5 Factors for Choosing Sheet Metal Fabrication

12 Aug.,2024

 

5 Factors for Choosing Sheet Metal Fabrication

5 Factors For Choosing Sheet Metal Fabrication

­Written By: Tony Varela

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Introduction:

One of the most adaptable building materials in the manufacturing industry, sheet metal has rightfully found its place as one of the most important materials in the industrial age.  Steel, aluminum, brass, copper, tin, nickel, titanium, or other precious metals are traditionally used to make sheet metal.  Thicknesses vary but are mostly broken into two distinctions; thin gauge and heavy plate.  Many different industries rely on the versatility and durability of sheet metal including aerospace, appliance manufacturing, consumer electronics, industrial furniture, machinery, transportation and many more.

 

Why Choose Sheet Metal?

Sheet metal offers plenty of advantages as compared to both non-metal alternatives and other metal fabrication processes, as well.  When compared to machining, sheet metal is much less expensive in both processing and material costs.  It does not have the extremely high tooling costs of injection molding, which makes sense at high volumes.

As found in machining, rather than starting with an expensive block of material, much of which is wasted in the milling process of removing unneeded material, sheet metal lets you buy what you need and use what you need with relatively low material waste.  The unused sheet can then be used for another project, while the shavings produced in machining, need to be discarded and recycled.

With the advancement of technology used in modern fabrication, automation and new CAD (computer aid design) programs make designing in sheet metal easier and easier.  CAD programs now have the ability to design in the same material you intend to fabricate with and will allow programming of the parts to come straight from the CAD model itself.  No longer is there a need to create a separate set of shop drawings to interpret the design.  Perhaps most significant, in a world of mass production, sheet metal has the ability to scale rapidly.  The greatest cost for sheet metal fabrication is in the first piece.  This is because the cost is all in the setup.  Once the setup is complete, and the costs are spread out across the larger volume of pieces being fabricated, the price drops significantly, greater so than most subtractive processes like machining.

 

1. How is Sheet Metal Being Used?

Sheet metal can be cut, stamped, formed, punched, sheared, bent, welded, rolled, riveted, drilled, tapped, machined.  Hardware can then be inserted to fix electronic components, metal brackets or other pieces of sheet metal.  To finish sheet metal, it can be brushed, plated, anodized, powder-coated, liquid painted, silkscreen, laser-etched, and pad printed.  And of course, parts can be welded riveted into complex assemblies.

Just like any other technology, the processing of precision sheet metal is constantly evolving.  Materials, processes, tooling, and equipment are becoming highly specialized which is improving the time involved to make common sheet metal parts and speeding up the design process as well.  To fully leverage all the technological advantages, it is important that you select the right supplier and know the differentiation between metal fabricators; architectural sheet metal (HVAC and ductwork), heavy plate fabricators (staircases, fences, heavy structures) precision fabricators (thin gauge sheet metal, enclosures, brackets etc&#;).

Along these lines, this white paper will explore key components of the precision sheet metal fabricator, precision sheet metal fabrication.  This paper will focus on:

  • Fabrication techniques
  • Common Materials
  • Design considerations
  • Finishing options

 

2. Sheet Metal Fabrication Techniques

By definition, sheet metal starts out flat, but before this, it comes from large cast ingot and the rolled into a long ribbon in the desired thicknesses.   These rolled coils are then flattened and sent as large sheets cut to different lengths to accommodate the manufacturing shop&#;s needs. While this paper focuses on bending sheet metal along a single axis, there are processes out there, hot and cold forming techniques that include bending and forming sheet metal along multi-axis points in one process such as deep drawing, hydroforming, spinning and stamping.  These processes are most commonly found in the manufacturing of products like automobile panels, aluminum cans, and complex formed consumer appliances.  Another similar process is progressive stamping which moves a ribbon along a series of stamping which forms and punches different stages.  At the end of these progressive stages, you are left with a finished part.

Cold forming will be the focus of this paper.  Examples of cold-forming processes are as follows

Cutting

  • Shearing was one of the longest standing means to cut sheet metal but has since been replaced by faster, more precise methods.
  • Punch Press use tools called punch and dies, which punches holes and shapes to make any number of patterns.  Particularly effective for cutting simple patterns that are more economical than cutting on a laser cutter or a water jet. Punch presses can operate at hundreds of strokes per minute making this a suitable center for processing parts quickly.
  • Laser Cutting works with a combination of oxygen, nitrogen, helium, or carbon dioxide to burn away material and produce a clean edge.  This form of cutting can hold very tight tolerances.
  • Photochemical Machining is a process of controlling the etching using CAD-generated stencils to leave a pattern that is chemically activated to remove unwanted material.

