When sourcing used machinery, you must prioritize the clamping force (tonnage) and shot weight to ensure they meet your production requirements. Inspect the screw and barrel for wear and tear, as these are critical for melt quality. Verify the tie-bar spacing to ensure your existing moulds will fit. Additionally, check the controller brand and version (e.g., Techmation, KEBA) to ensure parts and programming support are still available. Always request the original machine manual and maintenance logs to assess the equipment's history.