Custom Rubber Molder Adds Machining Expertise

Pierce-Roberts Rubber Co., known for its rubber-to-metal bonding, is now a single source for rubber and metal parts

By Mark Langlois

May 9, 2023

Pierce-Roberts Rubber Company is a 110-plus year-old ISO certified custom precision rubber molder, a specialist at combining rubber and metal. It is old school and new school. Of course, it keeps records of its 100-year-old rubber formulas, but today it tailors those formulas—for example, a World War II tire rubber formula, tweaking them to meet new high-technology demands.

“[It must be] Durable, but it must conduct electricity,” a recent customer said about its part requirements. Pierce-Roberts Co. President Chris Weber thought it over. Durable, no worries. Conductor, too? He said, “Let me work on that.”

It took about two weeks. Natural rubber is an insulator, not a conductor, but by changing the formula, Pierce-Roberts met the customer’s need. “A little touch here or there. Some new ingredients,” Weber recalled. He invited the customer to the Trenton, New Jersey factory and showed them what he had. They called back the next day said, “You knocked that out of the park.”

“The very next day they were on the phone talking about money for capital investment. We’re partnering on it,” Weber said. “They presented the problem. I showed them a solution.”

The rubber itself, Weber said, was extremely well tested and durable. Adding ingredients to the rubber turned it from an insulator to a conductor.

Pierce-Roberts Rubber Company is a custom molder, a custom mixer, and a custom formulator of rubber, which gives it an edge when working with customers who have an idea, but are uncertain of exactly which type of rubber to pick. Pierce-Roberts has helped customers make those decisions since 1911 with compression molding, transfer molding, and injection molding services.

Rubber-to-Metal Bonding Expertise

Pierce-Roberts, now roughly 112 years old, has a specialty in successful and durable rubber-metal combinations. So when a customer asks for a specific rubber that will meet durability, repeatability, hardness, and density standards, Weber searches the books. The new, 21^st century demands in aerospace, electric vehicles, and electronics were unknown in the 20^th century, but when customers want something new today, the company president puts on his chef hat. He changes the ingredients.

“Yes, we can do that,” Weber said. “The secret is the company and the process. It established a very good record keeping process. I have literally tens of thousands of formulas. It is incredible. I go to my books. I have an entire encyclopedia of all industrial era formulas. We know how to tweak the formulas. We can dial in the exact environment [and] what it needs.”

If an established customer decides they want a repeat component they ordered decades ago, they call Pierce-Roberts and they get an answer quickly. Weber searches the menu books, now digitized, for the old recipe.

Some of the books date back to the 1930s. Each rubber has its particular ingredients. Each combination of ingredients creates different properties, including specific modulus, tension, durability, elongation, tensile strength, and elongation, to name a few. But how many times is this bond supposed to work?

Imagine a door on a submarine, a door that appears to have a gasket sealing it against water. That gasket, rather than being a separate O-ring, is compression molded into place. The metal it attaches to may have been treated to hold that rubber for thousands of uses.

Some customers approach Pierce-Roberts with an idea. They may be  working on a custom pump, for example.

“They come to us and ask for a diaphragm or custom seal,” Weber said. “They’ll have drawings. The engineers send information and Pierce Roberts makes the parts and specifications for the rubber, according to the customer’s prints.

Sometimes a customer has very demanding standards. They might want a specific combination of rubber properties, perhaps a tensile strength of 1500 pounds per square inch, with 6 percent compression set and 300 percent elongation. The rubber must bond to a certain metal. Weber turns to the books.

“It is the rubber-to-metal bonding that is one of the key characteristics in manufacturing that we excel at,” Weber said. “We bond with every material. We’re specialists at that. Each one has a special process. The rubber has its own formula.”

Impossible Takes Longer

Some customers ask for the impossible. Weber said one customer wanted a silicone part that was 14 inches in diameter with no parting line in a specific area. It was 0.060-inch thick and 12 inches tall. That made it nearly impossible for other companies to make.

Pierce-Roberts changed the tooling and removed the parting line from the noted area. “Our manufacturing ability came into play there. We will replicate the part thousands of times a year,” Weber said.

Workers in the plant know the materials and they know the process. They train in how to prep the metal before putting it in a mold that will attach the metal and rubber under pressure and heat.

