Detailed Explanation of the Full Process of Injection Mold Development: From DFM Review to Mass Production Delivery
Injection mold development is a systematic engineering requiring cross-post collaboration. Decisions in every link will directly affect the appearance, dimensional accuracy, molding yield and service life of plastic parts. Many projects suffer from repeated mold modification, prolonged delivery cycle and increased overall cost due to insufficient early evaluation, unreasonable structural design and inadequate trial mold verification. The complete mold development process starts from product structure review, goes through scheme design, part processing, assembly trial mold and multi-round verification, until the mold is stably delivered to support customer mass production. All links are closely connected, and standardized control logic needs to be established to control risks at every point. The full process of injection mold development is explained in detail below.
DFM Manufacturability Review
DFM review is the starting link of mold development. Its core is to identify molding risks on product structures in advance and avoid large-scale mold modification in the later stage. The review team connects product, structure, injection process and mold design engineers simultaneously, checking the product wall thickness, fillet, demolding draft angle, undercut, weld line position, hole position, sealing structure and assembly tolerance item by item. The wall thickness should be as uniform as possible. Transition fillets are added at positions with sudden wall thickness change to reduce shrinkage, bubbles and deformation. Confirm the undercut demolding scheme, distinguish inclined ejector, slider or insert demolding. Evaluate the molding difficulty of tiny ribs, positioning posts and thin-walled areas on the product. At the same time, confirm the drying requirements, shrinkage rate, flame retardant or weather resistance and other special indicators combined with material characteristics, output the DFM review report, mark modification suggestions, and proceed to the next stage after product revision confirmation or risk acceptance.
Mold Scheme Design
After DFM confirmation, mold scheme planning is started to determine the number of cavities, parting line position, gate type, runner scheme, core pulling mechanism, ejection mode and cooling layout. Single-cavity or multi-cavity structures are selected according to order quantity, product size and precision requirements. Valve hot runners are preferred for mass production appearance parts, and cold runner three-plate molds are selected for small-batch products. The parting surface is preferably arranged at the product assembly joint or non-visible area to reduce the impact of appearance defects. Sliders or inclined ejectors are planned for positions with side holes and undercuts, and sleeve structures are adopted for deep tiny holes. The cooling water channel layout is planned preliminarily to ensure balanced cooling of the cavity, and exhaust positions are reserved at the same time. After the scheme drawing is completed, internal review is organized to confirm structural feasibility, processing cost and delivery cycle.
3D Detailed Mold Design
After the scheme review is passed, detailed 3D mold design is carried out, including mold base, cavity inserts, core, sliders, inclined ejectors, ejection system, cooling water channels, runners, fasteners and positioning parts. A unified processing reference is adopted during design to ensure reliable positioning of all inserts and prevent displacement after long-term production. Exhaust grooves are set according to material characteristics, balancing exhaust effect and flash prevention. Ejector pins and ejector blocks are arranged on non-appearance and rigid positions as much as possible to avoid whitening and cracking during ejection. All parts reserve processing allowance, mark heat treatment and surface treatment requirements. Interference check is carried out after the completion of 3D assembly to check interference of mold opening and closing, core pulling and ejection actions. Then 2D processing drawings and BOM are output, and processing tasks are issued synchronously.
Mold Part Processing and Heat Treatment
The processing link is carried out in sequence according to the drawings. The mold base is rough machined and precision ground to guarantee parallelism and flatness. The cavity and core are rough machined first, with heat treatment allowance reserved, and then finished after heat treatment. Conventional processing methods include CNC finishing, wire EDM, optical grinding and mirror spark erosion. Tiny features, narrow grooves and sharp corners are formed by spark erosion. The heat treatment of steel is strictly controlled according to hardness. Corresponding processes are selected according to product materials and output. Cavities with wear resistance and corrosion resistance requirements are added with PVD, nitriding and other surface coatings after that. Key dimensions are sampled and inspected synchronously during processing. Unqualified parts are repaired in time to avoid dimensional deviation found after assembly.
Mold Assembly and Pre-commissioning
After all parts are processed, the assembly process is carried out. The mold base, inserts, sliders, inclined ejectors, hot runners and ejection mechanisms are assembled in sequence according to the reference. During assembly, the fitting degree of parting surfaces, slider fit clearance, inclined ejector sliding clearance and valve pin centering are adjusted. Check the smoothness of mold opening and closing, without jamming and abnormal noise. After assembly, empty mold trial run is carried out, repeatedly opening and closing the mold to verify the synchronization of core pulling and ejection actions, confirm that limit and induction switch signals are normal. The hot runner system is powered on separately for temperature measurement to check whether the temperature control is stable and whether there is hidden danger of material leakage. Trial mold is arranged after empty mold acceptance.
T0 Trial Mold and Defect Rectification
T0 trial mold mainly verifies filling, exhaust, demolding and basic molding status, records injection parameters, collects samples, and preliminarily confirms whether gates, runners and exhaust are reasonable. When the sample has defects such as short shot, burning, flash, shrinkage, whitening, scratch and deformation, distinguish whether it is a process problem or mold structure problem. Problems that can be adjusted by process are optimized through mold temperature, packing, injection speed and cooling time first; for mold defects such as insufficient exhaust, inappropriate gate position, undercut scratch and uneven cooling, output the mold modification scheme, arrange part repair or reprocessing, and carry out trial mold again after rectification.
Multi-round Trial Mold, Dimensional and Performance Verification
T1 and T2 trial molds focus on full dimensional inspection. Video measuring instruments, CMM and calipers are used to check all key assembly dimensions, flatness and hole coaxiality, and compare with drawing tolerance requirements. Appearance parts are checked for gloss, grain, color difference and weld lines synchronously. Functional parts carry out assembly test, waterproof test, fatigue pressing, drop test and so on. Shrinkage compensation, cooling layout and sequential injection parameters are continuously adjusted until the size, appearance and function of samples all meet customer standards. Standard samples are sealed and retained, and molding process parameters are locked.
Mass Production Acceptance and Document Delivery
After sample confirmation and sealing, continuous trial production is arranged to verify the stability of continuous mold operation, check the dimensional consistency of multi-mold products, and observe whether carbon deposit, wear and abnormal action occur. After continuous mass production verification is passed, mold acceptance is initiated. Complete documents are delivered synchronously, including 3D mold drawings, 2D part processing drawings, mold flow analysis reports, steel material certificates, heat treatment reports, first article inspection reports, standard process cards and spare parts lists. Matching wearing parts of the mold are delivered synchronously to facilitate later maintenance for customers.
Mold Handover and After-sales Follow-up
After mold acceptance, mold disassembly, packaging and protection are arranged, and the mold is delivered to the customer factory. Synchronously connect with the injection workshop personnel of the customer, explain the mold operation points, hot runner debugging methods, daily inspection and maintenance requirements of the mold, and replacement process of wearing parts. Follow up the production status continuously in the initial stage of mold online, assist in solving sudden problems during mass production, establish a mold maintenance ledger, guide the workshop to clean exhaust grooves regularly, check slider clearance and maintain guide posts and guide sleeves to ensure long-term stable production of the mold.
