-Exploring the way to improve the surface finish of mold parts.
In our mold parts manufacturing workshop, a “surprise” about quality is quietly staged. A batch of mold parts after the completion of processing, through the finish detector inspection, the finish data is exciting. The original surface finish required by the customer was Ra0.08μm, but the actual test result reached Ra 0.069μm, and the surface finish exceeded the customer’s standard. This not only means that the appearance of the part is greatly improved, in actual use, it can also make the mold release smoother, extend the service life, and reduce the cost of use of customers. Because usually raw material is difficult to achieve this surface finish standard, and no corner deformation.
The “exceeding” of the surface finish is not accidental, but the result of JinChen team’s persistent pursuit of quality. It has won us high praise from customers, set a quality benchmark in the industry, and become a powerful driving force for us to constantly climb the peak of quality.
Now let’s explore the way to improve the surface finish of mold parts,
In the precision field of mold manufacturing, the surface finish of mold parts is a key factor in determining mold performance and product quality. From the daily use of plastic products, to high-stage electronic products, auto parts and mold parts surface finish are deeply affected the appearance of the final product , dimensional accuracy and service life. therefore, exploring ways to effectively improve the surface finish of mold parts has become the core task of the mold manufacturing industry to continuously pursue excellence.
- Optimization of equipment and process
(A) Selection and Maintenance of Precision Machining Equipment
High-precision processing equipment is the basis for achieving high surface finish of mold parts. Advanced CNC machining centers have higher positioning accuracy and repeat positioning accuracy, which can ensure the precise operation of the tool during the processing and reduce surface unevenness caused by equipment errors. For example, some high-end five-axis linkage machining centers have a positioning accuracy of up to ±0.001mm, which can keep the tool in the best posture to contact the parts during complex curved surface processing, avoiding surface scratches caused by improper cutting angles. At the same time, it is very important to regularly maintain the equipment, including lubrication of the lead screw and guide rails, precision detection and adjustment of the spindle, etc., to ensure that the equipment is always in the best working condition and provide stable guarantee for high surface finish processing.
(B) Precision Control of Cutting Parameters
Cutting parameters have a significant impact on surface finish. In terms of cutting speed, when processing aluminum alloy mold parts, appropriately increasing the cutting speed can make the cutting process smoother, reduce the probability of built-up edge, and thus improve the surface quality. Generally speaking, when the cutting speed is increased to 1500-2500m/min, the surface roughness can be reduced by 20%-30%. The selection of feed rate should also be cautious. A smaller feed rate can make the tool cutting marks finer and the surface smoother, but it will reduce the processing efficiency; a balance needs to be struck between the two. For high-precision mold parts, the feed rate can be controlled at 0.05-0.15mm/r. The cutting depth should be determined according to the hardness of the mold material and the performance of the tool. For mold steel with higher hardness, multiple small cutting depths can achieve better surface finish than one large cutting depth.
(C) Adoption of advanced processing technology
Electro-spark milling (EDM milling) is a new processing technology that removes materials through the discharge corrosion between the electrode wire and the parts. Compared with traditional EDM forming, EDM milling can produce more complex shapes and higher-precision surfaces, especially suitable for mold parts that are difficult to process with traditional cutting methods. Its processing surface roughness Ra can reach 0.1-0.4μm, which effectively improves the surface finish of the mold. In addition, high-speed cutting (HSC) technology also shows great advantages in mold manufacturing. It can achieve efficient and high-precision processing at high cutting speeds, reduce the impact of cutting force and processing heat on the parts, reduce surface roughness, and make the surface of mold parts smoother.
II. Control of Mold Materials and Pretreatment Processes
(A) Selection of high-quality mold materials
The quality of mold materials is directly related to surface finish. The key is to select materials with high purity and uniform structure. For example, when manufacturing injection molds, high-quality pre-hardened mold steels such as P20 and 718 are selected. They have low internal impurity content, fine and uniform grain size, and can maintain good stability during processing, reducing surface defects caused by material defects. Compared with ordinary steel, the surface roughness of high-quality mold steel after processing can be reduced by about 30% – 40%, laying a good foundation for subsequent polishing processes.
(B) Strengthening of Material Pretreatment Processes
Appropriate pretreatment of mold materials can significantly improve their processing performance and surface quality. Forging is a commonly used pretreatment method. Through repeated forging, the defects such as looseness and pores inside the material can be compacted and eliminated, and the grains can be refined, thereby improving the strength and toughness of the material, and also facilitating subsequent processing to obtain a higher surface finish. For example, after the raw material is subjected to three-upsetting and three-drawing forging treatment, its internal structure is more compact, and the surface roughness after processing can be reduced by 1-2 levels. In addition, annealing and normalizing treatment can eliminate the internal stress of the material, adjust the hardness, make it more suitable for cutting processing, and avoid processing deformation and surface quality degradation caused by the release of internal stress.
III. Innovation and Upgrading of the Polishing Process
(A) Application of Composite Polishing Technology
The composite polishing technology that combines multiple polishing methods can give full play to the advantages of each method and effectively improve the surface finish. For example, the process of combining mechanical polishing with chemical polishing is used to first remove most of the processing traces through mechanical polishing, so that the mold surface reaches a certain degree of flatness; then chemical polishing is used to further micro-flatten the surface, remove fine scratches and defects that are difficult to eliminate by mechanical polishing, and reduce the surface roughness to Ra0.05 – 0.1μm, achieving a mirror effect. This composite process is widely used in optical mold manufacturing and can meet the stringent requirements of high-precision optical components on the surface finish of the mold
(B) Investment in Automated Polishing Equipment
Automated polishing equipment uses advanced CNC technology and sensors to accurately control the pressure, speed and trajectory during the polishing process, avoiding the instability and errors of manual operation. For example, the robot polishing system is equipped with a force sensor that can monitor the polishing force in real time and automatically adjust it to ensure a uniform polishing effect on the surface of complex mold parts. Compared with manual polishing, automated polishing equipment can improve the consistency of surface roughness by more than 80%, greatly improving the stability and reliability of polishing quality, while also improving production efficiency and reducing labor intensity.
(C) Research and development innovation of polishing fluid and polishing tools
The research and development of new polishing fluid and polishing tools provides a new way to improve surface finish. For example, polishing fluid with special nanoparticles can fill the microscopic pits on the mold surface during the polishing process, play a role in repairing and smoothing the surface, and further improve the surface finish. At the same time, new polishing tools such as diamond polishing pads have higher wear resistance and uniformity, can maintain a stable polishing effect during the polishing process, and effectively reduce the surface roughness. They are especially suitable for mold parts processing with extremely high surface quality requirements.
In conclusion, improving the surface finish of mold parts is a systematic project, which requires coordinated efforts from multiple links such as equipment and process, materials and pretreatment, and polishing process. By continuously exploring new technologies and new methods, and continuously optimizing the operation and control of each step, mold manufacturing companies will be able to continue to move forward on the road of improving the surface finish of mold parts, produce higher quality molds, meet the growing demand for high-stage manufacturing, and promote the mold manufacturing industry to a new level of development.
