V4 BeyondPlastic – [PROCESS] Low-tech Mold
This is a plate mold made with accessible metal-working tools and machinery (angle grinder and MIG welder). Most of our other biomaterial heat press molds have been made on the CNC or engine lathe so far. We wanted to make a mold using tools that are easier (and cheaper) to come across. The main material tests for iterations of this mold were done using wheat bran.
In the first iteration of this mold, we used angled steel and sheet steel to create a square plate with 45 degrees opposite bevel walls. These walls offer the right depth and shape for a standard plate. They also help the material spread while the mold is under compression.
The bottom negative half for this mold was made using four pieces of 3cm angled steel cut at 45-degree angles to make a frame (19.5×19.5cm). The frame was welded onto a sheet of 5mm steel.
The top positive part was made by creating a smaller frame of 1cm angled steel, also cut at 45-degree angles. This frame was welded onto another sheet of steel. Supports were tacked in place inside the frame and then covered by a square sheet of steel to create an enclosed positive. I welded/ground the form to “refine” it a bit and to fill some gaps.
After testing it a few times I found that there was too much space in the bottom part of the mold, which made the plate way too thick. I cut a 5mm sheet of steel to fit in the bottom of the mold and beveled the edges so that it sat flat on the bottom of the mold, along the angled edges of the frame. This helped in reducing the thickness of the wheat bran plate.
The major pain points of this design, however, came from the lack of pressure building up along the top edge of the plate walls and in the corners. The mold refused to close entirely, and this lack of pressure produced crumbly, weak walls… not the crisp, sturdy, straight walls we were going for.
After multiple attempts adjusting the amount of material, temperature, water content, and press time we got the mold to produce a functioning plate with (somewhat) intact walls. The wheat bran plate finally started coming out of the mold in one solid piece when I let it sit and “cook” inside the mold for 10-15 minutes after removing it from the heat press. How material was packed into the mold mattered ~ a lot ~. Unlike the cup or bowl molds which we have used a lot here at Beyond Plastic, the material doesn’t all collect into the deepest point of the negative half of the mold. Since the plate is such a shallow shape, I thought pressure around the top edges could be created simply by getting the mold to close and having sufficient material. On one hand, the flatness of this plate mold compared to deeper vessels allows us to pre-spread the material into all the hard-to-reach places before pressing. On the other hand, for this to work effectively, enough pressure needs to build at the top, and this mold design wasn’t allowing for this.
After refining the material packing method multiple times we still couldn’t produce the right plate. Moving on, we decided to redesign the bottom half of the mold to create more pressure.
Images of process:
Wheat Bran recipes tests:
1. 145g WB, 30g water, 155C, 5min
2. 140g WB, 30g water, 155C, 3min
3. 160g WB, 68g water, 165C, 12min
4. 150g WB, 55g water, 155C, 14min
5. 150g WB, 55g water, 155C, 10min
6. 155g WB, 68g water, 152C, 18min
7. 160g WB, 35g water, 155C, 5min
8. 155g WB, 55g water, 155C, 12min
9. 150g WB, 10g coffee, 55g water, 160C, 12min
10. 160g WB, 59g water, 155C, 10min
11. 150g WB, 55g water, 135C, 10min
12. 170G WB, 60g water, 135C, 12min
14. 170G WB. 60g water, 135C, 10min, sit for 15min
15. 166G WB, 57g water, 135C, 12 min, sit for 10
PLATE MOLD – SECOND ITERATION:
Addition of walls –
The priority of the second iteration was the addition of walls on the bottom half of the mold. Walls ensure the build-up of pressure (especially at the top edges) while preventing any material from escaping the negative cavity.
For the walls, I welded four pieces of 6cm angled steel, then bolted this frame to a piece of sheet metal for the bottom part of the mold. Instead of using angled steel to create slanted walls, I beveled strips of wood, cut 45s on the ends, and glued them into a frame to sit inside the walls. I covered the open faces of the inset wooden frame with sheet metal.
We added some height to the top part of the mold by attaching layers of wood with contact glue. This allows for the top part of the mold to get pressed into the bottom part within the wall. It also allows for easy removal of the top mould after pressing (I added two screws in the wood as small handles, which worked well). This piece was also cut down to fit within the walls of the new bottom part of the mold.
This mold design was promising after the first attempt. The corners and walls came out much more compressed and sturdy. At first, the bottom of the plate was still too thick, so I placed the beveled sheet that I had used to reduce depth from the first version of the mold. It also required some sit/cook time after being removed from the heat press (10 min).
The walls of wheat bran plates from this mold were still too thick (about 1cm thick), which made the final product pretty heavy. To thin these out, I cut four pieces of metal and welded them to the four sides of the top mold.
After this adjustment, the walls were the desired thickness. However, the step at the top which provided decent compression along the top edge was gone, making the top edges of this new version a bit less crisp in some places. Pre-pressing (by hand) and getting material squeezed into the corners and along the edges when filling the mold before going into the press was crucial to how they came out. Once I got this part of the process dialed in, they were turning out pretty well and crisper along the edges.
Wheat bran recipe tests for Mold 2:
1. 175g WB, 50g water, 125C, 10min
2. 190g WB, 57g water, 135C, 10 min, sit for 10min
3. 190g WB, 67g water, 135C, 12 min, sit for 10min
4. 180g WB, 50g water, 135C, 12 min, sit for 10min
5. 180g WB, 63g water, 135C, 12min, sit for 10min
6. 100g WB, 33g water, 135C, 15 min, sit for 10min
7. 75g WB, 25g water, 135C, 15 min, sit for 8min
8. 180g WB, 55g water, 145C, 10min, sit for 10min
9. 170g WB, 48g water, 145C, 12 min, sit for 8min
10. 180g WB, 55g water, 145C, 10min, sit for 10min
11. 160g WB, 40g water, 145C, pre-press 5 min under 4 tons, 5 min for 10 tons
12. 140g WB, 40g water, 145C, pre-press 5 min under 4 tons, 5 min for 10 tons 13. 145g WB, 45g water, 145C, pre-press 5 min under 4 tons, 5 min for 10 tons
14. 160g WB, 45g water, 145C, pre-press 5 min under 4 tons, 5 min for 10 tons
15. 150g WB, 45g water, 145C, pre-press 5 min under 4 tons, 5 min for 10 tons
Some changes to make:
– Removal method of the pressed plate:
I’d say this part of the process was the least refined. The depth of the walls made pressed plates a bit tricky to remove. The sheets that covered the beveled wooden frame in the bottom of the mold created very sharp edges, and when the material was pressed in the mold, it often became stuck in these. In the next iteration, I would weld a bead along those seams. The base sheet on the bottom of the mold was removable, which was intended to make the pressed plate easier to release. However, material that was getting stuck in the edges made it cumbersome and often damaged the pressed plate, even when the base sheet was unscrewed from the walls.
– Wooden frame in the bottom part of mold:
Though the wooden frame is insulating, I question whether or not (for this part of the mold) the metal sheets that covered it became hot enough, which is necessary to bind pressed material. Instead, I would create the same frame using thicker metal and would weld it directly to the walls of the bottom part of the mold.
You must be logged in to reply to this topic.