“They understand the process. They’re crafts people,” Weber said. “My hand mixer has been here for 30 years. The apprentice mixer has been here for five years. Then we have another person training as well. We cross train and apprentice in all areas.”

Keeping the workers trained and interested in their work is critical. “We have to. We can’t let them stagnate. What if you want to learn something else? What if you want to go somewhere else? They show up every day, and they’re interested and honest about what they do.”

One important part Pierce-Roberts makes daily is an aerospace component that must be quality checked—each part, every day, for 10 specifications. “We check every one, every way, every day. Every part is checked and cleaned. Every part must be perfect. It is the single most important part we make,” Weber said.

Pierce-Roberts workers make a part from metal and rubber for a mining company conveyor belt. The part helps preserve the belts. The metal and rubber are combined in a 780-ton press that is heated to 340 degrees. The quantity of parts is so large it would typically go to a larger manufacturer, Weber said, but the parts manufacturing process requires too much handwork, so it isn’t profitable in a more automated shop. The Pierce-Roberts workers sweat in the heat as they press the finished part out of the mold.

“If the geometry of the part makes it too much work for others, we design our system to make it economical for both us and the customer,” Weber said. “These guys are no joke. They run three or four presses all day.”

Pierce-Roberts expanded its manufacturing processes in early 2023 when it bought Parlin Precision Products, a machining company that grinds, turns, and machines parts for electrical components, medical devices, and OEM applications. Pierce-Roberts is clearing space in its factory for the entire Parlin Precision operation. Many of the metal parts Pierce-Roberts formerly bought from other companies will be made in-house.

Machining Company Fits Right In

Parlin Precision Products, in its 40^th year of operation, is an advanced precision machine shop that offers machining of steel, tool steel, stainless steel, nylon, plastics, phenolic and polycarbonate. In addition to CNC milling and turning, it offered engineering and design assistance on work from prototype to production. Parlin is merged into Pierce-Roberts and is operating under the Pierce-Roberts name.

“We don’t have to go outside any more for our own machine parts. Now we’re fixing our machines with our machine shop,” Weber said. That is creating job growth opportunities at Pierce-Roberts. Workers are encouraged to cross-train in the machine shop. Parlin arrived with equipment that helped Pierce-Roberts with a step in its rubber finishing process, which was trimming rubber components.

“We have four seasoned machinists who have more than 20 years of machining experience. They’re training two new guys. That’s two employees from Pierce-Roberts [who are] training to become machinists. They’re young. They can see the growth of what we’re doing, and they want to be part of it.”

Among the first training steps for Pierce-Roberts workers is teaching the young workers to design metal parts and metal workflow using 3D CAD design.

“We adapted some of their (Parlin’s) equipment for our rubber needs. We automated trimming operations for a customer who asked us to increase production of rubber-to-metal bonded parts that need to be hand-trimmed. We were originally taking an hour to trim four pieces. Now we complete 30 pieces in an hour,” Weber said. The piece is a rubber-metal valve made of fluoro-elastomer and A26 steel.

Weber said the purchase of Parlin Precision is important because it gives product control to Pierce-Roberts Rubber Company and turns Pierce-Roberts into a single source for rubber and metal components. The one-stop shop can shape the metal, formulate the rubber, and bond them without waiting for anything from a supplier. The two firms produce parts for aerospace, material handling, mining, military, R&D for OEMs, medical devices, electronics, shielding, printing, and robotics, among literally every industry.

“This allows us to be an ITAR registered firm in a different realm of manufacturing,” Weber said. All machining operations are now under Pierce-Roberts’s ISO 9001-2015 certified process. “We are now one source for rubber and metal parts.”

With all that talk about centuries-old formulas, it’s important to remember that all of Pierce-Roberts’ machines and processes are tracked to ensure quality using Industry 4.0 tools.

“We’re tracking all manufacturing data, every cycle, every part, every day. Every mixture we make, every batch we make is fully tested before manufacturing,” Weber said. “We keep track of all that data. We have full traceability of components.”

The data is used to track quality, production goals, rejected parts, and  waste. “We know a job isn’t running correctly if we see the waste numbers going up. The molders are timed in a sense. We need to make sure those times and temperatures are correct,” Weber said.