Get a guide on sheet metal fabrication from insiders. This blog explores what sheet metal fabrication is, how it works, and its common materials and finishes. Also, we would like to give some tips for designing sheet metal parts.
What is sheet metal fabrication?
Sheet metal fabrication is a processing technology relative to thin metal sheets, including bending, punching, stretching, welding, splicing, forming, etc. The most obvious characteristic is the uniform thickness of the same part. It is featured by lightweight, high precision, good rigidity, flexible structure, and a beautiful appearance.
How does sheet metal fabrication work?
1. Blanking
There are many types of blanking. The main ones are as follows:
Shearing machine blanking
It utilizes a shearing machine to cut the material. It is mainly for mold feeding forming and preparation for processing, with a low cost and accuracy of less than 0.2 mm, but can only process bar or block materials without holes or cutting angles.
Punch blanking
The process applies a punch to cut the unfolded flat plate parts on the sheet into variously shaped parts.
Its advantages are short working hours, high precision, low cost, high efficiency, and suitability for mass production.
Laser blanking
Laser blanking uses laser cutting technology to cut the structural shape of the flat plate on a large flat plate. But it requires programming the laser program.
It can cut various complex flat parts, with a relatively high cost and accuracy of less than 0.1 mm.
Sawing machine blanking
It is mainly applied for aluminum profiles, square tubes, round tubes, round bar materials, etc., with low cost and low accuracy.
2. Bending
Bending is bending 2D flat parts into 3D parts. Under the pressure of the upper or lower die on the bending machine, the metal sheet first undergoes elastic deformation and then enters plastic deformation.
Its processing requires a bending machine and corresponding bending dies to complete under a certain bending sequence. The principle is to bend first without causing interference to the next cut, and then bend later if there will be interference.
Bending dies are divided into bending dies and straight dies. When bending aluminum sheets, cracks may occur, which can be avoided by increasing the width of the lower die groove or increasing the R of the upper die (annealing).
Matters needing attention when bending:
Drawing: quantity and thickness of sheet metal
Bending direction
Bending angle
Bending size
3. Stretching
In the process of fabrication of sheet metal, it is often necessary to stretch it out. Stretching is mainly for sample parts with special requirements. As the stress at each point of the stretched part is different, the thickness of the stretched material changes. Generally speaking, the thickness of the bottom center remains the same. The material becomes thinner at the bottom corner and thicker near the flange at the top.
4. Forming
Forming refers to the final sheet metal part formed after a series of processing procedures such as blanking, flanging, tapping, punching, riveting, bending, welding, etc., and then post-processing (surface finishing). It is the final form of sheet metal processing and the form we need to achieve. Sometimes, when there are multiple parts in a product, they should be joined in a certain way.
Above is the general process of fabrication of sheet metal. In the real world, every part is unique. So generally, the custom sheet metal fabrication processes vary for different projects.
Common materials for sheet metal fabrication?
1. Cold-rolled plate SPCC
Cold-rolled plate SPCC is mainly used for electroplating and baking paint parts, with low cost, easy formability, and material thickness ≤ 3.2mm.
2. Hot-rolled plate SHCC
The material thickness is normally ≥3.0mm. Hot-rolled plate SHCC is also applied to electroplating and baking paint parts, with low cost but difficult formability, mainly used for flat parts.
3. Galvanized plate SECC, SGCC, SECC electrolytic plate
They can be divided into N material and P material. N material is mainly not surface treated, with high cost, and P material for spray-painted parts.
4. Copper
Copper is usually used as a conductive material. Its surface treatment is usually nickel plating, chromium plating, or no treatment, with a high cost.
5. Aluminum
The aluminum plate is generally treated with chrome plating, and oxidation (conductive oxidation, chemical oxidation), with high cost, and can be silver-plated or nickel-plated.
The aluminum profiles are used extensively in various types of switchgear due to their complex cross-sectional structures. The finishing is the same as the aluminum plate.
6. Stainless steel
Stainless steel is mainly used without any surface treatment, with a high cost.
Common finishes for sheet metal fabrication?
The surface treatment of sheet metal products mainly includes polishing, brushing, sandblasting, powder coating, painting, electroplating, anodizing, electrophoresis, dip coating, silk screening, etc. The purpose is mainly to protect the material and apply a film on its surface to prevent oxidation and enhance the adhesion of the paint.
1. Polishing
Pre-polishing is the process of using hard or relatively hard polishing wheels to treat the surface of sheet metal that has been polished, which can remove the rough traces on the surface.
Fine polishing further processes the pre-polished surface using a soft material to remove the traces left by pre-polishing and obtain a bright mirror finish.
2. Brushing
Brushing involves grinding products on the working surface to form lines and achieve decorative effects. As the process can reflect the texture of metal materials, it is becoming more and more popular among users.
