I have recently acquired a 1982 Arburg 220-90-350 injection moulding machine, mainly just as a hobby to further my knowledge on injection moulding machines and control systems as I plan to modernise the control system by redesigning it from scratch using a PLC and HMI.
This is my first proper project involving hydraulics at this scale, the hydraulic pump motor works but I have no pressure at the hydraulic valves. There are two proportional valves on top of the pump, the pump has two large pipes connecting to the manifold and one small one.
What is the purpose of the proportional valves and do I control both at the same time, just one, if so what one? What is the small pipe doing, it is the small rubber hose connecting to the lower side of the pump?
I'm sure the control valves on the manifold are standard hydraulic valves and not proportional, is this right?
I'm thinking all I have to do is work out what the proportional values do on the pump and then control them and then control the valves on the manifold. Is this the right way of thinking?