Effective source control at the early stages of process and mold design is fundamental to ensuring stable deep-drawn shell quality. Before processing, a Direct Flow Analysis (DFM) is conducted, considering shell depth, corner radius, wall thickness, and drawing ratio. This allows for precise calculation of the number of drawing passes, preventing excessive single-drawing operations that could cause cracking. To address defects such as wrinkling, springback, and thinning, pressure ribs are added to the mold, and the die corner radius and pressure force structure are rationally designed. Carbide cores are used to improve mold wear resistance. Simultaneously, mold processing standards are standardized, and consistent mold cavity dimensions are ensured through slow wire EDM and mirror grinding. Regular standardized mold repairs prevent batch dimensional deviations caused by mold wear.
Strict control of raw material condition minimizes defects caused by material fluctuations. Upon receiving raw materials, batches are tested for elongation, hardness, and thickness uniformity. Different batches of steel, stainless steel, and aluminum are labeled and used separately. Coils undergo precision leveling to eliminate internal stress. Workpieces with high drawing difficulty are pre-annealed and softened. Before production, ultrasonic degreasing and oil removal are performed to prevent scratches and damage caused by oil and impurities. A standardized lubricant type and application amount are used to ensure consistent forming performance for each roll of material.
Standardize the parameters of the deep drawing stamping process to achieve standardized mass production. Fix parameters such as servo press tonnage, stamping speed, blank holder pressure, and slide stroke, avoiding arbitrary changes. For multi-pass, step-by-step drawing processes, set intermediate transition and shaping stations to correct shell deformation after each drawing, controlling wall thickness reduction within standard ranges. Regularly sample the first piece during production to confirm that the inner diameter, depth, bottom radius, and sidewall flatness are up to standard before mass production. Hourly sampling and retesting are conducted to promptly identify issues such as parameter drift and material slippage.
Improve the post-processing control of semi-finished products to unify appearance and dimensional standards. After deep drawing, uniformly use magnetic grinding or electrochemical deburring to avoid inconsistent burr sizes at the cut. For easily deformable shells, add a low-temperature stress-relief annealing process to eliminate residual internal stress from stretching and prevent subsequent dimensional springback. For surface electroplating, passivation, and anodizing processes, fix the solution concentration, soaking time, and baking temperature, and use multi-stage pure water cleaning throughout the process to reduce batch variations such as watermarks, plating peeling, and shell corrosion.
Establish a full-process inspection and traceability system to pinpoint the source of quality fluctuations. CCD vision equipment is used on the production line to detect surface defects such as shell scratches, wrinkles, and cracks in real time. A 2.5D image analyzer is used to inspect precision dimensions such as depth, inner diameter, wall thickness, and coaxiality. Regular salt spray, pressure resistance, and sealing tests are conducted, and each batch is recorded with material batch number, mold number, production parameters, and test data. Good products, rework products, and scrap products are differentiated. When batch defects occur, the problem is quickly traced back to raw materials, molds, and equipment, and process standards are optimized simultaneously to continuously stabilize the quality of subsequent products.
