The shortcomings and anomalies that should be noticed in the injection mold will affect the quality of the product!
The shortcomings and anomalies of injection molding are ultimately reflected in the quality of the injection molded product. The shortcomings of injection molding products can be divided into the following points:
(1) insufficient product injection;
(2) Product overflow;
(3) product dents and bubbles;
(4) The product has a seam;
(5) The product is brittle;
(6) plastic discoloration;
(7) The product has silver wire, markings and flow marks;
(8) The product is turbid at the gate;
(9) product warpage and shrinkage;
(10) The product size is not allowed;
(11) The product is pasted into the mold;
(12) Material paste flow path;
(13) The nozzle is flowing.
The reasons for this and the ways to overcome it are described below.
1. How to overcome the product under-injection The lack of injection of the product is often due to the fact that the material has solidified before it is filled in the cavity, and of course there are many Other reasons.
(1) Equipment reasons:
1 hopper interrupted material;
2 The hopper neck is partially or completely blocked;
3 insufficient feed;
4 The feeding control system is not operating properly;
5 The plasticizing capacity of the injection molding machine is too small;
6 The injection cycle caused by the equipment is abnormal.
(2) Reasons for injection molding:
1 The injection pressure is too low;
2 the injection pressure loss during the injection cycle is too large;
3 The injection time is too short;
4 The total pressure of injection is too short;
5 The injection rate is too slow;
6 The flow in the cavity is interrupted;
7 filling rate is not equal;
8 The injection cycle caused by the operating conditions is abnormal.
(3) Temperature reasons:
1 increase the temperature of the barrel;
2 increase the nozzle temperature;
3 Check the millivoltmeter, thermocouple, resistance heating coil (or far infrared heating device) and heating system;
4 increase the mold temperature;
5 Check the mold temperature control unit.
(4) Cause of the mold 1 The flow path is too small;
2 The gate is too small;
3 nozzle hole is too small;
4 The gate location is unreasonable;
5 the number of gates is insufficient;
6 cold material is too small;
7 insufficient exhaust;
8 The injection cycle caused by the mold is abnormal;
(5) Material reasons: The material fluidity is too poor.
2. How to overcome the product flashover:
The overflow of the product is often caused by the defects of the mold. Other reasons are: the injection force is greater than the clamping force, the material temperature is too high, the exhaust gas is insufficient, the feeding is excessive, and the mold is stained with foreign matter.
(1) Mold problem:
1 cavity and core are not closed;
2 cavity and core offset;
3 templates are not parallel;
4 template deformation;
5 The mold plane falls into the foreign object;
6 insufficient exhaust;
7 The vent hole is too large;
8 The injection cycle caused by the mold is abnormal.
(2) Equipment problems:
1 The projected area of ​​the product exceeds the maximum injection area of ​​the injection machine;
2 The presser template installation adjustment is incorrect;
3 The mold is not installed correctly;
4 The clamping force cannot be kept constant;
5 The injection molding machine template is not parallel;
6 The rod is deformed unevenly;
7 The injection cycle caused by the equipment is abnormal (3) Injection molding conditions:
1 The clamping force is too low 2 The injection pressure is too large;
3 injection time is too long;
4 The total pressure of injection is too long;
5 The injection rate is too fast;
6 filling rate is not equal;
7 the flow in the cavity is interrupted;
8 The feed amount control is too large;
9 The injection cycle caused by the operating conditions is abnormal.
(4) Temperature problem:
1 The barrel temperature is too high;
2 The nozzle temperature is too high;
3 The mold temperature is too high.
(5) Equipment problems:
1 increase the plasticizing capacity of the injection machine;
2 make the injection cycle normal;
(6) Cooling conditions:
1The part is cooled too long in the mold to avoid shrinking from the outside to the inside and shorten the cooling time of the mold;
2 Cool the parts in hot water.
3, how to avoid product dents and vents product dents usually due to insufficient force on the product, insufficient material filling and irrational product design, dents often appear in thick-walled parts similar to thin walls. The porosity is caused by insufficient plastic in the cavity, the outer ring plastic cools and solidifies, and the inner plastic shrinks to form a vacuum. Mostly due to the fact that the hygroscopic material is not dried well, as well as residual monomers and other compounds in the material. To determine the cause of the pores, it is only necessary to observe the bubbles of the plastic product appearing instantaneously after the mold is opened or after cooling. If it occurs instantaneously when the mold is opened, it is mostly a material problem, and if it occurs after cooling, it is a problem of mold or injection molding conditions.
(1) Material problem:
1 dry material 2 plus lubricant 3 reduce volatiles in the material (2) injection molding conditions 1 insufficient injection;
2 increase the injection pressure;
3 increase the injection time;
4 increase the total pressure time;
5 increase the injection speed;
6 increase the injection cycle;
7 The injection cycle caused by the operation is abnormal.
(3) Temperature problem 1 The material is too hot to cause excessive shrinkage;
2 the material is too cold, resulting in insufficient filling compaction;
3 The mold temperature is too high, so that the material at the mold wall cannot be solidified quickly;
4 mold temperature is too low, resulting in insufficient filling;
5 mold has local hot spots;
6 Change the cooling scheme.
(4) mold problems;
1 increase the gate;
2 increase the runner;
3 increase the mainstream road;
4 increase the nozzle hole;
5 improved mold exhaust;
6 balance filling rate;
7 to avoid interruption of filling flow;
8 gate feeding is arranged in the thick wall of the product;
9 If possible, reduce the difference in wall thickness of the product;
The injection cycle caused by 10 molds is abnormal.
(5) Equipment problems:
1 increase the plasticizing capacity of the injection machine;
2 make the injection cycle normal;
(6) Cooling conditions:
1The part is cooled too long in the mold to avoid shrinking from the outside to the inside and shorten the cooling time of the mold;
2 Cool the parts in hot water.
4. How to prevent product seams (sewing stitches)
Product seams are usually caused by low temperatures and low pressure at the seams.
(1) Temperature problem:
1 barrel temperature is too low;
2 nozzle temperature is too low;
3 mold temperature is too low;
4 The mold temperature at the joint is too low;
5 Plastic melt temperature is uneven.
(2) Injection molding problem:
1 Injection pressure is too low:
2 The injection speed is too slow.
(3) Mold problem:
Poor exhaust at the seams;
Poor exhaust of components;
The runner is too small;
The gate is too small;
The diameter of the three-channel inlet is too small;
The nozzle hole is too small;
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