Ian,
I would very much like to pick up where you left it at that conversation and I promise I won't disappear any day soon.
To address the question of the distortion here's a more in-depth view.
The technology that we use, and most others do is solvent inkjet printing. What basically happens in the printing process is that a piezo-electronic printhead shoots tiny droplets of ink pigment in an acetone solvent. The solvent "burns" into the material and leaves sort of a relief into which the pigment gets into and gets stuck there.
The printing process itself doesn't necessarily stretch the material, we are talking about self-adhesive vinyl here since it will be applied to a rigid substrate, but it leaves it susceptible to the stretching during application since the vinyl is much softer now.
If you leave the vinyl to gas off for 24 hours or so the ink will dry, the solvent gases will fume out and the stretching effect from the solvent is mostly gone.
The other stretching though comes from the mechanical forces that it endures during application to the rigid substrate.
If you have never seen solvent vinyl without the liner on it is almost rubery.
This is what the application looks like -
http://www.youtube.com/watch?v=-u4TxTBU80g#t=51As you can see the vinyl is quite stretchy so the distortion really depends on the direction you are applying the vinyl in. There may be some distortion in other directions as well but I think that it would mostly go in the direction of the application.
Now in this industry when you are doing serial cutting either via punching as is done in offset or via hand you leave some bleed. Bleed is basically some extra space or color around the image which is a tolerance so that if the cutting misses a bit that you don't get a white part there.
This image explains it perfectly:
To see just how much of a real-world problem the distortion really is tomorrow I'm gonna do a few prints, apply them straight out of the printer, ungassed, to a substrate and try cutting them based on a single cross-marker and then we can proceed from there.
Am I correct in thinking that the non-linear distortion is introduced when the print is affixed to the substrate? i.e. every piece will be "differently non-linear"?
OR
Is the non-linearity introduced at the print stage i.e. A batch will be non-linearly distorted with respect to the original but the individuals within a batch will be identically distorted?
The majority of the distortion would happen during application but I have reason to believe that either each or at least some of the pieces would be differently distorted. The reason for this assumption is that the distortion (stretching) is a result of mechanical forces applied on the vinyl during application. So for example you could apply some parts with less force and you could maybe pull a bit harder on a certain part and that could cause the distortion to increase on that part but not on the others.
Here is one thing I don't understand though, optical registration of print marks and cutting based on them is nothing novel in our industry. Pretty much any plotter cutter you buy has this option, even those shabby Chinese ones so it can't be that hard...I mean we are talking about a $500 or so and they cut the printed vinyl without fail every single time.
Here is an example of how that works -
http://www.youtube.com/watch?v=jV1v8dRdsn4#t=158It prints 4 of these marks (the black dots) total, one on each corter of the print then the cut head scans each dot and based on those it starts contour cutting the print based on the vectors you defined in your design software.
Same goes for the Zund and iCut system. You have to print these reg marks out and the camera scans these and based on them it cuts the print, no matter the distortion.
What I can't understand is how do they account for the distortion based on those registration marks ?
Demonstration of how the iCut system works -
http://www.youtube.com/watch?v=s3MeHLluzC0An even more impressive example, an iCut system on a laser cutter -
http://www.youtube.com/watch?v=F4OLzJsakagThat must be less than a millimeter in precision and from the description:
"Printed signs, displays or POS materials can be cut on an individual basis using laser technology and i-cut®. The cutting line therefore follows the exact printed specification. With other methods, slight distortions of the printed design create unsatisfactory results. However, i-cut® is an intelligent, easy to use system which recognizes any distortions in the printed design. No matter whether it is a linear or non-linear distortion or a rotation, the cutting path is adjusted automatically and dynamically. The cutting lines therefore always perfectly match the printed design on both flexible and rigid materials."
EDIT: Added the iCut demo