XY home position

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So I was in the shower and giving this some more thought, and it would be possible to create a simple optical registration system for the glowforge’s flyover camera that could be used somewhat effectively.

  1. have an optical registration point sticker in the homing area that the flyover camera would align to to give consistent 0,0 (if they arent doing this already… are you guys?!)

  2. have a standard square magnetic ruler with 3 optical registration points on each end and at the corner. Use the lid cam to ascertain the general location of the registration points, and the flyover cam to align exactly to them. The great thing about this concept is that you can place the corner anywhere you want. If you need to put it at an angle, as long as the cams can see the reg points it can determine what that angle is and it will do the rest. You just slide in whatever is to be engraved butted up against the corner of it and go.

Now obviously this would be something that would need to be supported in the software, so its not something any of us put together. If it turns out that more accuracy is needed for the user population these could both be solutions to that problem. The second one would be pretty useful IMO.

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This.

I keep wondering if you CNC guys are stressing over a function/feature of the old generation of machines that will simply be able to be ignored once you get your GF and pin the workflow down. A magnetic registration tool would avoid the pass-through issues of a hard stop up top, would make use of the magic eye (camera), and would give you a 0,0 point. Maybe it could be a poly-magnet that you could “lock” into place?

This could also be the first after-market glowforge tool. The Takitus Double-Oh MagLock Registration Corner.

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I think the difference between making for art and making for exact fit/detail is what we are concerned about here. I am with takitus on this one. I operate a CNC that has the ability to have an exact 0,0 point that can be specified.

Alignment scenario: Place a corner point anywhere inside of the cut area of the glowforge. If the camera on the laser head could be used to find a “virtual” zero point and then a second “x” axis point using visible or UV marker on the corner point template. You could then display a virtual x,y axis on the glowforge computer so you can align your drawing to properly zero and axis correctly to cut/engrave onto the part you are working on.

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Just one note on the angled thing: that might get a little weird for certain cuts and engraves. Rasters would either get done as if you had rotated the image on a perpendicularly registered piece, or the raster firmware would have to do everything at an angle, which might not always play nice with the fixed resolution of the steppers.

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your second point is what I’ve been trying to articulate, but you did it better. A corner bracket with something that would register where the 0,0 point would be, and that can be placed anywhere on the bed.

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Would be cool, the question is can the GF even be made to do this? Right now they’ve said the lid cam does the homing and alignment, and it hasn’t shown itself to be accurate enough to do something so detail oriented.

If they are able to leverage the head cam, I think it could be a possibility. (If it is able to determine location down to micrometerish precision)

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yep, The head cam is the better camera to utilize for this. The registration points would help determine what direction the piece is pointed in and angled. Although if you put it in the top right of your piece, your brain might start to hurt when you try and figure out where 15, -30 is…

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I think the answer to this question would help. I know @dan has tried to address it, but it’s still not quite answered.

To me, the question would be… I have 10 circles of wood. All the same size… 5" diameter, 1/4" thick, otherwise flat surface. I want to put a 1/4" hole in the dead center of 5 of them today. Then I want to do 10,000 other completely random things with my 'forge. Then I want to put a 1/4" hole int he center of the other 5 circles. How can I do that precisely?

Please somebody tell me if my thought problem is flawed and correct it.

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Sadly, they would have to build support into the software for something like this, so it’s not something I could do myself as it’s not open source.

I don’t think this is stressing over something old school and that the ‘new way’ is better, because CNC machines are designed for accuracy and repeatability, down to micrometers. To hide/remove that innate functionality, to some degree, contradicts its purpose for existing.

You’re a DJ right? I’m assuming you’ve used serato or traktor. It’s like if all the sudden the cue point of each track was off by a couple seconds, so instead of timing your mixes right you had to scramble at the beginning of each mix to get the tracks aligned. It’s like “I know you are digital and should be starting exactly where I tell you, but you’re not for some reason.”

It’s really cool/innovative what glowforge has done, but if you take away some of the foundations of CNC it leaves everything else a lot less stable.

For those people that don’t or haven’t used CNC machines before, you’ll find yourself wanting as much control as possible at some point. Example:

You’ve cut a bunch of pieces of nice material to fit together using 123D make. Only after you finish cutting them all out and trying to fit them together did you realize the program messed up and didn’t put some of the holes in the pieces (has happened to me many times already).

Oh no, you have to go back and put those holes in manually. You’ll say to yourself, I know this hole needs to be exactly 33.75mm from the top corner, but how do I get it there? If you can’t get it in the right place it’s not going to fit together, or you’ll have an oversized hole from multiple attempts that ruins the aesthetic of the piece. This is what I don’t want to run into, and why those old school CNC methods are so important.

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Exactly. Do other laser cutters, even the inexpensive K40 models have a reasonably accurate home position that is found or can be commanded on each power up?

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Haha it does! And I know I put it to the test because their software is really crappy, and there’s no e-stop on the machine so if there’s a reason I have to stop the job, I have to cut the power to it, cancel the job, then turn it back on and start again. It always goes to the same place no problem.

