II. Design Process - JV

The design process for this mechanism was conducted iteratively along with the Kinematic Analysis so that the input linkage could achieve full rotation. From the lengths of linkages provided in Figure P6-28 there would be a singularity at the end of the output sliders return, by shifting the height of the output slider from the input link and moving the ground position (O₄) this was eliminated and the input link could achieve full rotation. The manufacturing process chosen for this mechanism was 3D printing, this made prototyping easy in general and also specifically for me since I have access to a 3D printer at my house. Another reason I chose 3D printing was the ability to use printed pins and joints instead of fasteners, with this I would be able to snap my assembly together very easily.

I based my design off of attaching this mechanism to a flat plywood backing, O₂ will be on the DC motor output shaft which will be mounted to the backing, O₄ will also be mounted to the backing. Rails were also attached to the backing to guide the output slider and constrain its motion in the horizontal direction. Shown below is the base idea that I built my mechanism off of, the links are attached to each other with pins and joints.

SolidWorks was used to model this mechanism, the most noticeable design choice I made was to design links three and four as one part, this was done so that they could be printed together and once the support was cleared link three would be able to slide. If this wasn't done then link 3 would have to be inserted into link 4 and in my opinion the easiest option was to model them together. The pin and joint designs were based off of a source found online by Eiki Martinson (linked in Appendix), this is shown below. Basing off of this design was important because it meant that the thickness of the links were they are pinned needs to 0.25".

 Link 2

 Link 2 Spacer

 Links 3 and 4

 O₄

 Link 5

 Link 6

 

A spacer was needed for link 2 so that the link would not interfere with an extrusion on the face of the motor, the spacer is only 0.05". The thickness of link 3 within link 4 needed to be 0.25" for the joint, this meant that link 4 was 0.15" thick, and to make up for this an extrusion was needed at the interaction with O₄. The heights of O and Link 6 was calculated from the offsets of the motor, mounting, and linkages so that the were at the correct height to mount the backing board of the mechanism.