How does the clamping cylinder and ejector work on this 2 platen machine?

[Tezza91]

As my previous post. I am trying to work out how a recently acquired 1982 Arburg 220-90-350 works so that I can 1. get to know how it works and 2. build a new control system. For a few reasons, 1 so I can know the machine inside out, 2 so I can have loads of practice in PLC programming and control systems etc and 3 obviously I'll gain a working injection moulding machine.

Anyway:

The control side of the injection unit is simple enough to control.

But I'm having difficulties understanding the clamp side.

There are in total 6 hoses, 3 smaller ones on the ejector side and 3 large ones on the clamping cylinder. 2 small hoses do advance and retract of the ejector and 2 of the large hoses do advance and retract of the clamp cylinder. Each pair goes to a directional control valve labelled respectively. The two remaining hoses, one small on the ejector side and one large on the clamp side go to the same directional control valve labelled high pressure, it's these hoses that I don't know the function of.

What do these hoses do? When should they be fed?

 

[Pud]

The platens advance under low pressure until the mould safety is released (i.e. faces touching, nothing trapped and you haven't smashed any side cores etc). Then the high pressure is called to give whatever clamp force you have set. IIRC, Arburgs have a twin coaxial hydraulic cylinder, the smaller one giving the HP.


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[Tezza91]

Thanks! That is the most sensible and logical information I have received so far. Is there a separate low-pressure feed to the clamp directional valve? So the 3 hoses that go into the ejector side of the cylinder, 2 of which are ejector advance and retract, the 3rd is nothing to do with the ejector and is actually the advance or retract for the high-pressure clamp, is this the right way of thinking?