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18. Wildcard week

Historically, Week 18 has been about composites, like fiberglass. This year Neil is challenging us to use digital fabrication and our local resources to create something. The prompt was something like: there will never be enough weeks to cover everything so make/document the project you think should fill Week 18.

My proposal is that Week 18 should be about using digital fabrication to make a low-cost tool allowing the Fab Lab to be more accessible. Although Fab Labs are often used to make machines and tool, the machines I see are typically still fairly expensive.

Proposed Week 18 tasks:

  • Build a machine or tool that makes one of the Fab Academy processing more accessible.
  • Explain the innovation of your machine / tool
  • Explain how your machine / tool saves money, compared to the “traditional” fab academy approach

Vacuum Forming Machine: Molding and Casting

I love vacuum forming! It is an easy way to make molds of CNC or 3D printed objects. The best part is the machine can be made vary easily and it often times removes the need to expensive silicone when making simple molds.

The basic parts of any vacuum forming machine is the heater, material tray, vacuum table and vacuum.

Design Files

Vacuum Form Machine CorelDraw | Vcarve

The vacuum forming machine was made using the laser cutter to cut the 1/8” white acrylic and the Shopbot to cut all the wood pieces.

The heater is located on the top of this unit and encased in laser cut acrylic. I used an inferred heater from amazon and just removed the case prior to attaching it to the frame and covering it with acrylic.

My favorite part about this version of the vacuum forming machine is that it is designed to work with disposable plastic plates. Plastic plates make for an inexpensive and easily sourced vacuum form plastic. The material tray is cut to the shape of the plate. The two pieces of the tray sandwich the plastic plate allowing the user to move the plate up against the heater and down over the vacuum table.

Notice in the image above the two sides of the material (plate) holder extends. These are designed to be the handles for the plastic holders. This allows you to move the tray upand down from the heater to the vacuum table.

The vacuum table is a simple box made of ¾” plywood with a plate shaped piece of plywood on the top. This shape allows the plate to suction over the edge of the vacuum table with a nice seal. The holes in the top allow the air to pull the plastic against the 3D printed or CNC milled blank.

On the side of the box is a 2” hole that fits snug around a small shop vac. When they shop vac is turned on and inserted into the hole, the vacuum table sucks air through the holes.

I found it very difficult to hold the material tray and turn the vacuum on and off at the correct time. Ideally the plastic is pulled down over the blank before the vacuum is turned on. To make the timing easier, I recycled a sewing machine foot pedal to turn on and off the vacuum.

Molding and Casting

I used the CNC mill and the 3D printer to test a bunch of materials on the vacuum form machine. They all worked with varied levels of success.

  • Wood: this worked the best because the heat did not affect the wood and it was smooth enough to pop out of the plastic mold
  • 3D printed PLA: this worked but if the infill was under 15% with a thin shell the shell would deform against the hot plastic
  • Styrofoam: This worked one time. After the first use the Styrofoam started to melt.

I knew the mechanics of the vacuum form machine were simple, but I was impressed with how well it worked.

We used the machine to run a soap making workshop at Fab Lab Houston. This is a perfect example of why this machine is so useful. We were able to show a group of students how they could design a model in 3D on the computer. Use a CNC mill to quickly machine their blank. Then, make a mold that cost cents instead of the typical silicone costing dollars. Plus, there was no dry time for the mold.

The bars of soap came out beautifully. I am excited to experiment with chocolate.