Stratasys uPrint, Service Manual, Page: 19 / 383

2-8
Liquefier Temperature Control
The liquefier T/C connects to the controller board through the power distribution board.
The T/C generates a variable low level current that depends on the temperature of the T/C.
This analog signal from the T/C is amplified by the head distribution. It is then sent down
the umbilical cable to the PDB, and then to the controller board. An A to D converter in the
ColdFire chip converts the analog signal to digital. In order to improve temperature
resolution, this signal is biased. The lowest reading possible is
109.5 ° C. The highest reading
is 330 ° C.
The liquefier temperature is maintained at: Model: 310 ° C, Support: 300 ° C
Temperature control is accomplished using “pulse wide modulation” See Figure 2-3.
Figure 2-3: Pulse Width Modulation (PWM)
Actual power to the liquefier heater is supplied by the PDB, which is controlled by the
controller board. The head heaters are turned off and on 1000 times a second (pulses). The
duration of the 120 VDC pulse determines the average power being supplied to keep the
liquefier at temperature. Temperatures can be read using a volt meter at test points TP5 for
model, and TP4 support on the PDB (10 mV per degree C).