DFM (Design for Manufacturability) for injection molds refers to the process of evaluating and optimizing the manufacturability, assemblability, and cost control of molds during the mold design stage. The key points include the following aspects:
Product Structure Analysis
Wall Thickness Uniformity: The wall thickness of the product should be as uniform as possible to avoid areas that are too thick or too thin. Non - uniform wall thickness can lead to uneven cooling, resulting in defects such as shrinkage deformation, bubbles, and weld marks, and increase the difficulty of mold manufacturing and molding processes.
Demolding Design: Analyze the shape and structure of the product to ensure smooth demolding. Structures that are not conducive to demolding, such as undercuts, deep holes, and narrow slots, should be avoided. For unavoidable undercut structures, reasonable demolding mechanisms, such as sliders and lifters, need to be designed. However, this will increase the complexity and cost of the mold.
Ribs and Fillets: Reasonable design of ribs can improve the strength and rigidity of the product without increasing the wall thickness. However, attention should be paid to the thickness, height, and distribution of the ribs to avoid problems such as shrinkage. At the same time, the internal and external corners of the product should be designed as fillets as much as possible to reduce stress concentration, improve molding performance, and facilitate mold processing.
Mold Material Selection
Product Requirements: Select appropriate mold materials based on factors such as the production volume, precision requirements, appearance quality, and characteristics of the plastic material of the product. For high - volume products, mold steels with good wear resistance and high strength, such as P20 and H13, should be selected. For products with high precision and high surface finish requirements, high - quality mirror steels are required.
Machinability: Consider the machinability of the mold materials, such as cutting performance, grinding performance, and electrical discharge machining performance. Good machinability can reduce the difficulty and cost of mold processing and improve processing efficiency and accuracy. For example, some free - cutting steels can significantly increase the cutting speed without reducing the mold performance.
Cost Factors: Under the premise of meeting the product quality and mold performance requirements, try to select mold materials with lower costs. The prices of different types and specifications of mold steels vary greatly. It is necessary to comprehensively consider factors such as material cost, processing cost, and mold service life to achieve the best cost - effectiveness.
Mold Structure Design
Parting Surface Design: The selection of the parting surface should take into account factors such as the product's appearance requirements, demolding method, and mold processing technology. The parting surface should be as simple and flat as possible to avoid complex curved parting surfaces, thereby reducing the manufacturing difficulty and cost of the mold. At the same time, attention should be paid to the sealing of the parting surface to prevent plastic melt from flashing during the molding process.
Gating System Design: Reasonably design the gating system, including the shape, size, and position of the main runner, sub - runners, and gates. The gating system should enable the plastic melt to fill the mold cavity uniformly and quickly, avoiding defects such as insufficient filling, weld marks, and jetting. The position and number of gates should be determined according to the structure and shape of the product to ensure the balanced flow of the plastic melt in the cavity.
Cooling System Design: The design of the cooling system is crucial for the product's molding quality and production efficiency. The cooling channels should be evenly distributed around the mold cavity to enable the mold to cool quickly and uniformly, shorten the molding cycle, and reduce product deformation and warping. At the same time, attention should be paid to the diameter, spacing, shape of the cooling channels, and their coordination with the mold structure to avoid interference with other components.
Manufacturing Process Feasibility
Machining Accuracy and Surface Quality: Analyze whether the machining accuracy and surface quality requirements of the mold parts are within the capabilities of the existing processing equipment and processes. For parts with high precision and high surface quality requirements, advanced processing technologies and equipment, such as high - precision CNC machining centers and electrical discharge mirror machining, may be required. However, this will increase the processing cost and cycle.
Assemblability: The mold structure design should facilitate assembly and debugging. The parts should be designed with good interchangeability and assembly accuracy to avoid assembly difficulties or the need for a large amount of trimming. At the same time, consider the operating space and tool - using convenience during the assembly process to improve assembly efficiency.
Cost and Cycle Control: When conducting DFM analysis, comprehensively consider the manufacturing cost and cycle of the mold. By optimizing the mold structure, selecting appropriate materials and processing technologies, and other measures, under the premise of ensuring the mold quality and performance, try to reduce costs and shorten the manufacturing cycle to improve the market competitiveness of the mold.