3. Sandblasting
Sandblasting is the process of using a sandblasting machine to blow sand particles onto the surface of the workpiece, forming a layer of densely distributed pits on the surface of the workpiece.
Its major function is to remove dirt and rust on the workpiece surface, increase the adhesion of the workpiece surface, and prepare for subsequent surface treatment methods. It is commonly used for materials such as cold-rolled plates, hot-rolled plates, and aluminum.
4. Powder coating
Powder coating is a coating process that uses electrostatic discharge to adhere powder coatings to the working surface. After powder coating, it is thermally melted or cured to form a coating on the working surface.
5. Painting
Painting involves spraying various colored coatings onto the surface of sheet metal parts through methods such as spraying and high-temperature baking. It is used to beautify the appearance and increase the corrosion resistance of materials and can be liquid paint or powder paint.
6. Electroplating
Electroplating involves attaching a layer of other metals to the surface of sheet metal materials through chemical reactions to increase the corrosion resistance of metals and achieve a certain decorative effect. Common electroplating materials include zinc, nickel, copper, and gold. There are two types of electroplating: vacuum plating and water plating. You can read this blog to learn more about their differences.
7. Anodizing
Anodizing is the process of oxidizing the metal on the surface of sheet metal materials to form a dense protective film on the workpiece surface, increasing its corrosion resistance. There are generally two methods: chemical oxidation and anodic oxidation.
8. Electrophoresis
Electrophoresis methods are divided into anodic electrophoresis and cathodic electrophoresis. When the coating particles are negatively charged, the workpiece is an anode, and the coating particles adhere to the workpiece under the action of an electric field. Conversely, if the coating particles are positively charged, the workpiece is a cathode, and the coating particles adhere to the workpiece to form a film, known as cathodic electrophoresis.
9. Dip coating
Dip coating involves heating products in molten materials, and the heated metal combines with the surrounding molten material to form a certain thickness of surface material.
Depending on the raw materials used for dip coating, it can be divided into liquid dip (coating) and powder dip (coating). It is commonly used for materials such as cold-rolled plates and hot-rolled plates.
10. Silk screening
Screen screening prints various marks on the surface of materials, generally including flat-screen printing and transfer printing.
The main principle is similar to the imaging principle of photographic film, which is an exposure process. Flat screen printing is mainly used on general planes, but if there are deeper pits, transfer printing will be used. It is commonly used for trademarks, usage identification, warning signs, etc.
How do we do a quality inspection for sheet metal fabricated parts?
“I want my sheet metal parts to be scanned.”
Don’t request your sheet metal fabricator to do that again. It would make you look stupid.
Why? As the sheet metals are thin, so they are soft. Using a scanner to do the quality inspection is meaningless. Your inspection report would be all red.
Quality inspection SOP (Standard Operating Procedure) at X Rapid Technologies:
1. Product reception
After the fabrication of sheet metal parts is done, they need to be received by the quality inspector first. To ensure consistency with the order, the product quantity, specifications, and customer requirements should be carefully checked. Custom sheet metal fabrication requires customized inspection standards. If any problems or differences are found, they should be told to the production department or project manager and resolved on time.
2. Visual inspection
Visual inspection plays an important role in sheet metal quality inspection. The quality inspector should carefully observe whether there are scratches, oxidation, deformation, and other surface problems on the product and compare them with the standards agreed with the customers before production. If any appearance defects are found, they should be recorded and dealt with promptly.
3. Dimensional measurement
Dimensional measurement is one of the most commonly used methods in sheet metal quality inspection. Based on the product requirements, appropriate measuring instruments should be used for dimensional measurement. For instance, calipers or micrometers can be used to measure length, width, height, and other dimensions. The measurement results should be compared with the standards. If they exceed the range, corresponding measures should be taken and recorded.
4. Special inspection
According to special product requirements, some special inspections may be required. For example, a projector can be used for shape inspection, and an optical microscope can be used for microscopic defect inspection. The special inspection methods require quality inspectors to have corresponding professional knowledge and operating skills.
5. Record and report
After completing the quality inspection work, quality inspectors need to record the results and make a quality inspection report. The report should include product information, quality standards, quality inspection results, existing problems, and improvement measures. It can be used for internal management and communication with customers.
Tips for designing sheet metal parts
In the design process of sheet metal structural components, the primary task is to check whether the parts can be bent and formed to eliminate manual welding, disassembly, or excessive disassembly.
It is also necessary to scientifically set the elements of sheet metal structure, such as deformation position zone, minimum height of bending edge, etc., to produce accurate sheet metal products.
Kick off your custom sheet metal fabrication project with X Rapid Technologies. Welcome to be in touch!
