How to Make Plastic Injection Molds?

1. Plastic Injection Mold Design

A. Understanding Product Requirements and Design Specifications

Before designing an injection mold, it is necessary to have a thorough understanding of the product requirements and design specifications. This includes the end use of the product, dimensional requirements, material selection, yield requirements, etc. Understanding these requirements can help the mold designer determine the basic design parameters of the mold, such as the size, structure, and material of the mold. It is also necessary to understand the industry standards and design specifications related to the product to ensure that the designed mold meets the industry requirements.

B. Using CAD software for mold design

Modern injection mold design is usually done using computer-aided design software, CAD software can provide powerful design tools, so that mold designers can be more efficient and accurate design work. In the CAD environment, designers can create three-dimensional models, simulation analysis, check interference, etc., greatly reducing the design cycle and improve the design quality. Commonly used CAD software includes SolidWorks, AutoCAD, Pro/Engineer and so on.

C. Design Considerations: Gate Type, Cooling System, Ejector System, etc.

Gate type: The gate is the channel connecting the injection molding machine nozzle and the mold cavity, which has an important influence on the flow and filling of the plastic melt. Choosing the right type of gate (e.g. edge gate, center gate, side gate, etc.) depends on the shape, size and production requirements of the product. The design of the gate needs to ensure a balanced flow of plastic to avoid defects such as short shots, scorching, etc.

Cooling System: The cooling system plays a key role in injection molding, which determines the cooling rate and uniformity of the product, thus affecting the quality and productivity of the product. The cooling system usually includes cooling water channels, cooling fans, etc.. Designers need to arrange the cooling channels reasonably to ensure efficient heat transfer for fast and uniform cooling.

Ejector System: The ejector system is used to eject the product from the mold after it has cooled. Common ejection methods include ejector pin ejection and push plate ejection. Designers need to determine the appropriate ejection method based on the shape and structure of the product and ensure that the ejection system works smoothly and reliably to avoid product damage or mold jamming.

2. Plastic Injection Mold Steel Selection

A. Introduction of common injection mold materials

In the production of injection molds, choosing the right material is crucial because it directly affects the life of the mold, the quality of the product and the production efficiency. The following are some commonly used injection mold materials:

P20 steel: This is a kind of pre-hardened plastic mold steel, which has high hardness and good cutting processability after heat treatment and is widely used in less demanding plastic molds.

718H steel: this is a vacuum degassing refining treatment of high purity plastic mold steel, low internal stress, quenching deformation is small. It has good polishing performance and photo-etching etching performance, good processing performance.

S136 steel: This is a mirror plastic mold steel, after pre-hardening treatment, with excellent corrosion resistance, polish ability and wear resistance, suitable for the manufacture of long-life plastic molds.

Aluminum alloy: Aluminum alloy mold material has the advantages of light weight, good thermal conductivity, low cost, etc., but the hardness and abrasion resistance are relatively low, which is suitable for the production of small batch and less demanding plastic products.

B. According to the product requirements and mold life choose the right material

When selecting injection mold materials, factors such as product requirements and mold life need to be considered. The following are some selection principles:

Product requirements: first of all, according to the product requirements and quality standards to determine the performance requirements of the mold material. For example, the product surface finish requirements are high, should choose the material with good polishing performance; strict requirements on the dimensional accuracy of the product, should choose a good thermal stability, not easy to deformation of the material.

Mold life: The life of the mold directly affects the production cost and efficiency. If you need to make long-life molds, you should choose materials with high hardness, good wear resistance and excellent corrosion resistance. For short-life molds, materials with lower cost and good processing performance can be selected.

Economy and sustainability: In order to meet the product requirements and the premise of mold life, should also consider the economy and sustainability of the material. Selection of cost-effective materials can reduce production costs and improve economic efficiency. At the same time, the choice of environmentally friendly, recyclable materials, in line with the requirements of sustainable development.

3. Plastic Injection Mold Processing

A. Introduction of processing equipment and technology

In the process of injection mold machining, a variety of machining equipment and technologies are used. Common machining equipment includes CNC milling machines, electric discharge machining (EDM) machines, wire-cutting machines, grinding machines and so on. These machines are capable of achieving precise cutting, EDM, grinding and other processes on mold materials.

CNC milling machine is a commonly used machining equipment, through programming to control the movement of the tool trajectory in three-dimensional space, to achieve milling, drilling and other machining operations. EDM machine tools use the principle of electric spark discharge to remove material, and are suitable for processing mold materials with high hardness and brittleness. Wire-cutting machine tools utilize fine metal wires in high-speed reciprocating motion to cut materials by means of electrical discharge erosion. Grinding machines are used for high-precision grinding to obtain more accurate dimensions and surface quality.

B. Processing Flow: Roughing, Finishing, Assembly, etc.

Roughing: Roughing is the first step of mold processing, the goal is to quickly remove a large amount of material, close to the final shape. Milling, turning and other processing methods are often used to process the basic structure of the mold.

Finishing: On the basis of rough machining, finishing is used to obtain more accurate dimensions and surface roughness. Grinding, electrical discharge machining and other techniques are often used to ensure the accuracy and quality of the mold.

Assembly: After finishing, the various parts of the mold are assembled. This includes the installation of gates, cooling systems, ejector systems, etc. to ensure the exact fit and functionality of each component.

C. Critical Control Points and Precautions during Machining Processes

Equipment Selection and Calibration: Select appropriate machining equipment and ensure its accuracy and performance. Perform regular calibration and maintenance of the equipment to ensure the accuracy and stability of the machining.

