Two color injection molding principle target product feasibility analysis and Countermeasures

1 Overview
With the growth of social economy and the improvement of people's material and spiritual civilization, TV has become a necessity of daily leisure and entertainment. Through research, before consulting the performance and quality of TV sets, consumers are often attracted by the colorful and personalized appearance. Therefore, how to attract consumers' attention at the first time requires enterprises to work hard on the appearance and modeling. The development trend of TV products in the market today is: green environmental protection, crystal clear face frame and diverse colors It's not easy.
Two color injection molding principle
Two color injection molding is a special plastic injection molding method developed in recent years to adapt to the new trend. It can form products composed of two different colors or different plastics (such as a hard plastic and a soft plastic). In fact, it is a "insert molding" process of in mold assembly or in mold welding.
Its forming principle is to plasticize two different kinds of plastics in two cylinders respectively, and then inject them into the mold cavity to form plastic parts with two colors on the surface.
As early as the early 1970s, this technology has been proposed by Garne R and Oxley of ICI company in the United Kingdom, and then applied to the actual production by ICI company, and applied for related product patent technology.
3. Target feasibility analysis
1) Injection molding factory has successfully developed high gloss traceless technology, which can make face frame with strong stability and good strength. We can learn from Samsung's developed integrated molding two-color injection molding technology.
2) Cost control
From the mold cost, injection processing costs, injection material costs, secondary processing costs, design management costs to consider, are executable.
4. Feasibility analysis and evaluation of various countermeasures
1) the first mock exam is two chambers, and the experience is not good enough.
2) the first mock exam is two chambers, and the experience is not enough.
3) The positioning of the guide sleeve of the circular guide pillar is less difficult, less cost, short time and poor effect.
4) The positioning of the square guide post guide sleeve has the advantages of small difficulty, low cost, short time and poor effect.
5) The ejection structure is on the moving die side, which has the advantages of small difficulty, low cost, short time and poor effect.
6) Ejection structure in the fixed mold side, lack of experience, learn from, difficult, expected to be effective.
7) Cold channel rubber mouth, no difficulty, long time, low cost, poor effect.
8) Hot runner needle valve rubber mouth, no difficulty, long time, low cost, poor effect.
9) To ensure that the first cavity in the dynamic mold, lack of experience, learn from, difficult, expected to be effective.
5. Formulate countermeasures
The first mock exam is: three modules, two modules, one is external and the first; the other is the guiding of the square guide pillar; the ejection structure is placed on the fixed mould core; the design of the fixed mould push plate.
The first mock exam is the structure of the core (one mold, two chambers, first and later).
In the first mock exam, the mold structure is decided by the two plate two cavity structure in the form of CI. However, there are differences when determining the forming sequence. If the outer layer is first molded, the injection molding process is required to be high, and at the same time, the risk of "one damage and one loss" is also a danger. If the inner layer is first formed, the outer layer will use the side glue, which will not only leave glue marks, but also increase the difficulty of subsequent adhesive mouth machining.
After incentive discussion and comprehensive consideration of the advantages and disadvantages of the two schemes, the technical members finally decided to form the outer transparent part for the first time, with simple product structure and no screw column position, rib position and other structures; after 180 degrees of rotation, the inner opaque part for the second injection molding has many screw column position, rib position and other structures, and the mold core adopts the same shrinkage.
Countermeasure 2: positioning system (square pillar guide sleeve positioning)
In order to meet the requirements of the injection molding machine, the diagonal dimension of the mold should be smaller than the diameter of the turntable of the injection molding machine, and the precise positioning of the mold after the rotation action should be considered. In order to meet this requirement, the technical members broke the conventional design idea, and finally decided to use a square guide pillar and guide slider on each side of the mold to replace the traditional round guide pillar and guide sleeve positioning structure on the four corners of the mold; in addition, a square locator was added on the parting surface in the center of the mold cavity to ensure the accurate positioning of the mold.
The maximum dimension of the final mold is 1600 (1750) mm × 1150 (1320) m × 860.5 m, and the four corners are designed with 115m m × 45 ° chamfering, so that the distance between the two chamfering angles of the mold is 1885 mm, which is smaller than the diameter of the turntable of the injection molding machine of 2000 mm.
Countermeasure 3: after the second injection molding of ejector structure (ejector structure is placed in the fixed core), because there are more screw columns and ribs on the side of the fixed core, it will produce greater wrapping force, and the wrapping force is far greater than that of the moving core, so the plastic part will stay on the fixed core after opening the mold.
Considering that the weight of the moving die should be within the bearing range of the hanging turntable, the technicians found a new way to adopt the inverted structure of the fixed die and the moving die, and designed the ejection mechanism at the corresponding position of the fixed die core on the side of the fixed die. In order to ensure the ejection balance, pipe jacking was designed at all the screw posts of the plastic parts, and the ejector was designed at the appropriate position near the ribs Two ejector cylinders are used to drive the ejector mechanism to move back and forth.
Countermeasure 4: special structure (design of fixed die push plate)
After the first injection molding, the wrapping force of the fixed mold core side will be greater than that of the moving mold core side, and the plastic part will stay in the fixed mold core after opening the mold, which does not meet the requirements of action planning (after the first injection molding and opening the mold, the plastic part should stay in the moving mold core, that is, the turntable side of the injection molding machine). For this reason, after thinking hard and comparing with various schemes, the designer finally decided to set up a fixed mold push plate around the fixed mold core. At the same time of opening the mold, the push plate pushes the product due to the effect of the spring, so that the product stays in the moving mold core, and finally solved the problem.
Countermeasure 5: gating system
The hot runner needle valve gate is used in the mold, which can not produce the material handle (nozzle material) and no raised gate trace on the plastic parts, will not affect the appearance of the product, and there is no waste. The important thing is that it is very helpful to improve the surface defects of the plastic parts, such as weld marks, gas marks and so on.
6 Effect Inspection
Through the efforts of 2 months, the first trial was successful! The outer layer of the product is transparent, high gloss, no weld mark, shrinkage mark and other injection defects, and the inner layer of the product is opaque and red. Compared with foreign brand products, the two can be comparable; and the appearance quality of the product has been recognized by the quality personnel.
1) Compared with the two-color spray paint processing products, the two-color traceless injection molding products have a great improvement in the qualification rate, eliminating the traditional injection molding process of polishing, spraying, color coating and other secondary processing procedures, and the secondary processing cost is 21% less than the two-color spray paint processing In addition, due to the use of two-color traceless injection molded surface shell on the flat-panel TV, the beauty of the TV is greatly improved, and the sales price of the similar TV is 200 yuan / set higher than that of similar products.
2) By omitting the spray painting process, the delivery period can be shortened and the problems such as insufficient spray painting ability in peak season and difficult recruitment can be solved.
3) Product environmental protection, good appearance, popular with consumers, to meet the needs of product diversification, high quality, high added value.