Stratasys FDM 2000 Manual page 112

Reference
slice, we have noticed the toolpaths tend to become too wide and have diffi-
culty bonding between levels. We suggest you decrease your Z-slice height in
these cases.
Overflow and loose tips lead to excess material on the tips, which is the
primary cause for burn marks on the models. Burn marks can be greatly
decreased by cleaning the tips before starting each model, and then
selecting the road widths defined in the DEF file.
Whenever the temperature is rising, you should notice the display on
the Watlows flashing "rP". If this does not appear, shut off your
machine and restart it.
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Notes