Sheet metal fabrication is an indispensable part of the prototyping industry. Sheet metal fabricators are involved to help ensure that the final sheet metal product will meet its intended design specifications, perform reliably, and be produced efficiently and cost-effectively at scale. This article explores the vital role of sheet metal manufacturers in prototyping.
What is sheet metal fabrication?
1. Simple Definition
Sheet metal fabrication is a comprehensive cold-working process for metal sheets (generally less than 6mm thick). This process includes shearing, punching, bending, welding, riveting, die forming, and surface treatment. A distinctive feature of this process is that the thickness remains consistent for the same part.
2. Processes
NCT (Numerical Control Turret Punch Press) Processing
The Numerical Control Turret Punch Press is a flexible, automated machine that can adapt to frequent product changes. In the processing procedure, all the necessary operations and steps, as well as the relative displacement between the tool and the workpiece, are represented by digitized codes. This digital information is input into a dedicated or general-purpose computer via control media (like tape or disk). The computer processes and calculates the input information, issuing various commands to control the machine's servo system or other executing components. In this way, it can produce the products or parts automatically.
Common uses of an NCT include blanking (cutting), punching net holes, punching bulges, edge trimming, creating raised points, rib pressing, line pressing, and hole drawing.
Laser Cutting
LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. In laser cutting, an electronic discharge is the energy source, while a mixture of gases like Helium, Nitrogen, and Carbon Dioxide acts as the excitation medium. A laser beam is created by focusing this light with a mirror assembly, which then cuts the material. The cutting head, driven by a programmatically controlled servo motor, moves along a predetermined path to cut out workpieces in various shapes.
Laser cutting is generally used for material cutting, contour shaping, secondary cutting, line cutting, and crafting of irregular holes.
Press Brake Forming
In press brake forming, the upper and lower dies are affixed to the upper and lower worktables of the press brake machine. The worktable's relative movement, driven by hydraulic transmission, along with the shape of the upper and lower dies, facilitates the bending and shaping of sheet metal. The sheet metal manufacturers use either an upward-moving or a downward-moving type. The basic principle for bending sequence is to bend from inside to outside and from smaller to larger bends. Special shapes are bent first, followed by general shapes. The operations are sequenced such that earlier stages do not interfere with subsequent ones.
Bench Work
Benchwork employs various equipment including riveting machines, tapping machines, hole-pulling machines, wire drawing machines, leveling machines, and drilling machines. Each machine plays a specific role in the fabrication process.
Die Forming
In die forming, sheet metal undergoes processing through fixed dies, commonly including blanking dies and forming dies. Each die contributes to a particular aspect of the fabrication process.
3. Surface Treatment
Common surface treatments include powder coating, anodizing, electroplating, brushing, electrophoresis, silk screening, etc.
Powder Coating
This is a finishing process where a free-flowing, dry powder is applied to the surface of a metal. The coated object is then heated, causing the powder to melt and form a protective layer on the surface. This method is popular due to its durability and environmental friendliness.
Anodizing
Anodizing is an electrochemical process that increases the thickness of the natural oxide layer on the surface of metal parts, particularly aluminum. The process enhances corrosion and wear resistance and provides better adhesion for paint primers and glues. It also gives the metal surface a decorative appearance with a durable, anodic oxide finish.
Electroplating
Electroplating involves depositing a layer of metal onto a surface using an electric current. The object to be plated serves as the cathode in an electrolyte solution containing metal ions. When current is applied, metal ions are reduced and deposited onto the cathode, forming a thin metal coating.
Brushing
Brushing is a mechanical process where abrasives are rubbed against the metal surface to create many small scratches. The result is a pattern of fine lines on the surface that can help hide fingerprints and minor scratches, giving the material a more appealing look.
Electrophoresis
Electrophoresis, or e-coating, applies an electric field to cause charged particles to move in a carrier fluid. In metalworking, this is often used to deposit a protective coating onto a metal surface, providing increased resistance against corrosion.
Silk Screening
Silk screening, or screen printing, is a printing technique where ink is pushed through a mesh stencil onto a surface. Each color in the design requires its stencil. This method is often used for adding logos or designs to metal surfaces.
4. Materials
Typically, the following materials are extensively utilized in sheet metal fabrication:
Stainless Steel
This corrosion-resistant, durable, and aesthetically pleasing alloy steel finds broad applications across various industries, including food processing, healthcare, and chemical industries.
