Part One. Basic Knowledge of Sheet Metal Processing —— Advantages, Disadvantages, and Methods to Reduce Costs

2025,09,08

Sheet metal processing is a processing technology that applies force to thin sheet metals to deform them into three - dimensional shapes. Generally, sheet metal processing methods are divided into manual sheet metal processing and mechanical sheet metal processing. In manual sheet metal processing, tools like hammers are used to manually apply force to the metal sheets for forming. In mechanical sheet metal processing, materials are clamped between molds, and mechanical forces such as hydraulic pressure are applied for forming. This time, we will introduce the basic knowledge of sheet metal processing that designers should know. Here, mechanical sheet metal processing, which is a commonly used processing method in industrial products, is referred to as "sheet metal processing", and the parts made through sheet metal processing are called "sheet metal parts".

Key points of sheet metal processing

In sheet metal processing, various methods are used to apply force to sheet metal to form the target shape, and its principle is related to the properties of metal materials. When a load is applied to a metal material, the material will change the distance between its constituent atoms and deform while generating strain. At this point, the force (internal force) with which the metal tries to return to its original state from the start comes into play. Therefore, when the load is small, if the load is removed, the metal will return to its original shape (elastic deformation). When the load applied to the metal continuously exceeds a certain point (yield point), the metal cannot recover (plastic deformation). If the load continues to be applied, it will be overwhelmed and break. In sheet metal processing, what is important is to have the technology of processing while adjusting, so as to obtain the target shape through plastic deformation.

Processes of sheet metal processing

There are roughly 8 processes from sheet metal processing to delivery. Let's take a detailed look at each process.

There are approximately 8 processes in sheet metal processing:

Unfolding/Programming

Design drawings are mostly created using 3D CAD. However, since sheet metal processing must start from a single sheet of material, a process is required to "unfold" the 3D design into a flat sheet state before processing using CAD or specialized software. Once the drawing is unfolded, "nesting" is performed, which involves arranging the parts in a way that allows efficient extraction from standard-sized materials without waste. At the same time, the processing program is compiled.

Blanking/Cutting

The process of cutting the outer perimeter, inner holes, etc., of metal sheets (also known as blanking) mainly uses two types of processing equipment: laser cutting machines and turret punches. Generally speaking, laser cutting machines excel at high-speed cutting of outer perimeters and large holes, while turret punches have features such as being able to handle a large number of holes and forming processes. There is also a "laser-punch combination machine" that combines the advantages of both. Since each sheet metal factory has different equipment, when placing an order, it is best to categorize the processing according to the factory's equipment.

Laser Cutting Customization

Deburring

Regardless of the processing method used in the previous step, laser cutting burrs (slag), punch shear burrs, flash, etc., will be generated to some extent. The deburring process is to remove these. It can be done manually using a hand grinder or file, or using a deburring machine with a rotating large sandpaper.

In deburring for sheet metal processing, it is difficult to perform fine size control such as C0.2 or R0.2 like in cutting processing. In this regard, a drawing instruction like "no burrs" is ambiguous, but an instruction such as "hope to remove burrs to the extent that they won't cut hands" seems effective. When placing an order, it is best to reach a consensus with the processing factory on the allowable range of burrs.

Bending

The general bending process of mechanical sheet metal involves installing molds on a device called a bending machine and applying pressure to the cut sheet to bend it linearly at a certain angle. In a bending machine, the upper mold (punch) is mounted on the upper part of the device, and the lower mold (die) is mounted on the lower part. The upper part of the device moves up and down to bend the metal sheet. However, the angle obtained by bending varies depending on the material batch and rolling direction, so fine adjustments are needed each time, making processing difficult. But it can be said to be one of the most important processes in sheet metal processing because the ease and aesthetics of welding in subsequent processes vary greatly depending on the accuracy of the bending process. In addition, the "bending machine" is sometimes called a "folder" or "bender", etc., and they all refer to the same type of equipment.

Sheet Metal Bending Customization

Welding

Welding is a process that joins metals by heating them to melt and then cooling. In sheet metal processing, TIG welding and laser welding are mainly used. TIG welding, which uses a tungsten electrode, is sometimes called "argon arc welding" because argon gas is used as a shielding gas.

skilled welding processes

TIG welding can perform build-up welding by adding a filler rod to the molten part. On the other hand, since a large amount of heat is input into the material, deformation is likely to occur. The processing result largely depends on the craftsman's skills. Laser welding is a processing method that can suppress thermal strain and has the advantage that the processing process is easy to standardize. However, since it is based on base metal welding, it is difficult to use this method for parts that require build-up welding, and the processing method needs to be changed.

Finishing (including surface treatment)

The finishing processes of sheet metal processing include removing thermal strain caused by welding, grinding off the raised parts of build-up welding with a grinder, removing burns caused by welding through electrolytic polishing, and surface polishing (grinding, buffing), etc.

Assembly

This is the process of combining multiple parts and assembling them mainly using fasteners such as bolts, nuts, and rivets. It is mostly used in parts that do not require welding strength or need to be disassembled later. Assembly work is also called "fitting" and covers a wide range of work and processes, from small-scale assembly of parts to medium-sized units and final assembly of entire machines and equipment. In the sheet metal processing industry, some enterprises refer to the above-mentioned welding and assembly process as "assembly" (welding assembly).

Inspection

In the pre-delivery inspection of sheet metal products, visual inspection is usually carried out for both dimensions and appearance. In dimensional inspection, we mainly use calipers, scales, angle gauges, etc., to check whether there are errors in dimensions, hole positions, and accuracy by comparing the drawings with the finished products. In appearance inspection, we visually check whether the product has scratches and burrs. Some factories use image measuring instruments or coordinate measuring machines for inspection.

To be continued

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