Industry information

Solutions for injection molding fusion margins

2021-07-03

Solutions for injection molding fusion margins

The angle of the fusion mark:

      When the molten trace is less than 135 °, a suture is generated when the suture is greater than 135 °. It can be noted that the surface trace of the suture will disappear at 120 ° to 150 °.

It is generally considered that the mass of the suture is poor than the fusion line, since the less molecules are fused from the suture after the suture formation. Improve the temperature and pressure of the suture and the fusion line region can improve its strength. When considering plastic strength and appearance, it is generally not allowed to produce suture, and the reinforcing plastic of adding fibers is more like this, because the fibers are typically parallel to the suture; and cannot span the suture.


 Solution of the fusion mark:

one. Temperature

1.Temperature of materials

(1) Improve the temperature of the injection molding machine

If the temperature is in a reasonable range, try not to increase the temperature.

(2) Improve the temperature in the flow path

The flow path temperature is mainly affected by factors such as mold temperature, flow path form, water route, and radio speed, is the result of other factors.

(3) Reduce the temperature generated by the shear force.

Shear heat will increase the forefront temperature of the melt, which is not contradictory with the fusion of fusion, and shear heat is usually related to the relationship between the radio speed, GATE form, the flow path cross section, the material, the surface processing of the mold, and is difficult to control.

2. Temperature of the mold

(1) Improve the original temperature of the mold, this is one of the main methods of improving the fusion mark, but it is necessary to pay attention to whether there is an optional oil temperature machine, which requires the gap between the guide post, sleve package, causes the burns due to the thermal expansion of steel. Or inconsistenciation; need to consider whether the surface of the mold is heat treatment, mold life, molding cycle, cooling efficiency, and the like.

(2) Maintain the temperature of the work point.

Second. Speed

1. Injection speed increases the injection speed of the injection molding machine. The increase in injection speed is advantageous to improve the fusion mark, and even high-speed motor can be improved, but it is necessary to consider the appearance factors such as the surface requirements such as a spray, whether the clearance of overheating materials, whether the product will Because of the increase in radio, whether there is a flash, whether there is a stress mark, resulting in too high of the incident pressure.

2. Speed in the flow path

(1) Reduce the cross-sectional size of the cross-sectional area, if the cutting cross-section size may result in shrinkage and size, increased pressure, and the molding of the formation, deformation, burr, etc.

(2) Reduce the length of the flow path (excluding the thermal track) with shorter flow path length and smaller cross-sectional size under the conditions of product quality, and get the best cast system This is the problem that each CAE engineer must consider. If your flow path has been designed reasonable, reduce the length of the flow path, usually the space is not large. And this factor is improved to the fusion mark does not seem too obvious.

3. Speed in the cavity

(1) Improve the coolness of the cavity.

(2) Increase or decrease the wall thickness of the product to change the flow of the material. One of the factors that improve the fusion mark, the premise of changing the thickness of the thickness is the consent of the customer or related unit.

3. Pressure

1. Reduce the injection pressure injection pressure, the injection speed is not on, which is inconsistent with the income rate.

2. Increasing the short-term pressure pressure If the fusion mark is filling the end, this method has a significant effect, and the intensity of the binding is enhanced.

Four. Exhaust

1. Take advantage of the exhaust capacity of the flow molding machine (when the injection molding machine has this function)

2. Increase the exhaust tank of the mold. This is one of the improvement factors. If the insertion of the intake gas in the binding line is added more directly, the joint line region can be analyzed by MoldFlow, this result is very accurate.

3. Locally increase the overflow hole. Very good way, sometimes very effective. The cold material at the binding line can be brought to the overflow hole, and the post-trimming. It is important to note that many places of the binding lines are especially the surface, and it is difficult to add the cavity. And consider whether the trim is convenient, trimmed, and after the quality, etc.

V. gate

1. Change the position of the gate

2. Change the size of the gate

3. Change the shape of the gate

    The gate factor is the most direct factor, and the previous period will be introduced into the MoldFlow optimization. The combined line leads to the non-extra-extra-view surface or improves the quality of the combination. If the test is improved, it is difficult to change, and the mold may change, even if there is one Problem solves another problem. And will affect delivery, increase the number of test modules, improve the cost of the test mode (not low per test mode).

Sixth. Other

Using sequential injection molding

   Very good way, use moldflow to optimize the gate position and the binding line position, select reasonable delay time, and improve the binding line well. This is common in the TV surface and other mirror processing 8,000 appearance requirements. It is necessary to consider timing control to adopt a hot flow valve gate, and the number is much higher than conventional, and the cost of thermal fluid is high. If the production is not large, the cost is the main consideration. And even if it is used in this way, there will still be one to two bond lines. It is necessary to consider the presence of a position and fuel treatment method of fusion traces. It is also important to note that the timing controlled molding transfer and traditional molding is different. It is not usually slow to slow and slow down.

2. Use vacuum injection molding

There are some ways to add:

 1. Optimize the design in the previous period, try to avoid the joint line in a significant appearance or the weak structure, and make a large angle of the melt front edge binding.

 2. Make the binding line in the preior period of the filling process, such as the injection time for 2 seconds, the first front edge binding time of the melt is 1 second.

 3. Do not affect the quality of the filling, try to reduce the number of GATEs.

 4. Mechanic Wem (core) Do biting flowers (coarse pattern particles change the direction of the high molecular chain when the melt is integrated, making it a messy conjunction).

 5. If the front of the melt is mostly a cold material, you can try the extension of the flow channel cold.

 6. If the binding line is considered to be in the weak structure, it can be considered to change the flow rate of the flow along the flow rate of the melt to change the binding position.

 7. Add electric heating rods, the principle is also the degree of increasing the disorder of the molecular chain at elevated binding temperature.

 8. Variable die temperature technology, such as emergency heat, high temperature nitrogen, infrared, electromagnetic surface instant heating, etc. MoldFlow6.2 has an emergency heat control analysis module. This method is also an increase in the temperature of the joint, and the effect is very good. However, the cost is not low, the equipment, technology, and steel materials are high, and some patent issues are involved, and it is difficult to apply.

 9. IMD technology (including IMR, IMF) directly covers surfaces, more applications on electronic products such as Notebook. Its cost and technical requirements are high. Application range is limited.

 10. For products that must be binding lines and that it is really difficult to improve can recommend that customers or related departments use spray paint or change plastics color, this is helpless, for the next decision (but sometimes there will be this situation).

 Fusion marks, shrink, deformation, etc. are the most common quality abnormalities in the molding. There are many factors affecting their results, involving product structural design, mold structure, molding equipment, molding process, polymer material performance, etc., each factor has different degrees of impact, and interacting, thus solving each product The way is different, which is unfair. We need specific analysis of specific issues, looking for the causes of problems, think about the main influencing factors, and to find the most direct solution. Thus solve the problem with a shorter time. More importantly, it is to prevent the problem that MoldFlow optimization design in the product design phase, enabling the software to actually combine, and the possible problems will be processed in the previous design, and the subsequent issues are much less.