This is an article reprint from the October 2022 edition of Design-2-Part magazine.
MJM Industries has been making custom wire harness assemblies and custom over-molded cable for as long as 37 years, with new connectors, assemblies, harnesses, and wire processes being added as customers request.
MJM Industries offers engineering services to assist customers in their design and development process, including tooling and fixture design. Its engineering skills were put to the test during the COVID crisis.
“We started work during the pandemic with a customer with a 14AWG DC power cable with an over-molded circular power connector. Their completed product is considered critical since it transports blood and vaccines,” said Jill Cole, national sales manager for MJM Industries, in an emailed response. “We needed to move quickly to provide them with a design proposal for tooling and first articles of the completed assembly as soon as possible. Our team was able to produce in-house designed and built prototype tooling. After approval, the production was also fabricated in-house, which allowed them to stay on track with their fast-paced schedule.”
Over-molding is a process of molding plastic over plastic or metal to shield and protect the electrical connection or other materials inside the over-molding. The over-molding material forms a strong bond with the material underneath. In some cases, over-molding eliminates a need for assembly.
“We provide several cable assemblies for a leading manufacturer of hospital beds for orthopedic surgery. Another assembly is a basic wire process, plus connecting a sensor for an upper body therapeutic apparatus,” Cole said. “The assembly requires an over-mold for additional structural support because it is part of a swivel drive train that allows exercise from a seated, standing, or wheel-chair position without a seat removal. We make another assembly that is utilized in dental X-ray machines. The cable length is quite long and the connectors on either end require strain relief over-molding.”
Engineering expertise starts at the top
MJM Industries, which is ISO 9001:2015 certified, and serves a wide range of customers, including medical, industrial automation, military, aerospace, smart grid, water treatment, commercial off-road, aftermarket automotive, test and measurement, contract manufacturers, mass transit, and consumer products. It was founded in 1987 in Chesterland, Ohio. It now operates in 36,000 square feet in Fairport Harbor, Ohio, and as it adds new capabilities and processes, such as robotic soldering, injection and over-molding, 3D printing, and expanded engineering services, the company expects to expand. It employs about 95 people, with four engineers, including company president Eric Wachob, and one engineer on retention for special projects.
“We specialize in custom over-molded cable and wire harness assemblies, round, flat, and coaxial cable assemblies, flat flex cable assemblies, small control panel/box builds, and electro-mechanical devices,” Cole said. “Our engineering services include product design and process development, and tooling and fixture design. We are very pleased to have recently launched our own standard brand of M8 and M12 cable assemblies which could be utilized across all of the markets we serve, but especially geared towards industrial automation.”
As MJM Industries moved into the more complex requirements of Class III assemblies, which include those used in aerospace, it invested in robotic soldering and laser stripping equipment to elevate the level of workmanship to meet the precise specifications for producing the aero-space assemblies.
Training is key
Its teammates train extensively for their jobs, including OSHA training and training to meet the IPC/WHMA-A-620 standard, set by the Wire Harness Manufacturer’s Association and the IPC, founded in 1957 as the Institute of Printed Circuits. This quality training, along with its ISO certification, is important because the general assembly area of MJM Industries may be working on 60 different factory orders at one time for customers. They are supported by the engineering staff, by the quality department, test department, maintenance, molding technicians, wire cutting department, and stock room. “They follow manufacturing process definitions throughout the build and are required to show a first article for quality inspection at the beginning of their shift,” Cole said. “After they are finished with the production run, each assembly is inspected, and quality tested before shipment to the customer.”
Its other automated processes include wire cutting and crimping. However, its workforce is divided into teams trained for each harness or assembly in process. “As a contract manufacturer, our product mix is extremely diverse and so far, we’ve found that our team-mates do a good job on being cross-trained to help across several customer specifications, and can instantly react if a customer specification changes,” Cole said. “Molding is one of our specialties. We have several machines at our disposal that run materials such as PVC, PUR, Nylon, LCP, and hot melt,” Cole said. “Our engineering team designs our own molds, and we have the ability to fabricate steel, aluminum, or 3D tooling in-house.”
Broad wire harness expertise
MJM Industries specializes in Class II and Class III wire preparation for UL and non-UL-type wire ranging from 4/0 to 32-gauge, as well as molding and complex wire assemblies. It uses automated and semi-automated equipment to process various types of wire and cable with many types of terminations and connectors. Examples include flat and round-flat ribbon cable; discrete wire; coaxial triaxial cable; and composite and multi-conductor cable. It uses a 25-watt dual-axis laser stripper with the speed and power to strip varying mate-rial types and dimensions, something that makes MJM Industries a preferred provider for aerospace applications, Cole said. It offers molding capabilities that include vertical inject and vertical platens with a clamping range of 5 to 35 tons and auxiliary core pull capabilities. Its plant includes all related support equipment, including dryers, chillers, thermolators, and granulators to ensure that all products are manufactured to the highest standards. It includes an engineering testing lab and a fully equipped machine shop.
MJM Industries’ ability to over-mold earns it business from other companies that can fabricate a wire harness or an assembly, but must hire MJM Industries to complete the assembly with over-molding. Its over-molding experience also helps customers make informed decisions about their assembly. “Our team most often is asked about over-molding and what material we might suggest that would be compatible with their design,” Cole said. “In general, in order to get a good hermetic seal, we want similar material used for the jacket and mold material. For example, PVC cable jacket and PVC as the mold material base. However, depending on the assembly’s application and IP rating, we will work with the customer to assess the degree of bonding required for the level of ingress protection needed in the environment in which their assembly is used.”