Sheet metal fabrication is a simple yet diverse manufacturing operation. For product designers, companies and entrepreneurs that are new to interfacing with sheet metal companies, there are a number of terms denoting key operations you should know. From design to production and assembly, these terminologies will remain pervasive in your discussions, and having a full understanding of what means what is the first step to ensuring that you stay on the same page with your manufacturing partner. Here are 18 of the most common terms to give you a surface level understanding of sheet metal processing.
1. Sheet Metals
Sheet metal refers to a form of metals that have been processed into thin and flat sheets with no more than 6mm in thickness. Sheet metals typically range between 0.5mm to 6mm in thickness. Anything below this range is classified as a metal foil, while dimensions above this are called metal plates.
2. Metal fabrication process
Metal or sheet metal fabrication processes are the set of processes, individually or combined, that are used to make value-added end-use prototypes or finished parts from sheet metal materials.
3. Design for manufacturing
Design for manufacturing, or DFM as it is more popularly called, refers to a set of guidelines and instructions that detail the best design practices for each manufacturing operations. DFM rules for sheet metals vary from that form 3D printing, CNC machining or Injection molding. DFM helps to reduce the risk or likelihood of project failure, optimize cost and cut down on leadtimes.
The workpiece is the raw material being worked on or processed to make the final sheet metal part.
Machining refers to a subtractive manufacturing process where the stock workpiece is processed into a final part by removing unwanted parts from it. Machining is achieved through milling, grinding, drilling and turning operations.
6. CNC machines
CNC stands for computerized numerical control. CNC machines are complex engineering devices that can be fitted with a variety of tools for grinding, milling, drilling and cutting operations in a manner designated in the CAD and CAM files. CNC machines are multi-axis machines, providing them with the superior capability of making parts with the most complex of geometries quickly and accurately.
CNC machines can process sheet metals and hundreds of several other diverse engineering materials.
Forming is a sheet metal fabrication process that reshapes the sheet metal form without any loss in weight or structural strength. Cold forming does not use any heat or melting to form the part, but instead, employs mechanical operations like bending, stamping, ironing, punching and laser cutting to make the finished part.
Forging involves the application of compressive force to a sheet metal to shape the workpiece into the desired final form. Forging may be cold or hot forging. The former occurs below room temperature, and the latter above room temperature. The compressive force may be exerted with a die or hammer.
Cutting is a metal fabrication technique that uses power tools such as laser, waterjet, plasma arcs and more, combined with CNC machinery, to cut or split sheet metals into smaller cross sections.
Shearing is a sheet metal process that removes excess or unwanted materials from a workpiece. The process uses a scissors-like setup by placing two blades above and beneath the sheet metal. When the necessary shearing force is applied, the sheet metal is cut into the desired sections.
Punching is a subtractive technique that is used to remove material workpiece and create holes and shapes in sheet metal parts. Punching is achieved with the use of a mechanical punch press or a CNC machine equipped with a turret. The punch is responsible for housing the desired pattern and the press applies the force that creates the unique design of the press on the sheet metal.
Welding is one of the most popular sheet metal operations in the world. It uses a combination of heat, pressure and a special flame to join two or more metal materials together. There are MIG, TIG and Stick or Arc welding. The choice of welding technique depends on the material type and the desired strength of the bond to be created.
Stamping is similar to punching in the sense that a mechanical press and a die is involved. Unlike punching however, stamping simply creates indentations or patterns on the surface of the sheet metal rather than creating a hole that punches through the sheet metal. Stamping can also be used as a secondary process to cut, cast, punch or shape sheet metal parts as required.
Casting is a hot-forming process that involves the processing of a solid sheet metal stock into molten metal, followed by pouring the molten metal into a mold or die where it is left to cool and solidify into the desired shape or the shape of the mold/die.
Just as the name implies, folding is a cold forming process that is used to process sheet metals into desired geometries at an angle. Folding is achieved by using a press to hold the sheet metal in place, and the action of a punch and die to contour the workpiece into the desired geometry.
Extrusion is a non-subtractive process that uses the action of pressure to force a stock of sheet metal material through or around a die. The forced material is squeezed through (extruded) the die, adopting its shape and forming a cavity, before emerging at the other end in the geometry of the desired part.
Finishing refers to the array of cosmetic and functional processes that is used to improve the cosmetic appeal, functional properties and overall acceptability of a fabricated sheet metal part. Sheet metal parts may be sanded, polished, spray painted, anodized, etc.
18. Die & Press tools
The die and press may be considered male and female components of a very specialized tool. The die is a pre-fabricated tool that is made to the desired shape that will be indented or punched through the sheet metal part after application of pressure from the punch. Basically, the sheet metal lies between the press and the die. A compressive force applied to the press above hits the sheet metal, and delivers a hole or indentation that is the shape and size of the die into the workpiece.
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