Our Approach: Staying focused on what is best for our customer
Rubber Injection Molding
Rubber injection molding was adopted about 50 years ago and has since been one of the most efficient ways to mold rubber. The material is mixed and then 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.
This method is mostly used for larger parts and/or with very expensive compounds. This method utilizes less expensive tooling, but is not as precise as other methods of rubber molding. With compression molding, material is placed directly into the open cavity and then the parting lines are clamped and the part is formed.
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. With transfer molding 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. These runners are not able to be recycled and are deposited into the landfill waste stream. With cold runner designed molds it is common to see a 90% reduction in this type of waste.
Another method of waste reduction that is also very common at Rahco is cold pot transfer molding. This low waste design is great for most applications with the only the small sprues being relegated to landfill. It is common to see a reduction in waste of 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 piece part cost.
This method of molding has been a growing part of our business. 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 thereby reducing costs and keeping the parts free of contamination.
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 in order to ensure mutual success. If a mechanical bond is all that’s needed we can show you who this can be accomplished, resulting in an inexpensive but still robust option. 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. In addition, we will help in the overall part design as shutoff areas are required to control flash leakage.
Valve Gate Molding
Another great way to not only reduce but completely eliminate runner and sprue waste is to use a Valve Gate design. This 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. We will analyze your part geometry along with the cost of the rubber compound and illustrate how this might be the best option for your project.