Polyurethane Closed-End Punch Strippers
Worn-out strippers, slug pulling, and dimpled workpieces cost your operation time and money every shift. Polyurethane closed-end punch strippers from Polyurethane Products solve these problems at the source. Manufactured in Addison, Illinois, our closed-end strippers deliver the load-bearing strength of steel with the resilience and flexibility of advanced urethane elastomers, keeping your stamping line running accurately and efficiently.
Available in standard inch, metric, and NAAMS sizes, Polyurethane Products' polyurethane punch strippers are built for engineers, toolmakers, and procurement teams who need dependable stripping performance across high-volume production environments.
How Closed-End Punch Strippers Work
A punch stripper is integrated into the die assembly and serves a critical function: it holds the workpiece firmly in place before, during, and after the stamping stroke. Because the stripper contacts the sheet metal before the punch does, it reduces workpiece deflection and ensures a clean, accurate cut. On the retraction stroke, the stripper prevents the material from clinging to or riding up with the punch, eliminating slug pulling and surface marring.
The closed-end design is what sets these strippers apart from open-end alternatives. A solid face covers the bottom of the stripper, applying even pressure across a larger surface area of the sheet metal. This prevents the reverse dimpling and deformation that can occur when an open-ended tube simply pulls the metal upward during retraction.
During the first punching cycle, the punch pierces through the polyurethane face, creating a perfect, self-fitting seal around the punch profile. This makes polyurethane closed-end punch strippers particularly effective for oblong, irregular, and odd-shaped hole geometries where a metallic stripper plate would require expensive custom machining.
Why Polyurethane Outperforms Steel and Rubber
Traditional die assemblies rely on steel compression springs or rubber punch strippers to generate the stripping force needed to hold and release the workpiece. Both have limitations that polyurethane eliminates.
Conventional heavy-duty steel die springs produce up to approximately 500 lbs per 1/8" of deflection. Polyurethane Products' urethane compression springs achieve up to 2,600 lbs per 1/8" of deflection, delivering significantly more force in a smaller package. That compact footprint allows tighter center-to-center punch spacing on your die plate, so you can run more punches per stroke and increase throughput without redesigning your tooling layout.
Compared to rubber punch strippers, polyurethane offers superior tear resistance, abrasion resistance, and flex life. Urethane does not rust, corrode, or become magnetized, making it the preferred material in environments where corrosion, vibration, or magnetic interference rule out steel. It also resists oils and solvents commonly found on the shop floor, maintaining consistent performance over its full service life.
Additional performance advantages of Polyurethane Products' closed-end punch strippers include:
- High dielectric strength and nonmagnetic properties for sensitive applications
- Protection against surface marring and galling on finished or pre-coated materials
- Easier fitting and installation to the punch compared to steel spring assemblies
- Quieter operation that reduces shop floor noise levels
- Service life comparable to or exceeding steel compression springs
Durometer Options and Sizing
Polyurethane Products manufactures polyurethane closed-end punch strippers in multiple durometer ratings to match the deflection requirements of your specific application. The body of each stripper is made from a flexible urethane elastomer available in 80A, 90A, or 95A hardness, enabling maximum deflections of 35%, 25%, and 15% respectively. Selecting the right durometer ensures the stripper delivers optimal holding pressure without over-compressing or losing its rebound characteristics over time. Visit our Poly Grades page for full material specifications.
For applications requiring even greater rigidity at the stripper face, Polyurethane Products also offers hard-faced polyurethane punch strippers. These incorporate two grades of urethane that are integrally molded in the liquid state and heat-cured together. The 75 Shore D hard face provides a rigid encapsulation around the punch body, functioning similarly to a machined metallic stripper plate while retaining the flexibility and self-healing properties of urethane.
Hard-faced strippers are particularly well suited for hole shapes with sharp corners, such as star or polygon profiles, where standard elastomeric faces may allow slight material deformation.
Closed-end punch strippers are stocked in standard inch and metric sizes, as well as NAAMS-compliant configurations. Size charts, pressure ratings, and deflection data are available on our Downloads page.
Applications
Polyurethane Products' polyurethane closed-end punch strippers are used across a wide range of metal stamping and fabrication operations, including automotive body panel production, appliance manufacturing, electrical enclosure fabrication, and architectural metalwork. Any application that demands clean hole quality, minimal workpiece distortion, and reliable cycle-after-cycle performance benefits from switching to urethane strippers.
Request a Quote
Polyurethane Products is one of the largest polyurethane spring and punch stripper manufacturers in North America, supplying durometers from 20 Shore A up to 60 Shore D. Whether you need standard catalog sizes or a custom solution for a specialized die, our team can help you select the right polyurethane closed-end punch strippers for your application.
Contact us today at 800-772-7072 or request a quote online to get started.
Frequently Asked Questions About Closed-End Punch Strippers
Installation is straightforward. Push the stripper onto the punch shank. The inner diameter is slightly undersized by design, so it grips the punch body securely without additional fasteners. The stripper is then seated against the retainer via a backing plate. On the first press stroke, the punch tip pierces through the closed polyurethane face, creating a precise, self-conforming fit around the exact punch profile. No secondary machining or trimming of the stripper is needed.
Watch for visible cracking, chunking, or permanent compression set in the urethane body. If stripping force weakens noticeably, if slugs begin sticking to the punch, or if you see dimpling or burring on the workpiece that was not there previously, the stripper has likely lost its effective rebound and should be swapped. Polyurethane Products recommends inspecting strippers during routine die maintenance intervals.
The most common cause is excessive punch entry depth. Overentering the pierce punch compresses the urethane far beyond its intended deflection range, accelerating fatigue and shortening service life. A practical guideline is to limit punch entry to no more than one times the material thickness beyond the die face. Insufficient cutting clearance can also increase the stripping force required, overworking the urethane. Selecting the correct durometer for your material thickness and tonnage is equally important to avoid premature wear.
Yes. Closed-end polyurethane strippers are compatible with headed punches, ball-lock punches, and high-precision punch styles. The stripper slides over the punch body and is held in position by the retainer and backing plate assembly, so it works with any standard punch configuration. Polyurethane Products stocks sizes that align with common retainer systems used in the industry.
Yes. In addition to our standard inch, metric, and NAAMS catalog sizes, Polyurethane Products manufactures custom polyurethane products tailored to unique die designs. If your application requires a non-standard inner diameter, outer diameter, length, or durometer, our team can engineer a solution. Contact us at 800-772-7072 to discuss your requirements.
Polyurethane strippers do not fragmentize the way steel coil springs can when they fatigue and fail. A broken steel spring can send metal fragments through the die, damaging tooling and creating a safety hazard for operators. Urethane strippers degrade gradually and predictably, giving maintenance teams advance warning before replacement is needed. They are also lighter and easier to handle during die setup and changeover.
Further Urethane Punch Stripper Reading
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