How to choose a used injection molding machine?

Author:J           Date:2025-09-15

Core Parameters Precisely Matched

Injection Volume Matching the Product: Ensure the injection volume of the used injection molding machine is sufficient to meet your product weight. It is generally recommended that the total product weight (including runners) does not exceed 70%-85% of the machine's rated injection volume (based on PS). For non-PS materials, perform the following conversion:

Non-PS Plastic Injection Weight = (PS Injection Weight × Specific Gravity of the Plastic) / 1.05

Sufficient Clamping Force: Insufficient clamping force causes mold expansion and flash. Rough estimate: Required clamping force (tons) > Projected area of part (mm²) × 40 / 9800. Precise calculation requires consideration of plastic properties, part geometry, etc.

Injection Pressure and Speed: Select based on material flow requirements. High-viscosity materials require higher injection pressure.

Physical Compatibility Between Mold and Machine

Mold Size Compatibility: Ensure mold length, width, and thickness fit within the injection molding machine: Mold width ≤ tie bar spacing; Mold thickness must fall between the machine's minimum and maximum mold thickness limits; Mold height should not exceed the platen height.

Verify Installation Details: Check alignment between mold locating rings and machine locating holes; verify match between nozzle ball radius and gate sleeve ball socket radius; confirm mold sprues align with machine platen screw holes.

Comprehensive Equipment Condition Inspection

Inspect Exterior and Interior: Thoroughly examine the machine's exterior for visible damage or corrosion. Open the electrical control cabinet to assess dust accumulation and check wiring for signs of aging or burn marks. Focus on wear conditions of critical moving components such as the tie bars, screw, and barrel.

Review records and history: Request maintenance logs whenever possible to understand the machine's service life and past malfunctions. Inquire about the operating environment (e.g., temperature-controlled, dust-free) and production history (e.g., whether it was overloaded).

Test performance: Conduct a test run if feasible. Verify clamping force linearity and repeatability at different settings (e.g., 20%, 50%, 100%), observing pressure stability. Apply the same method to test the linearity of injection speed. Monitor for abnormal vibrations, noise, oil leaks, or other irregularities during operation.

Focus on Brand and After-Sales Support

Prioritize Reputable Brands: Prefer well-known brands with high market share and positive reputation. Their spare parts supply and technical support are typically more reliable.

Verify Legal Origin: Cross-check equipment nameplate information and request proof documents like purchase invoices or original contracts from the seller to ensure clear, legitimate equipment sourcing and avoid counterfeit goods.

Clarify After-Sales Service: Confirm with the seller whether warranty periods, technical support, and maintenance services are provided, and include these commitments in the purchase contract.

More Articles