Mine is the north eastern point on the bed. 
@dan @Tony
ok I think ive got it. (I feel like newton crosby right now)
- take an SVG of an asterix (snowflake would be even better). cut it out of a piece of material maybe 6x6. acrylic or mdf preferably.
- remove the inner piece, you wont need it.
- place a thin piece of acrylic or mdf down underneath the previously cut asterix outline, and make sure the asterix is in a different orientation than it was originally.
- Now try to place the asterix svg as accurately as possible over the asterix shaped hole left in the original material and run a lower power cut thats JUST BARELY ENOUGH to make it through whatever material you put underneath.
- if you can cleanly and consistenly make it through that material underneath without touching the edges of the previously cut asterix, then you know you are capable of reliably producing an exact cut repeatedly. If you burn the edges of the original piece or dont have a consistent depth through the bottom material, it means theres probably still some work to be done.
kind of like a laser version of operation =).
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well at that point it might be able to, which would be great! I still think an L shape guide with 3 registration marks would be incredibly useful. especially if you have an odd shape material
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@Hirudin, I am probably out of my depth here, but what I’m understanding is that is the alignment test exactly. Because the camera doesn’t move once the head is in such a place that the camera sees it as aligned exactly right to the reference it is looking for, then in theory the head is in exactly the same place as it was before. The problem seems to be (and, yes, I know I’m restating what’s been said, but it’s how I learn 
) Because the camera is attached to a moving part–the lid–there is a chance of the camera being in a slightly different place if something is keeping the lid from completely closing or the lid warps, or something. Part of me wonders about using two moving parts as your points of reference for homing (lid and laser head), but I’m just the arm chair quarterback, glad they have guys much more clever than me working on this stuff 
If i’m following, then that’s where glowforge is coming from. I can see how developing a way to also take some kind of reference from the bed itself, using the camera on the head could, in theory, be a way to check the lid camera accuracy, or provide another default method for more accuracy.
Not trying to argue or anything. I’ve been reading this homing discussion for a while and am just trying to wrap my head around it. Right now I’m not foreseeing a situation where I will need the .001 accuracy, but I know I haven’t even begun to guess at all the ways I will use the machine so I might very well need it badly.
@Tony, like others have said, thanks for joining in a shedding some light.
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Ok, thinking out loud (and replying to myself-which is normal because I talk to myself all the time). In theory adding a mark to the bed that he camera on the head lines up to exactly when the logo on the head lines up with the lid camera could, in theory provide an even more exact reference because now you are plotting through three points instead of just two. That would guarantee the lid, head and bed are all exactly the same relative to each other. Since the bed doesn’t move that would mean the head and lid camera have a “solid” reference to grab on to.
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I think that’s a good idea. At the beginning I thought the head camera would be used more. Right now the head camera seems to perform focusing duty… and that’s all.
I started a new thread about the camera and dat dair head.
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lol, I was reading your reply when you edited it. I thought my eyes just glitch out for a second 
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Thanks @Tony and @dan for the very eloquent and timely responses.
To summarize where I’m at now:
- I understand the head home procedure using the lid cam on the glowforge symbol on the cut head. It would appear to give a consistent result for the physical position in the Glowforge based on lid camera. Lets call this the “cut head home” position. There is an offset from this head home position that dictates the bounds of the cut area physically inside of the unit, but it is not tied to the UI ruler. The upper left corner of this is what glowforge calls the (0,0) position. I completely understand that the head does not need to move to this position, but it does need to know where it is located inside of the Glowfoge so it knows it’s physical limits.
- I totally get the idea that you can cut a template hole outline (either the big rectangle from @tony or the @takitus snowflake), turn layers on and off without moving the template, and then engrave the part inside it.
- @dan Thanks for the clarifying response on the UI snap to (0,0) point on the ruler not being currently available {added to your hopper} and tying the (0,0) from the UI to a known offset from the glowforge cut head zero {added to the hopper}
My concerns have been heard by @Dan and has graciously added them to the list of development hopper items.
My pestering the subject relates to not having to perform several extra wasteful steps.
Current scenario:
Taping down cardboard blank for each new part to be cut (material and landfill waste), cutting out a hole (laser waste), flipping settings in the cut file from box outline to real cut or engrave to be performed (time waste), placing my real part to be cut in the machine, cutting the real part (real benefit). Any changes to the SVG file, (say I add something to make the lower left corner which make the SVG exterior dimensions larger) will change the file position when it is opened in the UI causing me to have to make a new cut a positioning template.
