Printing to scale not accurate, and the reason


#1

I often print at 1:1 to a physical printer and use the print by taping or gluing it onto material I need to drill or cut - works very well for small parts…

Recently I noticed that in actual fact the print is off by about 1 to 2 mm over 250mm.

I at first suspected rhino might be the culprit – Autocad (which I no longer use) apparently has calibration command which can be used to fix or minimise this kind of thing.
Anyway, I was getting the same kind of results from other cad software, so it wasn’t rhino.

I found after a little research online that it seems to be a common problem with many differing CAD software and printing, and there were many differing suggestions and ideas, but very little in the way of conclusive solutions.

A possible work around is to scale every 1:1 output from the cad software to adjust for the individual printer’s variation…

However, “all” it is is the actual printer itself. I was fortunately able to access three differing (brother) laser printers to test, feeding them all the same test file direct from rhino, and two of them were off by slightly different amounts (1.5 or so mm), and one of them was spot on.

For what it’s worth the one that worked well in this context was a brother HL-3070CW, although manufacturing tolerances probably mean its unlikely that all machines of this model printer will be this accurate.

Unfortunately, if the printer you have is not printing accurately, but otherwise fine, there seems to be little you can do to fix it, since it is not actually broken…
Of course for many users this kind of accuracy is not necessary, but if you are looking at buying a new printer, and it is important that it be capable of printing to scale accurately, I’d suggest running a test file on it, and measuring the output to check it is acceptable.

cheers
rabbit


(Pascal Golay) #2

Hi Tony - in case it helps - there is, in ‘Printer details’ area in the Print dialog, a scale factor, so once the discrepancy is known, this can be set to something other than 1 to compensate.

-Pascal


#3

Well, there you go…! Already sorted…
Thanks Pascal.

—Sent from mobile device & email—


#4

The thing is that most printers rely on feeding paper through on different systems of rollers, and that there is always some paper slippage plus the calibration of the roller outer diameter to the linear paper feed. So, while in general they are reasonably accurate and repeatable in the width (carriage movement) direction, they are not nearly as accurate in the length (paper feed) direction.

Flatbed printers where the material to be printed doesn’t move are more accurate, but there is also some possible dilation of paper products because you are adding humidity with the ink. Printing on plastic or metal is much better…

This is why systems which need accurate registration of printed material and, say, cutouts made afterwards, rely on printing, then scanning the print back in (reference marks) and then scaling it internally as necessary before cutting.

So, I would just not expect too much accuracy from a roller-fed printer on paper. The same printer may not even have the same scale factor from day to day or print to print.

–Mitch


#5

In years past, I used to plot out full scale framing for boat building onto Mylar with ink pens on a large format HP plotter. EXPENSIVE! YIKES! but did save the builder from having to loft from numerical offsets. Now, I just email all the drawings and they can be dealt with full size on their plotter!


(David Cockey) #6

Or they have the frames/molds CNC cut, no paper/mylar drawings involved.


#7

I recently found that feeding a large format plotter (roller not flatbed) with a pdf gave more accurate length than feeding it their requested file type at a print bureau.

Pascals fix would seem the best and is good news.

Even flat bed scanners except for very expensive ones no doubt, cant do 100% which is even more of a pain. Had an Epson A3 at work, had to scale down by different amounts the resulting scan, my A4 Epson is no better.

Also the large format document imaging scanner at work gave some expansion lengthways.

Seems the manufacturers cant be bothered as no adjustments are offered.

Steve