Passthrough Alignment Tutorial with Manual Indexing

passthru

#1

I wanted to test some theories about pass-through use and to create a tutorial about how we can work around the camera alignment inaccuracies in the current state of the Glowforge software. To spoil the ending, here’s the final product:

I’ll be using Adobe Illustrator CC 22.0.1 (current version) primarily because I have a subscription via work. However, I am a total newbie with AI, so please feel free to point out other/better ways to do things if I end up doing them the hard way.

I wanted a simple shape that would likely point out any flaws in positioning. I found a set of french curves in an SVG file here: http://www.craftsmanspace.com/free-patterns/set-of-french-curve-templates.html, licensed with the Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0).

I figured expanding one of the more curly french curves to something over 30" long would provide some good practice. To cut this we need to create a multi-operation cut file with “panels” of cuts overlaid on each other within a 12 x 20 artboard. This artboard size will force absolute positioning in the GFUI.

The plan for cutting this piece will use a guide along the left edge that stays in place (via magnets) on the crumb tray. The first operation will mark the top of the first panel with a fiducial mark on the guide. Each panel will also mark the edge of the material being cut at the very bottom of the panel, exactly 10" down in the design. After each cut, the material will be pushed through by 10", the newest “bottom of panel” fiducial aligned with the mark on the guide.

Creating the Guide

I did some experimenting with a 12" x 20" artboard and some one-inch squares to see just where in the GFUI these would show up. I found that (0, 0) in the artboard aligns to (0, 0) in the GFUI (the top left corner of the bed image). However, it would not allow a square positioned at (0, 0) to be included in the design. Nudging it (in Illustrator) to (0.01", 0.01") allows it to be cut. Running some light scores determined that with material pushed up against the left edge of the crumb tray, the X position of 0 in the design is about 0.66 on the material (on my machine, YMMV). After determining that, I made a rectangle 1.5" wide and 10.5" tall and cut this out of a piece of cardboard from the box I was cutting up for this test (a used moving box). This would not take too much width and would be fairly easy to hold down with magnets.

Creating the Design

I created Artboard 1 as 12" x 20" to be my “output” artboard. This is where the final design will be placed.

I created Artboard 2 as 36" x 14" to hold my overall, unsliced design. I selected one of the french curves and placed it on Artboard 2 and scaled it to fill most of the height. I then used the Direct Selection tool to select the individual curves and looked for incongruities in the design. I found two points that were very close to each other, but not quite the same. I used the point averaging function to split the difference and make them a single point.

With the guide being 1.5" wide, the right side will be at 0.84" from the left side of the Artboard (1.5" - 0.66" margin = 0.84". To help align things, I placed a vertical guide at 0.84" on each artboard. This guide shows where the right edge of the guide will be and the left edge of the material being cut.

I’m going to slice the design into panels 10 inches high.

On Artboad 2, I put a score spanning guide, being 0.4" on either side of the edges.

The part on the left side of the guide will mark the guide to be the fiducial marker that subsequint marks are aligned with as we move the material. The first mark is at a Y position of 0.5". Since the panels are spaced every 10 inches, the following marks are at 10.5", 20.5", and 30.5". These marks are all just 0.4" on the right side of the guide–no need to re-mark the guide on these.

So that we can clearly see where the discontinuities between cuts will be, I’m also putting score lines across the design aligned with the fiducial marks.

Now, we need to cut the big design into pieces. One way to do this in Illustrator is to draw a line at the dividing line and use the “Object->Path->Divide Objects Below” tool. This will slice the paths of our design along the line. It also closes off the paths–something we don’t want–possibly because the curves we’re cutting are closed paths. To fix that, I used the scissor tool to remove the added line segments. At each cut, there are two lines to be removed, one from each of the split paths. For this design the process isn’t too bad. If we were filling these shapes, this closing would be appropriate. If someone knows of a tool that slices without closing, that would be nice to know about.

I grouped the pieces of the french curve within each section to make it easy to select them in the following steps.

Next we copy each section and move it to the 12 x 20 artboard. We are going to stack these up so that the top of each section starts at the same Y-value in the final design.

To make the copies, we select the group containing the design, and the group containing the fiducial(s) being included with the group. The first section we’ll copy both the top and bottom fiducials. The bounding box of everything being copied (and therefore the position shown for the group) will be the position of the top fiducial. We’ll set the Y value to 0.5" and the X value to the same value as in the source image.

For each of the other sections, we’ll only copy the bottom fiducial in that area. Again we can position the whole group so the X value matches the original X value of the fiducial in the source design, and the Y value will be 0.5".

Create a new layer for each section, putting the objects in that layer. This lets us easily view them individually on the output artboard.


For the last section, to help with alignment I initially included the top fiducial. This allowed me to position it the same way as the others. I then deleted these scores since they were included in Section 3.

