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Molded Devices, Inc.
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A Versatile, Flexible Plastics Process That You May Never Have Heard Of The following article was contributed by Molded Devices, Inc.
These pliers are an example of how the dip coating process can be applied to hand tool handles.
Photo courtesy of Molded Devices Incorporated.
Widely used but little known, dip molding and coating—using liquid vinyl—has applications in markets ranging from automotive to consumer products and medical devices.
Dip molding and coating is a plastics process that, while used commonly on many types of products that include everything from medical devices to hand tools to gasoline pump handles, remains largely unknown to plastics engineers and product designers. Yet, dip molding and coating, using a variety of liquid polymers, offers many advantages and, in certain applications, can even be an excellent alternative to the injection molding and extrusion processes.
Because dip molding and coating is a niche industry, most of the companies offering this service tend to be smaller, local operations. The exception to this is Molded Devices Incorporated (MDI), the largest contract manufacturer of custom dip molded and coated products in the United States. Molded Devices operates four dip molding facilities (Riverside, California; Oshkosh, Wisconsin; Miamisburg, Ohio; and Sellersville, Pennsylvania), and each location offers similar and unique capabilities.
Molded Devices’ Riverside, Calif., plant performs dip molding, rubber dip molding, transfer molding, and dip coating. The facilities in Ohio and Pennsylvania offer dip molding and coating, as well as secondary operations, including laser engraving, pad printing, hot stamping, and value added assembly. And the plant in Oshkosh, Wisconsin offers dip molding and coating, along with lower volume capabilities and value-added assembly.
There are a number of advantages and benefits of dip molding and coating that make these processes both cost-effective and time-efficient. The molds, called “mandrels,” are typically needed for the dip molding process or for custom applications, and are made from either aluminum or steel. These mandrels can be made in a matter of hours, making them extremely cost effective compared to the tooling required for other plastic processes. That means that samples can be provided in days, and production started in just a few weeks.
Depending on the number of mandrels needed for the project (based on the volumes required), capital costs are typically under $2500. In the dip molding process, the mandrels are heated and then “dipped” into the liquid polymer, natural and synthetic rubber, and even latex for certain applications. The material attaches to the mandrel, with the thickness of the product determined by the “dwell time,” or the length of time the mandrel remains in the liquid polymer. The mandrels are then placed in an oven using heat to cross-link or “cure” the liquid polymer into a solid state. This “cure time” can vary by part.
These parts are an example of the dip molding process.
Photo courtesy of Molded Devices Incorporated.
In the dip coating process, a specific product (such as plier handles) is heated and dipped into the liquid polymer, which adheres to the metal. In both dip molding and coating, the parts are then re-heated after dipping to cure the material on the mandrel or the part. The parts are cooled, and the material is stripped from the mandrel or, as in the case of hand tools or other products requiring a soft-touch application, left in place on the product. The more mandrels or parts that are used at one time, the lower the cost.
Additionally, dip molding or coating creates perceived added value to the product. Liquid polymers come in a wide variety of colors, and can be printed with corporate logos and other decorations to meet marketing promotional requirements. All of MDI’s materials are California Prop 65 compliant to ensure safety for all applications.
Another benefit is that whether you have a low-volume requirement or a high-volume production project, dip molding and dip coating can offer both time and cost savings. It can also be an alternative to the injection molding process in applications where part geometry is not too complex, and material with a high rigidity level is not an absolute necessity.
For example, a customer came to MDI with a grommet requirement specified in a thermoplastic elastomer (Santoprene) that would be produced by the injection molding process. However, the program for this component didn’t have the volumes needed to justify the injection mold required to do the job (the estimated annual units for this particular part were less than 10,000 pieces). Molded Devices was able to manufacture this component utilizing a proprietary process developed for other similar applications, and the tooling was designed and built for under $500! The company was also able to keep the per piece price within the customer’s budgeted range, making the grommets extremely cost effective at the lower volumes.
Molded Devices Incorporated works closely with a variety of OEMs across many markets, such as medical, aerospace and defense, automotive, construction, and industrial, to provide solutions to their dip molding and coating requirements. Dip molding and dip coating applications include the production of various sized medical balloons, endoscope components, and cannulas with highly customized material formulations and precise dimensional tolerances; protection for high-end glass and metal components against chipping, scratching, corrosion, static in PCB components; and many more highly customized applications.
Some of MDI’s most successful programs include working with global suppliers of medical devices for which they manufacture more than a million components and assemblies annually. The company manages entire programs for its medical device customers, including buying all the components and completing an in-house assembly operation for the different product lines. “Our customers see tremendous value in coming to a single-source provider for their products,” said Dave Schoell, vice president of sales for MDI.
Another project for which dip molding provided an ideal solution involved a customer that manufactures high-value titanium products requiring many different machining operations. After discovering a high rate of returns as a result of minor scratching or small “dings” in the product due to the handling of the products, the customer came to MDI looking for a solution. “Together, we developed a protective dip molded cover used in the plant to protect the product as it moved between stations during the various operations, greatly reducing returns and rework costs,” said Schoell.
Dip molding can also be used to compete in blow-molded applications for bellowed products. “One customer initially reached out to a blow molding company for a bellowed gear shift cover,” explained Schoell. “The blow molding company came back with tooling and cutting fixture costs in excess of $70,000. MDI made the mandrels for under $500 and a lower part cost as well.”
As seen by these examples, dip molding and dip coating can be used in a wide range of applications from protective coverings to medical applications, recreational equipment, sound dampening, and circuit board protection, as well as in fitness equipment, bumpers, soft grips on power tools where haptics (touch) are important, lawn and garden, steering wheels, and much, much more.
Headquartered in Tempe, Arizona, the MDI family of companies (moldeddevices.com) also includes state-of-the-art injection molding (ITAR, FFL and ISO13485 Certified) at its Tempe, Arizona, facility, making MDI an innovative “total solutions provider” to meet both injection molding and dip molding requirements. This state-of-the-art injection molding facility is equipped with full-service mold manufacturing, a quality laboratory, and clean room molding, and also offers two-shot molding, metal injection molding (MIM), and assembly operations.
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