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Causes of Splay Marks in Injection Molding Products

In this post, we’re going to analyze the causes of splay marks in injection molding products from the 5 points of view including:

  1. Mold
  2. Machine Setting
  3. Design
  4. Machine
  5. Materials

Causes analysis of splay marks

1. The first main reason why injection molding products have splay marks - Mold

(1) The water entering the mold is too little, 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 material or residual rubber.

(4) There are dead corners and residual glue in the hot runner , 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 clogged, resulting in spray 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 nozzle with cap, cold glue splay marks.

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

2.The second main reason why injection molding products have splay marks - Machine Setting

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

(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 the 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 injection 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, and the gas is 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 injection marks.

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

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

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

Splay mark

3. The third main reason why injection molding products have splay marks - Design

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

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

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

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

(5) The thickness of the product is too different, causing the material to flow and spray.

(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 splay marks.

(8) There is no air-inducing groove in the middle of the mold flow product to make the gas discharge from the middle to the back.

4. The fourth main reason why injection molding products have splay marks - Machine

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

(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, resulting in 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 unqualified pre-molding quality and splay marks.

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

5. The fifth main reason why injection molding products have splay marks - Material

(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.

(3) The material particles are too large, and the particles are uneven, resulting in splay marks caused by 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) Unclean nozzle or too much dust.