I am trying to work out how a recently acquired Arburg 220-90-350 from 1982 works so that I can build a new control system and get it working. It's a direct clamping machine with no toggle.

The injection side is quite simple, just 3 motors or cylinders each controlled by a separate valve.

The clamp and ejector side has me confused though, there is a directional valve controlling each cylinder (simple enough) but each cylinder has a 3rd line the same size as the others connected to another single valve labelled 'high pressure'. So to summarise, 2 hydraulic cylinders each with 3 hoses, 3 directional control valves controlling the 2 cylinders.

I can't begin to draw a schematic without further disassembling the machine so I am hoping someone can give me some reasons why a hydraulic cylinder would have 3 hoses of equal size, with 1 on each cylinder connected to the same valve.

Edit: On further investigation, I can confirm that non of the 3 hoses are connected together, i.e. there is not two in parallel.

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  • $\begingroup$ Valve or valve block? 2 delivery, one return? Same supply point for the 3 pipes or different? $\endgroup$
    – Solar Mike
    Commented Nov 10, 2020 at 9:14
  • $\begingroup$ One supply for the whole system fed from the pump. 1 main valve block (manifold), 3 valves, 2 cylinders each with 3 pipes. I am yet to work out whether two of the pipes are internally connected within the cylinder or whether all 3 pipes have a different function within the cylinders $\endgroup$ Commented Nov 10, 2020 at 9:49
  • $\begingroup$ Can you draw a P&ID sketch of the parts of the system you know? $\endgroup$
    – mart
    Commented Nov 11, 2020 at 8:23
  • $\begingroup$ Could be a pilot controlled locking valve body to protect from unintended retraction should the main pressure hose burst. $\endgroup$
    – user13416
    Commented Nov 11, 2020 at 15:18

1 Answer 1


So it turns out that the ejector cylinder is just a standard double-acting cylinder with 2 hoses, the remaining 4 hoses are all used for the clamping cylinder.

Two of the large hoses do retract and return at low pressure, the two remaining hoses one large and one small do the high pressure clamping.

This is standard for a 2 platten direct clamping machine. The platen closes under low pressure and when it is closed the high pressure gives it the final clamping force.


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