MINI TENSILE TESTER - Model D

The instrument is primarily used in packaging plants to monitor strength of heatseals as sampled from production lines. The Model D is small - about the size of a typewriter - and simple enough to be used by anyone after minimal instruction.

An optional dust-tight hood is available for the hostile environment of plant floor use. The tester can be placed on a table next to the packaging machine, so the operator can test seals routinely to fine-tune sealing conditions. Heatseal strength can then be maintained within specifications - neither too weak nor too strong.

TESTING PROCEDURE

In use, the operator cuts a 1"-wide strip through the seal, clamps the strip in the jaws of the tester and presses the start button. The instrument pulls the strip apart at the preset speed and displays the peeling/breaking force on a digital meter.

Seals can be any type: end seals, longitudinal, fin, lap, flat, serrated, impulse, bead, etc. The material sealed can be film, coated paper (or other substrate), or laminations - as long as it is flexible and can be tested by pulling one side of the seal away from the other. A strip cutter is available to prepare test strips quickly and accurately.

In practice, if the materials have been completely fused in the heatsealing process the seal itself will not separate. The material will break (usually at the seal edge), delaminate or stretch. Non-fused seals will peel apart. In any case, failure will occur at the weakest point in the structure and the model D tester will measure and display the force required. By inspection, the operator can determine type and location of failure. This information is essential in controlling the heatsealing step in packaging operation, as well as quality of incoming packaging materials.

FEATURES

Small in size, portable, and easy and fast to use, the Theller model D Mini Tensile Tester is a true precision instrument of great versatility:

• Its electronic load cell is accurate and reproducible to less than 6 grams.
  
  

• The electronic tachometer measures and displays speed of pull from almost zero to the top speed of 50 inches per minute.
  
  

• Readout of failure force and clamp speed is optionally in either English or metric units - at the flick of a panel switch.
  
  

• Electronic calibration is incorporated for quick and easy check and setting of the force-measuring circuits.
  
  

• The instrument can be used as general-purpose tensile testing machine when relatively short crosshead travel can be employed.
  
  

• With addition of optional quick-change hardware, the unit measures coefficient of friction, per ASTM D1894.

SPECIFICATIONS

PRINCIPLES OF OPERATION

The model D MTT employs two carriages that slide horizontally:

• The left carriage is attached to an electronic load cell that gives a digital readout of any horizontal force or pull exerted on it by the carriage.
  
  

• The right carriage is pulled horizontally away from the left carriage by a lead screw driven by a DC motor that can be set for any speed up to 50 inches per minute. The speed is read digitally on a panel meter.

In tensile/peel mode the carriages carry grips (manual or air-actuated) that hold the ends of the tensile (or heatseal) strip being tested. When the motor starts, the grips are moved apart at the set rate and the specimen is elongated to failure per ASTM F88. The digital meter displays the maximum force required.

COEFFICIENT OF FRICTION (COF) MODE

For COF mode, the tensile/peel grips are quickly removed from the carriages and the COF table is installed on the right (driven) carriage with knurled thumbscrews.