Cutting parameter setting: According to the mold material, tool type and processing requirements, reasonably set the cutting parameters, such as cutting speed, feed, depth of cut, etc.. The setting of parameters directly affects the processing efficiency, tool wear and processing quality.

Cooling and lubrication: In the machining process, ensure adequate cooling and lubrication to reduce tool wear, reduce thermal deformation, and improve surface quality. Choose suitable coolant and lubricant and check their quality and concentration regularly.

Quality control and inspection: During the machining process, regular quality control and inspection should be carried out. Use measuring instruments such as CMM, surface roughness meter, etc., to check the dimensional accuracy, form and position tolerance and surface quality of the molds, so as to detect problems and adjust the processing parameters or processes in time.

4. Plastic Injection Mold Trial

A. Preparation before mold testing

Prior to the mold test, thorough preparations must be made to ensure a smooth mold test. Preparations include:

Inspecting the mold: Make sure that the mold is not damaged, that all parts are properly installed, and that fasteners are securely fastened.

Cleaning the mold: Remove all contaminants, swarf and other foreign matter from the mold to ensure it is clean.

Prepare raw materials: Confirm the raw materials that will be used for mold testing and make sure that their quality, color, type, etc. meet the production requirements.

Check equipment: Confirm that the injection molding machine is in good condition and that all functions and parameters can be operated and set properly.

Safety preparation: Make sure all safety devices are installed and functioning properly to prevent accidents during the mold trial.

B. Adjustment and Optimization during Mold Trial

Adjustments and optimizations may need to be made to the mold, raw materials, equipment, and other aspects of the mold trial process in order to obtain the best production results. These adjustments and optimizations may include:

Adjustment of injection molding machine parameters: Depending on the nature of the raw material and product requirements, it may be necessary to adjust the temperature, pressure, speed and other parameters of the injection molding machine.

Optimize mold design: If problems with the mold design are found during the mold trial, such as underfilling, uneven cooling, etc., it may be necessary to optimize the design of the mold.

Adjustment of raw materials: If the results of the mold trial are unsatisfactory, it may be necessary to replace the raw materials or adjust the ratio of raw materials.

Improve the cooling system: according to the result of the mold trial, optimize the design of the cooling system to improve the cooling efficiency and reduce product deformation and defects.

C. Final inspection after commissioning

After the commissioning is completed, final inspection is required to ensure that the mold can be officially put into production. The content of the final inspection includes:

Product quality check: Check whether the products produced by the trial mold meet the quality requirements, such as dimensional accuracy, surface quality, physical properties, etc.

Production efficiency assessment: Evaluate the production efficiency of the mold, including cycle time, scrap rate, raw material utilization rate, etc.

Safety check: Re-confirm that all safety devices of the mold and equipment have been functioning properly to ensure the safety of the production process.

Record and report: Record all the data during the mold trial and debugging process and generate reports to provide reference for subsequent production and mold maintenance.

5. Plastic Injection Mold Maintenance

A. Routine maintenance and care measures for molds

Cleaning the mold: After each use, the surface and interior of the mold should be cleaned to remove residual plastic, impurities and dirt. Use special cleaners and tools and avoid using hard objects to scrape the surface of the mold.

Lubricate the mold: Regularly lubricate the sliding part of the mold, guide pillar, guide sleeve, etc. to ensure its smooth operation. Choose the appropriate lubricant and follow the recommended lubrication intervals.

Inspect fasteners: Regularly inspect the fasteners of the mold, such as bolts, nuts, etc., to ensure that they are tightened reliably and are not loose or damaged. If looseness or damage is found, they should be replaced or repaired promptly.

Check the cooling system: Regularly check the operation status of the cooling system to ensure that the cooling waterway is smooth and not blocked or leaking. Clean the cooling waterway to remove deposits and impurities to maintain good cooling effect.

Storage and Protection: When the molds are not in use, they should be properly stored and protected. Place the mold in a dry and ventilated place, avoid direct sunlight and high temperature environment. During storage, protect the mold from rust and damage by regular rust treatment and oiling.

B. Recommendations and Precautions for Extending Mold Life

Correct use and operation: When operating the injection molding machine, follow the correct operating steps and process parameters to avoid damage to the mold caused by excessive pressure, temperature and speed. Reasonably adjust the parameters of the injection molding machine to ensure good plastic melt fluidity and mold filling performance.

Regular maintenance and overhaul: Make regular maintenance and overhaul plans for the molds, including cleaning, lubrication, fastener inspection and cooling system maintenance. Timely detection and repair of potential problems to prevent their further development.

Control the production environment: Keep the injection molding production environment clean and dry to avoid the influence of dust, moisture and other impurities on the mold. Control the temperature and humidity of the workshop to avoid deformation and cracking of the molds caused by temperature changes.

Reasonable selection of materials and heat treatment: According to the product requirements and mold life demand, reasonable selection of mold materials, and appropriate heat treatment. High-quality materials and heat treatment can improve the hardness, wear resistance and anti-fatigue properties of the mold, thus prolonging the life of the mold.

Record and analysis: Establish a record system for the use and maintenance of the mold, record the operation of the mold, maintenance measures and damage. Through the analysis of the recorded data, potential problems can be detected in time, and corresponding measures can be taken to preventively extend the life of the mold.

6. Conclusion

Through the introduction of this blog, we can see that making injection molds is a complex and professional process. From design to material selection, processing, mold testing and debugging as well as maintenance, each step requires rigorous operation and fine control. Only by mastering these key steps and precautions, can we produce high-quality injection molds to meet market demand and improve production efficiency.