Sheet Metal Design
There are many considerations to be made besides the usual specifications of dimensions, material and general shape. Sheet metal design usually refers to a comprehensive plan regarding the part that includes the smallest details. Software programs are frequently used to create and visualize the part. They also are able to anticipate any potential problems, weak areas or stress points in the metal. Checklists and booklets are also helpful when assessing a part or product's structural integrity. Though sheet metal design varies with the part, there are some design features that should always be taken into account. This list includes bends, counterbores, countersinks, curls, dimples, embossments, extruded holes, flanges, gussets, hems, holes, lances, notches, ribs, slots, tabs, welding and plating. These are common product attributes that are found in metal cabinets, car doors, metal drawer tracks, storage tanks and other sheet metal products and must be carefully added or formed for a quality product.
The general design guidelines regarding tolerances are that the tolerance of the sheet metal should not be tighter than necessary to make the part functional. It is important to have flatness specifications consistent with the design so that unwanted bending or bowing does not occur making secondary checking and straightening unnecessary. The minimum and maximum bend of the sheet metal is a design factor that will prevent putting areas of the sheet metal under stress, thus weakening it or increasing the chance of product failure. Looking after the edge distortion while sheet metal is formed is important because that would affect the product's critical dimensions. Any bending or stretching that is unaccounted for is undesired; if it is not in the design then it should not be in the product. Still other design considerations include making certain that the edge-to-hole clearance is great enough, that hole diameters are correct, that corners are properly blanked out, that localized hardening is not a issue, that notches, tabs and cutoffs are placed correctly, that acceptable materials are being used that can withstand the fabrication process, that any countersinks are of proper measurements, that the taper of a drilled hole is precise and other similar concerns.