Commonly used grades include 201, 304, and 316, with 304 stainless steel being the most preferred due to its exceptional all-round performance and cost-effectiveness.
Aluminum Alloy
Primarily composed of aluminum and supplemented with copper, magnesium, and zinc, this alloy is renowned for its lightness, high strength, and superior heat and electrical conductivity. It is widely employed in industries such as aviation, automotive, and electronics.
Frequently used grades include 1060, 5052, and 6061, with 6061 aluminum alloy being a favorite due to its excellent moldability and weldability.
Carbon Steel
This variant of steel, where carbon is the principal alloying element, can be classified into low carbon steel (C≤0.25%), medium carbon steel (0.25%<C≤0.6%), and high carbon steel (C>0.6%) based on carbon content. Noted for its high strength and affordability, carbon steel is extensively used in machinery manufacturing, construction, and other fields.
Popular grades include Q235, Q345, etc., with Q235 carbon steel being the most commonly used due to its superior plasticity and weldability.
Copper Alloy
This alloy mainly consists of copper but includes elements such as tin, zinc, nickel, etc. This metal finds extensive application in electrical and instrumentation sectors because of its excellent conductivity and resistance to oxidation and corrosion.
Common grades include T2, H62, H90, etc., with T2 pure copper being the most frequently used due to its remarkable ductility and weldability.
5. Industries Served
Sheet metal fabrication serves nearly every industry, including the automotive, aerospace, electronics, electronics, construction, medical, energy, food & beverage, and telecommunications sectors.
What role does sheet metal fabrication play in prototyping?
Sheet metal fabrication plays a critical role in the prototyping phase of product development, particularly for products or components that are made from metal or will have metal parts. Here's how it contributes:
1. Design Verification
Prototyping through sheet metal fabrication allows designers and engineers to verify their designs in a tangible form. They can check for fit, form, and function, and make necessary adjustments before moving to high-volume production.
2. Material Testing
With sheet metal fabrication, the prototype can be made with the same material as the final product. It allows for accurate testing of how the material will react under real-world conditions, such as its durability, resistance to stress, heat dissipation, and more.
3. Cost-Efficiency
While creating a prototype can be relatively expensive on a per-unit basis, it can lead to significant cost savings in the long run. Identifying and correcting design flaws during the prototyping phase is much more cost-effective than making changes during mass production.
4. Performance Testing
A prototype created through sheet metal fabrication can be used for performance testing and quality assurance. It can undergo various tests to ensure it meets all necessary standards and requirements.
5. Process Development
During prototyping, sheet metal manufacturers can also fine-tune their fabrication process. This might involve determining the most efficient order of operations, identifying potential bottlenecks, and optimizing tooling.
Sheet metal fabrication in prototyping helps ensure that the final product will meet its intended design specifications, perform reliably, and be produced efficiently and cost-effectively at scale.
What are the differences between sheet metal prototyping and high-volume sheet metal fabrication?
For prototype sheet metal fabrication, the process commonly involves the use of advanced tools such as Numerical Control Turret Punches (NCT), laser cutting machines, CNC bending machines, and riveting machines. This approach allows for a relatively quick production cycle but comes with higher costs.
For large-scale sheet metal fabrication, the process typically involves custom-designed molds. While this method requires a substantial initial investment and has a longer production cycle, it guarantees the quality of the parts produced. Moreover, when this cost is distributed across the large volume of parts produced, the individual part cost becomes relatively lower.
How do sheet metal fabricators quote prototype parts?
1. Understanding the Project
The fabricator first needs to understand the requirements of the project. It includes the design, functionality, and aesthetics of the prototype.
2. Material and Process Selection
The type of material used and the fabrication processes required (such as cutting, bending, punching, etc.) significantly affect the cost.
3. Quantity
The number of prototypes needed will also influence the quote. A larger quantity could potentially lower the unit cost due to economies of scale.
4. Turnaround Time
The required turnaround time can impact the cost. A quicker turnaround time might increase the cost.
5. Design Complexity
Complex designs that require custom tooling or high precision may increase the cost.
6. Finishing Processes
Any required finishing processes, such as powder coating, electroplating, or brushing, will also be factored into the cost.
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