Not All Rubber Molding is the Same - Processes for Achieving Optimum Manufacturability

Designing a part for optimum manufacturability involves many considerations — and when we have the opportunity to get involved in a project in the beginning, all parties benefit.

As the leading supplier of high-engineered, precision molded rubber parts, we consider each design as a new entity. No part is exactly the same. Each intricate detail is a priority.

Racho will be intimately involved from the conceptual stages that lead to prototyping and carry it all the way to production — which, of course, includes rubber molding. In order to guarantee the best production, we use traditional methods as well as the latest technology and advanced controlled injection processes when creating a mold.

The most economically beneficial and waste eliminating molding process is selected to ensure first-time-through efficiencies with state-of-the-art systems. These commonly include:

Rubber Injection Molding

After the material is mixed, it is immediately pulled into continuous strips that are fed into a screw on the injection molding machines. When the mold is closed, the material in the barrel is injected into the mold cavities and cured. Rubber injection molding was adopted about 60 years ago and has since been one of the most efficient ways to mold rubber.

Compression Molding

This method is mostly used for larger parts and/or with very expensive compounds. The material is placed directly into the open cavity and then the parting lines are clamped and the part is formed. Often, compression molding utilizes less expensive tooling, but can be less precise as other methods of rubber molding, which may be unsuitable for select parts that would otherwise require a more exacting process.

Transfer Molding

This method is most often used for producing precision parts adhering to tight tolerances. We often incorporate hardened and self-registering cavity inserts in our rubber molds to ensure perfect registration along with dimensional and flash control. The material is “transferred” through sprues into the cavity while the parting lines are clamped and the part is formed.

Low Waste Molding

Rahco is very focused on driving out residual molding waste with every mold and production process we design.

In the injection molding area, it is very common for us to incorporate cold runner manifold systems with our molds. This design eliminates the primary and secondary runner systems that conventional hot runner molds produce, which cannot be recycled and are otherwise deposited into the landfill waste stream. Cold runner designed molds, however, experience a 90% reduction in this type of waste.

Another common method of waste reduction is cold pot transfer molding. This low waste design is ideal for most applications with the only the small sprues being relegated to landfill. Similarly,  reduction in waste is often over 90% when compared with a conventional hot transfer molding process.

When the volume of parts produced is high and or when the material cost is high, the above methods are quite effective in leaning out material waste and part cost.

Flashless Molding

This method of molding has been a growing part of our operation. At Rahco, we mold flash free parts using the transfer, low waste method. These molds are always made with hardened stainless steel cavity inserts and run in special vacuum presses. We use this process to eliminate cryogenic or die trim finishing, which keep parts free of contamination and also reduced costs for more savings we can pass to customers.

Insert Molding / Over Molding

Rubber over molding of any substrate can be achieved seamlessly. We like to get involved early in the design of these types of parts to ensure mutual success. If a chemical bond is required, we can design a process that will ensure a bond to the substrate that will not peel off. The most intimate type of chemical bond is where the rubber breaks away from the rubber, leaving rubber still securely bonded to the substrate. If a mechanical bond is all that’s needed, we can also support an inexpensive but still robust option. In addition, we will help in the overall part design as shutoff areas are required to control flash leakage.

Valve Gate Molding

This method is specific to injection molding and most often used when the quantity of parts to be produced is quite high and also when the material cost is high as well. The tooling cost increases with this design but is always justified with the reduction in material waste cost, as a Valve Gate design completely eliminates runner and sprue waste. We analyze your part’s geometry along with the cost of the rubber compound and illustrate how this might be the best option for your project.

STAYING FOCUSED ON WHAT IS BEST FOR OUR CUSTOMER

Molding processes and systems must be aggressively structured to ensure that all required materials, tools and processes are designed to support superior quality and manufacturing efficiency. Whether your goals are fluid or air sealing, dampening of noise, air transfer, and beyond, we can design the system that best suits your application with economics and performance top of mind.

If you’re developing new products, facing performance challenges with existing ones or concerned about the materials in your current parts and their alignment to specification — Rahco Rubber can help.