Now we need to assign colors to each part. We need to cut the design and lightly score the fiducials in each section, and we need to process the sections in sequence. We’ll use the colors that @marmak3261 determined to order the operations in the GFUI (Custom Inkscape, Illustrator, CorelDraw and Affinity Designer Color Palettes for ordering operations in GFUI):

0 0 0 1 black (#000000)
0 0 255 2 dark blue (#0000ffff)
0 100 0 3 dark green (#006400ff)
0 100 255 4 navy blue (#0064ffff)
0 255 0 5 bright green (#00ff00ff)
0 255 255 6 aqua blue (#00ffffff)
100 0 0 7 brown (#640000ff)
100 0 255 8 purple (#6400ffff)
100 255 0 9 lime green (#c8ff00ff)
255 0 0 10 red (#ff0000ff)
255 0 255 11 magenta (#ff00ffff)
255 100 0 12 orange (#ff6400ff)
255 255 0 13 yellow (ffff00ff)

We’ll only need 7 of those since we don’t need to print a fiducial on the last section.

Section 1 fiducials (both top and bottom): black
Section 1 design: dark blue
Section 2 fiducial: dark green
Section 2 design: navy blue
Section 3 fiducial: bright green
Section 3 design: aqua blue (cyan)
Section 4 design: brown

So here we have the final design with all of the layers shown.

Running the Cuts

Here we see the initial placement of the cardboard to be cut alongside the guide. Note there’s a bit of a gap at the top surface, the bottom surface is pushed up against the guide. Magnets are placed well outside of the area to be lasered.

Loading the design in the GFUI and setting the score for the fiduciary marks (top and bottom) and the cut operation.

After the cut:

The weight of the cardboard out the front of the machine made the curvy part pop up during the cut. It will be important to support the material front and back.

You can see the bottom fiducial mark here.

And here it is aligned for cut 2.

Ignore the first two operations and set the next two. Not much color difference between the two in the UI (not the same colors as in the design).

As the 2nd cut is underway, I caught this picture of the first cut partway out the back slot.

After the 2nd cut:

The last cut (cut 4) I didn’t have properly aligned against the guide. It was a short piece of cardboard left, and I didn’t notice it was at an angle.

This led to a significant error in the cuts

I repositioned it a little and re-ran the cut, leaving the final piece with less error.

Learnings

Working with cardboard did not allow for rigid alignment. This led to a little error to in the X axis, but the Y axis worked quite well. Here’s the juncture between cuts 1 & 2:

And between 2 & 3

Summary

That was my first project since cutting the Founder’s Ruler, and the first I’ve designed myself. I hope this can help others use the pass-through slot effectively. I think using non-squishy material for the guide and the project would have resulted in much more accuracy in the horizontal placements.

A Final Note on Alignment

The guide and the material must be the same thickness. If you don’t have the same thickness, you will likely experience Parallax Error when trying to line up the fiducial marks. Here’s a picture to illustrate.

Parallax Error

Edited: Fixed spelling error on parallax error diagram.
Also, be sure to read the messages below. There are some great tips and further ideas and refinements.


Continuous feed
Pass Though issues
So glad I got the passthrough
PassThrough
Maybe I missed something about camera and cut bed veiw
Looking for suggestions on cutting a long piece
Craft Room Sign
Help with forcing my passthrough to work
XY origin question
Thought it was going to be a success
Should I go for PRO according to my cutting area?
Where's the origin?
Pass through project advice
So we can get Pro Passthrough Material, but we dont have software to support it?
Pro Only - Passthrough Alignment Jig Templates :thinking:
Pro Passthrough Question/idea
Discussion of the April '18 update
Pro Passthrough
How to correctly use the pass through slots
#2

@Jules, If this looks like a good addition to the Matrix, can you add it and move it to the appropriate section?


#3

Brilliant! We’ve all been waiting for something like this and now you’ve done it! I will definitely try this once I get my Pro.


#4

Really great! Bonus points for noting paralax error!


#5

Thank you for your diligence and willingness to share the process! :+1:


#6

Yes indeed! Absolutely, positively! Excellent explanation! :grinning::+1:

(I’ve noodled with something similar, but without the slot to test it yet…your technique is pretty much exactly what I had in mind. I’m thrilled to see it work. Thank you!)


#7

Wow, what a write-up. Thank you! I too am new to AI as a GF owner. This is helpful.


#8

Looks amazing. I will have to read this again when I get to trying this. (Of course, :glowforge: might get the auto-align working by the time I get to pass-through. That is a nice feature, but I went Pro mostly for filter, increased power, and active cooling.)


#9

Nice tutorial!

I’ve been a HUGE proponent of a cheap Illustrator plugin from RJ Graffix for cutting up vector Illustrations for passthrough sized pieces. http://rj-graffix.com/downloads/plugins/#cuttingtools

I place a guide and zip the “table saw” tool right along the guide and it separates the design exactly how I want it.


Help with forcing my passthrough to work
Matching up cuts on the pass through slot - making a RC airplane
#10

I think I’m going to try a couple of those - i see they’ve got one for concatenating that might be tremendously helpful on some of the CAD imports. :grinning::+1:


#11

Not sure on the other tools - but the cutting tools, they give you 1,000 free uses as a trial.


