Frequently Asked Questions about Hot Runner System

Time：2022-04-25 08:54:43 / Popularity： / Source：

Problem: Cavity is not filled

Reasons: Melting temperature is too low; injection pressure is too small; gate is too small; hot nozzle is too small; mold temperature is too low; nozzle opening of melt cylinder is too small; hot nozzle is blocked.
Treatment: Increase temperature of hot nozzle and manifold, increase injection pressure, expand gate, increase mold temperature, install a large-size hot nozzle, increase discharge port of melt cylinder, and remove blockage.

Problem: Hot nozzle casting

Reason: Insufficient draw-back (reverse cable), too high melting temperature, too large gate, insufficient gate cooling, and incorrect hot nozzle type selected.
Treatment: Increase amount of draw-back (reverse cable), reduce temperature of hot nozzle or mold, select appropriate nozzle, and process correct gate size.

Problem: Hot nozzle does not work properly

Reason: There is a problem with heating wire or thermocouple, hot nozzle is blocked, expansion of hot nozzle is calculated incorrectly.
Treatment: Check/replace heating wire, check/replace thermocouple, clean hot nozzle, recalculate and process expansion of hot nozzle.

Problem: Poor color change effect

Reason: Color operation procedure is incorrect, hot nozzle type is incorrect.
Treatment: Refer to operation guide for color-changing operation procedure, select type of hot nozzle correctly.

Problem: There are more flashes on product

Reasons: Injection pressure is too high, temperature is too high, flatness of sub-template is poor, clamping force is insufficient.
Treatment: Reduce injection pressure, lower temperature of hot nozzle/sub-template/mold, and increase clamping force.

Problem: Scorch marks are produced on product or in gate area

Reasons: Insufficient air exhaust on mold, too fast injection speed, wrong gate size, and insufficient material drying.
Treatment: Increase exhaust, reduce injection speed, increase "J" size on mouth and socket size, dry material.

Problem: Gate cooled too early or solidified in the middle of processing cycle

Reason: Insufficient melt temperature, too small gate, excessive cooling of gate, too large direct contact area between hot nozzle and fixed mold, incorrect gate profile or incorrect type.
Treatment: Increase temperature of hot nozzle, increase temperature of mold in gate area, check nozzle socket of hot nozzle to ensure that direct contact area is minimized, check gate contour processing, correct gate contour if necessary.

Problem: Moire appears on corresponding part of product

Reason: Mold is too cold and melt temperature is not enough.
Treatment: Increase mold temperature and melt temperature.

Problem: Occasionally squeeze out cold spots from head of mouth core

Reason: Excessive heat loss from hot nozzle head
Treatment: Reduce direct contact area of head to a minimum.

Problem: There is plastic stuck to tip of bushing tip and direct mouth tip

Reason: Contact area between bushing tip and mold is not enough, heat dissipation is not enough.
Treatment: Increase contact area and enhance heat dissipation effect.

Problem: Thermal manifold cannot reach set temperature

Reason: Thermocouple has poor contact or failure, heating wire is open, heating wire connection is too loose or too short.
Treatment: Check whether thermocouple contact is normal and wiring is correct. Check heating wire loop.

Problem: Heat manifold heats up too slowly

Cause: A heating wire is open or wiring is too loose, air gap of heat distribution plate is insufficient, heat insulation gasket is excessively cooled, and thermocouple is in poor contact.
Treatment: Check all heating wires, increase air gap, require at least 10mm, or use a heat shield, add a heat shield to fixed mold fixing plate (bottom) or reduce cooling of fixed mold fixing plate, check whether thermocouple is in good condition.

Problem: Temperature of heat manifold is unstable

Reason: Poor contact of thermocouple.
Treatment: Check thermocouple.

Problem: There are metal fragments in melt

Reason: Fragments on screw of injection molding machine, metal fragments in injection material
Treatment: Remove metal fragments and repair impurities in plastic filter of screw.

Problem: Leakage at junction of hot manifold and hot nozzle

Reason: Expansion calculation is incorrect, W surface processing height is inconsistent, material of fixed mold fixing plate (bottom plate) is too soft, temperature of heat splitter plate is too high for a short time, and there is a problem with the installation of "O" sealing ring.
Treatment: Recalculate and check expansion, check and correct height of W surface, replace fixed mold fixing plate (bottom plate) with appropriate hardness, replace damaged parts and "O" seal ring.

Problem: Thermal splitter plate compensates for plug leakage glue

Reason: No spacer.
Treatment: Install spacers.

Problem: Oil (gas) cylinder does not work

Reason: No air/hydraulic oil enters cylinder, pneumatic/hydraulic cylinder system is stuck, system pressure is insufficient.
Treatment: Check pipeline and pump for leakage or blockage, check cooperation of cylinder and piston, check whether feed pipeline is excessively bent, whether piston and valve needle are flexible.

Problem: Cylinder system is bitten to death

Reason: Cylinder block, heat splitter plate, hot nozzle, etc. are not concentric, and fixed mold fixing plate (bottom plate) has too much heat.
Treatment: Adjust concentricity of cylinder block, splitter plate, and hot nozzle to increase cooling around cylinder block.

Problem: Cylinder block gets stuck after overheating

Reason: Cylinder block, heat distribution plate, hot nozzle, etc. are not concentric, and fixed mold fixing plate (bottom plate) has too much heat. Gasket and valve pin fixing nut are friction.
Treatment: Adjust concentricity of cylinder block, heat splitter plate, and hot nozzle, increase cooling around cylinder block, adjust gasket and valve pin fixing nut.

Problem: Glue is leaking around valve needle bushing

Cause: Valve pin bushing on heat manifold is too loose.
Treatment: Check diameter, height of heat distribution plate hole and valve pin bushing.

Problem: Sticky material on valve needle head

Reason: Valve needle does not emit too much heat.
Treatment: Reduce temperature of the hot nozzle and gate, increase the cooling time

Gud Mould Industry Co., Ltd