How to Solve the Splay Mark of PC Transparent Cup?

Case: injection splay mark

A small home appliance assembly factory specializing in blenders needs to produce a transparent PC blender with a single weight of 1668g.


However, during the mold trial, there were splay marks on the button holes on the side of the main body of the blender. And then during the trial production, there were splay marks at the unfixed positions around the body. The mold masters, engineering designers, and injection molding masters of the injection molding factory couldn’t find the reason.


Then the person in charge of this final assembly plant approached us. Our technician guided them to adjust the parameters, tried about 10 beers, carefully observed the mold and machine inspection data, and exited the injection station to shoot a few times to confirm the quality of the melt. Based on the above test, our technician gave them the following solutions:

(1) The insert at the puncture position of the sideways mounted button needs to add an exhaust part.

Because when the material flow passes through here, the mold has a puncture position, and the air flow is not discharged smoothly, forming a shot. The air is trapped, so the air flow needs to be led to the outside of the mold cavity. Then the separated molten glue flow can be better combined.

Replace contactor▼

Replace contactor
Replace heating ring

Replace heating ring▲

(2) Replace the heating ring and control contactor of the third section of the barrel.

Because the heating ring of this section is broken, the temperature displayed on the control screen is brought up by the two sections next to it. Therefore, when the PC material is melted in the barrel with defective parts, the quality of its melted glue is uneven,with gas and raw material particles inside. The injected PC material is generally unqualified, and there will be splay marks.

After 3 hours, the mold master corrected the exhaust of the mold as required. The injection molding master also replaced the broken heating ring and AC contactor.

Injection molding production of PC materials, especially Chimei 110, requires more precise control of mold temperature and melt temperature. After confirming that all aspects are met, our technicians began to guide them to try beer.

Set the melt speed to 40, the pressure to 100, the back cord to 3, and the injection speed to 20∽50. After trying 5 beers, the person in charge looked at the product and said it can be ready for mass production.

The machine was in normal production, and our technicians explained to the technicians of the injection molding factory the reasons for the formation of splay marks on the injection molded product within an hour of on-site observation.

Reasons for the formation of splay marks in injection molding products

There are mainly the following five aspects:
① Mold      ② Adjustment      ③ Design      ④ Machine       ⑤ Material

1. Mold

(1) The water entering the mold is too small, forming spray splay marks.

(2) The exhaust of the mold is poor, forming trapped gas splay marks.

(3) In the nozzle flow channel, the product has sharp dust corners, and the material flow produces decomposed splay marks or residual rubber splay marks.

(4) The hot runner has dead corners and residual glue, which decomposes the splay marks.

(5) The position of the temperature sensing line of the hot runner is improper, or the temperature control line and the temperature controller are abnormal, causing the temperature to be too high and decomposing the splay marks.

(6) The hot runner is blocked, resulting in splay marks.

(7) There is water seepage in the mold, which causes splay marks.

(8) The temperature of the hot runner is too high, and the inaccurate control causes the splay marks.

(9) Mold nozzles with caps, causing cold rubber splay marks.

(10) The core of the mold for round products is eccentric, resulting in uneven splay marks.

Mold reasons for Splay Marks

2. Machine adjustment

(1) The back pressure of the melt adhesive is not set properly. If it is too low, there will be water vapor splay marks. If it is too high, there will be decomposition splay marks.

(2) The glue injection speed is too fast, and the air is exhausted.

(3) Improper setting of the injection speed and position in the front section.

(4) The melting speed is too fast, and the air is involved to cause or decompose splay marks.

(5) The tail section of the glue injection is not finished slowly, resulting in trapped air and splay marks.

(6) The nozzle is half blocked, causing the ejection of splay marks.

(7) The mold temperature is too low, causing the cold glue splay marks.

(8) The exhaust groove on the parting surface of the mold is blocked, with air trapped. So it should be cleaned every 4 hours.

(9) The glue pumping position is too long, and the air is sucked in to cause the glue injection splay marks.

(10) The temperature of the barrel is too high, and the plastic decomposes splay marks.

(11) The temperature of the nozzle is too low, causing the cold glue splay marks.

(12) The temperature of the baking material is not set properly, and the drying time is not long enough to cause the water vapor splay marks.

Machine adjustment reasons for Splay Marks

3. Design reasons

(1) The design of the product nozzle of the mold is not smooth and the glue is inserted, causing the residual glue splay marks.

(2) The size design of the nozzle flow channel of the mold is too small, causing the material flow to spray.

(3) The water entry of the mold (needle point, square, circular, fan-shaped) is not designed properly, or the size is too small, resulting in the injection of glue.

(4) The exhaust position of the parting surface of the mold is improperly designed, or it is not deep enough to form trapped gas splay marks.

(5) The difference in product thickness is too large, resulting in material flow and splay marks.

(6) The design of the water entry position of the mold is not suitable, causing the injection splay marks.

(7) Exhaust is not designed behind the material flow at the mold penetration position, resulting in trapped air and material waste.

(8) There is no air-introducing groove in the middle air trap of the mold flow product, and the air trapped splay marks is formed by the gas passing through the middle to the back.

Design reasons for Splay Marks

4. Machine reasons

(1) Three small pieces, the barrel was damaged, and the quality of the pre-molding was not good enough, forming a splay marks.

(2) The injection nozzle and the mold nozzle R do not cooperate well, and the air is mixed into the nozzle.

(3) The heating pipe of the material barrel is abnormal, or the fan is broken, the material is not dried well, causing the water vapor splay marks.

(4) The heating temperature of the gun barrel is abnormal. And one section is broken, which is brought up from the side, resulting in the splay marks caused by the unqualified pre-molding quality.

(5) The back pressure valve is abnormal, which leads to the splay marks caused by the unqualified quality of the melt.

Machine reasons for Splay Marks

5. Material reasons

(1) The splay marks caused by not baking the material according to the baking temperature and drying time.

(2) There are foreign matter and miscellaneous materials in the material.

(3) The material particles are too large, and the particles are uneven, resulting in poor pre-plastic quality.

(4) The raw materials and nozzle materials are not evenly mixed, resulting in poor pre-molded quality.

(5) The quality of the granulated modified material is not good, and the material is not dried enough.

(6) The reaction splay marks caused by the blending of different batches of modified materials from different manufacturers.

(7) Splay marks caused by unclean nozzle or too much dust.

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