Stratasys J850 Manual page 81

The condition of the print heads directly affects the quality of printed models.
You may need to replace a print head if one or more of the following
symptoms occurs:
• The Head Optimization wizard determines that a print head is defective.
(See "Optimizing (Calibrating) Print Heads" on page 4-51.)
• There are noticeable grooves in the surface of printed models.
• Visual inspection of the head reveals that its surface is damaged—peeling
or bubbles in the nozzle area.
• The printer interface displays a warning or malfunction message relating
to a print head—
❒ Head Heater temperature timeout
❒ Head Heater thermistor open
❒ Head Heater thermistor short
The Head Optimization wizard guides you through the procedure of replacing
a print head, and configures printer components to enable you to perform it.
Only replace a print head with the aid of the wizard.
The entire print-head replacement procedure takes about 45 minutes, and
consists of the following phases:
A. Identifying the head(s) needing replacement.
This is normally done by the Head Optimization wizard. Otherwise,
evidence of physical damage to the head surface or a malfunction message
indicates which head needs replacing.
B. Preparing the print block for head replacement.
This is done automatically when you run the wizard.
C. Removing the defective print
D. Installing a new print
E. Optimizing the print heads (done automatically by the wizard).
F. Performing head
head.
head.
alignment.