Alternate scenario if line 3 hopper idea is implemented:
Place corner guide to a known position (using side walls or whatever clever method you want) inside the Glowforge cutting area and simultaneously place the part in machine, open SVG file move it to the UI (0,0) where it automatically snaps into position, then cut the part. Yeh! No special steps! Part is cut 100% accurately! No waste! Changes to my SVG size don’t matter! I put it at (0,0) and cut will be in the right spot on my part. Yeh!
PS on the ruler idea for the Hopper:
4) I’m on board with @takitus idea of having a tool you could place inside the glowforge to establish the (0,0) position and angle in a location other than the upper left corner utilizing the cut head camera. I suggested the same thing back in response line 137.
Get me the two things in line point #3, and this is icing on the cake that could wait a long time.
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What I understood from Tony’s response is that your #3 already exists, although it might need just a little extra work. It is not a snap per se, but if you open an SVG then it will always appear in the same position without you needing to move it. So as long as your drawing takes this into account you should be good. I admit it might take some experimentation, but only the first time.
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I guess I didn’t read into it that placing a max cut dimension rectangle around the exterior of every cut file, then placing what you wanted cut a known distance inside from these edges, would then result in a guarantee that when the SVG placed into the UI (without moving it) would auto locate the SVG’s “actual cut” correctly in a consistent location that would allow for a fixed 0,0 to be placed inside the the Glowforge’s cut area and consistent placement of the item to be cut resulting in the accuracy required.
Engineer, not an English major. Run-on sentences abound.
Exactly…
…and exactly.
No, tony was just referring to it that way to follow the conversation. The “upper left corner” actually changes with the head speed, as when you’re doing high-speed engraving the physical limits are different than when you’re doing slow cuts.
This is a key point: what is being discussed as “0,0” - that is, the northwest most addressible corner - will change with the speed you use.
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One more very important note: Tony’s request was not for hypothetical machining operations that illustrate your request, but actual use cases that you, personally, are thinking about doing that motivate your request, with the more detail the better. We don’t build features because we want a marketing checklist, but because of real-world problems that you help us understand are common and important to you (like the lightswitch example).
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OK, the camera doesn’t move. Fine.
Does the lid use some magical zero play hinges? They would have to be something special to have no play after lots of use.
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The lid snaps into place and is registered on all sides so it sits repeatably.
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Suppose I want to cut a large acrylic door for a 3D printer with holes for the hinges, door knob and a large engraved name, perhaps a decorative engraved border, perhaps a trench for a sealing strip.
For all but the first and last cut the corners won’t be visible. It will just be two edges and what it has cut already. Perhaps it can engrave fiducials in the waste margins as it goes.
Lots of examples where I have a part not was not created in a laser cutter that I need to add a secondary operation to the part. Creating text on a small ridge or detail inside a small dia circle. Being able to precisely place a part on the bed and perform that operation is highly beneficial in my mind. Again… artists may not care about precision greater than what the camera provides. People placing fine detail in specific locations on parts or designs do care.
Obviously you picked up on the fact that I robbed the picture above from work where the part is a large bore drive stub shaft. I would never obviously use that part in the glowforge. My point in using it is that the picture is irregular in shape with text registered vertically on a thin ridge. Text that is off center would ruin the part. Precisely placing the irregular part in the bed using a guide on the bed and placing the svg text drawing in a precise location in the UI makes this job easy.
.#2 on that list - Argh, it wasn’t a template for cutting out snowflakes, it was a test for them to see if they could accurately produce repeatable cuts.
It’s something I don’t think they’ll be able to do until down the road when edge detection is in place. It’s no easy feat, but if they are able to do it without a jig it might mean their software is accurate enough for me to not need to use a physical alignment tool
This is pretty much the need. Another example could be drawing a perfectly even outline around the apple logo on a laptop/phone.
For me, engraving text or accent lines which are perfectly centered on the ridge of a casted item just pulled from a mold is a need.
Another example I’ve run into is when using 123D make, sometimes the software glitches and doesn’t include the alignment rod holes in the template for the piece you cut. Happens all the time. I know exactly where they need to go in distance from 0,0, so I just put them in one at a time.
However if they are off just a little bit it will screw up the entire alignment of the pieces and I’ll have to do a bunch of rework which could take a while. I learned this the hard way when I didn’t type in the distance to the right number of decimal places and I had a ridge where the two connected. Big letdown.
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Is there a reason @tony or @jamesdhatch that “your” y-axis zero at the north edge? Seems un-intuitive. Does the interface for your machine have you put negative values for Y?
In junior high math the 0,0 point was always lower left… and CAD software follows that approach, though the 0,0 can be moved to any point and values can be negative. (i.e. if my 0,0 is at the top left of the screen, then anything in the middle of the screen will have a positive X value and a negative Y value. Of course, in CAD you can also rotate the display… but it’s pretty bad-practice to do so.
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