Gripper Pads Overview

Gripper Pads from PFA

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Durable, non-slip rubber pads for industrial and robotic applications provide strong gripping surfaces for grasping items using lower clamping forces, while also protecting parts during handling and assembly. The rubber elastomers, available in Buna-N, Neoprene, Silicone, and Viton® operate over a variety of broad temperature ranges and resist a variety of oils and corrosive elements.  Pads with backplates are cure-bonded to aluminum, carbon steel, and stainless steel plate for a molecular level integration of rubber to metal, offering a bond stronger than the base rubber itself.

Metal backing provides stiffness and support to the rubber, allowing easy attachment to gripper jaws or other structures. Typically sections are attached to fingers or fixed structures using high strength adhesive tapes available from PFA or with standard fasteners after modification.  Metal backed pads are easily machined to match custom applications, and holes may be drilled to provide quick attachment and removal.

Historically, Gripper pads have been available in 6” x 12” sheets of three surface styles bonded to Steel or Aluminum backing in only one material and durometer (Buna-N, 60 duro).  Along with these standard pads, sheets are now available in smaller 1.2” x 1.2” sections and some other materials and durometers.  Additional offerings are available by special order and may become available as standard products.  Unique pad configurations and styles are also available as bulk material or as finished parts from customer provided drawings or specifications.

Features & Benefits
  • High Friction Surface
  • Maximum Rubber to Metal Bond
  • Improved reliability for gripping parts
  • Compliant surface for a softer touch
  • Easy installation and replacement
  • Saves tooling and reduces waste
  • High return on investment (ROI)
Elastomer Material Properties Reference Chart
Elastomer Designation1Common Name(s)CompositionMin/Max Temerature5
Operating Range ˚C (˚F)
General Properties2General Chemical Resistance3
(Resistant to)
General Chemical Resistance
(Attached by)
NBRBuna-NNitrile – Butadiene-34˚C/121˚C
(-30˚F/250˚F)
Excellent resistance to petroleum based fluids, Good physical propertiesMost hydrocarbons, fats, oils, greases, hydraulic fluids, chemicalsOzone (except PVC blends), ketones, esters, aldehydes, chlorinated and nitro hydrocarbons
FKM/FPMFlouro-elastomer
Viton®4
Hexaflouropropylene – vinylidene fluoride-23˚C/204˚C
(-10˚F/400˚F)
Excellent oil and air resistance both at low and high temperatures. Very good chemical resistanceAll aliphatic, aromatic and halogenated hydrocarbons, acids, animal and vegetable oils.Ketones, low molecular weight esters and nitro containing compounds.
CRNeopreneChloroprene-34˚C/100˚C
(-30˚F/212˚F)
Good Weathering Resistance. Flame retarding. Moderate resistance to petroleum-based fluids.Moderate chemicals and acids, ozone, oils, fats, greases, many oils, and solvents.Strong oxidizing acids, esters, ketones, chlorinated, aromatic and nitro hydrocarbons.
SI/QSiliconePloysiloxane-62˚C/215˚C
(-80˚F/420˚F)
Excellent high and low temperature properties. Fair physical properties.Moderate or oxidizing chemicals, ozone, concentrated sodium hydroxide.Many solvents, oils, concentrated acids, dilute sodium hydroxide.
  1. ASTM D 1418-01a Standard Practice for Rubber and Rubber Latices – Nomenclature, ASTM D 1418-79, ISO 1629:2013
  2. From the “Sheet Rubber Handbook – Gasket and Packing Materials” publication #IP-40 of the Rubber Manufacturers Association (RMA).
  3. 1979 Yearbook of the Los Angeles Rubber Group, Inc.
  4. “Viton” is a registered trademarks of E.I. Dupont, Inc.
  5. The temperature range is determined by the base elastomer used. This chart depicts a general maximum temperature range for each elastomer. The temperature range for a specific compound may not reach these maximum limits. Higher temperatures may be considered if exposure is short or intermittent.
Approximate Weight per square inch

Weight is primarily determined by the type of backplate material and thickness of the elastomer. Weights below are based on the typical values for Knurled and Pebbled surface pads made from Buna-N (NBR material at 60 durometer) . Waffled pad weights are about .04 oz/in<sup>2</sup> less than those. Contact PFA for individual pad weight.