Hemming &#; The edges of the sheet metal are folded over itself or folded over another piece of sheet metal in this forming operation to achieve a tight fit or a stronger, rounded edge.  Hemming is a technique to join parts together, improve the appearance, or increase the strength and reinforce the edge of the part.  Two standard hemming processes include roll hemming and conventional die hemming.   Roll hemming is carried out incrementally with a hemming roller.  An industrial robot guides the hemming roller and forms the flange.  Conventional die hemming is suitable for mass production.  With die hemming, the flange is folded over the entire length with a hemming tool.

Bending &#; Most sheet metal bending operations involve a punch and die type setup when forming along one axis.  Punch and dies come in all sorts of geometries to achieve varied different shapes.  From long gently curves to tight angles at, below, or above 90-degree angles bending metal can achieve many different shapes.   Press brakes are generally needed when a sharp angle is desired.   Rolling and forming methods are used when a long continuous radius is desired in one direction, or along one axis.

 

3. Common Types of Sheet Metals

There are many different metals and alloys that come in sheet form and are ultimately used in the fabrication of manufactured parts.   The choice of which material depends largely on the final application of the fabricated parts, things to consider include formability, weldability, corrosion resistance, strength, weight, and cost.   Most common materials found in precision sheet metal fabrication include:

Stainless Steel &#; There are a number of grades to choose from, for the purpose of this white paper we will focus on the top three found in precision sheet metal fabrication:

  • Austenitic stainless is a non-magnetic &#; any of the 300 series steel &#; that contains high levels of chromium and nickel and low levels of carbon. Known for their formability and resistance to corrosion, these are the most widely used grade of stainless steel.
  • Ferritic &#; Stainless steels that are magnetic, non-heat-treatable steels that contain 11-30% chromium but with little or no nickel. Typically employed for non-structural uses where either good corrosion resistance is needed such as with seawater applications or decorative applications where aesthetics are the main concern.  These metals are most commonly found in the 400 series stainless steel.
  • Martensitic

    &#; A group of chromium steels ordinarily containing no nickel developed to provide steel grades that are both corrosion resistant and hardenable via heat-treating to a wide range of hardness and strength levels.

Cold Rolled Steel &#; A process in which hot rolled steel is further processed to smooth the finish and hold tighter tolerances when forming.  CRS comes in and alloys.

Pre-Plated Steel &#; Sheet metal material that is either hot-dipped galvanized steel or galvanealed steel, which is galvanized then annealed.  Galvanization is the process of applying a protective zinc coating to steel in order to prevent rust and corrosion.  Annealing is a heat treatment process that alters the microstructure of a material to change its mechanical or electrical properties, typically reducing the hardness and increasing the ductility for easier fabrication.

Aluminum &#; An outstanding strength to weight ratio and natural corrosion resistance, aluminum sheet metal is a popular choice in manufacturing sectors meeting many application requirements.  Grade offers excellent corrosion resistance, excellent workability, as well as high thermal and electrical conductivity.  Often found in transmission or power grid lines.  Grade is a popular alloy for general purposes because of its moderate strength and good

workability.  Used in heat exchanges and cooking utensils.  Grade and are commonly found in metal fabrication.  Grade is the most widely used alloy best known for being among the stronger alloys while still formable, weldable, and corrosion-resistant.  Grade is a solid structural alloy most commonly used in extrusions or high strength parts such as truck and marine frames.

Copper/Brass &#; With a lower zinc content brasses can be easily cold worked, welded and brazed.  A high copper content allows the metal to form a protective oxide later (patina) on its surface that protects it from further corrosion.  This patina creates an often highly desirable aesthetic look found in architectural or other consumer-facing products.

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4. Design Considerations for Sheet Metal Fabrication

Engineers designing sheet metal enclosures and assemblies often end up redesigning them so they can be manufactured.  Research suggests that manufacturers spend 30-50% of their time and 24% of the errors are due to manufacturability.  The reason behind these preventable engineering errors is usually the wide gap between how sheet metal parts are designed in CAD programs and how they are actually fabricated on a shop floor.  In an ideal scenario, the designing engineer would be familiar with the typical tools that will be used to fabricate the sheet metal parts while also taking advantage of designing within the CAD programs available sheet metal settings.

