Plastic Injection Molding
The application fields of plastic injection molding are very wide, including but not limited to daily necessities, household appliances, automotive parts, medical devices, industrial parts, etc. In addition, various plastic shells, parts, containers, pipelines, etc. all benefit from injection molding technology.
Plastic Injection Molding Manufacturers in Russia
Manufacturers are proficient in using injection molding as a plastic processing method to provide high-quality custom injection molding services. Plastic injection molding is an important processing method, which mainly involves processing solid plastic powder or particles into a molten state, injecting compressed air into the mold, cooling, and solidifying to form plastic molded parts. The main process is divided into mold closing, injection molding, pressure holding, cooling and solidifying, mold opening and ejection, and trimming.
Injection Molding Process
When Russian plastic injection molding manufacturers process, they need to pay extra attention to the molding process, such as:
- Injection Location
The injection position is one of the most important parameters in the injection molding process. Generally, the total weight of the solidified material (nozzle material) of the plastic part can determine the injection position. Sometimes, the injection position needs to be reasonably set based on the type of plastic used, the structure of the mold, and the quality and accuracy requirements of the product. The injection method for most plastic products in injection molding is more than three stages, and the injection positions include the residual position, the positions of each injection stage, the position of the melt endpoint, and the position of the reverse cable (withdrawal).
- Injection Time
Injection time refers to the time required to apply pressure to the screw, which involves the flow of plastic, mold filling, and pressure retention. Therefore, injection speed, injection time, and injection pressure are key molding conditions. There are two methods to find the correct injection time: appearance setting method and weight setting method. Although the injection time is short and has little impact throughout the entire molding cycle, adjusting the injection time plays a crucial role in the pressure control of gates, runners, and cavities. A reasonable injection time helps to evenly fill the melt in the mold cavity and is more conducive to improving the surface quality of the product and reducing dimensional tolerance values. The cooling time should be set to 10-15 times the injection time, and this pattern can be used as a basis to predict the entire molding time of the plastic part.
- Remnants
After the screw injection is completed, it is necessary to retain some of the molten material from the screw head, and not all of it needs to be injected, which can form a residual amount. The reservation of residues can prevent mechanical collision and friction accidents between the top of the screw and the nozzle from coming into contact; On the other hand, the repetitive accuracy of the injection volume can be controlled by this residual amount, improving the accuracy and quality of the product. If the residual amount is too small, the buffering effect will be lost, and if it is too large, it will lead to backlog.
- Screw Reverse
After the pre-molding of the screw is completed, to provide a larger space for the molten material in the measuring chamber, it will be regressed in a straight line for a certain distance, which will cause air to enter and internal pressure to decrease, thereby preventing the molten material from flowing out of the measuring chamber (through the nozzle or gap). This regressing action is called anti-extrusion, and the distance regressed is called anti-extrusion amount. Another purpose of anti-extrusion is to reduce the pressure of the nozzle flow channel system, reduce internal stress, and make it easier to extract the main flow channel during mold opening without the nozzle returning. The setting of the anti-extrusion amount should consider the viscosity of plastic and the condition of the product. If a large anti-extrusion amount is selected, it will cause bubbles to be mixed in the melt in the measuring room, and in severe cases, it may even affect the quality of the product.
- Cooling Time
The cooling process starts running at the beginning of injection molding, and cooling starts whenever the plastic part can be qualitatively determined. The general cooling time accounts for 70% to 80% of the entire injection molding cycle.
Daily Management of Plastic Injection Molding
Russian plastic injection molding manufacturers need to propose corresponding measures when facing problems such as product changes, substandard quality, and low employee efficiency. These measures can include the following stages:
Planning stage: Formulating a plan is the beginning of any economic management work, which is essential in all modern large-scale production processes. It is the guiding principle for all work and an important guide for employees. The first step in formulating a workshop plan is to establish the work objectives and various technical and economic indicators of the entire workshop. This can clarify the goals of each process and each employee, mobilize and coordinate each production link, closely integrate various production elements, and form a complete production system. With a plan in place, employees know the overall goals of their work; With a plan, there is a basis for inspection and improvement work; The plan provides a basis for measuring the results of each stage of work. The workshop only participates in the production and design stages, and the plan formulated by the workshop is mainly based on its production efficiency and the work objectives issued above. In addition to setting goals and production plans for each session, the workshop also needs to regularly develop maintenance and repair plans, equipment replacement and inspection plans, etc.
Organizational stage: Reasonable command is an important part of implementing plans and other management methods, and is an important means to complete plans within the specified time and achieve reasonable production.
Supervision stage:Supervision is the management activity of inspecting and supervising the implementation of various management systems, target plans, and the implementation of instructions issued by superiors so that they can all be completed within the specified time. It is a management activity that compares the actual production situation with the planned goals and standards during the execution of plans and various production and business activities, identifies the gaps between the two, analyzes the reasons for the gaps, and takes measures to reduce the gaps.
Production stage: As the plan is issued to the workshop, the workshop will directly implement production, so the production stage is the most critical and core step for the workshop. The content of the production process mainly includes technical guidance, which means that technical problems that arise during the production process require the help of workshop personnel to improve and solve them, including improving the process, transforming and innovating equipment, etc; In addition, the use of workshop equipment, regular maintenance, and material inspection; Also, it is to assist personnel outside the workshop in coordinating.
Analysis of the Problem of Air Streaks at the Gate by Manufacturers
Russian plastic injection molding manufacturers have found air marks on the sprue during the injection molding process. If the reason for the material not drying is ruled out, further consideration is needed:
- If the temperature difference between the melt or mold is too low and produces jelly, injection molded parts will produce injection marks, accompanied by matte air marks.
- The main reason for the formation of gate air streaks is that the first stage injection speed is too fast, which causes severe eddy currents when the melt enters the mold cavity, resulting in vortex air streaks. So, the first consideration for Russianplastic injection molding manufacturers after producing air bubbles is to reduce the speed of the first-stage injection.
- The thicker the wall thickness at the location of the gate, for example, if it exceeds 4 millimeters, it is easy to produce air marks. Because thicker wall thickness can easily cause eddy currents in the melt when entering the gate, resulting in the formation of air bubbles. The air ripple caused by this reason is difficult to eliminate by enlarging the gate and reducing the speed. At this point, it can be changed by moving the gate position to a thinner area.
- A gate that is too thin or too thin can also easily cause air and jet marks in the gate. Because thinner and thinner gates can cause the speed of molten metal entering the mold cavity to increase, that is, the injection speed will increase, resulting in injection marks, air marks, and even snake-shaped marks. Therefore, if the speed has been reduced to the minimum and pollution persists, it is necessary to thicken the gate, such as setting it to be greater than 0.5 millimeters.
- If the melt temperature is too high, plastic raw materials that are prone to burning will decompose more gas and cause air bubbles, such as the decomposition air bubbles in PVC materials.
- The smoother the surface of the mold cavity, the brighter the surface of the injection molded part, and the easier it is to produce air marks. The injection molded parts are too shiny, and even the slightest grain will be clear.
When plastic injection molding manufacturers encounter air or injection marks near the injection gate during the production process, they can refer to the above points for analysis and compare improvements. Among them, reducing the injection speed is the primary key means for us to improve the problem of injection marks and air marks, and the second is to check whether the size of the injection gate is too small or too thin. Drying raw materials is a fundamental step in ensuring production, and this cannot be ignored at any time except for materials with low water absorption that do not require drying.
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