How tight to print parts that are supposed to fit together?

[dmitrycy]

Hey everyone!

I'm thinking of adding a hinge to a part that I'm making. The hinge is simple - it's a cylinder cut into two parts, with a pin sticking out of the bottom part, and a recess for it in the top part. I modelled it in SolidWorks to have a perfect fit. However in practice, how much leeway should I leave for printing imperfections? Or is this not really a consideration? It's my first time printing something hence the newbie question.

Thank you!

[3dex ltd]

Have a look at this design on Thingiverse that has a similar hinge to the one you describe:
http://www.thingiverse.com/thing:106568

If you model things to have a perfect fit then in reality they are unlikely to fit when you come to assemble them (even if you print with PLA)

If we design anything we usually have a tolerance of either 0.5mm or 1mm. 1mm can give a rather loose fit so this is something that we usually use for parts that regular come apart like a box lid. Where as for something that has to fit together a 0.5mm gap gives a tighter fit.

I hope this helps.

[dmitrycy]

Thanks mate, will play around with the tolerances!

[MrCreosote]

You have to develop your own tolerances since you will determine what fit is acceptable.

Tolerance design is based on empirical rules established by past efforts. If you are starting from scratch, you have to develop these rules yourself through experimentation. Hopefully you can afford the time and cost to do this.

For Example, you have a hinge. To make a first estimate of tolerances, you have to specify an acceptable tolerance for the hinge assuming perfect surfaces.

Things like how close do you want the two parts to be held in alignment by the hinge?

You have to assume a clearance, then do a tolerance stack up to see what the various mis-alignment modes produce.

It can be daunting just at this stage depending on how much precision you require.

Once you establish your clearance and its tolerance, then you have to add more clearance due to printing surface roughness.

[dmitrycy]

Thanks man, appreciate the advice!

[ServiceXp]

Using Hatchbox ABS, I generally use .22 for most things, which will require a small amount of post print care.