3d Printing Threads
Updated: Jul 12, 2022
I have designed and printed dozens of screws and here's what I've learned:
Design from scratch or use thread feature?
Design intent
Print orientation and supports
Printing nuts
Clearance between nut and bolt threads
Print in place nuts and bolts
How small can these prints be?
Design from scratch or use thread feature?
Designing threads from scratch in SolidWorks can be a bit time consuming. It requires a thread profile and helix and a swept cut.
I prefer to use the Thread Function in SolidWorks for most applications of threads. It works exceptionally well..so I am not going to try to reinvent it. With the thread function, I just need a cylindrical extrusion (bolt shaft) and then I'm good to go.
There are a lot of options to choose from, if you want a fine thread or a thick thread they are all there.
However, it is good to know how to make your own threads because sometimes you will want a custom thread pattern. For example, if I am making a screw lid for a container, I would consider making it from scratch
Design intent
When you're designing a part, ask yourself:
Does it make sense to 3d print screws or should you use real nuts and bolts and design around that?
Real metal screws are always going to be superior for holding/fastening.
Pros: Super strong, ware resistant,
Cons: Adds to weight of project, requires a trip to hardware store, might not be able to find the dimension you need.
3d Printed Screws:
Pros: No trip to hardware store, light weight.
Having a fully 3d printed solution is an attractive selling point.
When I design products, I am thinking about my customer. I want them to be able to download my STLs print them and not have to worry about going to a hardware store.
Cons: Not as strong. Requires relatively more knowledge of CAD software, loads of trial and error to get tolerances down between the nut and bolt components.
Print Orientation and Supports:
These two variables must be discussed in tandem.
I designed my model and my STL was ready to print.
My first instinct was to print the model in a vertical orientation like this:
It does produce a decent looking print. However, if you are looking for a functional print, where the threads will experience considerable force, then it is a good idea to try a different print orientation so that the filament in the thread is perpendicular to the print bed. Like this:
Printing like this requires supports (light blue), so there will be clean up but it's really not that bad.
Printing Nuts
For printing nuts (internal threads), I usually just print them in this orientation with no supports.
Even with large threads, I will still print with no supports because it is a pain to pry out the supports from in-between threads in such a small space.
It is quite hard to pry out supports from internal threads and could render your print unusable or damage the thread of your 3d printed bolt if you try to force it through.
Clearance between nut and bolt threads
When designing two separate parts I go with a clearance of
When I was using big threads this clearance didnt work
Why?
Print in place nuts and bolts
It is definitely possible to do a print in place nut and bolt. It's one thing to design a bolt, and then a nut and then trust that you designed everything correctly. I don't want to get deep into a print and then realize that I made a careless mistake.
I recommend doing a split view and then visually checking clearance and running an interference detection.
How small can these prints be?
You can print working treads surprisingly small. They may not be practical in the traditional sense of a nut and bolt application but I'm sure there is a time/place where knowing the limits of this mechanism would be handy. For example, I printed this: Look how small this is...but it still screws! The diameter of this threaded rod is 6.03mm and it works. This actually impressed me when I designed and printed this. Not so much the threaded rod, but it was the internal thread on the nut that was amazing.