The debugging of plastic injection molds must be initiated according to mold trial notices issued by either the external cooperation departments or the production departments. The first step involves reviewing two sets of drawings: one is the product drawing for mold testing, and the other is the mold drawing itself.The product drawings help understand the products' material specifications, geometric dimensions, and functional and aesthetic requirements—such as color, spots, impurities, weld lines, and sink marks. The plastic injection mould drawings reveal key information about the required equipment, technical parameters, and whether the necessary tools and accessories are complete. Once reviewed, the drawings are passed to the next processes.
All equipment used for the plastic injection molding trials must be thoroughly inspected. This includes the oil circuits, water circuits, electrical connections, and mechanical movement components. Equipment maintenance must be conducted according to standards.
Technical parameters to check include:
The diameters of the locating rings.
Radii of the nozzle tips.
Nozzle orifice diameters.
Minimum and maximum mold thicknesses.
Mold opening strokes.
Tie bar spacings.
Ejection mechanisms, etc.
These parameters must meet the requirements of the mold trials. The trial equipment should match the actual production machines, as factors like temperature fluctuation, pressure variability, cycle times, and transmission stability can all affect product quality. Using machines with significantly higher clamping forces during trials, then switching to those with lower forces in production, may necessitate adjustments to molding conditions.
Verify the specifications, grades, brands, additives, and color masterbatches of the plastic materials to ensure they meet requirements. Materials with high moisture content should be properly dried. The correct material ratios must be determined. Ideally, the materials used should match what's specified in the design drawings, as the plastic injection moulds are designed based on the physical and mechanical properties of those particular resins. However, materials with good flowability, fast curing properties, and excellent thermal stability may also be used to test the mold structures. This ensures that features like wall thicknesses, rib distributions, and fillets are accurately represented, serving as references for potential mold modifications.
Before mounting the plastic injection molds onto injection machines, they should be carefully inspected against the mold drawings to identify any potential problems and carry out necessary repairs.
Checks should include:
Overall dimensions.
Locating ring sizes.
Sprue inlet diameters.
Compatibility of the sprue balls with the nozzles.
Cooling water inlets and outlets.
Heights and widths of clamp plates and spacers.
The gating systems and cavities should be examined by opening the molds. When separating the cores and cavities (moving and fixed halves), make sure to mark the directions to avoid incorrect assembly. Connect cooling circuits or heating elements for testing. If the parting surfaces use hydraulics or motors, test those systems as well.
Tools used for mold trials are specialized and should be stored in portable toolboxes for easy access. Every debugging technician should have a complete set.
Essential tools and accessories include:
Wrenches and spacer blocks.
Thermometers for checking plastic injection moulds' temperatures.
Calipers for dimensional checks.
Product inspection tools.
Common items like copper rods, copper sheets, and sandpaper.
Inserts are particularly important. Various inserts such as metal, plastic, rubber, and paper inserts, as well as shaping parts to maintain form after molding, must be carefully inspected. Failure to do so could damage the plastic injection molds and cause irreparable losses.
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