Thanks for the explanation! So if i take my Solidworks generated PDF files to the local Staples they should be able to print as accurately as my plotter - provided they have their hardware calibrated?
1)
Presuming their machine was capable of that kind of accuracy in the first place, which it isn't. Most laser and ink-jet devices are capable of ±1-2% dimensional accuracy brand-new out of the box. Large-format machine are generally much, much worse than that. I worked at a national top-ten prepress house for eight years. During the transition from traditional bluelines to digital ink-jet "bluelines," we had a top-of-the-line Epson large-format ink-jet printer set up with specialized software for printing "digital bluelines" and then overlays to show die-cuts. The best we were able to "calibrate" it was within about 0.0625" across a 48" print area. Changing humidity, changing paper stretch because of the amount of paper on the roll decreasing over time, changing paper stretch
because of the amount of ink being put down across different areas of an individual print, and so on, all made "calibarating" it virtually impossible. The solution was easy: We discovered that the customers just didn't care. Most people who aren't trying to make parts
from the drawing as a template, don't care at all.
And...
2)
Presuming they "calibrate" their hardware. Most consumer- and even "prosumer"-grade large-format printers don't have discrete X-, Y-axis scaling "calibration". At best, it's in the print-driving software, and even that is uncommon for anything but top-flight prosumer-grade equipment. Most have, at best, a simple size-scaling adjustment. And this even presumes that the copy center involved actually
does any "calibration" of the dimensional accuracy of their equipment. In college, I worked at a commercial copy center and, having used others later in my life (generally FedEX Office, not Staples), I can virtually guarantee that, unless you ask for it specifically, they
never calibrate their equipment. It just gets used, and service is called when it breaks down. If you ask them to calibrate it dimensionally, you're going to get blank looks, then be told that it can't be done and, if you press them, someone will go and try to find a manual that's been getting dusty on a back shelf for years. They'll ask you to come back on Thursday night because "the guy who's really good on that machine" will be on-shift then, and when you come Thursday night, you'll run through the same cycle until he finally finds the manual and sits down to read it.
In theory, yes, you should be able to get reasonably accurate prints. But it's not going to be true in practice, unless that particular location just
happens to have customers who need and request dimensional accuracy on a regular basis. And, if they do, the center probably has an engineering plotter for that work.
If you go ahead, a better test than a grid is to print a large-diameter circle and have them make a print. Go back the next day and get a second, identical print. Measure the diameter to see if the basic scaling is correct. Then lay them on top of each other, with light shining through, and see if the circles align all the way around their circumference. Then rotate one print 90°. See if they
still line up. Any X-Y errors - and inconsistencies between print runs on different days - will jump right out at you.
In the end, it really depends on what you really
need out of these printers. If their accuracy is better than your shop accuracy on the same part, it's "good enough." If you can - and need to - make things more accurately than those printers can print, then they're
not "good enough." Whether or not you "need to" is subject enough for an entire thread on its own. Unless you're building something with a highly laminar-flow shape, and are capable of achieving the needed accuracy in your own shop, you can probably get away with less printing accuracy than you might think.
