Injection Molding Machine (80T–650T Clamping Force)

Hydraulic vs. Servo-Hydraulic vs. All-Electric: Energy Consumption Trade-off

Machine type selection has a significant impact on energy cost over the machine’s operating life:

Hydraulic (fixed-displacement pump). Lowest purchase price. The hydraulic pump runs continuously at full speed regardless of machine cycle state, generating heat even during the idle (mold open) phase. Energy consumption: 100% baseline reference. Cooling water demand is high. Suitable for low-cycle-count applications (<200,000 shots/year) where energy cost is secondary to capital cost.

Servo-hydraulic (variable-displacement servo pump). The hydraulic pump speed is modulated by a servo motor in response to actual demand — near-zero consumption during dwell and mold-open phases. Energy savings: typically 30–50% vs. fixed hydraulic for a standard cycle. Faster injection response due to servo motor dynamics. Most cost-effective upgrade over fixed hydraulic — payback period is typically 18–36 months depending on energy cost and shift pattern.

All-electric (servo motor direct drive on each axis). No hydraulic circuit — each machine axis (injection, clamp, ejector) is driven by an independent servo motor with ballscrew. Energy savings: 50–70% vs. fixed hydraulic. Zero hydraulic oil contamination risk (critical for cleanroom, medical, and food-contact part production). Highest purchase price premium (30–50% over servo-hydraulic equivalent). Required for ISO Class 7 or better cleanroom environments.

For 2-shift production above 500,000 shots/year: servo-hydraulic pays back within the warranty period. For cleanroom or medical parts: all-electric is mandatory.

Screw L/D Ratio for Material Selection

The injection screw geometry determines which materials can be processed correctly:

L/D ratio 20:1 (standard). Adequate for most commodity thermoplastics: PP, PE, ABS, PS, PC. Standard for general-purpose machines.

L/D ratio 22:1 or 24:1 (extended). Better plasticizing for heat-sensitive materials (PVC, POM, PMMA) and filled materials (glass-fiber reinforced PA, PC/ABS blends). The longer screw provides more shear and heat transfer time to achieve uniform melt temperature.

Bi-metallic screw and barrel (hardened). Required for glass-fiber filled, mineral-filled, or abrasive materials. Standard screw and barrel wear rapidly with filled materials — wear causes dimensional variation in shot weight and surface finish degradation. Confirm the base configuration if ordering for filled material processing.

Match the screw geometry to your most demanding material. A machine specified for PP that later runs 30% glass-filled PA6 without a hardened screw will show premature barrel wear within 500,000–1,000,000 shots.

Tie-Bar Spacing for Mold Size Compatibility

The tie-bar spacing (horizontal and vertical distance between the four tie bars) determines the maximum mold width and height that can be physically inserted between the bars.

Before ordering a machine for an existing or planned mold, verify:

1. Mold width < tie-bar horizontal spacing (with clearance — typically 10–20mm per side)
2. Mold height < tie-bar vertical spacing
3. Mold depth (stack height when open) < maximum mold opening stroke

A mold that physically fits through the tie bars but exceeds the minimum clamping force calculation is the other common error. Calculate required clamping force: projected part area × injection pressure × safety factor (1.25–1.5) = minimum clamping force. Under-tonnage causes flash.

Factory Acceptance Test and Shipping Packing

FAT procedure. Before final payment and shipping:

1. Dry cycle (no mold): verify all axes operate to specification, e-stop and safety gate functions, temperature control response
2. Trial run with representative mold: 50–100 shots to verify clamp force stability, cycle time, part weight repeatability (<±0.5% shot weight variation)
3. Oil system check: hydraulic oil level, filter condition, temperature at operating pressure
4. Electrical safety: insulation resistance test, earth continuity check

Shipping packing. Injection molding machines are heavy (1,500–12,000 kg). Confirm packaging includes:

• Drain hydraulic oil before shipping (avoid spill during transport)
• Protect platens and tie bars with rust inhibitor and protective wrapping
• Wooden crating with crane lift points rated to machine weight
• Machine base bolted to pallet — not just resting on it
• Sea freight requires fumigation certificate for wooden packing materials (ISPM 15)