DIY Silicone Mold Making: Wax Pokeball Casting with Vacuum Degassing

Vacuum chambers remove air from materials by pulling a vacuum, making them ideal for silicone molds where you want to eliminate 99% of air bubbles before pouring; pressure pots use compressed air (typically 40 PSI) to force air bubbles to collapse, making them suitable for rigid resins with short open times where you need rapid bubble elimination before the material cures.

Pressure pot processing is a technique used to eliminate remaining bubbles in resin-cast objects. After initial vacuum degassing, the resin is placed in a pressure pot where pressure is applied to crush any remaining bubbles until they become microscopically small and invisible to the human eye. This two-stage process (vacuum degassing followed by pressure pot processing) ensures the highest possible clarity and structural quality in the final resin product.

A pressure pot is used to eliminate air bubbles from resin castings. After pouring resin into molds, the entire setup is placed in a pressure pot that crushes out all air bubbles. This produces significantly better results than gravity degassing alone. The witness cup technique helps determine when the resin has properly filled the mold before applying pressure.

Vacuum physically removes air bubbles from the casting material, while pressure simply squeezes bubbles to a less visible state. On rigid materials, bubbles don't come back after pressure casting, but on flexible materials like silicone and urethane rubber, bubbles can actually rebound back, causing deformities in molds or parts. Pressure casting serves as an insurance policy to catch incidental air bubbles produced as the material flows through the mold, and can help force material into extremely fine detail or small air pockets in the mold geometry. However, pressure alone doesn't always eliminate 100% of air bubbles.

Pressure pots suppress bubble formation in resin by applying positive air pressure during the curing process. Resin foams when water vapor enters the mixture from atmospheric exposure, interfering with the curing reaction. The pressure environment prevents air from entering, eliminating bubbles. Unlike vacuum systems, pressure pots work effectively because they prevent bubble formation rather than removing existing bubbles after they form.

Registration keys are small indentations or grooves created around the edges of the mold cavity that serve as alignment guides when assembling multi-part molds. These keys function similarly to Lego bricks, ensuring that the two parts of the mold align perfectly every time they are separated and reassembled. To create these keys, small indentations are made using tools like the handle of a brush or other pointed instruments placed strategically around the perimeter of the model within the plasticine.

Proper mold assembly requires installing sprues and vents using sticky wax adhesive. Registration dots must be created separately to avoid surface ridges that cause alignment problems. Release agents must be applied selectively to prevent unwanted bonding. The entire system ensures mold halves align precisely, creating clean parting lines and preventing flash in the final casting.

After establishing the basic mold geometry, designers add functional features essential for mold operation. This includes creating alignment pins and slots to ensure precise mold registration during assembly. Gate design determines plastic flow characteristics, with wider gates delaying solidification to improve filling of long, slender cavities. The sprue channel accommodates the machine nozzle's radius for proper plastic transfer. Ejection slots enable screwdriver access for mold opening. Air vents (typically 0.001 inches deep) at cavity extremes allow trapped air to escape during injection, improving fill quality. These features collectively enable reliable mold operation and consistent part production.

Place injection sprues at the lowest point of the mold and vents at high spots. When resin is injected at the low point, gravity forces air out through the vents at high points, eliminating air bubbles in the final part. Apply super glue to secure vents (using copper wire) and kicker to bond everything to the master part.

This segment demonstrates the practical creation of ventilation channels and registration keys in mold making. The instructor shows how to create ventilation channels (respiraderos) using heated tools to cut channels in plastilina, allowing air to escape as material enters the mold. The segment explains that without ventilation, air becomes trapped in mold sections, preventing complete filling and creating defects. The instructor also covers registration keys (llaves de registros) which are positive and negative sections that ensure proper alignment when joining mold halves. The segment emphasizes that proper ventilation and registration are essential for successful mold making, especially for complex objects with multiple sections.

Plastic manufacturing encompasses vacuum forming using porous aluminum molds that enable rapid prototyping of curved surfaces, and injection molding for producing first 500 units to prove business viability before scaling. Laser cutting complements these processes by enabling precise 2D cuts in acrylic and wood, with the ability to etch acrylic white for prototyping. Together, these complementary processes form a continuum from rapid prototyping to low-volume production, each serving distinct stages of product development.

Plastic injection molding is a mass manufacturing process where plastic pellets are melted by a reciprocating screw inside a heated barrel, then injected under pressure into a mold cavity where they cool and solidify; the process involves three main machine components (injection unit, mold, and clamp), utilizes a screw mechanism that provides 60-90% of the melting heat through shear action, incorporates venting systems to release trapped air, and relies on mold design features including parting lines, draft angles (typically 1-2 degrees), and ejector pins that leave characteristic witness marks on finished products.

Injection molding is a manufacturing process that creates plastic parts by injecting molten material into molds, involving three key stages: mold making (using CNC machines and electrochemical processes to create precise molds), injection molding (where automated machines inject molten plastic into molds and eject finished parts), and finishing/assembly (where workers perform quality control, apply coatings, and assemble final products); successful injection molding requires good design, quality machines, and experienced engineers working together.

Industrial injection molding involves melting plastic material and injecting it into a mold cavity under high pressure, with parts produced at approximately one unit every 60-70 seconds. Polycarbonate and ABS are common materials, with polycarbonate providing transparency and impact resistance while ABS offers toughness. Industrial machines can be extremely large, with some capable of producing parts at high rates. Molds (werkzeuge) are the critical capital assets, made from heavy steel weighing 2.8 to 7 tons, directly determining product quality and shape. Color changes require extensive cleaning and minimum production runs to justify setup costs.

Rotational molding is a low-pressure manufacturing process that creates hollow plastic parts by placing powdered plastic inside a mold, heating it in an oven while rotating the mold on multiple axes, and allowing the melted plastic to coat the interior surfaces uniformly; this technique enables production of large, hollow, or complex parts with consistent wall thickness and can incorporate additives like foam for insulation or water resistance.