What you can expect
We print with a 0.4 mm nozzle on calibrated printers, in PLA and PETG. Dimensions normally land within 0.2 mm of the file, which is enough for holders, lids, brackets and most replacement parts. A few things pull in their own direction, and knowing them lets you draw right from the start:
- Holes and inner dimensions come out slightly smaller than in the file, usually by 0.1 to 0.3 mm, and outer dimensions can come out slightly larger. The line of plastic is round and is pressed out a little at the edges.
- Height follows the layers. A part meant to be 10.1 mm tall comes out 10.0 or 10.2 mm with 0.20 mm layers, because the height is a whole number of layers.
- The first layer is pressed out a little against the plate, so the edge nearest the bottom gets a small lip, often 0.1 to 0.3 mm. A lid meant to fit a box can catch right there.
- The plastic shrinks a little as it cools. On small parts it does not show, on a part 200 mm long it can be half a millimetre. PETG shrinks slightly more than PLA.
- Sloping and curved surfaces have visible layers, and where support material sat the surface is rougher. A dimension against such a surface is less reliable than one against a smooth wall.
All of this belongs to the technique, not to one particular printer, which is why the terms of sale say that small deviations, normally within 0.2 mm, are not a defect.
How to draw parts that fit
Measure what the part has to fit against with callipers, not a ruler, and then add clearance on purpose instead of drawing exactly:
- Something that slides into something else, such as a lid into a box or a peg into a hole: 0.2 to 0.3 mm of clearance on each side, so 0.4 to 0.6 mm on the diameter.
- Something that has to stay put without a screw, a press fit: 0.05 to 0.1 mm of clearance on each side. Try one copy first, because here the tenths decide.
- A hole for a screw or a bolt: draw it 0.2 to 0.4 mm larger than the screw. An M4 screw wants a hole of about 4.4 mm.
- A hole for a nut or a bearing: draw it 0.1 to 0.2 mm larger than the part, and make the hole a little deeper than it needs to be.
- Holes that run horizontally through the part come out flat at the top. Draw them as a teardrop with the point upwards, or add 0.3 mm, and they keep their size.
- Chamfer the bottom edge by 0.5 mm, and the lip from the first layer disappears and the part sits flat.
Where you can, draw the part so it can be adjusted afterwards: a slot instead of a round hole, a groove that can be filed. More on walls, text and the smallest details is in the guide Layer height, infill and nozzle.
Layer height and material matter
Thinner layers give not only a finer surface but also more even dimensions on sloping surfaces and in horizontal holes. If the fit matters, 0.12 mm is worth its time. PETG gives a little and forgives a slightly tight fit, while PLA is stiffer and would rather crack than stretch. A press fit in PLA therefore needs more clearance than one in PETG, and a part that has to snap into place is better drawn for PETG.
When the dimensions are critical
Order one copy first and measure it. The deviations are systematic, so a hole that came out 0.2 mm too small does so across the whole batch, and you correct the file once. That is cheaper than five parts that do not fit.
Holes that must be exact are best drawn slightly small and drilled or reamed to size afterwards. PLA and PETG are easy to drill, file and sand. Threads straight in the plastic work from about M8 upwards; smaller threads get a nut sunk into the part instead.
If you need a fit tighter than a 3D print gives, or you are unsure how to draw the clearance, contact us and describe what the part has to fit against. We normally reply within 2 working days, and can in some cases adjust a file free of charge when the print is ordered from us.
How to order
Upload the file on Order a custom 3D print online. The dimensions are shown as soon as the file is uploaded, so check that they match what you drew. Choose material, layer height and quantity, and see the price before you order. If you are unsure about the fit, order one copy first.