The more that is known about the fabrication process during the design phase the more successful the manufacturability of the part will be.  However, if there are issues with the way certain features were designed, then a good manufacturing supplier should be able to point those out and suggest good alternatives to address them.  In some cases, the suggestions may

same time and unneeded costs.  Here are some considerations while designing sheet metal for fabrication:

  • Sheet metal fabrication is most cost-effective when standard tool sizes are used as opposed to costly custom tools that need to be made specifically for the job. If a single part becomes too complex, consider welding or riveting parts together that can be made using standard, or universal tools.
  • Because bends will stretch material, features such as holes, cut-outs, inserted hardware should be located well enough away from bends to prevent distortion of the hole. To help with this rule, remember &#;4T&#; which means located features four times the material thickness away from any bends.
  • Press brakes create bends by pressing sheet metal into a die with a linear punch, so the design does not allow the creation of closed geometry.
  • Sheet metal tolerances are far more generous than machining or 3D tolerances. Factors affecting tolerances include material thickness, machines used, and the number of steps in the fabrication process.  Suppliers generally will provide detailed tolerance specifications as it related to their shop and machines.
  • A uniform bend radius such as 0.030 in. (industry standard) should be used on every bend of a part to reduce multiple setups and accelerate production.
  • Welding thin materials can lead to cracking or warping. Consider other joining methods when working with thin materials.
  • Consider material thickness and manufacturers&#; minimum requirements when installing PEM hardware.

 

5. Finishing Sheet Metal

There are several different methods and reasons to finish sheet metal parts.  Depending on the material chosen, some finishing techniques protect the material from corrosion or rust while other finishing materials are done for aesthetic reasons.  In some cases, finishing can achieve both purposes.  There are finishing processes that include simple alterations to the surfaces of the materials.  Other finishing processes consist of applying a separate material or process to the metal.  Standard finishing techniques include:

  • Brushing is used to deburr and remove surface defects from sheet metal parts.  The surface pattern created is a uniform parallel grain resulting from the brush moving against the metal surface in one direction.
  • Plating is a process of coating a layer of metal to an object of different types of metal.  This process is done, commonly, for aesthetic purposes or more practical reasons such as corrosion resistance and protection from wear and tear.
  • Polishing sheet metal as a means of finishing is where a layer of oxidation and also a thin layer of the material itself is ground off.   In doing so it smooths out the metal, removing imperfections, and making it gleam once more.  Generally, start with a coarse grit of sandpaper, like a 40 to 80 grit and then work towards a finer grit to finish off the polish effect.
  • Powder Coating
  • Abrasive Sand Blasting, more commonly known as sandblasting or media blasting, is the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface or remove surface contaminants.

 

Concluding Thoughts

Selecting a material, in this case, sheet metal is the first step in any design process.  The process begins with the function of the part you are intending to design.  The function of the part will help determine the needed design.  Choosing a material and gauge are critical steps that involve balancing factors like strength, weight, and cost.  This is not a simple process but can be streamlined by using CAD models with the above design considerations found in this white paper.  The next real test, however, is prototyping.

While today&#;s engineering tools are powerful, it is only when you can see and handle a part that it becomes known whether the design will meet expectations.  Is it strong enough?  Light enough? Does it look, feel, and balance the way it should?  Does it sacrifice other components?  Even relatively simple components benefit from real-world try out before committing to hundreds or thousands of parts.   In some cases, it may take several prototype iterations to get the sheet metal part right.  With a good manufacturing supplier, this process

can be kept at a minimal impact on the overall project but getting it right earlier in the prototype process.

It is tempting for larger enterprises to outsource design to engineering service providers so they can focus on core activities.  However, selecting the right partner helps avoid further widening the gap between the ideal design and fabrication process and the all too common real-world scenario of poor designs making to the fabrication floor without resolution of design flaws.  Working with partners willing to collaborate, interested in knowing more about the manufacturing process, and involved in developing sheet metal products.  When selecting fabrication suppliers, look for companies with a proven track record in producing parts and who bring a vast wealth of fabrication knowledge to ensure fewer hiccups in the design to the fabrication process and product is brought to market faster.

