Introduction: A Simple 3D Printed Whitworth Quick Return Mechanism

By Greg Zumwalt
About: Our grandkids keep me busy!

"A Simple 3D Printed Whitworth Quick Return Mechanism" is another model I designed for a mechanisms class.

The motor used in this model is an N20 60RPM 6VDC gear motor powered by a 3VDC battery pack, thus the motor runs at approximately 30RPM. 

With the motor gear having 12 teeth, and the yoke gear having 24 teeth, the yoke gear rotates at approximately 15RPM and as such the arm completes its rotary translation cycle in approximately 4 seconds. The motion of the arm is faster from left to right than right to left due to the nature of the Whitworth Quick Return mechanism. In this model, the arm rotates += 14 degrees.

As usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.

Designed using Autodesk Fusion 360, sliced using Ultimaker Cura 4.12.1, and 3D printed in PLA on Ultimaker S5s.

Supplies

Soldering iron and solder.

Step 1: Parts.

I purchased an N20 60RPM 6VDC gear motor, a dual AAA switched battery case and two AAA batteries.

I 3D printed two "Axle.stl" and one each of the remaining parts at .15mm layer height, 20% infill and no supports.

This is a low precision 3D print and assembly model. Prior to assembly, test fit and trim, file, sand, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing and/or sanding may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate "ooze" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step.

The model also uses threaded assembly thus an M8 by 1.25 tap and die will assist with thread cleaning if necessary.

Attachments

Step 2: Assembly.

I assembled the model as shown in the video by performing the following steps:

  • Soldered the battery case wires to the gear motor.
  • Turned the battery case switch off then installed two AAA batteries in the battery case.
  • Pressed the gear motor into "Base.stl".
  • Pressed "Gear, Motor.stl" onto the motor shaft such that the shaft end was flush with the gear surface, then aligned the motor in the base to allow .5mm clearance between the motor gear and the base.
  • Positioned "Gear, Arm.stl" onto the base assembly and secured in place using one "Axle.stl" making certain that the gear rotated freely.
  • Positioned "Arm.stl" over the pin on the arm gear and the threaded arm hole in the base, then secured in place with the remaining "Axle.stl" making certain that the arm moved freely.

With assembly complete, I turned on the battery case switch and off it went!

And that is how I 3D printed and assembled "A Simple 3D Printed Whitworth Quick Return Mechanism".

I hope you enjoyed it!