Product structure details processing skills, four cases tell you improvement of plastic injection mo

Time:2019-07-15 09:04:52 / Popularity: / Source:

If you have experience in structural design, I believe you will know that after plastic products are molded, some thick offsets, shrink marks and thin steels will be found. These seemingly simple problems are always exposed during subsequent processing and forming, and they will be overwhelmed during test. We usually have a simple report asking plastic injection molding manufacturer to solve them themselves. In fact, many details can be optimized when doing structure, and it is very helpful for subsequent plastic injection moulding process and product molding. Now Martin, technicians from Gud Mould Industry Limited which is a China plastic injection molding manufacturer, will share technical details of product structure, and tells you how to implement improvement of plastic injection moulding process through four cases.

Case 1: Thick offset printing transition processing

plastic injection moulding process 
According to above picture, there are 2 problems.
1, left and right sides of buckle, there are steps with bottom edge, such a place is easy to get thick offset printing when molding.
2, buckle is too thick, it will cause shrinkage.
Q: What is cause of thick offset printing?
A: Thick offset printing is due to rebound of upright wall when glue is flowing there, which causes traces of pressure and cooling time that are inconsistent.
Take a simple list, you will pour a glass of water down stairs, you will find that when water flows away, there will be splashes of water through steps, and also a waterfall flowing down but not moving along stairs. Then at this corner when glue is full, it will rebound and fill, leaving traces of inconsistency between pressure and cooling time.

How to improve

1. Adjust parameters of injection molding part, like position shown in above figure. If molding machine is good, it can be improved without any structural adjustment. However, it can be designed at the time of structural design, which will reduce difficulty of subsequent plastic injection moulding process and adjust time of product testing.
2, 2 sides of buckle make transition reduce more than 60 degrees, mother button make ribs reduce.

As following is an improvement diagram

plastic injection moulding process 
According to above figure, wall thickness of female buckle is reduced to 0.8mm or more after reduced.
Q: Why is female buckle also erected without thick offset?
Answer: Female buckle has a small area of erecting and can be quickly filled up when shooting at high speed.

As following picture shows a large-area transitional reduction

In fact, this rubber-reducing transition design is a conventional design in the face of experienced structural designers of plastic injection molding manufacturer.

Case 2: Transition treatment of screw columns

plastic injection moulding process 
As shown in above figure, there are crater transitions at the bottom of self-tapping studs on left and right sides.
Q: Under what circumstances do you need to design a crater?
A: When wall thickness of stud exceeds two-thirds of average wall thickness of shell material, you need to design crater to facilitate glue and prevent shrinkage.
Q: What is shrinking?
Answer: Surface is inconsistent due to inconsistent internal molding cooling time, resulting in uneven shrinkage of plastic.
Take a simple list. When you fry eggs, you will put eggs into pot. You will find that protein around circle is cooked immediately, but egg yolk in the middle is still not cooked. This is caused by uneven heat.
When glue is formed, if thickness is same, then cooling time will be same. If thickness is inconsistent, thick central part will be cold slowly, resulting in uneven shrinkage of plastic and shrinkage marks.

As following is second improvement schematic

plastic injection moulding process 
As shown in above figure, when stud design size is high, a double layer design is required.
1, bottom of stud is designed to take oblique top bridge, which can improve shrinkage of appearance surface and reduce strength of mold cylinder. Of course, oblique top direction here still needs to be determined according to structural space.
2, stud needs to be strengthened to prevent force from bursting.

Case 3: Reinforcement simplifies design

plastic injection moulding process 
As shown in above figure, when designing reinforced ribs, a cylindrical transition design is needed to prevent rib position from shrinking. If rib position is not high, there is no need to make a cylindrical transition design.
plastic injection moulding process 
As shown in FIG
Reinforcement at A is likely to cause thin steel of mold, and it also causes problems such as formation of gas.
For improved effect at B, it is necessary to open ribs so that mold can be made into a T-shape, which strengthens mold and reduces problem of gas trapping.
As shown in above figure, when ribs that need to be made are too high, thin mold steel is also caused, how to improve.
As shown in above figure, here is same as treatment of screw column, and double-layer bridge design is used to improve problem of thin steel of mold.

Case 4: Mold insert detail design

plastic injection moulding process 
As shown in above figure, USB hole has a row break, so try to design a plane when designing structure, which can simplify plastic injection moulding process and enhance use of row life.
plastic injection moulding process 
As shown in above figure, red line position is front and rear mold parting line. Here there is a rear mold inserting through, insertion position has a C angle. Therefore when designing, it is necessary to make a step of reducing glue position, which is convenient for plastic injection moulding process and strengthen strength and service life of mold.
plastic injection moulding process 
As shown in above figure, when structural design has buckle for inserting mold, it is necessary to ensure that steel material inserted through mold is above thickness of 1.8 mm, otherwise steel material is broken by impact of injection pressure during molding in plastic injection molding manufacturer.

Sum up:

1, if surface of product has been sprayed or other surface treatment, it will help to improve post-thin offset problem. However, improvements can be made as much as possible during structural design, and other methods are backup options.
2, in structural design, not only to consider plastic strength of product, but also strength of mold, difficulty of molding, which helps project smoothly in plastic injection molding manufacturer.

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