Custom Injection Molding
Custom injection molding has high production efficiency and can quickly complete manufacturing processes such as injection molding. And the product has high dimensional accuracy and good repeatability, which can meet the production needs of various customers for high-precision products.
Injection Molding Services
When providing professional custom injection molding services, the most crucial thing for injection molding companies is to be able to design and produce from the customer’s perspective. A customer-oriented injection molding company that can provide customers with high-quality and professional injection molding services, producing precision instruments and advanced products.
Preparation Work before Providing Injection Molding Services
Before the company provides injection molding services, it is necessary to first study the customer’s needs and the shape of the product, choose the appropriate injection molding process and method, and install the mold reasonably and correctly on the injection molding machine before it can be put into use. During this process, it is also necessary to consider:
Mixing of Plastic Colors
Some plastic products require various colors, and accurate colors must be mixed during injection molding. The two most common color-matching methods are using masterbatch color matching and coloring particle color matching. The color matching of the masterbatch is relatively simple, just mix the plastic particles with them in a certain proportion. The colored particles are formed by mixing dispersants and pigments, with stricter control over the proportion. In addition, the dyeing of thermosetting plastics is simpler than that of thermoplastic plastics.
Preheating of Metal Inserts
Due to the difference in thermal conductivity between metal materials and plastic, plastic has weaker thermal conductivity and larger molding shrinkage, while metal has stronger thermal conductivity and smaller shrinkage. Therefore, when plastic products contain metal inserts, it is necessary to heat the inserts in advance, otherwise, it will cause cracks around the inserts and lower the strength of the products. To solve the above problems, when designing plastic products, it is necessary to increase the thickness of the plastic near the metal insert or preheat the metal insert in advance during processing, reduce the temperature difference between the plastic and the metal insert during heating, and slow down the cooling rate of the plastic around the insert. The shrinkage rate of the two is relatively consistent to prevent excessive internal stress around the insert.
Drying Methods for Plastics
Some plastics have strong water absorption, so before manufacturers provide injection molding services, they need to be dried. Different plastics have different drying requirements, so their drying time and temperature are also different. For example, the drying temperature of ABS is between 80-85 ℃, while the drying temperature of PC is as high as 120-130 ℃. There are also many drying methods, such as vacuum heating drying, airflow drying, infrared heating drying, etc.
Selection of Release Agent
For some plastic parts with complex structures that are difficult to de-mold, a certain amount of demolding agent needs to be sprayed on the core of the mold during injection molding to ensure smooth demolding of the plastic parts. Traditional release agents include white oil, zinc stearate, silicone oil, etc. Note that zinc stearate cannot be used as a release agent for polyamide. White oil can be used as a release machine for polyamide, and the release effect is the best. Silicon oil also has a good effect, but its use is relatively cumbersome, so it has not been widely used.
Precautions for Injection Molding Process
When manufacturers start providing injection molding services, they also need to pay attention to many key points in the process to ensure the normal operation of the injection molding machine and the high-quality output of the product.
Product Inspection before Injection Molding
Before starting the injection molding service, the injection molded products need to be inspected. To determine whether a product is qualified, the first step is to check its consistency with the final product and whether it meets the requirements of aesthetics and reliability. There are three steps for inspection, namely first inspection, patrol inspection, and finished product inspection. The first inspection is mainly to ensure that the produced products will not be scrapped or reworked; Inspection requires operators to promptly detect abnormalities during operation and report them for resolution to avoid damage; Finished product inspection is to inspect finished products, which need to be labeled, packaged, etc. according to customer requirements, usually through sampling inspection. A qualified finished product needs to have no defects, especially serious defects such as material defects, appearance defects, functional defects, etc.
Preparation for Startup
Before starting the injection molding machine, it is necessary to first check if there is any leakage in the main power supply. After closing the main power switch of the injection molding machine, the mold should be preheated according to the set temperature parameters. When the temperature reaches the specified temperature, a certain period of insulation must be carried out to ensure that the temperature of all parts of the machine barrel is uniform; Open the valve of the cooling water and cool the mold oil pump. After inspection and no abnormalities are found, the oil pump can be started to operate officially. Wait until the “motor on” indicator appears on the display screen before it can run. Focus on checking whether the safety door can function properly, and strictly prohibit behaviors that do not close the safety door; After starting and rotating the screw, check for any abnormalities; The protective covers and cover plates of each part of the equipment need to be properly covered; It is strictly prohibited for operators who are not involved in this job to operate, and it is also not allowed for two or more people to operate simultaneously; When placing the mold, it should be stable, accurate, and reliable. If any abnormalities are found during the mold closing process, work should be stopped immediately. Technical personnel should be notified for repair and troubleshooting. During repair, the operator must not leave.
Injection Molding Specifications
Strict adherence to injection molding specifications is required during the injection molding process to produce high-quality products. When conducting product trial molding, it is necessary to strictly follow the process specifications for trial molding, and the produced samples also need to be confirmed before mass production can be carried out if they meet the requirements; Operators must inquire with management or design personnel about the start-up requirements, quality requirements, processing requirements, packaging requirements, and precautions related to the product. It is strictly prohibited to operate production without being familiar with product parameters; Operators must strictly produce according to requirements, and unqualified products are not allowed to be put into use; The operator needs to inspect each product, and if there are continuous defects in the product, the maintenance personnel need to be notified for inspection; Keep the workbench clean and tidy, and do not pile up too many products; When trimming, be careful not to cut into the product itself, causing it to be scrapped.
Experience in improving the Quality of Injection Molding Services
After providing long-term injection molding services, injection molding companies can generally summarize their own experiences to improve the quality of injection molding services, so that the same errors can no longer occur, significantly improving the quality of injection molding and product accuracy. For example, selecting appropriate screws, adjusting appropriate indicators, and setting high-efficiency process parameters can significantly improve service quality.
Selection of Screws
According to the plasticizing effect, screws can be divided into gradient screws, mutation screws, and universal screws. Different screws should be selected according to different products, raw materials, and molds. For amorphous plastics with a wide range of softening temperatures, gradient screws can be used; For crystalline plastics with shorter compression sections and more intense plasticizing energy conversion, mutation-type screws can be used. For other plastics with strong adaptability, universal screws can be used
Debugging of Plastic Indicators
To improve the quality of injection molding services, it is necessary to adjust the shrinkage rate, molecular structure, and flowability of plastics. For example, the tighter the molecular structure of plastics, the stronger their shrinkage rate. Plastics with strong shrinkage rates are prone to defects such as uneven wall thickness during processing. Although plastics with tighter molecular structures have higher density, their toughness will decrease.
Setting of Process Parameters
When adjusting the process parameters, it is mainly necessary to adjust the back pressure of the plastic. The back pressure is mainly the reaction force generated by the melt on the screw, which can discharge air and make the plastic plasticization more uniform; The temperature of the mold is also a key parameter to ensure the normal flow of the melt. Mold temperature refers to the temperature of the internal cavity, not the displayed temperature of the molding machine. A suitable mold temperature can ensure the normal flow and cooling of the melt; There is also a setting for cooling time. Generally, when the product does not deform, the shortest possible cooling time should be selected to accelerate the molding speed and improve overall efficiency; The setting of injection speed also requires some experience. If the cooling rate and fluidity of the melt are fast, the injection speed can be correspondingly accelerated, but too fast injection speed can also easily cause flash and bubbles.
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