Printing on Polycarbonate (or Acrylic)

[rfer]

Hi All,

I am trying to print a camera calibration dot grid on a polycarbonate sheet I have. I need this grid to have a high tolerance. I have reached out to a number of places that specialize in printing on acrylic, but all are for photography, portraits, etc., and thus have very poor tolerances (+/- 0.5"). Does anyone know of a high tolerance printing place for acrylic printing OR a possible solution to this problem I have?

I am trying to avoid printing on paper and then gluing that to the bottom of the acrylic sheet if possible.

Thanks!

 

[IRstuff]

Please refrain from double posting.

I assume you meant high accuracy, but relative to what? Even silkscreen does way better than ±0.5"

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[dgallup]

I frequently print with an ordinary laser printer on mylar sheets. We use them as overlays on optical comparators for QC inspection. Very accurate.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[rfer]

Tolerance of +/- 100 microns. +/- 50 microns if possible.

 

[IRstuff]

OK, but relative to what? Are the fiducials that the grid needs to be aligned to? As you say, they print photos, so the resultant cannot possibly have ±0.5" positional errors within the finished photo.

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[rfer]

@IRstuff

So long as the dot grid pattern is accurate to itself to that tolerance then it is sufficient. So the pattern is floating.

If it is a square pattern, and d is the distance between each dot, I need the printed distances to be d+/-0.1 mm. If the pattern is accurate to this, but the whole pattern is off 2 mm, that is fine.

When they told me +/- 0.5", it must have been in reference to the centroid of the printed picture, and then they cut the acrylic to size or something, and yes, I agree +/-0.5" would warp a printed picture substantially if in reference to itself. Still, I am unsure if they could hit +/-100 um.

@dgallup

When printing on mylar w/ a laser jet, how do you feed the mylar into the printer?

Thank you all!

 

[TugboatEng]

It doesn't hurt to try. Every printer is going to be different. Yours may feed mylar as if it were paper. You may also spend the next 30 minutes picking bits of mylar out of the rollers. I think tossing out a damaged a printer or many is cheaper than making a specification, let alone finding a printer that meets said specification.

 

[IRstuff]

Depends on the printer and the mylar. A standard office copier has a straight-through paper path that allows stiffer or longer media to be printed on. Or, you can take your mylar and PDF of your pattern to a local descendant of Kinkos or other print shop and ask them to print the pattern.

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[TugboatEng]

Good point. We can make a specification. Really cheap printers or large format printers may have straighter feed paths that may perform better with mylar film. We never did get an overall dimension, did we?

 

[btrueblood]

Not mylar, but overhead transparency sheets are usually made of cellulose acetate or similar...and are made to feed through laser printers. I've used them for various purposes from optical comparator inspections to cheap and quick rotary encoder wheels.

Polycarbonate sheet is tough to mark, the stuff doesn't laser etch well or react to any chemicals that won't weaken or dissolve it. Acrylic takes a CO2 laser etch very nicely. PVC film is what our local graphics shop prints things on (signs and whatnot for trade show displays), and they have clear film that they can print to. Seems like whatever material and methods used, you could have the sheet printed, then measure the actual pattern very accurately by a secondary means (optical comparator) before using it to calibrate your camera?

 

[IRstuff]

What is the purpose of the sheet material? Most people just use paper, and any printer with 300 dpi or greater would ostensibly meet your requirement.

In any case, why not just buy a chart and not have to deal with self-calibration issues?

http://store.imatest.com/test-charts/iso-cpiq-standard-test-charts.html

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[rfer]

Hi All,

Dimensions of the polycarbonate sheet are 270 mm x 380 mm x 6 mm.

Purpose of polycarbonate sheet is to serve as a target for a laser pattern (bottom side of sheet is frosted). Camera w/ computer vision application measures the laser pattern.

Having the grid printed on the frosted surface of the polycarbonate sheet simplifies the problem (no need to print sheet out, cut out holes in it and line it up with the polycarbonate sheet and glue it on. No need to deal with glue refractive indices, etc). If everything goes to plan and final application works well, we will have multiple of these setups in 5 different counties so simpler saves me work in the future.

 

[IRstuff]

What specific property of the laser are you trying to measure?

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[rfer]

Hi IRstuff,

Apologies for the delayed reply. I am trying to measure the length of the laser projection on the flat acrylic sheet. I found out a subset of one of my company's machine shops has the ability to print directly onto acrylic and was able to print this pattern accurately enough for my application.

Thank you for your help!