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Narrow fit parts: issues

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Posted · Narrow fit parts: issues

I have an Ultimaker3, it prints nice but when I print some parts which must be combined later (narrow fit!) then these parts didn't fit at all.

Parts are allways too big.

 

Print PETG with 40mm/s, 245'C nozzle, 80'C bed.

 

Bedleveling calibrated.

Also tried calibrating the steps (X,Y, Z and extruder).  Used all kind of filament, Ultimaker brand or whatever: same results..

 

As long you print something which doesn't need to be printed very accurate then the printer is ok.

 

Is there somebody who have this same problem and nows how to fix it ?

 

 

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Posted · Narrow fit parts: issues

There has to be a clearance between the parts.

 

If you slide a part into a 20MM hole the part going into it would have to be around 19.5MM in diameter and it would fit pretty snug, may need to be 0.4 or 0.3 MM smaller than the part it goes into but it does have to have a little bit of clearance.

 

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Posted · Narrow fit parts: issues

Set all speeds to the same value and stay at 40mm/s or even lower to 30mm/s. 

It is important UM3 (and higher) to equalize the speeds.

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Posted · Narrow fit parts: issues

Layer lines, blobs, strings, hairs, ringing and thickening at corners, always cause inaccuracies. I usually make a couple of small test models to try which tolerances work best for a particular model feature. Depending on the required fit, I usually take between 0.1 and 0.5mm tolerance for my UM2-printers. Printing slow and in thin layers also helps.


For example for inserting M4 nuts (which have a diameter of 7.0mm between flats for steel, and 7.2mm for nylon, in my inventory) into a 3D-printed cage, I made this test model with 7.2, 7.3, 7.4 and 7.5mm hex cages. Then I tried what worked best, and I used that for the real design. Steel nuts are hard to force into too small holes in a PLA model, but for nylon nuts it is easier.

 

image.thumb.png.cc97a3b20f290085de92f39208528f7e.png

 

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Posted · Narrow fit parts: issues
2 hours ago, geert_2 said:

Steel nuts are hard to force into too small holes in a PLA model, but for nylon nuts it is easier.

 

@geert_2  - you can modify the shape of the pocket a bit, makes assembling much easier and distributes forces a bit better:

 

nut_pocket.thumb.PNG.a050911960b6a5dd86ad78c10c637712.PNG

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