The advantage of a two-color vertical injection molding machine is that it optimizes the copolymerization of soft and hard materials and realizes the molding of multiple materials at one time through a mechanized and automated process. It can be used for a variety of product designs in all industries. Colorful graphics and stylish finishes are molded, thus increasing product functionality and market value. Two-color injection molding is mainly used to produce multi-color chips. Bicycle two-color handles, hardware multi-color overmolded handles, two-color watch straps, two-color toothbrush handles, and multi-color hard rubber overmolded products.
So what are the critical points of the process of two-color injection molding?
1. The shrinkage rate of the two-color mold depends on the A-shot products. Because the A shot product has already held the whole plastic product, the B shot product will not shrink a lot. If A is complex and B is soft, because A shot has formed most of the products, the shrinkage rate of B shot products is generally set to 5‰ can be.
2. In the design of the B-shot mother mold, to avoid the secondary mother mold rubbing, a suitable product has been formed in the glue position. You can design a part to avoid being empty. But we should carefully consider the strength of each sealing bit, i.e., whether there will be in the injection, the plastic deformation under the considerable injection pressure, resulting in the second injection of phi.
3. Two-color mold usually needs two master mold pressure once the product seals glue. Generally speaking, the height of the pre-pressure theoretical value of 0-0.05mm, the width of not less than 0.2mm. Injection molding tuning, pay special attention to, A shot products with B shot products. A shot product size can be slightly larger to be pressed more tightly with the other male mold in the second molding to achieve the role of sealing glue. Note that in the second injection, the flow of plastic will not impulse an excellent product to be molded to deform its rubber position.
4. The interface should be on the bottom or outside when the mold is designed to transport water, not on the inside. Otherwise, it will not transport water quickly when the machine is in production. (This is the opposite of ordinary injection molding). And each cycle of water in and out of the same surface, not into the water in the upper, out of the water in the lower side, because the rear mold to rotate 180 degrees.
5. Two-color molds must be careful to choose the location of the gate, A good choice of latent feeding products so that the product and the runner can be automatically cut off. When it is not possible to use submerged gluing, you can consider a three-plate mold or hot runner mold. If the primary material is a pointed gate, make a concave round wave boy avoid touching through the secondary material due to the residue of the primary feeding point.
6. Two-color mold injection molding usually choose different colors of the same plastic and can be two different plastic raw materials, this time to consider the integration of the two materials, shrinkage rate differences, processing parameters. Two-color injection molding products are generally abs, pc and other hard plastics with the soft plastics, (nylon material is required to unique, suitable TPE) due to the cost or application of the relationship, to fully consider the use of two materials between the bonding and integration, the combination of the two materials at the mold processing (generally will have embossed pattern phenomenon or the need to make the seal mold groove) and the thickness of the material thickness. To make the two plastics “stick” more tightly, we should consider the “stickiness” between the materials and the roughness of the exterior of the mold.
7. Transparent and non-transparent designs: a shot to do non-transparent, two shots to do the lens, a shot try to use PC melting point high, two shots with PMMA. Non-transparent parts of the width of the bar as far as possible in 0.5-0.6 to avoid shrinkage.
8. Three plate mold water mouth designed to automatically demolding action, pay special attention to the soft rubber water mouth of the demolding action is reliable. If possible, the primary material flow channel needs to set up a pop-up device to facilitate fully automatic production (the operator is located on the secondary side, the primary water outlet can not be taken). Otherwise, it is challenging for the injection production can not automatically stabilize the production.
9. Secondary and a rubber bit with the surface, in addition to considering the secondary pre-pressure value, also need to do an excellent job of the secondary exhaust, exhaust slot control at 0.03 ~ 0.06mm (because of the consideration of a plastic material elasticity, the secondary, exceedingly soft rubber is very easy to form trapped gas, and hot secondary melt in a defect formed on the difficult to control).
Secondary formation of burrs trapped gas, a pressure injury and other repair effect depend mainly on the molding process engineering The effect of the secondary formation of burrs, trapped air, primary pressure wound, etc. depends mainly on the on-site processing countermeasures of the engineering staff during the molding process (corresponding to the addition and subtraction of glue, reinforcement gear glue, exhaust, etc.)