What Is Sheet Metal Fabrication?
Sheet metal fabrication is the method through which various manufacturing processes are carried out on sheet metal to produce useful parts. There are five manufacturing processes involved in the sheet metal fabrication; designing, cutting, bending, assembly and finishing. Some of the commonly used sheet metals include stainless steel, aluminium, copper and zinc.
The sheet metal materials come in thin gauges of about 0.006 to 025 inches thick. The sheet metal fabrication process is cost-effective especially when producing hollow or partially flat parts. Material wastage in this process is minimized and the process is also very fast leading to high output.
Focus On Blue Prints From Design Engineer
Designing stage comes before anything else. The design done by an engineer relies on the requirements given by the client. Some engineers may prefer to use hand-drawn diagrams which can best suit simple projects.
However, currently, most engineers use computer-aided design (CAD) to create precise and more complex blueprints. The use of CAD allows for complex and accurate designs as per the specifications. CAD files are also needed for laser cutting of sheet metal.
Testing Through A Prototype
After the design is done and checked using the specified requirements by the client, it is possible to create a prototype.
The prototype is used for testing the functionality of the end product especially if multiple and replicable parts are to be produced.
At this stage, the client and the fabricator can make adjustments where necessary in order to come up with precise parts.
Cutting Sheet Metal With Shear
This method uses shear forces to cut the sheet metal in a process known as shearing. Shear cutting employs power-driven tools to manually cut through the sheet metal. Such tools include circuit saws, lathes, drills, band saws, and milling machines.
Shear cutting can be done through the use of three basic processes – shearing, punching, or blanking. Shearing is fairly accurate, cheap and is capable of cutting various sheet metals, and is preferred when producing basic shapes. However, shearing is not suitable for hard metals like tungsten and the process can also create burrs on the sheet metal.
Waterjet Cutting Sheet Metal
The waterjet cutting method uses a high-powered jet stream of water with any abrasive tool for cutting large sheet metals. Since it doesn’t employ the use of heat, it is suitable for cutting heat-sensitive and softer sheet metals.
This method has various limitations for instance it cannot be used with 3D structures, it is not very accurate. Another downside is that the abrasive material cannot be reused leading to a lot of wastage and the surface is dull.
Laser Cutting Sheet Metal
The cutting process using laser method is very fast and is suitable for cutting custom designs.
Also cut is designed through a computer aided design process meaning there is no need for retooling for every cut.
Fabricators prefer using this method because it does not create any damage to the sheet metal including thin sheets.
Plasma Cutting Sheet Metal
This method uses accelerated plasma beams to cut through the sheet metal. It is recommended for cutting sheet metals that have good electrical conductivity.
Bending Or Forming Sheet Metal To Suitable Shapes
At this stage, the metal sheet can undergo various processes in order to come up with desired shape and design.
Bending – can be done through a machine called brake to create V shapes, U shapes and angles of different degrees. Sheet metals of thinner gauges are easy to bend.
Decambering – makes it possible to undo the bend or bend the sheet in the opposite direction from the first bend.
Stamping – this process uses a mechanical or hydraulic stamping press with a die and tool. It can be used for curling, embossing, drawing, hemming, and flanging.
Spinning – a lathe tool is used for this method to rotate the sheet metal while it is pressed against a tool. This process is suitable for making rounded sheet metal products like cylinders and cones.
Wheeling – is used for making curves on the sheet metal through the use of wheels
Rolling – involves feeding the sheet metal in between two rollers for the purpose of reducing its thickness and increase the consistence.
Expanding – is the use of external forces through a tool called stretcher to create stretches on the already cut sheet metal.
Punching – this process uses a punch and die for creating hole in the sheet metal. The sheet metal is positioned in between the punch and the die, when the punch is pressed down, it creates a hole on the sheet metal.
Curling – the process that is used to remove burrs from the produced part to create smooth edges.
Welding Or Joining Sheet Metal Parts
There are various techniques that can be used for joining sheet metals.
Sheet metal welding is the process through which two or more sheet metal parts are joined together by the use of heat. The heat applied is used to melt the metal surfaces then they are pressed or hammered together to create the joint. There various welding processes that can be used to create this type of joints.
MIG welding – is a continuous process that uses a wire and a shielding gas in its operations. It is particularly suitable for high production and flexibility.
TIG welding – can be used for both spot and continuous welding processes and is suitable for thin parts.
Resistance welding – is done by heating the material through an electrical resistance process. This process is recommended for welding iron and steel.
Projection welding – requires the use of studs so that the current is directed on the stud which heats to create welds.
Laser welding – produces less heat during welding and can be used for welding sheet metals that are heat sensitive.
The choice of a welding process depends on factors like sheet metal material, sheet thickness, finish requirements, application temperature. Materials that can be welded include iron, aluminium, stainless steel and copper. Some benefits of sheet metal welding include; permanent joint, leak proof joints, strong joints, complex joints. There are a few disadvantages including difficulty in inspection, warping issues, change in material properties.
Alternative Ways Of Joining Sheet Metal
Riveting creates permanent joints and it works when holes are created on the adjacent sheet metal parts. The riveting process involves putting the rivet in the already punched hole on the sheet metal parts. Additionally, through the use of a rivet machine, the rivet mandrel is pulled to fasten the joint. Moreover, the pulling process creates a diametrical expansion on the pin against the work piece and rivet head securing them in position.
The available rivet types are Oscar rivets, solid rivets, drive rivets, flush rivets and semi-tubular rivets. Riveting technique has various advantages; low material and operational costs, blind joints, can allow part disassembly. Some of the disadvantages for this technique include; setting up the riveting is difficult and a lot of stress is concentrated at the joint.
This technique employs the use of screws, nuts, bolts, studs or standoff to fasten sheet metal parts. You can use:
- Machine screws – this is suitable for applications that require multiple assemblies and disassembly procedures. Machine screws work best when coupled with additional techniques like riveting and clinching.
- Self-tapping screws – a low-cost method meant for one-time assembly for sheet metal parts. A pilot hole must be created on one of the sheet metals before they are joined.
The choice of screw type depends on; sheet thickness, material, cost, and structural requirements. Some advantages of screw joining are temporary joints, can create a blind joint, a wide variety of screws, easy and reliable. However, you may need gaskets for waterproof joints.
Clinching technique uses a cold forming process to create permanent joints between sheet metal parts. A button-like positive link between layers of sheet metal parts is created. This technique can join different types of sheet metals with different sheet metal thicknesses. Some of the advantages of clinching include; low operational cost, permanent joint, does not additional fasteners.
Closely related to this is metal folding or tab joint. It can be used for joining soft steel, aluminium, copper and brass sheet metal parts. Some of the advantages of tab joint technique include, no need for additional fasteners, low cost and can join dissimilar sheet metal parts.
Just like clinching, adhesive bonding also creates permanent joints between two sheet metal parts. Sheet metal parts joined through this technique can be disassembled through the use of chemicals. The joint is achieved through the application of adhesives in between the two sheet metal parts being joined together. Pressure is then applied to aid in sticking the two parts together.
Several types of adhesives are available such as cyanoacrylate, acrylic-based, epoxy-based and silicon-based adhesives. There are various factors to consider when selecting the type of adhesive e to be used. Factors like the material, surface geometry, bonding strength and moisture content in application.
Fabricated Sheet Metal Parts Finishing
For all your sheet metal fabrication needs, contact KDMFAB now.