What Are the Methods of Sheet Metal Fabrication?

Shaping sheet metal can be accomplished through a variety of techniques, yet these techniques typically fall into two main categories: the processes of cutting and forming.

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The diverse methods for cutting and forming sheet metal necessitate a range of specialized tools, which can consequently elevate production costs. Therefore, grasping the different sheet metal fabrication methods available is crucial for devising the most effective designs for specific applications.

The fundamental approach to sheet metal fabrication commences with a flat metal sheet and a technical drawing (often in DXF or CAD format). This drawing will guide the procedures for cutting, shaping, and finishing the base material.

It could entail something as straightforward as a single bend to create angle iron or intricate laser cutting followed by bending at the edges for computer enclosure panels. When these processes are intertwined, the initial step involves cutting, followed by formation, finishing, and finally, joining the components together.

Utilizing DFMPro for Effective Sheet Metal Design Standards

DFMPro offers pre-set design guidelines focusing on Design for Manufacturing (DFM) principles which assist in creating superior quality parts while minimizing costs. Some of the prevalent sheet metal design standards include parameters such as the least distance between holes, cutouts, and slots, as well as the proximity of these features to edges and bends, limitations on multiple bends in the same direction, minimum bend radius, minimum rolled hem radius, open hem, tear drop hem, and minimum flange width among others.

DFMPro's sheet metal design standards are highly adjustable and allow for the configuration of the existing design rules in accordance with specific organizational standards. Additionally, they offer the flexibility to easily incorporate new manufacturing design principles into the current framework.

Essential Sheet Metal Design Standards

The following section outlines notable design standards for working with sheet metal. These guidelines can assist companies in preventing product rejections and rework stemming from engineering oversights, which can lead to increased costs and delays in delivery to customers.

Minimum Distance from Extruded Hole to Part Edge

Extruding metal is among the most intense applications in press working, producing significant friction and heat. If an extruded hole is positioned too close to the edge of a component, it might lead to deformation or tearing of the material. It is advisable that the minimum distance from extruded holes to the part edge should be three times the sheet thickness.

Minimum Distance Between Extruded Holes

A designated distance should be maintained between extruded holes in sheet metal designs to avert deformation. It is suggested that the minimum space between two extruded holes must be at least six times the thickness of the sheet metal.

Minimum Hole Diameter

The diameter of holes in sheet metal should not be excessively small. Smaller holes are created through piercing, which necessitates the use of smaller punches. However, small holes require smaller tooling, which may break during operation. Hence, it is recommended that the diameter of any hole be at least equal to or greater than the thickness of the sheet metal.

Maximum Embossment Depth

Embossing involves forming small, shallow raised features on stamped parts. This operation primarily relies on stretching as a mode of deformation, which can lead to excessive thinning or material fracturing. Therefore, the maximum embossment depth should not exceed three times the thickness of the material.

Minimum Bend Radius

Specifications for minimum bend radii can differ based on material type and application. For instance, aerospace applications may necessitate higher bend radii. If the radius falls below the recommended level, issues with material flow in softer metals and fracturing in harder materials may arise. Thus, the minimum inner bend radius should be at least equal to one times the material thickness.

Curl Feature Considerations

Curling involves creating a hollow, circular roll along the edges of sheet metal. The curled edge enhances the structural integrity of the edge while ensuring safer handling. Curls typically remove sharp, untreated edges for safety. Recommended guidelines include:

• The outer radius of a curl should be no less than twice the material thickness.
• The size of any hole should be at least equal to the curl radius plus the sheet thickness from the curl feature.
• Bends should be placed at a distance of at least the curl radius plus six times the material thickness from the curl feature.

Guidelines for Hem Features

Hemming refers to folding metal back onto itself. In sheet metal applications, hems serve to reinforce edges, offering a safe surface for touch. Hems not only remove sharp edges but also obscure imperfections and create secure connections with minimal fastening. Moreover, hems can even effectively double the thickness of the metal in regions that require enhanced support. Recommended guidelines include:

• For teardrop hems, the inner diameter should equal the material thickness.
• In the case of open hems, the bend will lose its roundness when the inner diameter exceeds the sheet thickness.
• For bends, the minimum distance between the inside of the bend and the outside of the hem should be five times the material thickness, plus the bend radius and hem radius.

Notch Feature Recommendations

Notching is a shearing operation that removes a portion from the outer edge of the metal strip or part. If the distance between the notches and bends is too small, it may result in distortion of the sheet metal. To prevent such situations, notches should be situated at an appropriate distance from bends relative to the sheet thickness. This process is economical due to its low tooling costs and the availability of a limited range of standard punches. The DFMPro design recommendations for notches include:

• Notch width should not be less than 1.5 times the material thickness.
• Notch length can extend up to a maximum of 5 times the material thickness.
• The suggested corner radius for notches is 0.5 times the material thickness.

If you wish to delve deeper into sheet metal fabrication parts, do not hesitate to reach out to us for an expert consultation!