Manufacturing and Assembly - JS

3D Printing Links and Laser Cutting Acrylic

The primary driver for link dimensions were 6mm pins initially used in the pin joints. Prior to printing all the links, the 3D printer tolerance was determined by printing a small sample with holes of different dimensions. This ensured the links would require minimal processing and sanding after printing. The following figure shows one of the samples with 6mm pin:

After refining the 3D printer tolerances, the links were drawn and dimensioned in SOLIDWORKS and 3D printed. The final links are shown below:

The initial 3D printed tolerance piece ensured all the pin joints were close to 6mm, but all the link holes still needed to be sanded to ensure the links rotated smoothly about the pins.

1/8in acrylic was used to ground the mechanism. A piece of scrap acrylic was used initially to refine the locations for the input link pin, slotted pin, and slider joint length prior to cutting the final piece:

Finally, the initial mechanism pin joints were all comprised of the 6mm x 24mm slotted pins, and held together by 6mm o-rings.

Due to the short pin lengths, there was little room to work with between adjoined links. The o-rings also did not adequately hold most of the joints together, so links had a tendency to pop off the joint during operation. Additionally, the short pins left little clearance above the ground, so the joints would catch the edges of the ground board and slider slot.

Rebuild, Redesign, and Refinement

Bolts and nuts were subsequently used to keep the links from separating during operation. Long bolts and the o-rings were also added to allow more clearance between joints and the ground. The increased clearance between links and ground, as well as solid joint construction ensured the mechanism could rotate easily without issue. However, the o-rings had a tendency to brake the links, so were replaced with washers.