With the development of society today, sheet metal fabrication industry has also developed rapidly. Now sheet metal process involves all walks of life. For any sheet metal parts, it has a certain processing methods, that is the so-called process flow. To understand sheet metal process, you must first know the choice of sheet metal materials.
The materials (for sheet metal process) commonly used are cold-rolled plate (SPCC), hot-rolled plate (SHCC), galvanized sheet (SECC, SGCC), copper (CU) brass, copper, beryllium copper, aluminum plate (6061, 6063, hard aluminum, etc.), aluminum profiles, stainless steel (mirror surface, hairline surface, matte), which is depending on the role of the product. The choice of materials is different and we generally need to consider the product from its use and cost.
● Cold-rolled steel SPCC, mainly used for electroplating and baking paint parts, low cost, easy molding, material thickness ≤ 3.2mm.
● Hot-rolled steel SHCC, material T ≥ 3.0mm, is also used for electroplating, painting pieces, low cost, but difficult to shape.
● Galvanized sheet SECC, SGCC, SECC, Electrolytic plate are divided into N material and P material. N material is not used for surface treatment, and the cost is high. It is used for spraying parts.
● Copper, a conductive materials. The surface treatment is nickel, chrome, or no treatment. Feature is high cost.
● Aluminum sheet is generally treated by chromate (J11-A), oxidation (conductive oxidation, chemical oxidation), silver plating, nickel plating.Feature is high cost.
● Aluminium profiles; pieces of material with complex cross-section structures are used extensively in various insert boxes. Surface treatment is same with aluminum plate.
● Stainless steel; mainly used without any surface treatment, high cost.
For drawing reviewing and numbering the process of the part, we must first understand technical requirements of every part; Drawing auditing for the process flow is the most important part.
● Check whether the drawings are complete.
● Check whether the label, dimension and view relationship is clear, complete.
● Check assembly relationship and important size as assembling requirement.
● The difference between the old and new drawings.
● Translation of foreign languages.
● Code number conversion.
● Drawing problems and feedback.
● Quality requirements and process requirements
● The formal issued production plan must be accompanied by a quality control chapter.
Tips for plans: unfolded drawing is worked based on 3D drawings of parts and made to their corresponding 2D drawings.
● Reasonable unfolding methods, which is convenience for saving materials and processing.
● Reasonable methods of selecting on clearance and edge wrapping, T=2.0, leave 0.2mm for clearance, T=2-3, leave 0.5mm.
Short edge is wrapped with long edge (Like door panel)
● Reasonable consideration of outside tolerances dimensions: take the maximum negative tolerance and half positive tolerance.
While take maximum positive tolerance and half negative tolerance for tolerances dimensions of holes.
● Burr direction
● Draw a cross-sectional view for extraction, riveting, tearing, punching (bumps), etc.
● Check material, plate thickness, tolerance of thickness
● Special angle, inner radius of bending angle (usually R=0.5)Confirm by bend testing.
● Emphasize places which are easy to make mistake.
● Draw enlarged view for places with many dimensions.
● Emphasize places to be protected from being powder coated.
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