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TB 047 Rev 1 – Drag Diagnostic
Overview
Drag torque is defined as the torque required to move an axis at a constant slow jog rate A higher
drag value is an indication of a problem with the mechanical system which will in return affect the
proper operation of the control unit The cause of excessive drag may be the result of poor
lubrication gibs too tight debris in the ways or misalignment in the bearings Having the availability
to readily check the drag values graphically on the machine allows for preventative maintenance to
ensure the proper operation of the CNC machine Drag diagnostic is an advanced feature available in
control systems with CNC7 software version 6 00 and above
Steps for performing the drag test
1 First go to the proper screen as follows F1 Setup → F3 Config → Password 137 → F4 PID
→ F6 Drag Choose the axis you want to check by pressing F1 Press Cycle Start once you
are ready to start the procedure
2 The drag diagnostic program will command the machine to go to a limit switch along the axis
chosen The machine will reverse direction moving to the opposite limit switch and then
reverse again moving to the starting limit switch Approximately 200 torque values for the
chosen axis will be recorded during he drag procedure Data is saved into drag_x out
drag_y out or drag_z out in the C \cncm directory depending on the axis label for the axis
under test
3 Upon completion of the test the graph showing the data plot will be shown on the screen To
open up a previously saved plot from the main menu press F2 Load then select the desired
drag plot file in the cncm directory Once the file is loaded press F8 Graph to display the data
4 Data displayed should remain between the red horizontal lines that bound the acceptable
operating range which is 25% of the maximum power that can be supplied to the motor If
drag exceeds 25% of the maximum power anywhere in the axis the message “ excessive axis
drag ” will be displayed on the screen Refer to Figure 1
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TB 047 Rev 1 – Drag Diagnostic
Z \tech\Technical bulletins\TB047\TB047_rev1 odt Page 2 of 3Figure 1
TB 047 Rev 1 – Drag Diagnostic
Document History
Rev1 created 2024 03 19 by 490
• Updated from previous TB format to match current formatting
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