You might find this little tool useful:
This is a block with a series of vertical and horizontal holes from ⌀1 mm to ⌀3.6 mm (nominal) in 0.1-mm increments. I print this block with any new printer / new material at the layer thickness and speed I use most often and keep the blocks as references.
Then, when I want to print a part with a hole in it that will end up printed at the final diameter without any rework (or very close, but usually it ends up exactly right) I use the gauge block I printed with the printer and the material I intend to print the part out of to find out which nominal diameter hole I need to use in the model for the hole.
For instance, the block in the photo was printed on a Prusa Mk4 with PLA at 0.2 mm layer thickness. If I want a ⌀0.8-mm vertical hole with no interference in my final part in PLA out of that printer, I’ll need to model a ⌀1.2-mm hole. I know that because the shank of a 0.8-mm drillbit will slide freely in the vertical hole marked ⌀1.2 in the block.
Or if I want a hole that I can screw an M3 screw into without having to run a tap through it, the block tells me I would have to use a ⌀3.2-mm hole to fit a ⌀3-mm pin in freely, and I back off 0.4 mm to get a hole in which the screw thread will engage well but reasonably lightly, or 0.5 mm for a tighter engagement (but with a bit more risk with horizontal holes near an edge, because the layers might separate) so I know I’ll have to model a ⌀2.8 or ⌀2.7 hole in the model.
I use those gauge blocks all the time. They save me a lot of time on parts that I print often because I never have to ream or thread the holes: they come out the printer just right and ready to use.
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And for anyone who winds up struggling with this when trying to gauge their own printer, make sure this option is enabled:
This is in Prusa/Slic3r and its derivatives. If this is disabled, the final outer wall perimeter can wind up being pushed out by some fraction of the width of the wall behind it, which will have the net effect of shrinking vertical holes in your model (and other critical clearances in the X/Y dimensions) by an unpredictable amount.
This won’t solve the fact that the filament is going to shrink a bit when cooling. Although you should already be scaling your models to account for this
Your slicer should also be able to compensate for this already.
PLA only shrinks about 0.3% which is negligible unless you are designing with super tight clearances. A 6mm hole, for instance, will be out 0.018mm which is probably scraping against the XY resolution limits of most consumer 3D printers anyhow.
Other materials can definitely shrink more. ABS is harder to manage than PLA, but for instance Nylon/PA’s shrink rate is comparatively immense – around 2%. The various engineering polymers that are filled with something like carbon or glass fibers actually tend to shrink less than their raw counterparts.
I wish I could print nylon, but the old oven I’m converting into a heated chamber is buried in the back of my garage.
My Qidi has a heated chamber and can allegedly do it stock, and I’ve had an unopened spool of pure Nylon sitting in the printer cabinet for over a year.
But I’m chicken.
If your nozzle can withstand it, glass filled is way easier to print.
What’s the deviation tolerances of the actual hole sizes? I’m American so I’ve only machined using inches or converting metric to inches. So are we talking +/-.005 or +/-.0005? Decided to make gages for hydraulic tube sizes for real time quality assurance from our picking and packing department to use. Ended up going with counter sinking pins for carpentry but never found a female gauge option for the male tube connections. Wasn’t important enough to spend any more time or money on. That’s also why I said fuck the machining gage pins, they’re expensive as fuck. What you made tho is exactly what i was looking for.
It depends on the material and printer and the orientation of the hole. Vertical holes (or up to 20 degree from vertical if they’re angled) are the most accurate because you basically exploit the printer’s X and Y locating abilities. Horizontal holes will always end up ovalized because horizontally they’ll be correct, but vertically they can only have a dimension that’s a multiple of the layer height.
With the aforementioned Prusa Mk4 printer and PLA, all the vertical small holes I print usually end up under ±0.05mm / 0.002" from the desired diameter. If the dimension is very important (for example, holes for a pogo pin holder that needs to fit with interference, otherwise it would fall off) I’ll print it 0.1mm / 0.005" undersized and then I’ll ream the hole just enough to get the proper fit. It’s quick but not as quick as not reaming the hole obviously 🙂
Note that our printer is in a closed enclosure and that seems to make a difference for repeatability: if I leave the doors open, the diameter of the final hole varies a bit more. Nor a lot more but noticeably.
If I’m reading your comment right, you might be talking about gauging for inspection purposes, but that’s not what OP has here. I’d call it more of a printer calibration block.
This is damned impressive.
Thanks! 😊
I came in here to ask about part shrinkage, and it seems you’ve got that figured out.
You might consider incorporating this into one of the filament test slides.
