I tried to be smart. I made "printer calibrator" feature, which supposed to aid precise printing by letting the user to enter a calibration values (horizontal and vertical) for a specified printer. This value can be obtained by printing several lines that differ a little bit in length. The user can measure the 200 mm lines, and select the line, that is precisely 200 mm-s and the user can just read the calibration value that's written on top of the line. I thought that that's a simple yet smart idea for precise printing (for paper models).

kaPOW!!!

The printer is unable to print two same-sized print! The vertical ~200 mm size (that is "rolled out") varies 1 mm (I just printed two copies, so the variation can be even bigger).
This makes it impossible to make precise models, 1 mm is just enough for pieces NO TO MATCH. Especially if the model needs more pages. Even 0.5 mm is too much for modelling.

So, by the technology (rolling paper), is it impossible to make precise prints? Or is it only my cheap HP 1018?
Or back to paper-and-pen modelling and to the trash with my project?

Total despair

Laser yeah? I think you are screwed. The paper feed will never have the same alignment and there is also slippage. Some types of paper thermally expand by a large margin, especially if the humidity is high. I suggest you to try different kinds of paper, preferably something ticker and less prone to humidity. For example, those thicker art/sketching paper might do the trick. Or perhaps something that is not pulp based. Just don't try plastic, otherwise it will melt to the fuser and you can junk the entire printer. However, some transparency overheads are actually printable, so you can try that. These might reduce problems with expansion, but may not necessarily help with alignment. Inkjet printers don't have thermal expansion problems, but they have a moving head which may get out of alignment.

Something else that you'll likely run into is the fact that many printers aren't designed for solid printing layouts, but for text printing. Oddly enough, putting a series of small dots on a page that group together to appear as letters is a very different problem set compared to putting a straight line on a page.


If you want to do precision layouts, explore the world of plotters. They're designed for precision layouts.

Something else that you'll likely run into is the fact that many printers aren't designed for solid printing layouts, but for text printing. Oddly enough, putting a series of small dots on a page that group together to appear as letters is a very different problem set compared to putting a straight line on a page. [/quote]
That's actually a good point. Laser printers use electrostatic attraction to deposit the toner. If the charge build-up is high, it's quite possible that the print pattern swells a little due to mutual repulsion.

Take apart your printer and reuse the rails and stepper motors to build a CNC plotter that uses a Sharpie marker. Problem solved!

EDIT: actually, it probably doesn't use steppers, it probably uses regular DC motors and optosensors to count revolutions.

The kind of inexpensive proofers in a typical home or office are not really capable of the kind of precision you're looking for. For that, you actually need a press like a professional printer would have, and even then they only do alignment for specific runs.

Could always take the lame route taken in electronics fab, and keep printing until you get some that match up well enough to make your model.

Pretty lame route to take, I know.

Maybe though there is a better option, and do something interactive. Print a small handful of markings that you expect people to use just as a coordinate system, then target tablets. Have people fold against the tablet, and show the folding instructions there instead of on the paper. Use the paper only for producing a coordinate system.

Just wondering though, but when you say that there is an innacuracy in the print, do you mean that the entire printed images is transformed linearly, or are there different transformation in different parts of the image? If it's just linearly, then the fab approach may work, you just include in your image a number of markers that you expect to line up. When you get a set that match, you start folding.

Are you sure you haven't selected some kind of printing scaling? Untick the print scaling box.

Thanks for the hints. Yup, building a printer for myself is a good idea (I guess I'l do something like that in the future, I even have an dea), but expecting he users to do the same would be unfeasible (this is about the Paper Modeler program I'm developing).
I'll experiment with different paper materials though. Or won't care about it, it's the user's problem. I'll leave the calibration printing feature, I'll warn the users, I'll suggest paper types, but I can't do much more about it.

Maybe I'm overreacting it a bit. Casual modellers won't use my program, they'll just download the unfolded Pikachu model and print it with their crap printer. While more interested users who are enthusiastic enough to work with a program on their own models (and care about preciseness), will probably do something about the issue if I warn them about it. Maybe simply printing it as many times as it takes to produce precise models. Or taking the files (in .pdf format for example) to a professional printing supplier. I'll add a "print vector graphics only" feature for real plotters, professional modellers paint the models anyway.

Are you sure you haven't selected some kind of printing scaling? Untick the print scaling box.

If I print two copies in sequence the result is he same: 1mm variation.