JigMark would work too.

If you design the jig to press to the top/back and setup your file to match that, using the full bed space, couldn’t that give you consistent results?

It would be close, but the way the feet of the bed are designed, it still has a bit of play in it. Theres gonna need to be some additional guides built to make sure theres no shifting on the x axis. Some snug fitting L shaped pieces in the corners might work

My thought is that there should be something that you can push against where variations are more or less eliminated. The back is fixed, for instance. Make the jig sit on the bed rather than fixing to it any way, then brace against fixed positions, like the back. Design the workfile with this in mind?

It can.

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I went to cut my full bed jig. My idea was to put a larger piece of plywood up against the back and side and cut out a 20x12" hole. That would give me a fixed corner to use as my reference corner. It would be up off the honeycomb a bit because it would be resting on the frame of the tray but that shouldn’t be a problem (need to order cuts so the pieces fall after they’ve been engraved).

Short of it - doesn’t work.

The back does make a good fixed surface to butt the plywood against. The problem is the rails for the Y axis travel are the only reliably fixed things on the sides. Unfortunately, the X axis rail rides on the Y rails with some pretty robust brackets. Those will bump into any frame or jig that extends past the tray edges.

If the back & side aren’t both used to lock the jig into place it won’t provide a repeatable reference corner. Anything keyed off the tray is potentially skewed due to the slight variation that can occur with the tray only resting in the dimples on the floor.

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I want you all to know I have realy enjoyed the thoughtful and articulate discusion on this.

I agree that it is absolutely necessary that it be possible to do fast and efficient piece work. Especially for owners of the Pro. I’m curious what process will win out.

@dan. As a special request for business users I’m going to simply request to see progress or a direction that the team is going use to solve this problem.

I must say that it is quite impressive and pleasing that issues like these are now dominating the front line but they are important nonetheless.

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I’m a bit rusty at this, but my intuition is screaming that somehow utilizing a fourier transform can be utilized to solve this positioning problem. I can’t quite put my finger on it. Any engineers or mathematicians want to weigh in? I remember something about reducing the spherical intensity profile around a beam spot to a single point. I think it is called spatial filtering.

All this talk of jigs registered to the case of the machine seem to ignore the fact that the origin of the motion system is registered to the lid camera, so any play in the lid hinges would lose registration with the jig. The only way to make a jig accurate is for the cameras to locate it. In which case there is no benefit from it being registered to the case.

This is unless the lid has special zero play, zero wear hinges, but why would it when Glowforge intend to register with cameras?

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It’s definitely been discussed in the other thread starting about here: XY home position - #35 by takitus

It was the whole reason I floated the idea for a fiducial ruler should the 0,0 point from the camera registration seem to change too much, and them not being able to compensate by using the head camera for homing. I also floated the idea of having a set fiducial marker the head camera could use to set 0,0, which would always be the same, maybe attached to the shifting bed, or maybe attached to the frame somewhere and it would be our job to stabilize the bed.

Either way it’s definitely been brought up, just not in this thread til now =).

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I agree. It means we’ve gotten over the doubts about delivery (“will I get mine?”) to “when I get mine I’m going to need to do this.”

It’s a seismic shift in forum attitude - doubt appears to be mostly extinguished and we’re moving on to practicalities of use :slightly_smiling_face:

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I think you guys have hit on the philosophical difference at the heart of the glowforge in this area, and I’m starting to feel like this is going to be the real long term make or break. Like you’ve said a couple of times in this thread @palmercr, the hardware of the glowforge just doesn’t support a hard 0,0 because everything is relative to the camera in this setup. If the camera skews just a little (microns) then 0,0 moves as well relative to the physical bed of the glowforge.

I know I’m really just restating what you guys have already said, but just two things are missing from this system working as flawlessly as a hard (mechanical) 0,0. The computer vision has to be able to detect the edges/corners of the piece at a sub-kerf kind of accuracy, and then it has to be able to place the design onto what it sees with that same accuracy. The second part of that is easy if the first part is working. And looking back at what glowforge has said in the past it seems obvious (now) that is the system they are shooting for. In reality, it would make it very easy, much easier than a mechanical 0,0. You could, for example, make your self a jig to hold your 20 dog tags (the jig is just there to save time and hold the dog tags that way to you have to place each engrave on each dog tag). The camera finds and sets 0,0 at the top left edge of that piece of material and sets the orientation based on the overall skew of the material on the bed, or scales to fit, or whatever. If it is precise enough it won’t really matter how you lay your material in there, it will just work. The real problem right now is the computer vision isn’t that accurate yet. Here’s hoping they get there soon! :smile:

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Yes, well summarised. I don’t know if all the people asking for 0,0 have given up on the cameras being accurate enough or just don’t get the GF philosophy.

With the current state of the art computer vision and accurate cameras you should even be able to scatter 20 dog tags at random and have GF place the same design on each one. I.e. if it can locate one and can orient it accurately it can recognise and locate many. It just needs a bit more coding. The only time you should need a jig is when things need holding in place, like pens that would roll.

The main issue, and this is fundamental to GF, is will the cameras ever be sub kerf accurate. This is where faith is required as there has never been an example of them being anywhere near accurate enough, lots of examples of them not. The pass through example was very encouraging but it was an out of focus low res photo amongst a group of much better photos and when somebody asked for a close up the cleaners had binned it! So I suspect sub kerf accuracy is not there yet, even in development. But then I will be accused of being negative about the announcement that most people found positive.

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Not exactly what the GF philosophy is, but they can still have the camera based approach as they invisioned it, while providing numeric inputs for us to use. If they dont want it to clutter up the UI they can just have an ‘advanced mode’ checkbox in the settings for those of us that want that.

Ive looked at the code, and it would be pretty easy to implement something like this. Hopefully its the case that theyre just working on promised functionality and this will come as soon as they have some time to slip it in.

I like and appreciate your objectiveness. I much prefer it to rabid fanboyism and made up facts.

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Amen.

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