Poly Seal Industries

Poly Seal Industries is a leading provider of molded and custom rubber goods with the ability to support projects from the design and engineering phases through final delivery to the customer.


Molding of a Rubber Knife for the Food Industry

A customer in the food production industry needed a rubber knife that would cut uncooked dough into a specific shape while the dough passed through on a special conveyor. The customer's original design needed to be re-engineered to improve the consistency of the cut, while increasing durability of the knife. Molding of a Rubber Knife for the Food IndustryThe original design was difficult to mold and still hold the required tolerances and it did not function to the customer's satisfaction. Our engineering team worked with the customer to co-design the new rubber knife. Factors that figured into this new design included: a food grade elastomer, which could not be affected by oils, extreme durability (tens of thousands of cut cycles per day) and compliancy that would prevent damage to plastic trays that the knife cut against. Once the design was completed, we designed the production process to produce a part that met the highest quality at the lowest possible cost. The process utilizes mills, calendars, die cutting machines, and a 300 ton molding press. The material used for the knife is a carboxylated nitrile rubber that encapsulates a spring steel insert. Overall part dimensions are 1.5" wide by 14" in length.

For more information on our project, or the processes involved in manufacturing this part see the table below or contact us directly.

Rubber Knife Project Highlights

Project Scope
A large food manufacturing company needed a rubber knife as part of their automated production line. They needed to reengineer the part to improve the consistency of the cut, while increasing the durability. Prior design was difficult to mold and hold tolerances; cutting edge was not consistent in quality.
Product Description
Its function is to properly cut the uncooked dough into a specific shape while the food passes through on a conveyor belt. The knife has to cut cleanly through the dough and not damage the plastic tray that the dough sits on, at the rate of tens of thousands of cycles per day. The rubber has to be food grade, not affected by oils, and extremely durable.
Capabilities Applied/Processes
Co-Engineering – Design
Die Cutting
Equipment Used to Manufacture Part
Mill, Calendar, Die Cutter, 300 ton compression press
Overall Part Dimensions
1.5" x 14"
Tightest Tolerances
Material Used
Carboxylated Nitrile rubber, with a spring steel insert
Material Finish
Additional Facts
Acts like a squeegee/knife in the machinery
Die cut edge
In process testing/inspection performed
Physical testing of rubber before molding: durometer, tensile, compression set, Die B tear, abrasion resistance
Industry for Use
Food production
2000 per delivery
Delivery/Turnaround Time
3 Weeks
Delivery Location
Berkeley, CA
Standards Met
Customer Specifications, RMA tolerances, Food Grade
Product Name
Rubber Knife
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