Part TypeWeight (oz./in.2)
Steel Backed .53” thick.82
Aluminum Backed .25” thick.22
No backplate, .25” thick.17
No backplate, .13” thick.07
Gripper Pad Coefficient of Friction

Gripper Pads provide 50% – 400% more grip than metal to metal alone. Frictional effects depend on part material, surface finish, and clamping force. Lighter forces and rougher finish typically achieve the most grip strength, while any ability to conform to a part shape further enhances grip strength.

The coefficient of friction for an application in which steel fingers grip a steel or aluminum part is estimated to be .28 and .32, respectively. ASTM D 1894 friction test of a PFA knurled pad at light forces (loading a sample at .07 lbs/in2 on a polished surface) demonstrated a coefficient of friction of 1.22. Historic test data of PFA knurled pads (loading full pads at 1.4 lbs/in2 on a ground surface) demonstrated a coefficient of friction of .53 (on steel) and .78 (on aluminum), respectively. Values in the range of .48 to 1.0 provide a good approximation for untested applications and a good starting point for calculations. As fluids on parts and other non-ideal conditions will impact performance, friction coefficient values provide a good approximation of relative benefit when adding gripper pads to an application.

The coefficient of friction is used in conjunction with tooling weight and robot acceleration to calculate the required grip force for a specific application. The following formula can be applied as a good approximation when attempting to determine the minimum grip force. An additional safety factor of 10X may be required depending upon the application.

Grip Force (lbs) = [Tooling Weight (lbs) + Dynamic Force (lbs)] / [Coefficient of Friction]

Finger MaterialFriction Coefficient for Steel PartFriction Coefficient for Aluminum PartFriction Coefficient ASTM D 1894
Knurled Pad.53.781.22
Waffled Pad.48.87-
Pebbled Pad.52.76-

The coefficient of friction test for two sample part materials was conducted for the three gripper pad types. The test results were generated under ideal laboratory conditions. Actual performance may differ. In this test situation a metal sheet with a 63 microinch ground finish was placed between two 72 square inch gripper pads and a compressive load of 200 lbs was applied perpendicular to the contact area. All surfaces were clean and dry. In other situations the coefficient may be lower due to lubricants introduced into the system; or much higher for low clamp forces or if the rubber is able to conform to the part.

