Basic Knowledge of Sheet Metal Processing

Sheet Metal Processing

Sheet metal processing is a processing technology that applies force to a thin plate-shaped metal to deform it to create a three-dimensional shape. The processing methods of sheet metal processing are roughly divided into manual sheet metal and mechanical sheet metal. Manual sheet metal is to use tools such as hammers to manually apply force to the metal plate to form it. Mechanical sheet metal is to clamp materials between molds and apply hydraulic pressure, etc. mechanical force to form. This time, we will introduce the basic knowledge of sheet metal processing that designers should know. We will refer to a processing method commonly used in industrial products, that is, mechanical sheet metal, as "sheet metal processing", and parts made of sheet metal processing as "sheet metal processing".

The Main Points of Sheet Metal Processing

In sheet metal processing, various methods are used to apply force to the sheet metal to form the target shape. The principle is related to the characteristics of the metal material. When a load is applied to a metallic material, the material changes the distances between its constituent atoms and deforms while creating strain. At this time, the force that the metal tried to return to its original state from the beginning acts, so when the load is small, if the load is removed, the metal will return to its original state. When a load is continuously applied to a metal beyond a certain point, the metal cannot recover. If the load continues to be applied, it will be overwhelmed and break. In sheet metal processing, it is important to have the technology of processing while adjusting in order to obtain the target shape through plastic deformation.

Process of Sheet Metal Processing

There are roughly 8 processes in sheet metal processing until it leaves the factory. Let's look at each process in detail.

1. Deployment/Programming

Design drawings are mostly drawn using 3D CAD, but sheet metal processing must be processed from a sheet, so it is necessary to use CAD and special software to "unfold" into the state of a sheet before processing. Once the drawing is unfolded, "composition", that is, the parts are laid out, so that the parts can be efficiently obtained from standard-sized materials without waste, and the machining program is created at the same time.

2. Punching/Cutting

In the process of cutting the outer circumference and inner hole of the metal plate, which is also called blanking, two types of processing equipment, a laser cutter and a turret punch, are mainly used for processing. To roughly distinguish, the laser processing machine is good at high-speed cutting of the periphery and large holes, and the turret punching machine is also capable of processing a large number of holes and forming processing. There is also a "laser punching compound machine", which realizes the advantages of the above two at the same time, and each sheet metal factory has different equipment, so when ordering, it is best to classify and process according to the equipment of the processing factory.

3. Deburring

No matter which processing method is used in the previous process, laser cutting burrs, punching shear burrs, flashing, etc. will be generated to a certain extent. The removal of these is the deburring process. It can be done manually with a manual angle grinder or file, or with a deburring machine that spins large sandpaper.

In deburring of sheet metal processing, it is difficult to perform fine dimensional control such as C0.2 and R0.2 like cutting processing. In this regard, a drawing instruction such as "no burrs" is ambiguous, but an instruction "desires to remove burrs to an extent that does not cut hands" seems valid. When placing an order, it is best to reach a consensus with the processing plant on the allowable range of burrs.

4. Bending

The general bending process of mechanical sheet metal is to install a mold on a device called a plate bender, and apply pressure to the cut sheet to make it bend linearly at a certain angle. In the plate bending machine, the upper die is installed on the upper part of the equipment, and the lower die is installed on the lower part. The upper part of the equipment moves up and down to bend the metal plate, but the bending angle varies with the material batch and rolling direction, so every Fine-tuning is required every time, and processing is difficult. However, it can be said to be one of the most important processes in sheet metal processing, because the difficulty and aesthetics of the welding process in subsequent processes will vary greatly due to the accuracy of the bending process. In addition, "plate bending machine" is sometimes called "bending machine", "bending machine", etc., and they all refer to the same kind of equipment.

5. Welding

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

TIG welding can perform overlay welding by adding filler rods to the fusion zone, but on the other hand, deformation tends to occur due to the large amount of heat input to the material. The result of processing depends largely on the skill of the craftsman. Laser welding is a processing method that can suppress thermal strain, and has the advantage of easy standardization of processing technology, but because it is based on base metal welding, it is difficult to use this method for parts that require surfacing welding, and the processing method needs to be changed .

6. Finishing

The finishing process of sheet metal processing includes removing the thermal strain caused by welding, using a grinder to cut off the raised parts of the surfacing welding, using electrolytic polishing to remove burns caused by welding, and surface polishing (grinding, polishing), etc.

7. Assembly

This is the process of combining multiple parts and assembling them mainly using fastening parts 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, also known as "assembly", covers a wide range of work and processes, from the small assembly of parts to the final assembly of medium-sized units and entire machines and equipment. In the sheet metal processing industry, some companies refer to the above-mentioned welding assembly process as "assembly" (welding assembly).

8. Check

In the pre-shipment inspection of sheet metal processed products, the size and appearance are usually visually inspected. In the size inspection, we mainly use calipers, scales, angle gauges, etc., and check whether the size, hole position, and accuracy are wrong by comparing the drawings with the finished product. In the visual inspection, we visually inspect the product for scratches and burrs. Some factories use image measuring machines or coordinate measuring machines for inspection.