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Measuring RPM

Modified on Saturday, 31 January 2015 11:52 PM by mpieler Categorized as Consultants Corner
Measuring RPM
Vol. 27 #2, November 2000

Sometimes during an extrusion trial, you need to verify the screw speed and to make sure that the tachometer is calibrated correctly. If a hand tachometer is not available, sometimes people will place a mark on the drive quill and count the revolutions while measuring the time with a stopwatch.

This procedure work fine for screw speed up to about 100 to 120 rpm. Once the extruder is turning at speeds higher then 120 rpm, it is difficult to visually count the mark on the drive quill. A method that can be used for counting high speed revolutions, is to count the "clicks". By holding a pencil, scale, screwdriver or any other similar object and letting it lightly rub against the drive quill where a key or keyway may be located. Now, it becomes easy to count the screw revolutions or "clicks" each time the key or keyway passes by the stationary object that you are holding.

- Timothy Womer, New Castle Industries

See also:
  • Maximum rate of an extruder
  • The extruder drive
  • Twin screw extruder operating range

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