Automated beverage container friction testing system

01

Choose the friction method for the contact that matters

US patent application 2002/0194895 explains why container friction matters on the line: PET has a static coefficient of friction above 1.0, so preforms pile into cones in boxes and jam feeder rails, and when rows of bottles from the blow moulder or depalletizer are merged into single file the pressure between bottles rises and high friction makes them stick and jam; it notes that the ASTM D1894 film method suits planar surfaces only, not curved bottles, and that a Japanese conveyor-load method cannot give a bottle-to-bottle value. [1]

For glass, US patent 10,351,470 describes an AGR International tilt table: three containers in a pyramid, the bottom two constrained, the table tilted by a motor at 3.6° per second until the top container slides and hits a trip bar that stops the motor and brakes the table to avoid reading too high; lubricity is read as the slip angle or as the coefficient of static friction, and in that patent a slip angle below 15°, preferably below 13°, is treated as lubricous enough. [2]

For aluminium cans, US patent 6,190,738 describes an incline plane mobility test: two base cans on the platform, a third laid on top about one inch from their open end, the platform raised slowly until the top can slides, repeated with the base cans rotated to give eight readings, and the result reported as the average incline angle or as the coefficient of static friction, the tangent of that angle. [3]

Editorial calculation: since μs = tan(slip angle), 15° corresponds to μs ≈ 0.27 and 13° to μs ≈ 0.23; state in the specification whether limits are given as angles or as coefficients. [2] [3]

Give the supplier the containers (material, size, coating or lubricant, preform or finished bottle), the contact to be tested, the method and report your specification uses, the speed or tilt rate, load, number of repeats, conditioning and ageing time after forming, environment, data output, and whether films and labels must also be tested on a flat sled.

02

Set speed, load, ageing and reporting

The PET bottle patent describes a tester that rotates one bottle in a chuck at a set speed against a stationary second bottle pressed down with a set force, records the torque at the moment of slip and the torque to keep constant speed, and computes μ = (torque / R) / F2, where R is the rotating bottle's radius and F2 the contact load derived from the applied force through a lever ratio; in its examples on 20 oz bottles, rotation speed and ageing time after forming had a significant effect on the measured coefficient while applied load from 100 to 1,000 g did not, with mean values of about 1.1 to 1.6. [1]

Intertek summarises ASTM D1894 for plastic film and sheeting: a specimen on a sled of specified weight is pulled across a second surface at 150 mm/min, 64 mm square specimens are tested against a 254 × 127 mm second surface, and the static coefficient is the initial force reading divided by sled weight and the kinetic coefficient the average force during uniform sliding divided by sled weight. [4]

Editorial note: because speed and ageing changed results in the PET patent's examples, fix the test speed, the time between forming and testing, and the conditioning in the specification, and compare suppliers' instruments on the same samples.

03

Bottle pyramid, can pyramid, rotating-bottle torque and flat sled

04

Holders, tilt or rotation drive, load, torque sensor and slip detection

The sources detect slip in two ways: the sliding glass bottle hits a trip bar that stops the tilt motor, while the PET tester reads the torque at the moment the rotating bottle starts to slide. [2] [1]

05

Friction range, tilt or pull speed, normal force and container size for a tester quotation

The speeds in this table — 3.6°/s tilt, 150 mm/min sled pull and a set rpm for the rotating bottle — belong to different methods, so name the method before comparing any instrument's speed range. [2] [4] [1]

06

Send the containers, method and report together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Containers: [glass; PET; cans; preforms; sizes]
Contact: [container on container; on guide; film on film]
Method: [tilt table; incline; torque; sled]
Conditions: [rate; load; ageing; conditioning]
Report: [angle; static or kinetic COF]
Supply: [software; calibration; fixtures]

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