MK Products Copperhead Weldhead - Manual (Page 18)

CopperHead ® Owner’s Manual - Page 10
The CobraTig ® uses the home switch closure as an absolute indicator of
rotor position and times the duration between switch closures as one com-
plete revolution. Dividing this time into 60 seconds gives the rotor speed in
rpm.
Using this information the CobraTig ® calculates the two sets of error param-
eters: Gain and Zero Offset for both Motor and Tach. For the Motor parame-
ters, the Gain is a measure of the multiplying factor error on the speed. The
Zero Offset is the error of the speed where it should be going at zero rpm but
in actually it is slightly non-zero. The CobraTig
® then calculates the adjust-
ment coefficients based upon these error parameters to properly adjust the
motor speed commands in order to give the correct weldhead rotor speed.
For the Tach parameters, the motor speed is directly read by the CobraTig ® ,
using the tachometer feedback from the weldhead motor, in two ways: 1)
The analog tachometer signal is used by the analog closed loop motor servo
to control to the commands provided from the CobraTig
® control system.
2) The analog tachometer signal is converted to a digital signal, using an
analog multiplex analog to digital converter technique, and then Interpreted
by the digital CobraTig
® control system. It compares on what it has calcu-
lated from its timing data versus what the tachometer is giving corrected by
the same coefficients mentioned above. Similarly, a gain error, “Gain”, and
an off-set error, “Zero”, are derived. Reference the Sample CobraTig
® Cali-
bration Printout in Table 3.
Sample CobraTig ® Calibration Printout
M K P r o d u c t s . C o b r a Ti g 1 5 0
M O TO R C a l i b r a t i o n r e p o r t
MOTOR gain: -4.6% Zero offset: 0.30 RPM
TACH gain: 1.9% Zero offset: 0.02 RPM
W E L D E R C a l i b r a t i o n R e p o r t
CURRENT D/A converter gain: 3.1% DAC offset: -1
CURRENT D/A converter gain: 3.6% DAC offset: 4
CURRENT A/D converter gain: -2.1% ADC offset: 0
VOLTAGE A/D converter gain: -0.3% ADC offset: 0
What does all this mean to the operator? It means that the CobraTig ® will
calibrate the weldhead to its own motor voltage output and compensate for
calculated errors derived during the Motor Calibration Sequence.
The Motor Gain percentage is exactly how much the CobraTig ® will compen-
sate for with a particular weldhead connected.
Should these MOTOR & TACH gain values return with number of 0.00% and
0.00 RPM, the calibration is considered invalid and should be re-run.
Section C Accessories
Other than Collets, tungsten holders/extenders, and a cooler, there are no
other items needed to operate the weldhead with the orbital power supplies.
There are however, accessories available that enhance the operation of
the weldheads so that they may be more widely used with other orbital
equipment supplied by MK Products, Inc.
Benchmount
The CopperHead ® weldheads can be used while held in the operator’s
hand. However, at times it may be necessary for the operator to use both
Table 3