Designing a Mold: #

Based on the dimensions of one of the outfinite corridor pavers, I designed a brick in Fusion that ideally will be able to house a solar panel, epaper screen, batteries, and a microcontroller setup.

The Fusion process this week consisted of creating the positive object (the brick), putting a box around it, then using the combine tool to cut out the object. I selected the box as my target body, the object as the tool body, set the operation to cut, and kept the tool.

Once I had the negative of my object, I drew a line and cut the body along that line into two pieces. I modified these pieces so that there was a finger joint on the bottom. I then added a lid, cut this body, added a finger joint between the two main pieces and added two two finger joints to sit on top of the mold. Because I didnt create the correct positive object the first time, I had to modify the mold by using the sweep tool and the extrude tool to add and remove parts of the final body.

The dimensions of the street brick design are 5 3/4 inches wide, 11 11/16 inches long, and 2 7/8 inches tall. The design includes a 1 inch depression that is 3.25 inches wide and 9.75 inches long to account for a solar panel and epaper display as well as a 0.14 inch lip to receive a piece of 1/8th inch plastic that will serve as the cover. Not knowing what the consistency is of drystone, I also designed a lid with two holes so that material could be poured through.

To print this design, I followed my notes from Week 4 and changed the print thickness to 20mm, and set the infill grid to 7%. Once the print was complete, which took a multiple tries given that two of the machines stopped working during my first set of prints, I sprayed the PLA with a few layers of Krylon UV Resistant Crystal Clear Acrylic Coating. This was done in order to prevent the drystone from sticking to the mold.

Casting with Drystone: #

Following the instructions on the back of the drystone bag, which indicated to mix 18-20 parts water to 100 part drystone by weight, I set aside a series of pre-measured cups with 3 lbs of drystone and 0.6 lbs of water. Before filling the mold, I placed two clamps on the brick in order to prevent any mixture from falling through the seam. As per the instructions, I added the drystone to the water, mixing as I went. I was a bit surprised at how little water was needed for the drystone and for future mixes, I might add more water. The mixing process was a challenge given the tools at hand – wooden mixers and paper cups – and as with the ratio, I will also look to find a more appropriate set of mixing tools next time.

With the first batch mixed, I scooped it out of the cup and added it to the mold. I then proceeded to tap and shake the mold in order to bring air bubbles to the surface.

I repeated this process, and followed it by adding a layer of aggregate in order to act as fill. The brick wasn’t quite filled, so I added another batch – this time with 2 lbs of drystone, 0.5 lbs of water, and a half cup of aggregate. I mixed all of this together, pour it into the mold, and once again tapped and shook it to remove air bubbles, and this time to settle the aggregate into the mixture.

Once it looked like there was enough material in the mold, I used a piece to run across the edges and remove any excess drystone mixture. I then put the lid on the brick, tighthen the clamps on the sides, and added weights to the top

After 35 minutes, the drystone mixture was cured and I proceeded to remove the mold by tapping on each piece with a small piece of 2x4.

Class Notes: #

• Watch out for bubbles –> stir in a shearing motion
• If possible fill from the lowest to highest point –> include vent at top
• Silicone is mostly inert
• Options this week: 3d printing or machining
• The goal for this week is to avoid seeing any of the milling or 3d printing lines

Recitation Notes: #

• Why build a machine?
  • to better understand the world around us and how to fix and repurpose the tools around us
  • helps to think in modules/parts

Group Assignment Notes: #

For this weeks group assignment, we mixed silicone and rockite and filled in two separate molds.