Hot Runner Serial Column 3

 

Hot Runner FAQ

 

No fill cavity

Reasons: low melting temperature, small injection pressure, small gate bush, small nozzle, low mold temperature, the nozzle of melting barrel is too small and nozzle clogging.

Solutions: increase the temperature of the nozzle and manifold block, increase the injection pressure, expanding the gate, raise the mold temperature, the installation of large-sized nozzles, enlarge the discharge port of the melting barrel and clear the clog.
 

 

Nozzle salivation

Reasons: withdrawing is not enough, high melting temperature, large gate bush, insufficient gate cooling, and the wrong choice of nozzle.

Solutions: enlarge the withdraw volume, lower the nozzle or mold temperature, choose the right nozzle, process the correct size of gate, contact us when choosing a proper nozzle.
 

 

Nozzle work abnormally

Reasons: heating wire and thermocouple problems, nozzle clogging, and the calculation of nozzle swell capacity is not correct.

Solutions: check/replace the heating wire or thermocouple, clear the nozzle, recalculated and process the swell amount of the nozzle.

 

Poor results for color-change

Reasons: incorrect color-change operating procedures, and the wrong choice of nozzle.

Solutions: use the operating Manuel for reference and contact us when choosing a proper nozzle.

 

More flash products

Reasons: large injection pressure, high temperature, poor quality of the parting line formation, insufficient clamping force, the mold base plate or the fixed clamp plate and the moving clamp plate (top clamping plate)of the injection molding machine are not flat.

Solution: reduce the injection pressure, and lower the temperature of the nozzle/manifold block/mold, increase the clamping force, dressing the moving clamp plate/ fixed clamp (top clamping plate) of the injection molding machine.

 

Burn mark on the products or at the gate area

Reasons: insufficient mold exhaust, high injection speed, wrong size of gate bush, insufficient material drying.

Solutions: increase in exhaust, lower the injection speed, increase the gate ”J” size, dry the material.

 

Excessive wear of nozzle sharp when inject glass fiber materials

Reason: core material of the nozzle is too soft.

Solution: replace it with the carbide nozzle core.

 

Too big gate mark

Reasons: big gate bush, wrong choice of nozzle and incorrect gate contouring.

Solutions: downsize the gate bush, choose the proper nozzle.

 

Gate cooling starts too early, or in the middle of processing cycle that starts to solidify

Reasons: low melt temperature, small gate bush, excessive gate cooling, and nozzle in direct contact with the fixed mold surface is too large.

Solution: increase the nozzle temperature, increase the temperature of the mold at the gate area, and check the nozzle to make sure the direct contact surface is the smallest.

 

Weld marks appear on large flat products

Reason: the wrong choice of nozzle.

Solution: choose the proper nozzle.

 

Moire appears at the products gate area

Reasons: mold is too cold, the melt temperature is not enough and there is cold material in the runner.

Solutions: improve the temperature of the mold and the melt.

 

Cold material appears in the products

Reasons: the wrong choice of nozzle and the nozzle sharp is too cold.

Solutions: choose the proper nozzle.

 

Cold slug crowded out occasionally from the nozzle core or sharp

Reason: excessive heat loss of the nozzle sharp.

Solutions: reduce direct contact area of the sharp down to the smallest, choose the proper nozzle

 

There are plastics adhered to the bushing head and the front of the sprue 

Reason: insufficient contact area of the bush mouth head and the mold, insufficient heat radiation.

Solutions: increase the nozzle contact area and enhance the heat dissipation.

 

Hot manifold can not reach the set temperature

Reasons: thermocouple is in bad contact, the heating wire circuit, and the heating wire connection is too loose or too short.

Solutions: check if the thermocouple is in good condition and the connection is right, and check the heating wire circuit.

 

Hot manifold temperature increases too fast

Reasons: one of the heating wires is in a circuit or the connection is too loose, inadequate air gap of the hot manifold, thermal insulation pad over-cooling and thermocouple is in bad contact.

Solutions: check all the heating wires, add the air gap to at least 10mm, or use the thermal insulation board, add thermal insulation broad to the fixed clamp plate or decrease the cooling to it.

 

Hot manifold block temperature instability

Reason: thermocouple is in bad contact.

Solution: check the thermocouple.

 

Melt has metal fragments in it

Reason: debris on the screw injection molding machine, Metal fragments in the plastic material.

Solutions: remove the metal fragments, repair the screw, and filter out impurities in the injection molding machine.

 

Material leakage on the joint surface of hot manifold block and the hot nozzle.

Reason: wrong calculation of swell amount, inconsistent processing high degree of W surface, fixed clamp plate too soft, in a short time the hot manifold temperature is too high, and the O-rings installed incorrectly.

Solutions: recalculated and process the swell amount, check and correct the W surface, replace the fixed clamping plate with a harder one, replace the damaged parts and the O-rings.