Engineering and design assistance are an important part of Tempron’s service in making parts like this sanitary pinch valve diaphragm, which shows fabric reinforcement. Photo courtesy of Tempron Products.

Tempron Products specializes in bonding Teflon to rubber, metal, and plastics   

 MILFORD, Mass.—Customers come to Tempron Products Corp., a small contract manufacturing firm in New England, for highly specialized parts. Much of Tempron’s work involves making high-performance diaphragms and seals, mainly for chemical pumps and valves. These products are used in various industries—including medical and biomedical—for  metering, filtering, and testing.

“We make parts that are really difficult to make, and nobody else really wants to do it,” said Bob William, vice president of Tempron Products, in an interview.

What separates Tempron from most other parts suppliers is its ability to manufacture custom diaphragms and seals by bonding a precision elastomer, or rubber, to materials such as fabric, PTFE (Teflon), metal, or plastics. Although some of the parts are made entirely of rubber, most are bonded to Teflon, and many are reinforced with glass filler or fabric.

“The work we do is more Teflon-faced, where it’s bonded, than just silicones or plain rubber,” said William. “I don’t like to say, ‘plain rubber,’ though, because these are special elastomers, which are expensive.”

Diaphragms for metering pumps, William said, must be produced to exacting requirements because the pumps are called upon to perform critically precise metering.

“It’s not a normal pump that just pushes out a bunch of liquid all at once. Every stroke is calculated so that what comes out of the tube at the end is extremely precise, because the samples and testing that they do have to be perfect,” William said.

Similarly, precision is essential when gases are drawn into the diaphragm. Volumes must be metered exactly to ensure the testing will be accurate. Tempron can meet these needs for precision largely because its team pays close attention to detail and performs regular inspections and testing. “We really care about what we do, and we’re very, very careful with how we handle everything,” William added.

Parts produced by Tempron end up being used in the medical and biomedical, water purification, chemical process, and ultra-pure semiconductor industries, according to the firm’s website. William said the parts will not delaminate because they’re not actually laminated—they’re bonded.

Samples of parts produced by Tempron Products. Photo courtesy of Tempron Products.

“There’s a bonding agent between the Teflon and the elastomer, and the fabric, and even down to the metal cores,” he explained. “So, we have to properly prep everything. Anything that comes in as metal is totally cleaned. We’ll even sand-blast it to increase the surface area, plus get off any surface dust or residues from the machining, because anything [that’s left] on there will cause us a problem when we go to bond and mold everything at once.”

Tempron molds custom rubber (elastomer) parts using compression molding machines that also do transfer molding, but not injection molding. The process requires a sound, well-built mold, and involves the application of heat and pressure. The rubber and bonding agents are placed in the mold and clamped down in a hydraulic press, where heat and pressure are applied for a predetermined amount of time before the parts are removed.

“It’s not just heat and pressure—it’s how much heat, and how the pressure is applied,” William explained. “Without heat and pressure, you’re not going to vulcanize the rubber.”

William said one of Tempron’s key offerings is the engineering and design assistance that it provides to customers, preferably right from the beginning of their projects. Knowing how a Teflon material will move in a mold, Tempron’s engineers can recommend where a parting line should be located to achieve the specified outside diameter of a part.

“If we can give any input to the design of a part, it will often help in not only making the end product better, but in keeping costs down, as far as how you’re going to process it [the part],” he said.

That assistance could involve recommending the right materials to use for a particular part, or using computer-aided engineering (CAE) analysis to predict optimum part geometries and properties.

“Every elastomer is totally different. We mix all of our own products here,” William said. “We do all of our own compounding, so we have total control over our materials, as far as the elastomer part goes.”

Process and mold design—and, farther down the road—prototyping and testing—are also part of the mix. In one example of process and mold design, the company developed what it called an innovative method to consistently manufacture miniature rubber-covered rollers that have total indicator runouts of under 0.002 inch. “The molding method saved the customer nearly half the original production cost,” Tempron said on its website.

“It all starts with a good dialogue with your customer,” William told D2P. “You have to know what they’re looking for, what they expect, and then move on from there. It’s also knowing what to check. You’ve got to be very particular as to every little detail on the parts coming in, to the parts going out, and everything in between. You really want to give them something that is absolutely perfect when it goes out the door here.”

William said a diaphragm could have a metal core with an adhesive agent on it. Other constituent materials can include rubber; a piece of fabric with adhesive; more rubber; and a piece of Teflon, also covered with adhesive. “It’s a thermoset adhesive, so it bonds to the rubber in the mold at the same time the rubber is cured,” he said.

The metal core in a pump diaphragm—particularly the size of the head—will affect how the diaphragm can flex. It’s an important consideration, William said, because on some of the pumps, even though it’s hard to see how much the diaphragm is moving, it’s actually vibrating. Each of those tiny vibrations is pumping out a certain amount of liquid or air.

“You’d want fabric in there because if there’s more room for the diaphragm to extend, you don’t want it to overextend and stress the Teflon,” William explained. “Teflon will bend, like plastic, but [you don’t want to] stretch it too much. If it stresses, with the chemicals at the base of the diaphragm’s seam, it could delaminate.”

Tempron ( has made parts for medical diagnostics instrumentation in the past, and is wide open to  doing more work for medical customers, especially as demand for testing supplies and diagnostics continues to rise.

“We’re open to new customers and new ideas. We always love something new to come through here because that’s where we get all our excitement and fun,” William said. “That’s the best part of my job—trying to get a new part to come out of the mold properly, and figure out all the little nuances as to how we can make the part better.”

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