Gripper Pads Drawing

Dimensions mm (inches)
Click Part Number to view in Store

Part No.SurfaceLength
A**
mm (inch)
Width
B**
mm (inch)
Overall Thickness
C
mm (inch)
Pad Thickness
D
mm (inch)
Plate Thickness
E
mm (inch)
Durometer***
±5 Shore A
Elastomer***Plate Material***
GP-702-1A-1.2-1.2Knurled30.48
(1.2)
30.48
(1.2)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
60NBR-BunaN
(Black)
Carbon Steel
GP-702-1A-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
60NBR-BunaN
(Black)
Carbon Steel
GP-704-1A-1.2-1.2Knurled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
60NBR-BunaN
(Black)
Aluminum
GP-704-1A-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
60NBR-BunaN
(Black)
Aluminum
GP-706-1A-6.0-12.0*Knurled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
60NBR-BunaN
(Black)
Elastomer Only**
GP-706-2A-6.0-12.0*Knurled304.8
(12.0)
152.4
(6.0)
3.3
(0.13)
60NBR-BunaN
(Black)
Elastomer Only**
GP-134-1A-1.2-1.2Knurled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
35SI-Silicone
(Blue)
Aluminum
GP-134-1A-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
35SI-Silicone
(Blue)
Aluminum
GP-334-1A-1.2-1.2Knurled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
30CR-Neoprene
(Brown)
Aluminum
GP-334-1A-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
30CR-Neoprene
(Brown)
Aluminum
GP-504-1A-1.2-1.2Knurled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
65FKM-Viton®
(Orange)
Aluminum
GP-504-1A-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
65FKM-Viton®
(Orange)
Aluminum
GP-508-1A-1.2-1.2Knurled30.48
(1.2)
30.48
(1.2)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
65FKM-Viton®
(Orange)
316 Stainless
GP-508-1A-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
65FKM-Viton®
(Orange)
316 Stainless
GP-732-1A-1.2-1.2Knurled304.8
(12.0)
152.4
(6.0)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
35NBR-BunaN
(Black)
Carbon Steel
GP-732-1A-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
35NBR-BunaN
(Black)
Carbon Steel
GP-734-1A-1.2-1.2Knurled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
35NBR-BunaN
(Black)
Aluminum
GP-734-1-6.0-12.0Knurled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
35NBR-BunaN
(Black)
Aluminum
GP-701-1-1.2-1.2Waffled30.48
(1.2)
30.48
(1.2)
13.5
(0.50)
10.2
(0.37)
3.3
(0.13)
60NBR-BunaN
(Black)
Carbon Steel
GP-701-1-6.0-12.0Waffled304.8
(12.0)
152.4
(6.0)
12.7
(0.50)
9.4
(0.37)
3.3
(0.13)
60NBR-BunaN
(Black)
Carbon Steel
GP-703-1-1.2-1.2Waffled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
60NBR-BunaN
(Black)
Aluminum
GP-703-1-6.0-12.0Waffled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
60NBR-BunaN
(Black)
Aluminum
GP-705-1-6.0-12.0*Waffled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
60NBR-BunaN
(Black)
Elastomer Only**
GP-733-1-1.2-1.2Waffled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
35NBR-BunaN
(Black)
Aluminum
GP-733-1-6.0-12.0Waffled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
35NBR-BunaN
(Black)
Aluminum
GP-801-1-1.2-1.2Pebbled30.48
(1.2)
30.48
(1.2)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
60NBR-BunaN
(Black)
Carbon Steel
GP-801-1-6.0-12.0Pebbled304.8
(12.0)
152.4
(6.0)
13.5
(0.53)
10.2
(0.40)
3.3
(0.13)
60NBR-BunaN
(Black)
Carbon Steel
GP-803-1-1.2-1.2Pebbled30.48
(1.2)
30.48
(1.2)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
60NBR-BunaN
(Black)
Aluminum
GP-803-1-6.0-12.0Pebbled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
4.8
(0.19)
1.5
(0.06)
60NBR-BunaN
(Black)
Aluminum
GP-805-1-6.0-12.0*Pebbled304.8
(12.0)
152.4
(6.0)
6.4
(0.25)
60NBR-BunaN
(Black)
Elastomer Only**
GP-805-2-6.0-12.0*Pebbled304.8
(12.0)
152.4
(6.0)
3.3
(0.13)
60NBR-BunaN
(Black)
Elastomer Only**

*No metal plate

**Elastomer only pads may show some dimensional contraction. Use A=11-5/8” and B=5-3/4” actual for planning on 6” x 12” pads and assume nominal A & B dimensions for all metal backed pads (+/- .050”), nominal thickness (+/-.020”), and nominal squareness for smaller sizes as these are cut from standard 6” x 12” pads.  For custom machined sizes and make to print items, contact PFA.

***Durometer +/- 5 Shore A as shown.  Polymer Type Abbreviations: CR = Neoprene (Chloroprene),  NBR = Nitrile Butadiene Rubber (Buna-N), FKM = (Also FPM) High Temperature Fluoropolymer (Viton®), SI = Silicone (Polysiloxane), backing plate material is Aluminum (6061-T6), low carbon steel (10 gauge), or 316 Stainless Steel (or similar).

For custom sizes, please contact PFA.