Two-color injection molding is one of the more popular advanced injection molding methods at present, offering meaningful savings potential and new design possibilities for product manufacturing. This article mainly discusses the development status and trends of two-color injection molding, especially focusing on the application of automotive lamps.
#1 The Definition Of Two-Color Injection Molding
The multi-color and multi-material injection molding process refers to the combination of several plastics into multi-functional parts in one manufacturing process or one production unit. This technology uses a variety of materials for injection molding production, and combines the characteristics of different materials for assembly or other suitable bonding methods during the molding process to improve the functionality and aesthetics of the product, and provide for product manufacturing. Significant savings potential and completely new design possibilities are opened.
This article mainly discusses the current development status and trends of two-color injection molding, which is more popular in the industry. Thanks to the diversified design advantages of the two-color injection molding machine, it has been widely used in many fields such as the mobile phone industry, the pen industry, the automobile industry, the home appliance industry, the hand tool industry, and the daily necessities industry. This article takes the automobile industry as a representative, The application of two-color injection molding technology in the field of automobile lights is introduced in detail, especially the solutions to various injection molding problems.
#2 Necessary Conditions For Multi-Color Injection Molding
The matching materials of multi-color injection molding must meet two basic compatibility conditions, namely, bonding compatibility and processing compatibility.
Multi-color injection molding also puts forward new requirements for injection equipment. As far as the injection unit is concerned, parallel and same direction, parallel and opposite, horizontal and vertical L-shaped, Y-shaped same-directed single-cylinder injection structures can be used. As far as mixing nozzles are concerned, special nozzles such as patterns, waves, flow marks, gradients, and interlayers can be selected. As far as mold clamping is concerned, standard type, vertical turntable type, horizontal turntable type, rotating shaft type, manipulator rotation type and other mechanisms can be selected.
One of the key factors in multi-color injection molding is the variability of computer control programs. Because even for the same type of multi-color products, if different mold designs are used, different electronic control programs must be matched.
#3 Multi-Color Molding Technology For Car Lights
With the development of the national economy, the automobile industry has become a pillar industry of the country. The current rapid development of the automobile industry puts forward higher and higher requirements for automobile lighting.
The quality of automotive lighting is very important to driving safety, so the laws and regulations of various countries in the world have strict requirements on automotive lighting. The design of lamps must not only meet the safety requirements of laws and regulations, but also meet some other requirements. For example, the appearance should be integrated with the appearance of the entire car, beautiful and practical, and meet the requirements of aerodynamics, so that the driver and Passengers feel comfortable and convenient. Therefore, the design technology of car lights is also changing with each passing day along with the development of the automobile industry.
#4 New Progress In Multi-Color Injection Molding Technology
Combined with the observation of important foreign exhibitions in recent years, European and American manufacturers have upgraded to several basic molding technologies in addition to traditional multi-color products, such as car lights, air-conditioning panels, and TV frames, in the field of multi-color injection molding. Combination” presentation, such as two-color molding plus in-mold labeling (IML), two-color molding plus in-mold combination (IMA), two-color molding plus stack mold (StackMold), two-color molding plus IML plus IMA Sandwich injection, etc., all of which can be completed on one injection molding machine. Therefore, more and more attention has been paid to multi-color injection molding technology, and it not only presents multi-color technology, but also must be combined with other technologies to create higher benefits. This is the goal that the industry must challenge in the next stage.
#5 The Material And Process Characteristics Of Car Lights Enclosure
Car lights are generally composed of a base and a lamp housing. The material of the base is usually a thermosetting material – BMC (bulk molding compound), and the lamp housing can be processed from PMMA, PP, ABS and other materials, usually two-color or three-color. In terms of the production process of two-color car lights, special attention should be paid to the injection part of the two-color injection molding machine. The center distance between the two screws corresponds to the center distance of the two-color mold. In addition, the following important points need to be strengthened:
1.Factors Affecting The Stable Molding Of Car Lights
- Control unit response: switching point is too long, noise interference, command output instability, temperature instability;
- Noise of oil pressure system: pressure instability, valve positioning quality, hysteresis, oil pipe damping change;
- Differences in mechanical systems: oil seal internal leakage, damping, friction difference, screw check valve positioning, check effect;
- Uneven plasticization: difference in plasticization quality;
- Mold temperature control.
2.Frequently Asked Questions About Special Plastic Material Tubes Design For Car Lights And Tail Lights
- The screw is idling and does not feed;
- The torque required by the screw is too large to rotate;
- The plastic is not completely melted;
- Screw metering is unstable;
- uneven plastic mixing;
- Low-temperature molded plastics are prone to temperature rise;
- There are bubbles in the molded product;
- The inside of the molded product is easy to spit black and turn yellow;
- The screw rod is easy to corrode, wear and tear, and has a short service life.
3.The Main Design Points Of The Screw Barrel Group
The plastic plasticizing screw barrel group is the heart component of the injection molding machine, responsible for the transportation, melting, mixing, metering and other functions of plastic raw materials, so the plastic plasticizing screw is closely related to the quality of molded products.
The main purpose of improving the plasticizing screw is to:
- Improve the shear mixing effect;
- Uniform mixing;
- Improve plasticizing ability;
- Ensure the temperature uniformity of the melt.
4.Design Focus Of Special Screw For Tail Light
- L/D ratio: 21~23;
- The surface roughness needs to be extremely smooth to avoid accumulation;
- Increase the corrosion resistance of the electroplating layer thickness;
- Compression ratio: 2.3, feeding section: about 50%, compression section: about 30%, metering section: about 20%.
5.Countermeasures Against Poor Light Emission
- Scorching—reduce the injection pressure, multi-stage deceleration injection, and vacuumize the mold;
- Silver streaks – thoroughly dry the plastic pellets, increase the back pressure, reduce the temperature of the melt, and reduce the rate of injection;
- Air bubbles—increase the back pressure, reduce the temperature of the melt, use a dehumidifying dryer, and increase the size of the gate or runner;
- Bonding line – increase the temperature of the melt, increase the filling speed, increase the exhaust and mold temperature;
- Burr – increase the clamping force, reduce the filling pressure, and reduce the temperature of the melt;
- Shrinkage-uniform thickness design, increase the holding pressure and time, and replace the check valve.