Servo Valve & Drive Repair on Molding Machines
Independent · third-party repair
Injection Molding Hub
Servo Valve & Drive Repair on Molding Machines
Independent third-party repair of servo valves, proportional valves, and servo drives off injection molding
machines. Van Dorn, Cincinnati, HPM, Toshiba, Demag, Husky, and other machine builders. Component-level
rebuild, bench testing, and donor parts service for valves the OEM no longer supports.
Years on molding-machine valves
Donor parts pool
Warranty on repairs
Where Valves Sit
Hydraulic valves on a molding machine
An injection molding machine runs hydraulic-control loops on four main motion axes. Each axis has its own
valve work, its own typical failure pattern, and its own bench procedure when the unit comes off the
machine.
Injection unit
Servo or servoproportional valve controlling injection speed and back-pressure during the shot. Closed-loop with feedback for shot-to-shot consistency. Typical bench work: pilot stage clean, spool wear, coil rebuild.
Clamp circuit
High-flow proportional directional valve handling clamp open, close, and tonnage. Larger spool, higher flow ratings. Typical bench work: spool service, seal kits, driver-card checks where present.
Ejector and core
Smaller proportional or directional valves on the ejector circuit and mold-core actuators. Typical bench work: coil and spool service, plus contamination cleanup from old hydraulic fluid.
HPU and pressure control
Pressure compensator valves and pump-control proportionals on the hydraulic power unit. Typical bench work: poppet seat work, pressure-gain trim, and seal replacement.
Machine Builders
Molding machine OEMs we see
The shop has worked on valves and drives off most major injection molding machine builders since 1975.
The OEM-integrated valves on these machines are typically Bosch Rexroth, Vickers, Atos, Yuken, or Moog
depending on the build year.
Cincinnati Milacron
HPM
Toshiba (industrial)
Demag
Husky
Sumitomo
JSW
Engel
Krauss-Maffei
Negri Bossi
Battenfeld
Nissei
Mitsubishi
Arburg
Nigata
Sending a valve from a molding machine? The brand on the valve nameplate matters more than the machine
builder. Common brands: Bosch Rexroth,
Vickers,
Atos,
Yuken,
Moog.
Common Faults
What usually fails on a molding-machine valve
Molding-machine valves run cyclic hydraulic loads continuously, often near process temperature. The
failures we see most often fall into the categories below.
| Pilot stage and feedback | Pilot-pressure null shift on closed-loop servo and servoproportional valves, contamination in the pilot path, and feedback wire wear after thousands of injection cycles. |
|---|---|
| Spool and body | Spool wear, contamination scoring from old hydraulic fluid, sticky spool action, internal leakage past the spool, and seal failure on the clamp-circuit body. |
| Coils and onboard driver | Burned proportional coils, failed onboard driver-card output stages, blown signal-conditioning components, and open windings on the pilot stage. |
| Cyclic and thermal wear | Heat damage from running near process temperature, hardened seals after thousands of cycles, corroded connectors, and evidence of prior on-machine repair attempts. |
Workflow
From part number to ship-back
Same four-step path through the shop whether the unit is a discontinued 1980s injection-circuit servo or
a current production proportional with onboard electronics.
-
01
Get in touch
Call or email with the valve part number, the molding machine model, and which axis it came off (injection / clamp / ejector / HPU).
-
02
Bench review
Tech opens the valve, inspects spool and pilot stage, and runs it on the hydraulic stand to confirm what failed.
-
03
Cost & approval
We call back with the cost and a rough turnaround. Nothing is started without your sign-off.
-
04
Repair, test, ship
Failed components replaced from inventory or off donors, the valve verified under pressure, and shipped back.
FAQ
Common questions about molding-machine valve repair
Industry-specific questions. For brand-specific FAQs, see the dedicated brand page or the valve hub.
My machine is a Van Dorn (or Cincinnati / HPM / Demag). Do you work on those valves?
Yes. The valve on the machine is what matters more than the machine builder. Most molding machines run OEM-integrated valves from Bosch Rexroth, Vickers, Atos, Yuken, or Moog. Send the part number off the valve nameplate and we can confirm coverage.
Do you repair the servo drive on the molding machine too?
Yes. We service servo drives and amplifiers off molding machines on the same bench as the hydraulic valves. See the servo drive repair hub for the brand directory.
What if the valve is beyond economic repair?
If the valve is not fixable, we will let you know and help source a replacement: a rebuilt match if we have one on the shelf, or a comparable cross-brand alternative.
Can you recover programs from valves with onboard electronics?
Most failures are hardware, and in most cases the unit comes back with its program unaffected. Corrupted programs are rare; if one is already corrupted before the unit reaches us, that’s the one thing we can’t recover.
Do you provide test data with the repair?
Each repaired valve is bench-tested before it ships. Performance graphs and detailed test data are available for purchase.
What is the warranty?
One year on parts and workmanship for repairs and rebuilt units. Standard exclusions apply for contamination, improper installation, and out-of-spec operation. Flushing and filtering the hydraulic system before reinstalling a repaired valve is recommended.
More from NC Servo
Related repair hubs
Broader category hubs, related machine pages, and technical reading on testing and failure causes.
Valve repair hub
Full directory of 20+ valve brands with dedicated pages.
Servo drive repair hub
Component-level board work on servo drives, amplifiers, and motion controllers.
Van Dorn brand page
Valve repair specifically off Van Dorn injection molding machines, including OEM-integrated valves.
Industrial valve repair
Heavy-industrial valve work across presses, mills, and process equipment.
Repair vs replace
When component-level repair makes sense versus buying new or rebuilt.
Servo valve failure causes
Common reasons servo and proportional valves fail in industrial service.
Molding machine valve down?
Give us a call or send a part number with the machine model. We’ll check the donor pool, suggest a rebuilt
match if we have one, and walk through repair or cross-brand options if we don’t.