Rockwell Automation 1771-QDC, D17716.5.86(Passport) PLASTIC MOLDING MODULE - Manual (Page 222)

Tune Your Machine
Chapter 10
10-14
Shot Size
(PPC61)
Shot size (measured from cushion) is the amount of molten plastic needed
to fill the mold (figure 10.3). Determine it with these general steps:
1. Start with a shot size you know will NOT fill the mold.
2. Enter a ram(screw) transition position about 1/2” from ram bottom.
3. Run a shot with transition on position.
The end-of-hold position will be at ram bottom, because mold
cavities continue to fill during pack and hold.
4. While continuing to transition on position, slowly increase the shot
size until the end-of-hold position is
above ram bottom
approximately equal to cushion
5. The shot size is correct for the mold/part you are tuning when:
the end-of-hold position is approximately equal to cushion
all cavities on the mold are being fully filled
Cushion
(PPC62)
Cushion (measured from mold end) is the length of molten plastic you
want remaining in the barrel after filling mold cavities (figure 10.3). The
QDC module adds this length to shot size length to determine where to
terminate plastication.
Ram (Screw) Position for Transition
(IPC61)
This position setpoint (measured from mold end) determines where
injection ends and pack (or hold) begins (figure 10.3). Enter a position
value equal to or slightly greater than the top-of-cushion position,
depending on whether your part requires additional plastic compressed into
the mold during pack and hold.