Print true to scale

jochen_ritter

Hello!

Our CNC-Mill is broken right now, so i wanted to manufacture a small bracket per drawing paper print, glueing it to the material and doing it the old way.

I discovered now, that even with the print option "no size change" and with 100% scale, the printing is not true to scale, but loses ~3% size. Tested this with the onshape-generated pdf in chrome and in pdf xchange.

When i measure in the pdf draweing with the tools of pdf xchange, the numbers are correct. But it doesnt print correct.

Does anybody have an idea?

martin_kopplow

No other idea than printing it out in 103% resp. 97% or so to compensate. It should not happen in the first place, and I just tried with my setup (Win/Firefox/Adobe Acrobat/HP LaserJet): In my case it does not happen. I get an error of less than a line width for a 100x200mm slab I test printed on A4, which is within reasonable tolerances. Maybe there is some setting in your workflow that assumes someting. In one printer driver I have on a laptop, for example, "print at original size" is not necessarily equal to "print at 100% scale". You may want to try and see if it makes any difference.

jochen_ritter

Update:

I tested it on the same pc with another printer, a Ricoh SP213W. This one gives me a print with a size of roughly 100.6 %..... so, a small error but still enough at lager parts.

So i suppose the error must be on the printer driver side.

I will search for settings in the drivers later.

nick_papageorge_dayjob

I had a similar issue a while back (while doing the exact same thing, adhering the printout on a piece of sheetmetal to cut on the bandsaw).

I traced it to two things in my case:

On my computer, if I had "full scale" selected in the printer dialog box, it would be off slightly. However, if I hand typed in "100%", it would be accurate.

The second was I was using a browser to open the pdf and print from it. I forgot which browser now, but one browser was printing precisely, and the second was not.

Ste_Wilson

However, if I hand typed in "100%", it would be accurate.

That's madness!

jochen_ritter

I didn´t write it accurate enough, but thats what i meant with '"100% scale" in my first post. I tested the full scale  option and the manual 100% option.

Oliver_Couch

Printing to scale is tricky because it's quite a long chain of bits that talk to and reinterpet each other. Particularly in this case.

Original software (Onshape Drawings) -> PDF Generation (Another part of Onshape) -> PDF Viewer Software (Generates Post Script) -> Printer Driver (Of which there may be an option - default microsoft or manufacturer. Interprets and sends as commands to) -> Printer Electronics (which in turn controls) -> Printer Mechanical parts

And depending on the specifics, the PDF viewer may or may not change settings in the driver and printer, and vice versa.

Usually you can assume most parts of the chain are fine. Configuration issues are usually in either or both the PDF Software, the Printer Driver, or sometimes in the Printer Electronics.

Make sure they're all set to the correct paper size.

And language of the UI can be confusing. Eg. "Full scale" may actually mean fill the page. You always want to do the custom scale -100% option.

You've just got to work through all the settings, make sure it's set to 100% everywhere (both pdf viewing software and the print driver) and do not scale to fit and turn off all the safety rails that make sure your text documents don't come out cropped.

I'd recommend avoiding the JavaScript based PDF viewers in most browsers. Printing perfectly to scale is a nche use case. Most users dont care if their text or photos are a tiny bit too small as long as they arent cropped, so this is what the browser viewers cater to.

You're best to use a dedicated full featured viewer like Adobe Reader DC or PDF X-Change Editor, or Foxit to print from.