Coefficient of Friction Testers
Coefficient of friction (COF) testing is a measurement of surface friction i.e. the force required to pull a material sample, at a specified speed, for a specified distance over a horizontal surface, which is covered in the same material.
To find out more about coefficient of friction testing visit our Knowledge Centre.
Coefficient of Friction Tester
A computer-controlled test system from the Mecmesin MultiTest-i range, is the ideal solution for coefficient of friction testing. Coefficient of friction values are automatically calculated for you using Emperor™ software. The full test is displayed graphically on a PC screen, helping you to identify anomolies, such as 'stiction', where the surface judders during dynamic slip. A range of diagnostic tools offer further analysis options to gain more detailed information from your tests.
A horizontal test table
The test table complies with BSI / ASTM standards and ensures a level platform throughout testing.
A sled weight
With one test specimen attached to the table and another laid directly on top, the sled weight is used to move the top specimen. The force is recorded by the loadcell and transmitted to Emperor™, which displays the full test and automatically calculates the static and kinetic coefficients of friction.
Testing Frictional Forces
Friction testing is a measurement of surface friction i.e. the frictional force required to pull a material sample, at a specified speed, for a specified distance over a horizontal surface. In frictional force testing (COF testing), the sample is normally wrapped around a metal block of specific dimensions and mass - called a 'sled', and another sample of the material is attached to a horizontal table.
When a universal test machine, such as the Mecmesin MultiTest 1-i is used for measuring the force of friction / COF testing, a pulley wheel is used to transfer the tensile force applied by the stand to a horizontal friction force on the sled.
Two distinct calculations are then made to ascertain the coefficients of friction:
- Motion initiation force / sled weight = coefficient of static friction. This is the maximum (peak) force required to initiate movement of a material
- Motion maintenance force / sled weight = coefficient of kinetic friction. This is the average force required to maintain movement of the material
Coefficient of friction testing values are particularly important within the packaging industry, where materials go through various processes in order to produce a final product.
A wide variety of packages are produced by converting bulk plastic film or sheet, paper or foil. Form-fill seal converting machinery needs to move, feed, shape, stretch, cut, weld, fold and apply tensile load to raw material, and to do all this at high speed. Finished packaging products must move quickly and efficiently along the production line. Each surface has its own distinct frictional value, which determines if they have the tendency to adhere or slide apart from one another.
Benefits of Friction testing (COF Testing)
- Optimising production levels
- Minimising problems caused by misfeeds
- Removal of need for guesswork / trial and error
- Compliance with industry standards
Common standards used for determining coefficient of friction values include:
- BS EN ISO 8295:2004 Plastics, Film and Sheeting. Determinations of the coefficients of friction
- ASTM D1894-0 Standard Test Method for Static & Kinetic Coefficients of Friction of Plastic Film and Sheeting