An injection molding preventive maintenance checklist organizes press care into daily, weekly, monthly, quarterly, and annual tasks covering the hydraulics, barrel heats, clamp unit, and screw and barrel. Daily checks take about 10 minutes: hydraulic oil level and temperature, leaks, safety interlocks, barrel zone temperatures, mold water, and a quick cycle time and cushion check. Logging readings like shot cushion, heater band amps, and tonnage balance catches wear long before it shows up as scrap or a down press.

Introduction

An injection molding preventive maintenance checklist gives operators and techs a consistent routine for hydraulic, hybrid, and electric presses. A press that's down isn't just lost machine time. It's lost material, scrapped parts, and late shipments. Most failures in hydraulics, heaters, and clamp components give early warning signs if someone is looking. This guide is for plant managers, molding supervisors, and maintenance leads who want a practical routine they can keep at every press, plus the readings that show which presses are drifting.

Before You Start

Follow your facility's lockout/tagout (LOTO) procedure for any task that requires opening guards, removing panels, or putting hands between the platens or near the barrel. Always defer to the OEM manual for lubricant types, intervals, and torque specs. The intervals below are starting points. Tighten them for multi-shift or high-load operations.

Daily Injection Molding Maintenance Checklist (~10 minutes, start of shift)

• Hydraulic oil: check reservoir level and confirm temperature is within the OEM range.
• Leaks: inspect hoses, fittings, and manifolds for oil, water, and air leaks.
• Safety: test gate interlocks, E-stops, and the mechanical safety bar.
• Barrel heats: confirm every zone reaches setpoint and holds steady.
• Feed throat and hopper: confirm throat cooling flow, dryer temperature, and material level.
• Mold temperature: verify TCU or chiller setpoints and water flow to the mold.
• Clamp area: clear plastic debris from platens, tie bars, and ejectors.
• Lubrication: check the central lube reservoir level on toggle machines.
• Process check: compare cycle time and cushion to standard, and note any new noise.

Weekly Injection Molding Maintenance Checklist (~30 minutes)

• Clean and lubricate tie bars (if not on auto-lube) and look for scoring.
• Inspect hoses and cables for abrasion, cracking, or kinks; secure loose runs.
• Check water flow and the in/out temperature difference across the oil cooler.
• Clean dryer filters and hopper magnets; verify dew point if equipped.
• Inspect the nozzle for drool, leaks, or a damaged seat, and clean as needed.
• Check robots, conveyors, and granulators for safe, normal operation.
• Confirm mold clamp bolts and quick-mold-change clamps are secure.

Monthly Injection Molding Maintenance Checklist (~1 hour)

• Heater bands: measure amp draw on each zone with a clamp meter and replace weak bands.
• Thermocouples: inspect wiring and seating; replace any that read erratically.
• Toggle linkage: inspect pins and bushings for wear and confirm lubrication at each point.
• Hydraulic filters: check indicators and replace elements as needed.
• Mold protection: verify low-pressure mold protection settings are active and correct.
• Check ring: trend cushion consistency to catch check-ring or barrel wear early.
• Electrical cabinet: clean filters and confirm cooling fans run.

Quarterly Injection Molding Maintenance Checklist (~2 hours)

• Pull a hydraulic oil sample for particle count, water, and viscosity.
• Check accumulator nitrogen pre-charge pressure (if equipped).
• Inspect the heat exchanger for scale and descale if the temperature difference is dropping.
• Measure and record platen parallelism; investigate if out of spec.
• Check tie bar stretch or tonnage readings across all four bars.
• Inspect motor-pump couplings and listen for pump cavitation.

Annual Injection Molding Maintenance (plan downtime)

• Pull the screw and measure flight OD, barrel ID, and check ring wear.
• Replace hydraulic fluid and filters, or extend the interval based on oil analysis.
• Verify calibration of pressure transducers, temperature controllers, and position sensors.
• Check and re-level the machine and inspect machine mounts.
• Run an infrared scan of the electrical panel for hot connections.
• Inspect tie bar bushings, platen slides, and the ejector system for wear.
• Review the year's logs and schedule any trending repairs before they fail.

Which Injection Molding Readings Should You Track?

A checked box confirms a task was done. A logged number shows whether the press is wearing. Track these readings monthly against spec:

• Hydraulic oil temperature
• Cycle time vs. standard
• Average shot cushion
• Oil cooler temperature difference (in/out)
• Heater band amps (lowest zone)
• Accumulator pre-charge
• Platen parallelism
• Tonnage balance (max deviation)

A cushion that keeps drifting often points to check-ring or barrel wear. A shrinking cooler temperature difference points to scale. Catching these trends early turns an emergency teardown into a planned repair. The downloadable checklist includes a 12-month readings log built for this.

Why Calendar-Based Press Maintenance Falls Short

A calendar schedule treats a press running around the clock the same as one running a single shift, and a paper checklist only works when someone fills it out. Cycle-based maintenance services each press based on how hard it's actually running.

Caddis machine maintenance software connects to your presses and schedules preventive maintenance work orders from actual cycles, not the calendar. It sends text or email alerts when temperature, vibration, amperage, or downtime crosses a threshold, and works on any press brand or age. For setup steps, see how to set up a preventive maintenance schedule.

FAQ

How often should an injection molding machine get preventive maintenance?

Presses need daily checks of about 10 minutes, plus weekly, monthly, quarterly, and annual tasks. High-volume or multi-shift presses should run on tighter intervals than the OEM minimum.

How do you know when a screw and barrel need replacing?

Trend shot cushion consistency monthly and measure flight OD, barrel ID, and check ring wear annually. An inconsistent cushion is often the first sign of check-ring or barrel wear.

How often should hydraulic oil be changed in an injection molding machine?

Typically once a year, but quarterly oil analysis for particle count, water, and viscosity tells you whether you can safely extend that interval or need to change sooner.

Does this checklist apply to electric presses?

Yes, most of it does. Skip the hydraulic-specific tasks on all-electric presses, and follow the OEM manual for drive and ballscrew maintenance.

What's the difference between preventive and predictive maintenance for presses?

Preventive maintenance follows a fixed schedule. Predictive maintenance uses condition data, like cushion, temperature, and amperage trends, to service the press when it actually needs it. Read the full comparison.

Conclusion

An injection molding preventive maintenance checklist turns press care into a 10-minute daily habit and a logged record that catches hydraulic, heater, and clamp problems before they cost you material and shipments. Download the free checklist to keep one at every press. When you're ready to move beyond paper, book a demo to see how Caddis schedules maintenance from actual press cycles.