--- title: "Cartridge valve of an injection molding machine" url: "https://www.imspares.com/injection-molding-machine-parts/hydraulics/cartridge-valve/" --- # Cartridge valve of an injection molding machine How slip-in cartridge (logic) valves switch the large flows of clamp and injection circuits in an injection molding machine manifold, faults and servicing. A cartridge valve is a valve built to fit into a bore in a manifold block instead of being bolted on as a separate body. On injection molding machines the most common type is the **two-way slip-in cartridge valve**, also called a **logic valve**: a spring-loaded poppet that opens or closes a large passage in the clamp, injection or ejector circuit, controlled by a small pilot valve on its cover. On the drawing, the cartridge valve is shown in section in the left end of the manifold block. ## How a slip-in cartridge valve works The valve has four main parts: - a **sleeve** (bush) with the seat, sealed in the bore by O-rings and backup rings; - a **poppet** that closes on the seat; - a **spring** behind the poppet; - a **cover** bolted over the bore, with the pilot passages and small orifices, and often a pilot valve mounted on top. The two main ports are **A**, under the poppet, and **B**, through the side of the sleeve. Above the poppet is the **control chamber**, connected to port X in the cover. The poppet has three pressure areas: the area facing A, the ring-shaped area facing B, and the area facing the control chamber, which equals the other two together. - When the control chamber is **pressurized**, the force on its large area plus the spring holds the poppet on its seat, and the valve is closed. - When the pilot valve **vents** the control chamber to the tank, pressure at A or B lifts the poppet and oil flows. The same cartridge does different jobs depending on its cover and pilot valve: an on/off directional function, a check function, a pressure-limiting function with a pilot relief in the cover, or flow limiting with a stroke limiter. Slip-in cartridges and their cavities follow ISO 7368 and come in standard nominal sizes such as NG16, NG25 and NG32. ### Why cartridge valves are used They pass large flows with a low pressure drop, switch quickly, and their poppet seals on a seat with very little leakage, unlike a spool. Several cartridges in one block replace large spool valves and much of the piping, which is why they are common in the clamp and injection circuits of medium and large machines. See the [valve manifold](https://www.imspares.com/injection-molding-machine-parts/hydraulics/valve-manifold/) page for how the block is built. Our high-flow [cartridge valve](https://www.imspares.com/parts/hy-cv-08/) for manifold blocks is rated to 35 MPa and listed for various standard cavities. ### Screw-in cartridge valves Smaller cartridge valves screw into threaded cavities: check valves, relief valves, flow controls and small solenoid valves. They are used in compact blocks and in auxiliary circuits. ## Signs of a faulty cartridge valve - A cylinder drifts, or loses position or pressure, while the cartridge should be closed: the poppet seat leaks, or the O-rings between sleeve and bore let oil bypass. - A movement is slow to start or does not start: the poppet sticks, an orifice in the cover is blocked, or the pilot valve does not switch. - A movement does not stop when commanded. - Shocks or banging when the valve switches. - Heat in one area of the block, from oil passing through a leaking cartridge. Because the cartridge is hidden inside the block, the symptoms point to a circuit rather than to a valve. Use the diagram and the action table on the [hydraulic circuit page](https://www.imspares.com/injection-molding-machine-parts/hydraulics/hydraulic-circuit/) to narrow it down. ## Why cartridge valves fail - **Contamination**: particles score the poppet and seat, or hold the poppet off its seat. - **Seal wear**: the O-rings and backup rings harden with heat and age. - **A broken or weak spring**. - **Blocked orifices** in the cover; orifices also set how fast the valve opens and closes, so a wrong orifice after a repair changes the switching. ## Inspecting and replacing a cartridge valve 1. Identify the cartridge on the circuit diagram and find its position number on the block. 2. Lock out the machine and relieve the pressure, including the accumulator through its safety block. 3. Clean around the cover. Loosen the cover bolts evenly, because the spring pushes against the cover. 4. Lift off the cover, take out the spring and the poppet, and pull the sleeve with a suitable puller if it must come out. 5. Inspect the poppet and seat for scoring, the seals for damage, and the orifices in the cover. Note the orifice sizes, and keep each valve's poppet, spring and cover together: never mix them between valves. 6. Clean the bore, fit new seals lubricated with clean hydraulic oil, reassemble, and tighten the cover bolts evenly to the torque in the machine manual. 7. Test the movement at low pressure and speed first. ## What to send for a replacement quote The nominal size of the cartridge, the type of cover and the model code of its pilot valve, any markings on the cover and sleeve, the position on the circuit diagram, and photos of the cover and nameplate. Add the machine model and serial number, then [request a quote](https://www.imspares.com/request-quote/). The other valves on the block are covered on the [directional valve](https://www.imspares.com/injection-molding-machine-parts/hydraulics/directional-valve/) and [check valve](https://www.imspares.com/injection-molding-machine-parts/hydraulics/hydraulic-check-valve/) pages. The [hydraulic system guide](https://www.imspares.com/injection-molding-machine-parts/hydraulics/) covers the rest of the circuit. ## Questions ### What is a logic valve? Another name for a two-way slip-in cartridge valve. It is a poppet valve that opens or closes a passage depending on whether its control chamber is pressurized or vented, and several are combined in a manifold to switch large flows. ### Why use cartridge valves instead of spool valves? They handle large flows with a low pressure drop, switch quickly, and their poppet seals on a seat with very little leakage. That suits the clamp and injection circuits of larger machines. ### Can I replace only the seals of a cartridge valve? Yes, if the poppet and seat are not scored. Fit new O-rings and backup rings on the sleeve, keep each valve's parts together, and check that the orifices in the cover are clear. ### How do I find which cartridge valve is faulty? Use the hydraulic circuit diagram and its action table to see which cartridges take part in the faulty movement. Check their pilot valves and covers first, since they are the easiest parts to reach. ## Replacement parts - [HY-CV-08 Cartridge Valve](https://www.imspares.com/parts/hy-cv-08/): Hydraulic cartridge valve for injection molding machine manifold blocks.