 

 

Source:

The Aluminum Association. &#;Aluminum Alloys 101,&#; (n.d.) Retrieved from https://www.aluminum.org/resources/industry-standards/aluminum-alloys-101

Australian Stainless Steel Development Association. &#;Types of Stainless Steel&#; () Retrieved from https://www.assda.asn.au/stainless-steel/types-of-stainless-steel/austenitic

A.J. Sedriks, in &#;Encyclopedia of Materials: Science and Technology,&#; () Retrieved from
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/stainless-steel

Top 5 Factors to Consider When Buying Metal for Industrial ...

Selecting the appropriate metal for industrial use is a crucial choice that affects the efficiency, robustness, and affordability of your projects. With so many different metals available, each with its own special qualities and traits, it&#;s essential to take certain aspects into account in order to make well-informed judgments. You will learn about the five most important considerations when choosing metals for industrial applications in this extensive guide, which will help you make sure your projects function up to par.

Mechanical Properties: Tailoring Metals to Performance Requirements

Understanding a metal&#;s mechanical characteristics is crucial when choosing it for industrial usage. A variety of qualities are included in mechanical properties, including elasticity, toughness, hardness, and tensile strength. The capacity of a metal to resist pulling forces is determined by its tensile strength, while its hardness establishes its resistance to deformation or scratching. Elasticity is the metal&#;s ability to regain its previous shape after deformation, whereas toughness is the metal&#;s ability to withstand stress without breaking. Take into account the particular performance needs of your industrial application. High tensile strength and hardness metals, such as steel alloys, may be perfect for applications needing structural integrity and load-bearing capacity. Conversely, high-toughness metals may be advantageous in situations where impact resistance is crucial, such as heavy equipment or construction.

Corrosion Resistance: Protecting Against Environmental Challenges

Metals in industrial environments are always at risk for corrosion, which may jeopardize structural integrity and need expensive replacements or repairs. Evaluating a metal&#;s ability to withstand corrosion is essential, particularly when exposed to corrosive agents or extreme environmental conditions. Because chromium forms an oxide layer that protects against corrosive substances, stainless steel, for example, is well known for its remarkable resistance to corrosion. So first, take your industrial application&#;s operating environment into consideration. To explore the best options, you can also look up online metal supplier options.

Temperature Tolerance: Matching Metals to Operational Environments

Temperature variations are common in industrial applications; thus, choosing metals with the right temperature tolerance is essential to avoid structural damage or reduced performance. The rates of thermal expansion, melting temperatures, and conductivities of various metals differ. Metallic materials having high melting points, such as tungsten or molybdenum, may be appropriate for high-temperature applications, such as industrial furnaces or aircraft components. On the other hand, because of their capacity to retain structural integrity at very cold temperatures, metals like stainless steel or aluminum alloys are favored for applications needing low-temperature resistance or projects in cryogenic conditions. It is vital to comprehend the temperature circumstances that your metal will face during its operational lifespan in order to choose a material that is resilient to these difficulties.

Cost Considerations: Balancing Performance and Budgetary Constraints

Cost is a major factor when choosing materials in industrial settings. While it may be tempting to give financial limitations first priority, in order to guarantee the long-term sustainability and effectiveness of your initiatives, you must find a balance between cost and performance. Prices for different metals vary depending on availability, extraction methods, and alloy compositions, among other variables. For example, while aluminum is sometimes more costly than steel, in certain applications its corrosion resistance and lightweight nature may make the difference. Consider ownership expenses as a whole as opposed to just the original cost of materials. Throughout your industrial components&#; anticipated lifetime, take into account expenses associated with maintenance, repair, and replacement.

Formability and Machinability: Tailoring Metals to Manufacturing Processes

When working on an industrial project that requires precision machining, complicated forms, or sophisticated patterns, it is essential to take into account the formability and machinability of metals. Formability, which is important for applications requiring shaping or manufacturing, is the ability of a metal to deform without breaking or shattering. On the other side, machinability refers to the ease with which a metal may be formed, machined, or cut into certain parts. Give top priority to metals with outstanding formability and machinability when choosing them for applications requiring complex designs or accurate machining. For example, alloys made of aluminum are highly formable, which makes them perfect for complex shapes or extrusion. Because of its varied machinability, stainless steel is often used for applications that call for precise machining procedures.

Conclusion

Selecting the ideal metal for industrial usage necessitates a systematic process that takes several aspects into account. Every element affects the entire performance and longevity of your industrial projects, from temperature tolerance, corrosion resistance, and mechanical qualities to formability, cost, and other factors. This tactical method protects against any obstacles, encourages operational effectiveness, and eventually adds to the prosperity and durability of your business ventures.

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