Urethane bending pads
Deflecting polyurethane pads, V-die inserts, protective film, retained-pad geometry and load limits in press-brake bending.
Tags: tooling, sheet-metal, press-brakes, polyurethane
On this page
A 50 mm urethane pad shortened by 10 mm has 20% nominal compression and 40 mm remaining height. In a separate example, 20 kN spread uniformly over 200 × 50 mm gives 2 MPa nominal average pressure. Neither calculation models local contact, required tonnage or finished bend angle. The retainer constrains where the urethane can displace.
What a bending pad does
Polyurethane Products describes rectangular forming pads in steel retainers and triangular inserts in conventional V-dies. Both deform to change how the sheet is supported. Polyurethane Products, forming-pad explanation
| Arrangement | Role in the bend | Distinction |
|---|---|---|
| Deflecting pad in a retainer | Displaces around the descending punch and sheet | Retainer geometry participates in forming |
| V-pad insert | Occupies a steel die's V-cavity | Steel die remains part of the support |
| Thin protective film | Separates the workpiece from the lower tool surface | A contact barrier, not a bulk forming pad |
The first two descriptions follow Polyurethane Products; the film role follows Mate's March 27, 2019 article. Mate lists film thicknesses of 0.015 and 0.030 inch, equivalent to 0.381 and 0.762 mm. These are film products, not recommended pad thicknesses. Polyurethane Products, Mate protective film
Retainers, cavities and punch length
Polyurethane Products' POD pads have square or rectangular sections for sharp or radius V-bends. Its PUD family instead addresses 180° U-bends. The POD description specifies steel-channel retainers, a longitudinal molded hole to reduce deflection load and provide stress relief, and a punch at least as long as the pad to prevent its ends digging into the elastomer. Polyurethane Products, POD and PUD families
Selected POD examples from that page are:
| Pad | Width × height | Longitudinal hole diameter | Listed retainer |
|---|---|---|---|
| POD-112 | 2.25 × 2.25 inch | 1.00 inch | CR2222 |
| POD-312 | 3.00 × 3.00 inch | 1.25 inch | CR3030 |
| POD-315 | 3.00 × 3.00 inch | 1.50 inch | CR3030 |
These are assembly dimensions for named products, not a universal gauge or force rating. The page's gauge entries lack a common material basis sufficient to convert them here into a general maximum sheet thickness. POD dimensions
UTEC's Exact-A-Form is a separate contoured pad for conventional female V-dies. Its page describes use without a special retainer and attachment with its double-faced tape. That arrangement does not transfer to every rectangular pad or replace a POD system's specified channel. UTEC Exact-A-Form
Check attachment, holder section, punch and pad lengths, and room for displacement together.
Radius support and surface behavior
Mate's July 6, 2020 large-radius article describes urethane counterpressure as a way to keep sheet against a radius punch and reduce multi-breakage, where the sheet lifts away and develops a smaller center radius. This concerns contact during bending; elastic recovery after unloading can still change the final angle and radius. Mate large-radius bending
Polyurethane Products identifies internal heat from repeated stressing as a common pad-failure mechanism, and explains that molded holes can reduce stress and deflection load. Its discussion does not supply a universal cycle rate, maximum pad compression or service life. Polyurethane Products, pad stress and heating
Engineering interpretation: reducing direct metal contact can improve appearance, but pad use alone does not guarantee an accepted finish. Debris, cut sheet edges, coating condition and localized contact can still affect the surface. Likewise, hardness, outside dimensions and color do not alone establish a pad's complete force–displacement behavior or suitability for a given material.
Worked examples: displacement and nominal pressure
Original hypothetical arithmetic: assume an initially 50 mm-high pad shortens vertically by 10 mm in a particular setup:
Height reduction / original height = 10 / 50 = 0.20 = 20%
Remaining height = 50 − 10 = 40 mm
This is an axial geometric ratio, not a 20% loss of material volume or an allowable-deflection specification. The model says nothing about lateral bulging, cavity closure, temperature or the load needed to reach that displacement.
For a separate assumed load of 20 kN distributed uniformly over a projected 200 × 50 mm area:
Nominal average pressure = 20,000 N / 10,000 mm²
= 2 N/mm² = 2 MPa
Real contact is not necessarily uniform and changes through the stroke. This average is neither a measured peak stress nor a hydraulic pressure setting. It does not predict forming force; that requires the particular pad, containment, contact and sheet behavior. A material hardness number cannot be substituted directly for this pressure.
Coverage and source dates
Mate explicitly dates its film article March 27, 2019 and its large-radius article July 6, 2020. No technical issue dates were established for the cited Polyurethane Products or UTEC pages; copyright and crawl dates are not revisions.
This reference covers press-brake pads and adjacent protective-film terminology. It does not establish universal sheet capacity, forming tonnage, permitted compression, stroke, springback correction, temperature limit or tool life. Pad formulation, geometry, retainer, punch and workpiece form a specific system. A published product example does not establish a shop's installed tooling or approved production settings.