#12

Instead of scored fiducials (which as your point about parallax illustrates can be hard to get exactly correct on the subsequent pieces, you might want to consider a fixed physical alignment method. I use (on other lasers & CNC) finishing nails. Instead of a scored fiducial I “drill” a hole the size of the finishing nail and place a nail through it and into the bed (a wasteboard in the CNC and a sacrificial underlayment on the laser).

The other thing to consider is that when using wood, it’s easier to dislodge a spacer like your left side fixture because of the mass behind the movements. I use wood for a spacer - again either pinned to the side or inflexibly fixed to the machine. I usually do a piece of wood that goes all the way to the left side of the machine I’m using so it’s butting up against something that’s not moving. For fore/aft movement prevention I butt it against the front or the back of the machine to the side of the doors. That makes the jig referenceable to the machine vs just the tray - the machine walls are in a constant position, the tray can move on the GF.

I don’t have my Pro yet but I’ll build a similar jig for that. I’ll pin it to the crumb tray after drilling a couple of small holes in the tray edge to allow for finishing nail pins. That isn’t modifying the machine so should not affect the warranty (except maybe for the tray).

I did some stencils (19.5" wide by 28.5" long) for an artist locally for some street art he was painting. The stencils were individual colors that after each was painted formed a 4 color picture. So I had to get 4 stencils for each painting that were all oversized to register to each other correctly after being cut. Relying on the bed to provide the registration wouldn’t work.


#13

I worked up some pegs that fit down into the grid holes last night. Idea being - one peg hole in the design somewhere, cut the hole for it first then proceed, and rails along one side - should give perfect 3 point registration.

(I’ll test it once i get my machine. And that’s assuming that the pegs will fit in one of the new tray grids.)

Anyway, no rush, it should work out pretty well given the tutorial above. (And I don’t have to write it up! YeeHaw!) :smile:

Whoop! Time for the F360 webinar…


#14

Yep that will work too. I have cutting some honeycomb pegs on my list. @takitus or @karaelena posted about their design back early this year. Was waiting for my machine so I can match my honeycomb specifically.

I do try to make my registration pins as small as possible though so they don’t get in the way of my design.


#15

A lot of good thoughts here. I think that making the guide run the full length front to back of the machine would make it less likely to slip. It would need to have tabs at each end, probably vertical would be easiest, to keep it from sliding through the slots.

The crumb tray has the lips on the sides that are exactly 20” apart. If you wanted a guide to overlap them, it would need to be contoured on the bottom. Having seen the discussions about measuring the thickness of the crumb tray, I was concerned about whether pass-through material would lie flat on the tray, but the front and back of the tray are level with the honeycomb.

It seems like pinning to the tray has the same problem of possible movement. I do not think this is a significant issue since you can be consistent in pushing the tray to the stops…say left and back.

The thing I like about having the fiduciary marks generated by the design is that it completely removes variations of calibration. The design is completely self contained.

Combining that concept with pinning, however suggests the following to me: make small registration pin boards that fit into laser-drilled fiducial holes in both the guide and material. The pin boards would be small boards, maybe 1” square with pegs (e.g. finishing nails cut off) sticking through the bottom.

The guide fiducial holes would be cut during the first panel and each panel would cut the corresponding holes at the bottom. Having two pins in each side would prevent pivot errors from introducing slop.

You could also have a pair of such fiducials on the door side of the guide and process the cut in two passes. First pass, cut the fiducial holes. Then cut the design, having the registration pins holding both the top and bottom of each panel.

The benefit to having the pin blocks sit above the material is that you only have 1/4” of slot height, so putting sacrificial material under the product uses up some of that thickness. Your stencil example would be OK with that. 1/4” ply not so much.

So, lots of refinements possible!


#16

What a nice write up!! Your efforts are very appreciated!


#17

That looks great! And $10 is cheap. Looks like I’ll have to wait a bit, however, until they get CC 2018 supported.


#18

I’m on CC18 (for Mac) and it works great. Not sure if you’re on PC. Looks like the PC-version hasn’t been updated yet :frowning:


#19

Yep. Windows here. I don’t do Macs.


#20

Correct & correct. Pinning to the crumb tray is for pinning the alignment jig that is locked into the same place all the time by the side/front or back. The pins to the tray force the tray into the same position all the time - so any movement back and forth due to slip in the little divots in the base won’t affect registration. The jig is always in the same position and because the tray gets locked to the jig, it will also always be in the same position.

For the GF my jig will be to the edge of the black rim on the left side up to the edge of the honeycomb so you still get the full bed available. As they improve the usable bed size until it gets to the full 20" size it will still work.

Then you can use pins in the bed for your fiducials because they’ll always be in the same place - not just within the execution of that project but for all of your projects. :slight_smile:

The other machines I use have bed height adjustments so the use of a sacrificial board to pin the fiducials to isn’t an issue. For the GF you’d need to make a bed that you could replace the crumb tray with. If you’re good with pinning the jig to the crumb tray as I’ve outlined you don’t need to create a sacrificial board.

I outlined the whole process in a posting last month on using pass-thrus in general and suggestions for how to do it with the Pro.