Brownish or silvery streaks caused by thermal damage to the melt. Excessive temperature, long residence time or high shear are the main causes.
Solution guide →U-shaped silvery streaks caused by moisture in the granulate or on the mold surface. The core of the solution is correct pre-drying.
Solution guide →Matte, silvery or white marks left on the surface by air that cannot escape during filling. Solved with decompression and venting settings.
Solution guide →Color differences caused by poor pigment dispersion, masterbatch incompatibility or thermal damage. Materials with metallic pigments are particularly prone.
Solution guide →Fibers visible on the surface of glass-fiber reinforced materials; a matte and rough surface. It arises because the plastic-to-fiber shrinkage difference is 200:1.
Solution guide →Streaks, air hooks, folding, inflation, discoloration and sink marks seen in thermoplastic foam injection molding — and the separate solution logic for each.
Solution guide →Bubbles formed inside or on the surface of the part by air trapped during injection. Solved within the triangle of decompression, back pressure and venting.
Solution guide →Evacuated voids formed inside thick sections when shrinkage cannot be compensated. The transfer of holding pressure and the sizing of the gate are decisive.
Solution guide →Bubbles formed by the thermal degradation products of the material. Prevented by managing temperature and residence time.
Solution guide →Atypical advance of the flow front, unbalanced filling in multi-cavity molds and core shift. Shear-induced viscosity differences are much larger than generally thought.
Solution guide →A snake-like rough mark starting from the gate. It is caused by undeveloped frontal flow; solved with the injection profile and gate design.
Solution guide →Very fine concentric grooves on the surface, like a record. A sign of a high cooling rate; solved by increasing temperature and speed.
Solution guide →A concentric matte corona around the gate. These are micro-notches caused by excessive shear; eliminated with the speed profile and gate geometry.
Solution guide →The part does not fill completely. Cushion control, pressure/speed, venting and the runner are examined in that order.
Solution guide →Black burn spots formed by trapped air igniting spontaneously. A pure venting problem.
Solution guide →Regularly alternating matte and glossy bands on the surface. The cause lies in the material; the most effective intervention is the injection speed.
Solution guide →The visible notch and mechanical weak point where two melt fronts meet. Improved through temperature management, gate position and venting.
Solution guide →Matte/glossy areas arising from the mold surface being replicated differently. Pressure peaks, wall thickness transitions and temperature homogeneity are the main suspects.
Solution guide →Whitening caused by excessive deformation or ejection under residual pressure, and cracks that appear over time.
Solution guide →Depressions, raised spots, gloss differences or punch-through at ejector areas. Process, geometric, mechanical and thermal causes are separated.
Solution guide →Bending, cracks, fractures or sunken ejectors formed as the part comes out of the mold. Solved with the shrinkage management rule: low shrinkage for a part wrapping a core, high shrinkage at ribs.
Solution guide →Scratches formed during ejection on textured surfaces. The rule: as surface roughness increases, the draft angle must increase too.
Solution guide →Partial or complete breakage of the film hinge. The gate position, wall thickness and making the first movement while hot are decisive.
Solution guide →Weak adhesion between the two components, melting of the first component and warpage from the bimetal effect. Compatibility of the material pair is decisive.
Solution guide →The surface pulling inward opposite material accumulations such as ribs and bosses. It forms when thermal shrinkage cannot be compensated; the solution starts with optimizing the holding phase.
Solution guide →A film spilling out of the parting surface, ejectors and vents. The clamping force, pressure peaks and sealing surfaces are checked.
Solution guide →Bending/twisting as a result of different shrinkage values within the part. Mold temperature, wall thickness, material and holding are managed together.
Solution guide →Dimensions/weight varying from shot to shot are the sign of an unstable process. The melt cushion, non-return valve wear and effective holding time are checked.
Solution guide →Low-molecular-weight components separating from the melt and building up on the mold surface. It spoils surface replication and leads to corrosion and frequent cleaning stops.
Solution guide →Surface layers separating and peeling off. Weak bonding between layers caused by impurities, incompatible colorant, moisture or excessive shear.
Solution guide →Melt that has frozen in the nozzle/gate being carried into the part with the next shot; it leaves a comet-tail mark. Solutions via the nozzle temperature and a cold slug well.
Solution guide →Fine threads sticking to the part at the gate area. Common with PP, PE and materials with a narrow processing window (PA, PBT, POM).
Solution guide →Dark specks caused by wear, thermal damage or contamination. Prevented by systematic purging and regular mechanical cleaning.
Solution guide →For equipment-related problems (drying, dosing, mold temperature control, feeding), choosing the right auxiliary equipment is the permanent solution. Contact us for an on-site review and recommendation.
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