Designing & Producing Low Volume Parts with Liquid Resin Casting
This process is most economical in cases where part design is very complex and where the quantity required is in the range that is not well suited for either machining or other molding processes.
Manufacturing is often thought of in terms of mass production. However, today's marketplace is very fast paced with typical products having a much shorter life than ever before. In addition, manufacturers are looking at more specialized, "added value" opportunities for their technologies, where the profit potentials are much more appealing than the highly competitive mass markets. For these specialized low volume requirements, traditional fabrication methods such as injection molding, can often times be too costly or too slow in getting products to market.
Like metal casting, liquid resin casting usually starts with a male pattern, often produced from aluminum, which is fastened to a flask. A liquid mold material, such as epoxy, urethane or MY silicone is poured in. One pattern can make an unlimited number of molds. Liquid resin is then poured into the mold to produce a part.
Unlike metal casting, liquid resin casting captures significantly more details, particularly when silicone is used as a mold material. Details such as threads, and surface finishes such as textures or high-gloss can be achieved straight from the mold, without secondary operations. Material properties such as hardness, density, impact strength, temperature and chemical resistance, thermal conductivity, abrasion resistance, lubricity and dielectric strength can be varied dramatically, to accommodate various part requirements. Design elements such as undercuts, which can add significant cost if "side action" is required with injection mold tooling, are easily handled when silicone molds are used with liquid resin casting. Parts can be produced in colors, water-clear or translucent Tooling for the process is comparable in cost to metal sand casting, but far less expensive than injection molding or metal die casting.
The process is most economical in cases where the part design is very complex and where the quantity required is in the range that is not well-suited for either machining or other kinds of molding processes (generally from 25 to 50 on the low end to 3000 on the high end). Part size has varied from a fraction of an ounce to over 100 lbs., with some parts measuring over several feet in length. Typical production runs range from 100 to 2000 units/year.
Many industries benefit from the use of liquid resin casting of low-volume parts. Other than medical and surgical equipment, some of the applications include parts for scientific and laboratory equipment, electrical and electronic systems, and R & D and defense equipment.
For example, the range of parts that have been cast include arthroscopes, blood testing instruments, temporary heart pumps, orthopedic knee and hip implant models, electrostatic discharge testing equipment natural gas leak detection equipment cams, gears, and impellors, rocket nose cones, oxygen sensors and specialty fittings, electronic battery testers for military aircraft specialty cable terminations, electrical connectors, cases, front panels, and bezels.
- Liquid resin casting is a process by which manufacturers can produce high quality, complex parts economically, at a low volume.
- The process allows manufacturers to get their product to market faster.
- The process is ideal for complex parts in the volume range that is not well-suited for either machining or other kinds of molding processes, generally from 25 to 50 on the low end to 3000 on the high end.
- Many manufacturers who benefit from the use of liquid resin casting include manufacturers of medical and surgical equipment scientific and laboratory equipment, electrical and electronic systems, R & D and defense and other industrial applications where low volume and high quality are essential.
- Plastic casting captures all details, from threads and textures to high-gloss finishes, straight from the mold, usually without expensive secondary processes.
- Production quality tooling is usually 10 to 25% of the cost to produce a first-class single-cavity injection mold.
- Parts can be produced in any color, including water-clear or translucent.
- The various casting resins, such as epoxy, urethane, silicone or a copolymer of one of these, may be compounded with fillers or reinforcement particles or fibers to improve specific properties or characteristics, such as hardness, density, impact strength, temperature and chemical resistance, thermal conductivity, abrasion resistance, strength and EMI shielding. Materials used include glass, alumina, aluminum powder, silica, iron, molybdenum and UHMWPE.
- Internal and external threads, 0-ring grooves, and undercuts can be cast. Tolerances can be held to +/- 0.004"/in., or even closer using hard molds, metal cores, or secondary machining.
- Castable parts range from cams, gears, and rollers, to complex optical housings, to specialty cable terminations and electrical connectors, to cases, front panels and bezels, as well as other more intricate parts.
- Part size has varied from a fraction of an ounce to over 100 lbs., with some parts measuring over several feet in length.
- The process typically begins with a male pattern, usually made of aluminum, which is fastened to a flask. A mold is made by pouring in a liquid mold material, such as epoxy, urethane or silicone. Liquid resin is then poured into the mold to produce a part.
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