Magnum Venus Plastech Megaject MKIV Revision 1_6 - Manual (Page 38)

Megaject MK V Issue 1_6 Page 38 of 41
Appendices
Mould Pressure Guard (MPG)
A fluid pump driven by a piston type air motor will deliver an amplified injection pressure.
For example; a standard machine uses an 11:1 air motor/pump ratio. This could result in the
actual pump pressure being amplified eleven times, thus 3 bar could become 33 bar when
the mould cavity becomes hydraulically full.
The MPG is designed to control the Megaject pump speed, and thus injection pressure, to
prevent injection pressure exceeding an adjustable preset limit.
Operation
Set the maximum injection pressure on the MPG preset level gauge using the MPG
regulator. (Suggested initial setting – 2 bar)
If the resin pressure is below the preset pressure, then the automatic regulator will
remain fully open allowing full mains pressure to the resin pump regulator.
If the resin pressure exceeds the preset level, the ‘MPG signal pressure’ will reduce
proportionally closing the automatic regulator and limit air pressure to the resin pump
regulator. This slows or stops the resin pump, reducing resin pressure until it
matches the preset level. During operation, a small leak of air will occur from the
MPG sensor block. This is normal.
The MPG preset level may be adjusted during an injection to achieve optimum pump
output speed at the safest injection pressure.
Several factors will affect the optimum setting of the MPG regulator, e.g. fibre volume
fraction, mould size and rigidity, resin viscosity, required resin delivery rate etc.