What clearance should I leave between parts that are supposed to fit together perfectly when using a .6mm diameter nozzel?

[sean513 0]

Ultimaker 2+

 

Here's the thing that I'm working on putting together (the purple stud on the bottom right should be up higher like the one on the left).

 

 

Notice how the purple studs fit into the red ring? Well, most of the parts are like that in one way or another. That is, most of the parts need to start right where another part ends with no gap and without being too tight.

 

Are there any good rules of thumb for knowing how much smaller a male part needs to be to fit into a female part? I want a good fit but I don't want to have to jam them in.

 

I'm doing this at the library and just getting down there and setup is an ordeal. The blue cylinder (4x102mm) alone takes almost 4 hours to print with a nozzle size of .6mm. ...I imagine this is how it must have felt when people had to program on punch cards, lol. Except, this isn't just a logic thing. It's an experimentation thing and it's taking up a ton of my time.

 

How can I get these parts to fit together perfectly like they do in my model?

Edited August 4, 2019 by sean513

[Smithy 1,145]

This is very difficult to say and depends on many factors. Material, layer height, printing speed, flow, temperature etc. all have an influence on accuracy.

 

I usually start 0.2mm clearance and split the object to make a few test prints that are printed quickly.

 

Also keep in mind that holes are generally smaller with 3D printing than you drew them. As a guide you can assume 0.4mm.

 

Try to extract the relevant parts of your model to quickly make multiple test prints without having to wait hours.

 

[johnse 31]

I would add to what @Smithy says: when you print the test parts with holes/slots in them, make sure they are 2-4mm thick. If there’s any elephants foot going on, the first layer or two will be significantly smaller than the rest of the hole. This can be easily remedied with a craft knife after printing, 

[geert_2 558]

Usually I also start with a clearance of 0.2mm, and then adjust as trial and error indicates. However this is on a 0.4mm nozzle.

 

As Smithy says, small holes tend to get closed down a bit, and small rods tend to get too big (slightly overextruding). Also layer height has a big influence, as well as the amount of blogs, strings, ringing and other defects.

 

Probably you will need to post-process tiny holes anyway. I always go through them with a drill (see pic): manually, not electrically, because that melts the plastic.

 

The tiny purple things probably won't print correctly at all, so you would be better off using standard nylon screws or pins, or whatever you need.

 

[johnse 31]

4 hours ago, geert_2 said:

The tiny purple things probably won't print correctly at all, so you would be better off using standard nylon screws or pins, or whatever you need.

 

That was my thought initially, but with the scale @sean513 mentioned they look like they are 3-4mm diameter. Should print fine, but probably want to be sure there are taller parts and/or cooling towers being printed at the same time.

[Umo_Alex 4]

Trial and error indeed. For instance, after some trials with PLA and my usual settings I came up with 0.1mm.

Worked great with whatever I printed but trying to print the same things with ABS messed up the fitment.