The valve manifold of an injection molding machine is a steel block drilled with oil passages that carries the hydraulic valves. Directional and proportional valves bolt onto its faces, cartridge valves sit in bores inside it, and the drilled passages replace most of the pipes between them. Depending on the machine, there is one main manifold or several blocks, often one for each group of movements, mounted close to the cylinders they serve. The drawing shows a manifold block with the six kinds of valve it typically carries, and the pressure (P) and tank (T) lines.
How a valve manifold works
Inside the block, a pressure gallery from the pump feeds every valve station, and a tank gallery collects the return oil. Each valve station on a face of the block is a standard bolt pattern (ISO 4401, the Cetop sizes) with the P, T, A and B openings in fixed places. The A and B passages lead through the block to outlet ports, where the pipes or hoses to the cylinder are connected.
Cartridge valves sit in machined cavities. The passages are drilled from the outside, and the openings that are only needed for drilling are closed with threaded plugs or pressed-in plugs. Test points let a pressure gauge be connected to the important passages.
Putting the valves on one block gives fewer joints and so fewer leak points, shorter oil paths and a compact layout that is easier to service than a set of separate valves and pipes.
The valves on the manifold
Directional valve
A solenoid valve that switches oil between the two ports of a cylinder or motor to start, stop and reverse a movement. See the directional valve.
High-flow solenoid valve
A larger, pilot-operated directional valve: a small solenoid valve on top shifts the main spool. It is used for clamping and injection on large machines and is covered on the same page as the directional valve.
Proportional valve
Sets pressure or flow in proportion to an electrical signal from the controller. See the proportional valve.
Relief valve
Limits the system pressure and sends oil to the tank above its setting. See the relief valve.
Cartridge valve
A poppet valve inserted into a bore in the block, for the large flows of the clamp, injection and ejector circuits. See the cartridge valve.
Check valve
Lets oil flow one way only, for example from the pump into the block. See the hydraulic check valve.
Common manifold problems
- External leaks at the valve mounting faces, cartridge covers, plugs and port fittings, usually from hardened or damaged O-rings.
- Damaged sealing faces: scratches across an O-ring groove or burrs on the face.
- Stripped bolt threads in the block, from over-tightening or bolts of the wrong length.
- Internal leakage that looks like a manifold fault but usually comes from a valve, a cartridge seal or a plug inside the block.
- Trapped contamination: after a pump failure, debris stays in blind passages and keeps damaging new valves until the block is cleaned.
- Cracks in the block, which are rare and a reason to replace it.
Servicing a valve manifold
- Lock out the machine and relieve the pressure, including the accumulator through its safety block.
- Clean the outside of the block before opening anything.
- Photograph and mark each valve's position and orientation. Valves of the same size fit every station of that size, so it is easy to swap them by mistake.
- Cap every open port at once.
- Replace the O-rings with the correct size and a material suitable for the oil and its temperature, and check the grooves.
- Clean the faces; remove burrs carefully with a fine stone, never with a grinder.
- Use bolts of the original length and grade, and tighten them evenly in a cross pattern to the torque in the machine manual.
- Bleed the air, check for leaks under pressure, and test each movement at low speed first.
After a pump or valve failure that left metal in the oil, remove the valves and have the block flushed, change the oil and filters, and check the cartridge bores for debris before refitting. Our article on hydraulic oil problems explains why contamination keeps causing failures.
What to send for a replacement quote
A manifold block is specific to the machine. Send the machine model and serial number, the block's part number (stamped on it or on a label), the page of the hydraulic circuit diagram that shows it, and photos of every face with the valves in place. A drawing of the block is the best basis for making a new one. For the valves that mount on it, see our control valves, then request a quote. The hydraulic system guide shows where the manifold sits between the pump and the cylinders.
Updated by the IMSPARES technical team.