Moving Parts Advice

[EGR 3d]

Hi everyone,

I am new to 3d printing and this is my first post on this blog. I am an undergraduate engineering major at a small university and we recently purchased our first 3d printer. I have some self taught experience in designing but still have a lot to learn. As one of my first projects, I would like to build a leg mechanism with 3d printed pin joints. The printer I will be using is the Mark One made by MarkForged (https://markforged.com/mark-one/) and the joints will be printed in nylon. I'm wondering how much clearance I should design between the outer ring of the pin and the inner hole of the housing? I intend to print the pin separate from the two connected pieces but if I can print the hinge in two pieces with the pin built in, all the better. Keep in mind, I would like to final result to be a smooth (relatively) single axis hinge. Any advice?

[LambdaFF]

Well... the advantage of 3D printing is that you can experiment quite easily.

Otherwise, when I studied engineering we had a convenient table that gave component tolerance ranges if you were looking for tight fits, loose fits, ...
ever heard of something like this ? http://www.langlet.fr/bdd/docs/4-tol...justements.pdf

Yes, it is in french, but look at the tables, you'll find something similar in english easily.... it is an iso norm after all.

[3dex ltd]

Hi EGR 3D

When we are designing a part that has to move we usually give it either a 0.5mm clearance or a 1mm clearance.

1mm clearance is perfect for parts that have to be moved frequently such as a box lid and 0.5mm clearance is better suited to parts that have to fit together but only move occasionally.

A clearance of anything more than 1mm will give a very loose fit with lots of play so we wouldn't recommend going above 1mm.

I hope this helps you.

[curious aardvark]

there is a great little print test that has pins and gaps in decreasing sizes.

I discovered that my machine can print 0.3mm gaps and above but not 0.2mm gaps.

This is for gaps printed in situ. printing parts seperately is a totally different proposition. As you can sand the peg easily and quickly to fit to whatever tolearance you like.

Buggered if I can find it. Was a 3dprint article with ten different print tests. the only one I tried was the gap fit one.
I'll upload the stl file later.

All printers are different. So running a test print is the best way to find out what your machine can do.

[djprinter]

I suggest printing a test model with different tolerances and see what works, each printer is unique.

You could also error on the tight side and as long as you use thick enough walls you can file it down to a prefect fit after--more work, but reliable results.

[curious aardvark]

I suggest printing a test model with different tolerances and see what works, each printer is unique.

You could also error on the tight side and as long as you use thick enough walls you can file it down to a prefect fit after--more work, but reliable results.

Damn why didn't I think of any of that ;-)
Oh wait I did :-)

Anyway here's the test print files page: http://www.thingiverse.com/thing:533472
The negative space tolearance test is the one you want: http://www.thingiverse.com/download:872739