SILICONE RUBBER TOOLING TECHNOLOGY AND INDIRECT METHODS OF RAPID TOOLING

When compared to traditional machining procedures, rapid tooling (RT) technology and silicone rubber tooling technology can minimize your time to market for injection molded items.

For small batch injection molding, aluminum-filled epoxy resin molds can be utilized instead of traditional steel molds.

LSR (liquid silicone rubber) parts are durable & can be used in a variety of applications. It is vital to build a mound quickly and effectively in order to reduce time to market for new injection molded items.

SILICONE RUBBER TOOLING TECHNOLOGY STEPS

  1. Design The Master Pattern

Some of the most common type of Silicone Rubber Tooling Technology are 3D printing (3DP), stereolithography (SLA), or laser sintering.

First, a three-dimensional computer-aided design is used to create the pattern (CAD). The CAD model is then edited with special software to slice it into layers and generate many 2D drawings. The pattern is then created using the chosen technology.

The pattern’s surface must be improved because silicone rubber will completely copy it. The material used to create the pattern must meet a certain requirement: it must have adequate surface tension to allow wetting of the surface during mold production.

  1. Casting Of The Silicone

The mold’s initial sub-step is to choose the right silicone rubber for it. It must be tough at high temperatures, have a high service temperature (which is a quality shared by all silicone materials), be resistant to compression.

To corroborate the material selection, a study of the stress-strain and isochronous curves is required. Many manufacturers advises using cured silicone rubber as “reinforcement” (recycling silicone rubber from past projects, for example), which will reduce the consumption of virgin silicone.

Inside the mold box, the pattern and cured silicone are inserted, and the optimal layout of the cured silicone in the box area is as uniform as feasible. The silicone rubber and catalyst are mixed together and poured into the box.

  1. Injection Of The Components

The melting or processing temperatures of the items that can be injected into silicone rubber molds must be lower than the silicone’s higher service temperature. The shorter the mold life, the greater the temperature of the part material. The conditions in which the substance is injected are also a concern.

Because higher pressures can shatter the mold and lower pressures can prevent the cavity from being filled, multiple CAE software’s can be used to compute the processing parameters.

Rapid Tooling Through Indirect Methods

Several pattern-based procedures for quickly manufacturing molds have been developed, with varying costs, lead times, and process capabilities. The accuracy of these processes is influenced by the RP technique that was used to build the pattern.

Silicone Rubber Molds (RTV)

Silicone is a flexible (albeit pricey) substance that may be molded around a master pattern to create a cavity. Master patterns are frequently an RP model, thanks to rapid prototyping processes. Urethane or epoxy prototypes are made with silicone rubber molds.

Making a rubber mold entail creating a master design, finalizing it to the desired appearance, and then casting RTV silicone rubber around the pattern to create the mold. The figure is suspended within a box using translucent material, then silicone rubber is poured to completely surround the model.

The hollow can then be used to mold two-part thermoset materials. Polyurethane, which comes in a variety of mechanical qualities and can replicate the mechanical and thermal properties of elastomers, ABS, nylon, and other common thermoplastics, is one of the most popular.

To avoid air bubbles in the molded component, polyurethane is commonly injected into the silicone rubber chamber under vacuum. Before the silicone rubber tool starts to disintegrate, it can usually create roughly 20 polyurethane pieces.

Liquid Silicone rubber tooling allows for quick and economical molds, as well as good part cosmetics and the use of numerous materials. Small or large pieces can be processed using this method. The process’s fundamental flaw is that the urethane materials’ characteristics differ from those of the thermoplastic materials utilized in manufacture. Individual part prices are relatively high due to material costs and labor demands.

Silicone Rubber Tooling Technology can be employed as a production method despite its limitations. Bastech (Dayton, OH) is now using silicone rubber tooling to produce an instrument housing with high visual criteria, such as texture, but low strength needs.

Vacuum Casting

Placing a silicone tool in a vacuum chamber with a polyurethane resin allows plastic items to be vacuum cast. Before being poured into the silicone cavity, the two-part resin is blended and de-gassed.

The cavity is opened, and a polyurethane part is removed after the two-part resin undergoes an exothermic reaction. After that, the silicone chamber is closed, and the procedure is repeated.

RIM

The Reaction Injection Molding (RIM) technique, unlike vacuum casting, does not require the use of expensive vacuum chambers and mixing devices. A simple resin injection system with two pressured chambers is used in the process.

comparison to vacuum casting, the cure reaction time is substantially shorter. The tools can endure up to 100 shots because there is no temperature cycling and the contact time between the resin and silicone rubber is substantially shorter.

RTV Silicone Rubber Tooling Technology has the advantages of being quick to make, reproducing detail admirably well, and creating a small quantity of plastic components quickly.