What level of dimensional accuracy can be expected?

[Wisar 86]

If I am printing a part with a hole that is 7.95 millimeters in diameter what level of accuracy should I be able to expect for that hole when it is printed? +/-.??mm? Assuming a reasonably well calibrated UM2?

Thanks,

Will

[xeno 108]

That depends on a multitude of factors,

filament, temperature, speed, infill, wall thickness..........

best is to make a small test print with the hole size you want, and dial in all the settings, then print the object.

or buy a 7.95mm drill to drill out the holes to the exact diameter  (what I usually do)

Edited July 12, 2015 by Guest

[Wisar 86]

Gotcha on all the factors. It seems like I spend more time calibrating for each new thing that I print, filament that I use, and sometimes even the time of day. That is a good idea on calibrating for a measured hole for a particular print. I have done that in the past but did not on this particular print. Did end up drilling the hole out and I would guess that I am within .05mm of the design. Not sure I will be able to get much closer than that.

[neotko 1,417]

On simplify3d there's an option to compensate the material fluctuations. You print with the settings a cube. Meassure and input the difference. Then when you print with that settings you can compensate the output. Ofc it changes with each material/heat/etc. so you need to do it with each material/settings if you want to keep getting accurate prints. But the nozzle and layer height also affect the holes etc. So for your sollution propably it's better to use a drill...

[Wisar 86]

neotko,

Assuming you are talking about horizontal size compensation? I do use it but had not thought about it as part of a workflow that might take into account a different material. Might could do a little test before doing a particularly dimensionally demanding print. A single global setting is probably not good enough given all the variability.

Cheers,

Will

[danilius 118]

If you regularly have to print dimensionally accurate holes, it makes sense to buy a large quantity of filament from the same batch. This will help eliminate one big factor.

After that it's just a matter of printer smaller or bigger holes until you dial in the shrinkage, and create a profile to suit.

[xeno 108]

Even if you dial in all the factors to compensate for print deformation,

you still could get some size differences due to object size, layer cooling times and wall thickness around the hole,

I just chose to get as close as I can, and use a drill to make it accurate.

as a tip, make the wall thickness a little more, so you have some material left when you drill the holes

Edited July 13, 2015 by Guest

[danilius 118]

 

@xeno, I do likewise. I am far too impatient to want to fiddle around with a hundred tests when a drill will do the job far quicker and more accurately.

[JohnFox 25]

Depends on wether the hole is horizontal or vertical. I suspect that your hole, if printed vertically would come come out about 7.8mm, ( at least on my printer ). I have a lot of holes to take 3mm bolts and routinely print them with 3.2mm diameter to get a perfect fit. Horizontal holes are more accurate but the tops of them are a bit distorted when the gap is being bridged.

[danilius 118]

 

@JohnFox, this I think is typical of FFF printing at the moment, in that your experiences will vary quite wildly from mine. I fine horizontal holes to bear little relation with the intended result!

[gr5 2,192]

There are many factors that affect the final dimension but they tend to be consistent even when changing filaments.

The biggest shrinkage is on vertical holes and is caused by the PLA acting like a liquid rubber band as it is being laid down. It shrinks quite a bit in the first millisecond but is still liquid and so it has tension and is pulling inward. This is difficult to compensate for in software but you can do it.

Rather what I do is in cad I make the vertical holes a bit larger. Also I often make small test prints for pieces that need to fit together. After a while you get really good at it.