Friction

Friction is the resistive force that occurs when two surfaces interact. It plays a fundamental role in engineering and manufacturing. There are two main types of friction: static and kinetic. Understanding and quantifying friction is essential for ensuring product safety, performance and process efficiency.

Accurate friction measurement enables manufacturers to control material behaviour, anticipate wear, and maintain consistent quality. For example, in packaging lines, too much friction can cause jamming, while too little can lead to slippage. Friction testing is therefore a critical quality assurance process.

Static friction

Static friction prevents an object from moving when a force is applied. This is crucial in applications such as keeping items in place on conveyor systems or maintaining closure integrity in sealed packages.

Kinetic friction

Kinetic friction occurs once motion has started and is typically lower than static friction. In automated handling systems, this governs how smoothly materials move and helps prevent erratic behaviour or mechanical wear.

Understanding the COF formula

The coefficient of friction (μ) is a dimensionless value calculated as:

  μ = F / N
  where:
  F = frictional force
  N = normal (applied) force

This ratio allows engineers to compare surface interactions. Higher values indicate greater resistance, while lower values suggest smoother movement. For example, testing the COF of packaging films helps determine how much grip is needed on high-speed packaging lines.

Industrial relevance of COF

In manufacturing, COF affects how materials feed, move, and stay in place. In plastic film processing, COF impacts how materials are guided and tensioned. In paper packaging, it influences how sheets stack and how reliably machines operate.

Static vs kinetic friction testing

Static friction testing measures the force required to initiate movement. Kinetic friction testing evaluates resistance during continuous movement. Both are used in quality control and material specification.

Equipment and relevant standards

Friction testing typically involves a sled tester with a flat platform and calibrated weights. Mecmesin’s FPT-H1 system automates this process, offering consistent sled placement and test speed control.

Common standards include:

• ASTM D1894 – Friction testing for plastic films
• ISO 8295 – COF measurement for plastic films
• TAPPI T549 – Paper-on-paper friction

Plastic film processing

Plastic films must maintain precise COF levels to feed correctly through wrapping and sealing systems. Slip additives influence surface characteristics, so regular COF testing ensures consistency.

Paper-based packaging

Friction affects how sheets of paper feed, stack and move through machinery. Maintaining the right COF reduces machine downtime and material waste.

Accurate friction testing can be affected by sled misalignment, variable speeds or inconsistent surfaces. Mecmesin’s FPT-H1 tester and precision sled kits help mitigate these issues by ensuring controlled conditions.

Standards-compliant systems

Mecmesin’s friction testing systems comply with ASTM and ISO standards and offer high repeatability across materials including paper, plastic and textiles.

Flexible for both R&D and production

With programmable routines, configurable sleds and pass/fail logic, Mecmesin testers are suited for research, development and routine quality checks.

For tailored advice on coefficient of friction testing, contact a Mecmesin applications engineer for support in choosing the right equipment and ensuring compliance with your industry’s requirements.