Skip to main content

Creating Threaded Parts for 3D Printing

image021_7e0c9bf91f394d3bfeea5bdd5147153f5f3a5695.jpg

All too often parts are designed perfectly in a CAD software, yet when it comes time to 3D print for prototyping/volume production purposes we run into tolerance issues. This is due to 3D printing being an “Additive” technology and therefore adding slightly more material in certain areas. We see this issue occur mostly with snug tight fits as well as threaded assemblies. The below is intended to help guide you through the design for 3D printing process and save time/money on the number of prototypes.

When designing threaded parts for 3D printing, it’s important to provide clearance for the threads to mesh together. If the parts are toleranced too tightly, they will not fit! A good rule-of-thumb here is to leave a distance between male and female threads of 1-2 nozzle widths.  

image031_76d760dedbc6b1d27e0ccc1344b613925dffb39c.jpg

The parts above were printed on a 0.25mm nozzle at 0.1mm layer heights. I left a distance between threads in this model of 0.6mm, or a distance of just over two nozzle widths.

When modeling the parts, it is important to make sure there is enough clearance for the non-threaded surfaces to slide past each other.  That is, if you did not include the threads, could the male part slide easily into the female part? If not, the surfaces need more clearance before creating the threads.

 

I modeled these parts in PTC Creo using the “Helical Sweep” tool.  The Helical Sweep tool in Creo asks the user to define a profile for the sweep (here, just a straight, vertical line along the surface where the threads will be placed). It also requires a “pitch” dimension. The pitch is the distance between threads on your model. In my example, I chose 3mm arbitrarily as the pitch for my design.  It’s important to note here that the male and female parts must have the same pitch distance, or the threads will not articulate. If you are looking to replicate a standard screw, the pitch height can be found online. (Here’s a good link to metric thread pitch lengths!)

image011_9b6e0ea2717f5c0e450730ce58ff2b902163b423.jpgAnother important aspect of threaded parts is the thread profile.  I have found that triangular threads are more reliable than rounded threads, as rounded threads tend to slip when over-tightened.  In the printed example above, the protruding threads have an isosceles right triangle profile, with a height of 0.6mm.  The female threaded top has a thread profile with a triangular height of 0.9mm. This gives just over 1 nozzle-width between the male and female threads.

image001_32d57d9712270efa15190aec215da465ac784e90.jpgAside from normal threaded parts, 3D printing provides an excellent platform for designing captive screws.  The model to the left was printed as one piece and can expand or contract, but will not separate.  Stay tuned for my next post, where I will go into detail about creating, printing, and utilizing captive screws in mechanical designs.

 

Kiana - SD3D has not written a bio yet…
DesignSpark Electrical Logolinkedin