Electric Screwdrivers and more!

How do I setup the EDU1AE/TOP to achieve the entire published torque range?

Posted By: Jim Chase on Feb 3, 2010

This Blog topic comes from Norm Wenzler at Intek Marketing in Southern California.  Norm is a manufacturers' Representative for KolverUSA in Southern California.

Question: Why can't I cover the entire published torque range for the PLUTO 3?

Answer: The published torque specification for the PLUTO Screwdrivers is dependent on the joint being used.  To generate data to duplicate the published specification for the PLUTO 3 use the following test method:

Equipment: Kolver K5 Torque Tester with two M6 rundown kits to simulate Soft and Hard joints.  Take the rundown kits apart.  To simulate a hard joint, stack the Belleville washers so they fit inside each other and reassemble the rundown kit. To simulate a soft joint stack the washers in pairs, facing each other, and reassemble the rundown kit.

Note: This example uses the EDU1AE/TOP/LTP controller

SOFT JOINT TESTING (20 Rundowns):

• For Minimum Torque, set on Soft joint, with the torque level to MIN and the RPM to 400 =  2.1 in/lbs average.
• For Maximum Torque, set on Soft joint, with the torque level to MAX and the RPM to 1200 = 15.5 in/lbs average.

HARD JOINT TESTING (20 Rundowns):

• For Minimum Torque, set on Hard joint, with the torque level to MIN and the RPM to 600 =  5.6 in/lbs average.
• For Maximum Torque, set on Hard joint, with the torque level to MAX and the RPM to 1000 =  29.3 in/lbs average.

Note: The Break-Time (available on the Hard Joint setting only) must be set so the tool slows down before the joint is seated.

PUBLISHED TORQUE RANGE: is 3Nm to 10%.  This is converted to 26.4 to 2.6 in/lbs in North America.  You can see from the testing (data available upon request) that we achieved a low of 2.1 in/lbs on a soft joint and a high of 29 in/lbs a hard joint.  It should be noted that the entire torque range could not be achieved on either the hard or soft joint (i.e.: resulting torque is joint specific).  It should also be noted that all Pluto tools are only recommended to be used to 85% of their Maximum torque specification.

Further: repeating the Soft joint MIN torque level test at 400 RPM with the M8 rundown kit (instead of the M6) yielded 5.6 in/lbs.  This test is a good example of the joint effecting the resulting torque.

JOINT THEORY: Moment of inertia and/or Mass are the variables at work in the examples outlined above.

Why the M8 rundown kit yielded higher torque than the M6 rundown kit can be explained by the difference in diameter and weight between the two: the M8 rundown kit is larger and heavier resulting in a higher moment of inertia and requiring more energy to stop.  Because both tests were done with the same setting the M8 test turned further and resulted in more torque.

Another question is:  why did the Soft joint yield lower torque than the Hard joint?  The variable in this case is the joints ability to absorb the energy generated by the moment of inertia.  Think of the screwdriver as an automobile traveling at 65 miles/hour.  The Soft joint simulates hitting a series of barrels filled with water; the barrels absorbed the energy of the moving car and bring it to a stop.  The Hard joint simulates putting your breaks on and coming to a stop; because their is nothing to absorb the energy of the moving object it takes longer to stop.  This is the reason the Hard joint setting in the EDU1AE has a break-time parameter.  The tool has to slow down, lowering the moment of inertia, before it can stop consistently.  Even so, the Hard joint does not absorb the energy as well as the Soft joint does, resulting in the tool turning further and applying more torque.

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