Making curved panels in a vacuum press requires a reliable bag and evacuation system. The wood should be kiln dried and glued with the grain in parallel direction since wood has different shrinkage rates across grain versus with grain. What polyurethane glue manufactures recommend is to wet the substrate (not the veneer, it will wrinkle) before applying the poly glue, thus it has sufficient moisture to cure when in a vacuum bag. You can coat your plastic parts with Crisco for a mold release and pour the plaster into them to create plugs.
Vacuum forming is used to make many different products from thermoplastic sheets. While I hold the layers together I remove the nail and drive the #6 x 1¼ screws through the sandwich and into the wood block embedded in the mold. The vacuum now holds the arch in its shape and the bag can be removed from the form. Some home-made vacuum formers I saw on the Internet stapled their plastic to to their frames.
Coating the entire mold with epoxy will improve stability by preventing the absorption of moisture by the wood. I started by drilling a large hole in the side of the box for the nozzle of my shop-vac, which would provide the vacuum. The number of samples that one is able to get from a wood pattern depends on the size of the part and the thickness of the material.
Model Makers, Inventors, Design Studios, Theaters, Specials Effects companies, etc…. The Hobby-Vac machine is perfect for prototype parts and packaging, display models, signs and even volume production of high quality parts. This is only necessary because no relief angles were designed into these pins, and the plastic holds really tightly onto them after vacuum forming. On small panels, you can coax the sandwich into a curve and/or pull back on the edges of the bag.
I have a soft plastic vacuum cleaner attachment which is tapered, so it forms a pretty good seal when pushed into the hole (you can see it in the photo; it’s gray). A note on form design here: when you unclamp your dried part, it is going to spring back” a little bit from the stresses in the bent wood. The plastic holds onto them quite tightly, even though they were sprayed with a teflon mold release agent before molding. Wood patterns are a common material to vacuum form but probably the most obvious. Whether it takes 65 seconds or 75 seconds to evacuate a vacuum bag is not critical.
The Vacuum Connector is completed with the Connector Surround (12), a 6 ^A x 10 inch piece of cardboard Photo Backing having a space cut out to snugly fit around the Airtight Vacuum Connector (9). The two sheets are heated from the top and bottom, once they have reached forming temperature, the two female molds come together bonding the two halves while the material is still hot. With a vacuum straight edge, it can be placed anywhere on the sheet and when vacuum is applied it will pull straight down.
Suitable materials for use in vacuum forming are conventionally thermoplastics The most common and easiest to use thermoplastic is high impact polystyrene sheeting (HIPS). Marc, I went to a school that taught us how to vacuum bag composites like fiber glass, and other materials. Twin sheet forming is great for industrial applications and packaging where strength is essential.
Once the specifications of the part have been met, the wood pattern is then used to create a Cast aluminium mould for regular production. I will stick to the only method I’ve tried, and that is vacuum formed plastic palettes. Our experience with forming spherical shapes gave us an edge up on the challenge of forming chromium plated hemispheres for the security industry a few years later.
The idea is that I will make molds of them using vacuum forming, then fill the molds with plaster to make all the copies I need. The function of the box is to confine, control and direct the vacuum force originating from, in this case, an household vacuum appliance while balancing and broadening its effect over the area of the Moulding Surface. Make the seal by lightly squeezing all three an opening, just pull apart the bag layers, insert parts or make adjustments then reseal. The following is a brief description of the properties and characteristics of various mold materials.
The shiny side is placed towards the veneer and glue and the edges of the barrier sheet are folded over onto the innermost layer of ply and taped into place. A lot of force will be exerted to hold the parts and you do not want your form to fail in the middle of the glue up. When possible, I prefer my forms to be solid wood. Even webbing itself, again with practice and given sufficient vacuum force, may be eliminated. Vacuum Tanks: A tank acts as a reserve in cases of a power failure or, in the case of an electric pump, stretches out the on/off cycles with a leaking bag.