The original pinch valves were cracking during herbicide and fertilizer spraying causing a big, leaking mess.

Minneapolis, Minn.—Robinson Rubber Products, a designer, developer and manufacturer of custom-molded rubber products, extruded rubber products and precision rollers, has several new capabilities to bond molded rubber components to your parts to deliver superior performance. Bonding rubber to your part can also eliminate secondary operations and extra components, plus reduce weight and costs.

A leading manufacturer of agricultural spraying equipment was having trouble with field failures when the rubber tubes with pinch valves that feed the spray nozzles began failing during the peak spraying season. The flanged tubes are opened to allow spraying and the pinch valve is pinched closed to stop the spray. Between the high pressure, aggressive chemicals and pinch cycles, the existing tube was failing during critical planting and fertilizing time, causing chemicals to leak and uncontrollably spray all over. Not only was this making the spraying operation terribly inefficient, it was wasting expensive chemicals and potentially contaminating fertile farmland with high concentrations of liquid compounds. It also unnecessarily exposes people and animals to these chemicals.

Complicating the situation, the company’s current supplier for the tubes could not determine what made some parts fail and other parts not. Each lot was tested and there were passing and failing pieces in every batch, with no consistency. Worse yet, “bad” parts looked the same as “good” parts, so ferreting out bad parts was impossible. Good parts were experiencing 250,000 cycles to failure, bad parts only 10,000. After seeing Robinson Rubber at a local trades show, the spraying equipment manufacturer asked if they could solve the problem.

Robinson Rubber worked on various rubber formulations to deliver longer life to the pinch valve. Imagine the reaction when prototypes delivered 3,000,000 cycles before failure, a twelve-fold improvement! After supplying the redesigned pinch valve for over 15 years, there has not been one field failure.

The one funny twist to this story demonstrates the enormous impact formulations have on product performance. While there were no product failures, pinch valves that sat on a distributor’s shelf for more than a couple months went from shiny jet black to chalky gray. While none of these parts failed, there was a perceived quality issue. When farmers went to routinely change out the pinch valve, and they saw the chalky gray rubber, they thought they were getting old, defective parts.

To eliminate the parts changing from black to gray, chemists at Robinson Rubber ever so slightly tweaked the recipe by changing a small percentage of one of the ingredients. The recipe was changed to 329¾ total parts from 330 parts. This slight change got rid of the chalky residue, but parts now went from 3,000,000 cycles to 10,000 cycles to failure! They were shiny black, but significantly weaker. It’s the mastery of these slight formulation nuances that can make the difference between a great part and a poor one. Soon the gray pinch valves became known in the farming community as the ones that don’t fail, versus the shiny black ones that did. In the end, Robinson Rubber showed engineering creativity to solve a problem quickly, with high quality, lower cost and fast speed.

Using up to 20 engineering grade polymers and more than 2,000 unique formulations, Robinson Rubber works with you to deliver the best rubber solution possible. Let us develop a proprietary custom formula for you using our in-house compound formulation and mixing capabilities.

Substrate materials include acetal, aluminum, brass, bronze, carbon steel, copper, ductile iron, fabric reinforcement, glass-filled composites, mineral-filled composites, nylon, PEEK, PES, phenolics, PTFE, PVDF and stainless steel. Molding an appropriate rubber gasket, support, seal, o-ring, mount, bushing, cover, wheel or other part directly to your part delivers an integral part that is less likely to leak, crack or otherwise fail in the field. Bondable substrates include single or multiple component substrates that are die cast, injection molded, stamped, waterjet cut, CNC machined or wire formed. We can also bond rubber-tometal-to-plastic-to-fabric combinations. “Providing sophisticated bonded assemblies of high quality is our specialty, with over 70% of our rubber being bonded to substrates,” says Jay Beck, President of Robinson Rubber. “This process delivers high performing components to our customers with virtually zero returns,” says Beck.

Substrate parts include but are not limited to chain pads, conveyor pads, diaphragm assemblies, electrical insulators, ground spool valves, impellers, inflatable butterfly valve seats, motor mounts, non-invasive medical devices, power drive assemblies, sanding disks, special wheels, valve assemblies, vibration isolators and vibration mounts.

If you are an engineer struggling with trying to come up with components that will perform multiple functions in challenging conditions, check out rubber’s capability to bond to a variety of substrates, eliminate parts and lower assembly costs. A Polymer and Material Selection Guide is also available.

To learn more, email, visit, or call toll free 1-877-619-5825 or 763-535-6737 for more information