Quick Answer
Every injection molding factory should keep critical spare parts in stock to minimize production downtime and avoid delays caused by unexpected equipment failures.
The most commonly recommended spare parts include:
- Hydraulic seals
- Hydraulic hoses
- Oil filters
- Heater bands
- Thermocouples
- Solenoid valves
- Contactors and relays
- Sensors
- Screw tips and check rings
- Lubrication components
The exact inventory depends on machine age, production volume, and the availability of replacement parts in your region.
Why Is Spare Parts Inventory Important?
A production line can stop for days or even weeks if a critical component fails and replacement parts are unavailable.
Keeping essential spare parts on hand helps:
- Reduce downtime
- Improve maintenance response time
- Protect delivery schedules
- Reduce emergency freight costs
- Improve overall equipment efficiency
For many factories, the cost of lost production is much higher than the cost of maintaining a spare parts inventory.
Which Spare Parts Fail Most Frequently?
Not all machine components require stock inventory.
Focus on parts that:
- Wear naturally
- Have predictable service lives
- Frequently cause downtime
- May require long lead times
These are the components that provide the highest return on inventory investment.
Category 1: Hydraulic System Spare Parts
Hydraulic components are among the most important spare parts to keep available.
Recommended inventory:
Hydraulic Seals
Used in:
- Cylinders
- Pumps
- Valves
Seal failures are common and often inexpensive to repair if replacement parts are available.
Hydraulic Hoses
Hydraulic hoses deteriorate over time due to:
- Pressure
- Heat
- Vibration
A damaged hose can stop production immediately.
Hydraulic Fittings
Common fittings are inexpensive and useful to keep in stock.
Solenoid Valve Coils
Coils are relatively low-cost and can fail unexpectedly.
Many factories keep spare coils for their most commonly used valve models.
Hydraulic Pumps (Optional)
For large factories operating multiple machines, keeping a spare pump for critical production equipment may be worthwhile.
Category 2: Heating System Spare Parts
Heating system failures are among the most common causes of machine downtime.
Recommended inventory:
Heater Bands
Barrel heater bands wear over time and should be readily available.
Thermocouples
Thermocouples are inexpensive but essential.
A failed sensor can stop production even when the heater itself is functioning.
SSR Modules (Solid State Relays)
SSR failures can create heating problems and temperature control issues.
Temperature Controllers
Some factories keep backup controllers for critical production equipment.
Category 3: Screw and Barrel Components
Complete screw and barrel assemblies are expensive, but certain wear parts should be stocked.
Recommended inventory:
Screw Tips
Check Rings
Check Ring Seats
These components experience wear during normal operation and can affect shot consistency.
Factories processing abrasive materials should pay special attention to these parts.
Category 4: Hydraulic Oil and Filtration Components
Proper filtration protects expensive hydraulic equipment.
Recommended inventory:
Hydraulic Oil Filters
- Return filters
- Pressure filters
- Suction filters
Breather Filters
Often overlooked but important for contamination control.
Hydraulic Oil
Many factories maintain emergency stock of approved hydraulic oil.
Category 5: Electrical Spare Parts
Electrical failures can cause immediate machine shutdown.
Recommended inventory:
Contactors
Relays
Circuit Breakers
Fuses
Power Supplies
These components are relatively inexpensive and often easy to stock.
Category 6: Sensors and Switches
Sensors are common failure items in injection molding machines.
Recommended inventory:
Proximity Sensors
Limit Switches
Pressure Sensors
Temperature Sensors
A failed sensor can stop production even when all mechanical components are functioning normally.
Category 7: Lubrication System Components
Automatic lubrication systems are often neglected until problems occur.
Recommended inventory:
Lubrication Pumps
Grease Distribution Blocks
Lubrication Tubing
Lubrication Fittings
These items are relatively inexpensive but important for machine longevity.
Category 8: Servo System Spare Parts
For servo-driven injection molding machines, consider stocking:
Cooling Fans
Servo Motor Encoders
Communication Cables
Servo Drive Components
Complete servo motors are typically purchased only when needed, but smaller support components may justify stocking.
What Parts Usually Do NOT Need to Be Stocked?
Some parts rarely fail and are expensive to store.
Examples include:
- Machine frames
- Platens
- Toggle assemblies
- Major castings
These components are usually ordered only when necessary.
How Much Spare Parts Inventory Should a Factory Keep?
There is no universal answer.
A common approach is:
Critical Parts
Keep immediately available.
Medium-Risk Parts
Maintain limited stock.
Low-Risk Parts
Order as needed.
Focus inventory spending on components that can stop production.
How Do You Identify Critical Spare Parts?
Ask these questions:
If the Part Fails, Does Production Stop?
If yes, consider stocking it.
Is Lead Time Long?
If replacement takes weeks, inventory may be justified.
Is the Part Inexpensive?
Low-cost critical parts are usually worth stocking.
Does the Part Fail Regularly?
Frequently replaced parts should generally remain in inventory.
Spare Parts Inventory Mistakes to Avoid
Stocking Too Many Expensive Parts
Not every component needs to sit on a shelf.
Ignoring Small Components
Many shutdowns are caused by inexpensive items such as sensors or relays.
No Inventory Tracking System
Unused inventory often becomes obsolete.
Waiting Until Failure Occurs
Emergency purchasing is usually more expensive than planned inventory management.
Recommended Spare Parts Checklist
A basic injection molding machine spare parts inventory should include:
✓ Hydraulic seals
✓ Hydraulic hoses
✓ Hydraulic oil filters
✓ Breather filters
✓ Heater bands
✓ Thermocouples
✓ Solenoid valve coils
✓ Contactors
✓ Relays
✓ Fuses
✓ Proximity sensors
✓ Limit switches
✓ Lubrication components
✓ Screw tips
✓ Check rings
✓ Approved hydraulic oil
This list covers the most common maintenance-related failures in many injection molding facilities.
How DAYAMAC Supports Spare Parts Supply
DAYAMAC, the injection molding machine division of DAYA MACHINERY, helps manufacturers worldwide source and supply critical spare parts for injection molding equipment.
We provide:
- Hydraulic system parts
- Screw and barrel components
- Heater bands and thermocouples
- Electrical components
- Servo system parts
- Maintenance consumables
- Industrial sourcing services
Our team helps customers reduce downtime by identifying and sourcing the right spare parts before emergencies occur.
Common Questions
What is the most important spare part to keep in stock?
Hydraulic filters, heater bands, thermocouples, sensors, and hydraulic seals are among the most commonly stocked items.
Should factories keep a spare hydraulic pump?
For critical production equipment or high-volume operations, maintaining a spare pump may be justified.
How often should spare parts inventory be reviewed?
Most factories review inventory quarterly or at least annually.
Are electrical components worth stocking?
Yes. Small electrical components frequently cause machine downtime and are relatively inexpensive to store.
How can I decide which spare parts are critical?
Focus on parts that can stop production, have long lead times, or fail regularly.
Contact DAYAMAC
Need help sourcing spare parts for injection molding machines?
DAYAMAC provides:
- Hydraulic system components
- Screw and barrel spare parts
- Heater bands and thermocouples
- Servo system parts
- Electrical components
- Industrial sourcing and supply solutions
Contact our team to build a cost-effective spare parts strategy and reduce unexpected production downtime.