WPI UltraMicroPump II Instruction Manual page 25

UltraMicroPump II
direction you want the plunger holder to move in and quickly tap the run/stoP
key a couple of times to unwind the tension on the drive screw and move the
plunger holder away from the end of its travel. if the holder cannot be moved away
from the stop end easily by this method, then contact techsupport@wpiinc.com
for assistance. the pump may have to be returned for mechanical disassembly to
correct this.
Stalling
the umP2 may stall for a number of reasons. the most likely cause is that the
pump motor cannot push the syringe plunger for the following reasons:
1. more than 400 g is required to push the syringe plunger. the syringe should not
be a gas-tight (i.e., teflon-sealed) piston greater than 250 microliters in volume;
this syringe type requires more force than the motor can push. if you require a
large volume syringe (over 250 µl), please use a liquid-tight plunger.
2. needle blockage. the micropipette or the needle might be blocked by a
tissue mass in or outside of the needle, or the needle tip may be too small for the
programmed injection. check for normal operation of the pump in air with and
without the syringe attached. too high a delivery rate through a too small tip can
cause tissue damage and overtax the pump.
3. syringe misalignment. the syringe must be axially aligned to the umP2 body
in the clevises and the syringe plunger button must be centered in its holder to
properly inject along the length of the syringe. A small misalignment of the syringe
plunger can cause pulsating waves in the injection and an incorrect amount of
delivery.
4. mechanical damage. if the umP2 plunger carrier is loose (a condition which
can be caused by overtravel), the pump must be returned to WPi for repair.
23
World Precision instruments