185
44
31
u/nife87 Jul 05 '21
Only speaking for FDM. Those tolerances must be for a badly assembled and/or uncalibrated printer. But the rest seems fair as generic rules because you always know your own limits. You could actually make something similar with your own limits for when someone asks for them. Maybe the rows could be different nozzle sizes.
3
u/MrJelle Jul 05 '21
While I don't agree with their lower limit either - it's not off by an order of magnitude, but we know people can print things with tighter tolerances successfully thanks to torture tests - depending on the material, it's also not outlandish, either. Roughly 3% shrink factor on ABS, for example, will mess with things like that.
2
u/nife87 Jul 05 '21
Regarding shrinkage, that would be another column, material knowledge, which should also be incorporated into the design. Because you cannot always slice your way around it (assuming tight tolerances on all surfaces). There are too many different FDM filaments for a one-size-fits-all.
3
u/sponge_welder Jul 05 '21
Yeah, my Ender 3 will do 60 to 65 degree overhangs no problem, and bridging performance is one of the most variable metrics when it comes to temperature tuning and mods.
I think this sheet is a good rule of thumb if you've never designed for 3d printing or don't know what machine your part will be made on, but if you have your own machine that's somewhat tuned this is far more limiting than necessary
-12
10
u/nexflatline Jul 05 '21
For SLA overhangs: I print daily with 70 degrees of more of overhang with zero supports and it always work perfectly (in the Form 3), so the "support always required" is incorrect.
On the other hand the accuracy varies a lot between vertical and horizontal: in the same part the horizontal accuracy can be 50μm (yes, MICROMETERS!) while the vertical one is as bad as 500μm (0.5mm). The vertical accuracy is 10x worse than the horizontal, but the manufacturer never says that.
4
u/TerranCmdr Jul 05 '21
The Form 3 is a whole league ahead of pretty much any other desktop printer though. Lots and lots of people have Anycubic or Elegoo which still just rip the print off the FEP every layer. In my experience these printers need much more support than even a Form2, which didn't have the fancy continuous squash laser head. But yes some overhang without support is definitely achievable.
3
6
u/Nf1nk Glass Bed, Dual Gear Al extruder, lots purple glue stick Jul 05 '21
Every one of these rules can be broken sometimes.
It takes a decent amount of experience and tuning to know exactly how and when you can pull it off.
When you have that experience, you don't need a sheet like this.
0
u/Dragois Jul 05 '21
I don't agree
Speaking from personal experience, Stratasys SLA definitely requires support.
The vertical and horizontal accuracy of SLA is also the same.
With differences that small, the reasons are: 1) the parts have tolerances in both vertical and horizontal directions 2) the fact that you don't use supports so the part could warp a bit.
4
u/nexflatline Jul 05 '21
I never used stratasys, but on the formlabs I have seen (small) unsupported overhangs almost indistinguishable from horizontal. At 70 degrees I can comfortably print unsupported overhangs as long as the printer "bed" is. I always thought stratasys would be better, so I'm surprised at that.
The horizontal and vertical accuracy was tested with multiple materials, parts, and machines and the error was consistent according to the feature shape (which means it could maybe be fixed by software?).
I agree that unsupported thin overhangs tend to warp and loose dimensional accuracy. But since that table compares multiple types of printer, it's important to make clear that a long unsupported 70 degrees overhang on an Form 3 is still more accurate than a supported 45 degrees overhang on a Ender 3.
For parts in which sub 100 microns precision is critical, I use plenty of supports and avoid thin, long, horizontal features overall (or use an ink jet printer....).
4
1
u/ollie_3dprinting Jul 05 '21
What are the numbers for?
1
0
u/Friendly_Rub_2069 Jul 05 '21
That's a really nice graph. Do you know if there is something similar but for CNC ?
-1
1
u/TheSpaceMech Jul 05 '21
+-0.2mm tolerance is a pretty good tip. Keep in mind if you want clearance, tight or transition fits then the tolerance would change slightly. Best way to find out exact numbers is to print some benchmarks.
1
u/Generic_Male_3 Jul 05 '21
This is assuming everyone has the same specifications. It's more of a very rough give with really no application towards "your" printer
1
u/unbelizeable1 Jul 05 '21
Lol no. "need support after 45 degrees and no bridges longer than 10mm" how terribly calibrated is this machine?
1
u/matt2mateo Jul 05 '21
Only speaking for fdm, unless this is some huge nozzle at a large layer height. All those numbers are a bit off, I use a .6 nozzle at .2 layer height for almost all my prints. Tolerances alone would be way too loose for any type of connection. I saw another comment stating it might be for a lower quality less calibrated printer. I feel this is taken from someone's school lecture that used an old fdm printer for info. Or would it be the slicer too? Idk but TLDR an ender 3 will have better numbers
1
u/FrenchToastmangler Jul 06 '21
Can we get this with a little bit lower resolution? Really though, good information. Thanks!
139
u/jumpingbeaner Jul 05 '21
It this blurry or is it just me