Over the last few months several friends and myself have been planning and launching a startup that is focused on building a high-end props for haunted houses using the latest technology available. One of the bigger challenges we have faced is prototyping on the fly. One of our props utilizes a timing belt to supply its motion, and nailing down the speed / torque ratio is crucial for the props functionality. Instead of buying several different sets of timing pulleys, I decided to simply print a few with varying tooth counts for prototyping. The production models will feature a manufactured set of pulleys, but for prototyping needs, the 3D Printed samples will work just fine.

Knowing what I know about the 3D Printing community, I did a quick Google search before jumping in and trying to design a pulley from scratch. The community did not let me down either. A Thingiverse user who goes by the name Droftarts had uploaded a customizable timing pulley script that allowed for a dozen or so timing pulley tooth profiles. While this script was awesome, it was difficult to use because many of the customizer options did not make sense as to what they controlled. A quick read through the description and the instructions proved to be fruitless, but then I scanned the comments.

A comment by Thingiverse user roipoussiere pointed me to a version of the script that he modified to make customizing the timing pulleys easier. The new script basically does the same thing, but adds tabs, and names the fields correctly. Additionally users can now simply select the needed tooth profile by name instead of just a numeric identifier.

To test things out, I simply created a 26-tooth XL profile pulley, and then printed it on my Lulzbot AO-100 using a spool of Sky Blue Excelfil PLA from Voltivo. The print below was made with the following settings:

 

• Extruder Temp: 206c
• Bed Temp: 65c
• Layer Height: 0.35mm
• Infill: 100%
• Infill Pattern: Rectilinear
• External Perimeter Speed: 60%
• Perimeter Speed: 40mm/sec
• Infill Speed: 40mm/sec
• Vertical Shells: 2
• Top Layers: 2
• Bottom Layers: 2
• Bed Meterial: Gladd with 3M Blue Painters Tape
• Print Time: 1-hour 11 minutes
• Filament Used: 3 Meters

The print turned out very nice so I decided to move forward with the experiment. I measured the shaft of the motor, and adjusted the pulley’s shaft size in the customizer to be 1mm larger than needed since I know that my AO-100 prints about .75mm smaller than the actual model measurements. I also adjusted the layer height from .35 to .30 in hopes of a smoother tooth profile. Adjustments were made to the external perimeter speed as well from 60% to 40% and the end result was exactly what I was looking for.

 

As you can see the end result is a set of timing belt pulleys that work well enough to get a prototype up and running with the correct ratios. You might notice some flaws in some of the blue prints. My Printer lost calibration during this series and I spent most of the prints fine tuning things, and as you cans ee with the red filament, I managed to dial it in pretty well. I used two of these gears on a project my new company, Terror Tech, is building, and they worked perfectly.