The k40 software has a really poorly designed job queueing system. Sometimes you start a new cut/engrave but it will resume something else which you didn’t know was in there. You have to cut the power hopefully before it ruins the piece.

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One way to do it, (and I’m not saying it is the only way), but if you do not precut the circles from the wood, and cut them at the same time that you drill the holes into them, is by creating them that way in the file. They will be 100% perfect no matter where you place them on the sheet. The little center hole and the outer circle will travel together as one unit.

Then you can do however many you need, set the file aside, come back later and do the rest.

If you have a bunch of pre-cut circles that you absolutely have to add a little centered circle to later, you can create a jig for it:

  1. Create a design file that has circles of the exact diameter that you need (the larger circles). Make those circles have lines of one color. (Illustrator, Inkscape, CorelDraw)

  2. Inside the file, center your smaller circles inside the bigger circles. (You can do this with a couple of clicks, and it’s perfect, each and every time.) Make the smaller circles a different color.

  3. Send the designed file up to the Glowforge cloud. :glowforge:

  4. In the Glowforge software:

Turn off the small circles.

Set the large circles to cut.

Put a large piece of material (Cardboard, wood, chipboard or whatever you want to use into the machine so that it butts up against the upper left corner of the machine. Fit it snugly against the left and back wall.)

Cut the large circles out of the cardboard and remove the centers.

Put your round wood pieces into the holes in the cardboard.

Turn off the large circles in the Glowforge software, and turn on the small holes to cut.

Cut the Small holes in the center of your wood pieces.

When you take everything out, you should be able to re-use the jig to put holes in more wood pieces, if you place the cardboard in the same relative location each time.

_Note: This would only have to be done for something that you intend to do over and over again…unless you are mass-producing something, you would not need to mess with it.)

We should also be able to affix a more or less permanent stop/origin into the machine, by just cutting down a piece of wood to rest in the back and block the non-laserable area. Then you can butt smaller jigs right up against that.

Lots of ways to deal with it…

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I think that’s the problem we are pointing out. There is no way to put the cardboard back into the glowforge, re-open the file, and have the drawing and the part magically appear in exact same correct spot.

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I think one of our beta or pre-release people should be able to answer this pretty definitively. Get a piece of wood or acrylic or whatever that fits solidly against some corner-like part of the interior. Create a simple vector engrave file that covers part of that piece. Run the file without adjust its position in the interface. Do some other stuff, cycle power on the GF etc. put the piece back where you put it the first time. Run the file again. Rinse, repeat until you’re comfortable with your sample size. Either there will be multiple offset copies or there will be one deeply scorched version. (Or some other alternative I haven’t considered)

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How can we know there is no way to have the same file come into the software in the same place? It seems to me that this should be exactly what happens, since to do otherwise would require the explicit introduction of a random number; as long as you don’t manually drag it to a new location after it loads, it will almost certainly be in the same place the second time you load it.

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The problem we are discussing is that we have no reasonable acknowledgement that the home position of the glowforge is exactly the same every time. From what we’ve been told it is not, which would negate the purpose of making one of these… =\

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Lets say I need to add lettering to this irregular part. If I burn the letters in the wrong spot, I lose $200 and have to make the part over again.
I know that the lettering needs to be placed 6" over in the x direction, and 2" up in the y direction.

If I could place my jig on the glow forge, have it pick up the two points on the jig, count that as (0,0) and place an x axis along that line, I could place my drawing for the lettering on (0,0) and engrave it in exactly the correct location.

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My approach would be to use the :glowforge:'s superpower — place the part on the bed, and use the camera to make sure the text is in the proper place.

True — I wouldn’t try that on my first go out of the box, but once I’m comfortable with the unit, I will absolutely be trusting with one-off parts.

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The variable here is actually the means with which they are homing the head of the laser. From what we know the lid camera looks to see if the logo on top of the laser head is in the correct spot. However, being at the edge of the cameras viewable area and it using a wide angle lens, the ability for it to be as accurate as we might need has come into question. And as the machine does not use limit switches there is no secondary means of verifying that the location is exactly the same as it was last time.

Problems that I can see arising from this approach are:

  • camera can shift or become physically moved over time by accident. (Materials hitting it when removing them etc), and/or slight manufacturing differences in placement
  • lid doesn’t close at the exact angle it did when purchased
  • resolution of camera isn’t high enough to accurately determine location within an acceptable margin of error
  • smoke or other contaminants causing visibility of lens to change
  • discoloration or distortion of homing logo on laser head

I think you get the idea. Without some way of making sure the head starts at the exact same position every time, any thing being permanently attached to the laser bed as a reference will also be inaccurate.

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In this case, you would need to create a hole shaped like the part, in some sort of design software, include the lettering exactly where you want it to be in the file, and proceed according to the second description in my last post.

Creating jigs is just locking certain design elements into place relative to the whole…if you are trying to get something exact by eyeballing it, it ain’t gonna work.

If it doesn’t have to be exact, you can use manual placement via camera - should be good for about 90% of most users needs.

To get exact, requires 3-Point Registration, and the machine is not coded to do that.

I’m gonna be lazy and link to my earlier comments on it:

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