Week 8: Molding and Casting

Designing my part

Since I am making a record player, I wanted to use this week to design some feet for the record player. For anything that makes music, the music quality is best preserved when the vibrations that get passed along to the resting surface is minimized. Most speakers will use either a rubbery foot that absorbs the vibrations from the speaker or a hard, pointed foot that minimizes the surface area between the speaker and the table. I wanted to design both a rounded foot and a cone-shaped foot so I could test out these two geometries. I used Fusion360 to make the positives of my design.

For the rubber feet, I cut directly out of the stock material in my design because I can cast it in one step using the wax as the mold. For the plastic feet, I placed the positive in a square so that I could cast a rubber mold.

Milling the wax

Anthony helped me set up toolpaths for my design in Solidworks. I decided to first use adaptive clearing to clear out most of the material. The surface finish and finer details were accomplished using parallel toolpath along both the x and y direction with a step size of 0.0625". We were able to reduce the estimated machining time from 8 minutes to around 4 minutes but adding bounding boxes for our parallel toolpath (although the machining took around 20 minutes).

We used the Shark to mill. The process of milling out my design was:

  1. Use the bandsaw the cut off the correct amount of stock.
  2. Tape down my stock on the bed of the Shark.
  3. Zero the x and y position by eye.
  4. Zero the z position using the touch plate.
  5. Load the gcode onto the machine and begin the job.

Making the mold and casting

I first whipped up a batch of the OOMOO. For the hard foot, OOMOO will become the rubbery mold where I can cast other materials. For the soft foot, I wanted to see if OOMOO was a good material to absorb vibrations.

I was pretty happy with the results of my OOMOO cast. The foot I cast was actually sturdier than I anticipated which was nice.

The negative for the cone-shaped foot also turned out well.

For my next cast, I decided to cast another rubber foot made of Mold-Max which has a 24-cure time. I used the vaccuum chamber to de-gas the mold as well.

I also used the rubber mold to cast the cone-foot out of Smooth-On Liquid Plastic 365 which took about 30 minutes to cure.

I wanted to also do a test cast using Smooth-On Liquid Plastic 305. This cured very quickly (~15 minutes).

Out of all 4 materials I tried out, I visually liked the rubbery parts (dome-shaped feet) the best. Compared to the OOMOO, the mold max felt better. I think the OOMOO is too wiggly for my purposes. I'll probably stick with the mold max for my final project.