Designing sheet metal is not an easy task. Engineering professionals still take their time to carefully design sheet metal based on their clients’ needs and preferences.
Professional CAD + CAM design services are often the most effective option for non-experts when designing sheet metal products. However, enthusiasts or budding designers can also learn the art of sheet metal design. Whichever group you belong to, there are some key things to consider when designing for sheet metal fabrication.
If you want to succeed in your sheet metal design process you will need to consider a number of variables. Before you begin your design, make sure you have thought about the type of metal, finish, complexity, dimensions, tolerance and tools you want to use.
Read our guide to learn all about sheet metal design.
What Should I Consider When Designing Sheet Metal Parts?
There are many variables to consider when designing sheet metal parts. This includes room for cuts and bends, the type of finish, the kind of sheet metal, the design, its thickness, and the complexity.
Although sheet metal designs are most common within the manufacturing industry and mass production, they aren’t limited to this industry. Engineers and those in similar fields can design their own sheet metal parts with the right knowledge and types of software.
Unfortunately, not even experienced engineers are exempt from making blunders when designing sheet metal parts. Following the guidelines associated with Design For Manufacturing (DFM) will mitigate issues during the design process.
DFM is the optimisation of a product, part, or component’s design which ensures a cheaper and easier design process. Efficient engineering and design is part of DFM, which generally occurs during the product design stage, making it so any mistakes can easily be rectified, consequently reducing related costs.
The details required in your plans depend on the specific type of file for laser cutting, bending or other process required. If supplying just a PDF flat pattern and DXF file for your metal fabricator, you’ll need to ensure all the necessary details are covered, including flat and side views, angles and measurements. For increased accuracy, provide a STEP file (.stp) for use with CNC technology.
Below is a list of considerations when designing sheet metal parts. Keep in mind that this is not an exhaustive list and simply serves as a recommendation of factors to consider.
1. Factor In Room For Cuts And Bends
When designing sheet metal parts, you must consider the room, space, or allowance needed to create cuts and bends. It is critical to consider the bend allowance too, which is the length of the neutral axis between the bend lines or the bend arc.
During the bending process, the material is stretched, which is why the K-Factor is important. This is the ratio between the neutral axis to the thickness of the material. The K-Factor is necessary to calculate flat patterns because it indicates how much material will stretch during the bending, which is critical when creating the design in CAD software.
To calculate the K-Factor, you will need to divide the bend allowance by the bend angle. K-Factor will change based on the V to be used (typically 8 to 10 times the metal thickness) and the blade used for each thickness. Your sheet metal fabricator can provide you with their average K-Factor and give more guidance on what to include in your patterns.
Typically, the minimum requirements for sheet metal folding patterns are:
- Flat pattern with fold line, measurement to the fold line, degrees to be folded and radius of the fold
- Side view with overall measurements of the folded part, angle in degrees and the bend radius
As an example, see the Bending & Folding Information Needed at Kanyana Engineering, with an average 0.39 K-Factor.
2. Choose Your Finish Before You Start Designing
It is important to know the type of finish you need or want for the metal sheet as early as the design phase. Different finishes serve various purposes, so designing with the finish in mind will result in a stronger, more polished product.
Finishes serve one of two purposes: protection and aesthetic enhancements.
Chemical conversion finishes will protect the part by altering or modifying the surface’s properties. If such a finish is applied to your sheet metal, you may consider using galvanised, galvannealed or anodised metal since these already come with a protective layer or zinc coat.
On the other hand, aesthetic finishes are usually done via powder coating, which also provides protection, although minimal and less durable. Silk screening is another type of aesthetic finish used for sheet metals meant to brandish an image or text.
Fair warning, though, some metals, although durable, may also restrict the flexibility and adaptability of your sheet metal parts when used. For instance, galvannealed steel cannot be welded due to the toxins given off during the process. Instead, you may use a different metal and add a zinc coating after welding to combat this. There is also a chromate conversion finish, which gives sheet metal parts electrical connectivity and provides a primer layer for painting.
3. Find The Right Sheet Metal For Your Project
Different types of sheet metal will provide different properties, advantages, and disadvantages. Understanding which type of metal to use early on will help the engineer design the part with the specific kind of sheet metal’s properties in mind.
Taking such properties into account as early as the designing stage will ensure the production of a more efficient product. Common sheet metals used are different types of steel – including cold rolled steel, galvanised steel, and stainless steel – as well as aluminium and copper.
Factors to be considered when choosing are:
- Expected wear on the part due to daily use
- Protection from corrosion
- Mechanical properties (tensile strength, yield strength, ductility)
- Conductivity (primarily for electrical applications)
Best practice for flat patterns and other sheet metal designs is to note the material type, material thickness and quantity on the patterns of documents provided.
4. Consider Metal Thickness If You’ll Need To Weld It
Metal thickness affects the speed at which heat is removed from the weld, leading to different microstructures within the weld and different amounts of fusion. In addition, sheet metal thickness and shape directly affect how accessible or achievable the desired weld will be.
Since metal melts under high temperatures, sheet metal that is too thin will not bode too well. The generally accepted minimum material thickness for standard sheet metal welding is 0.040 inches (1.016mm). Anything thinner than this will likely result in a mess of melted metal.
The metal thickness will also impact sheet metal folding – the inside fold radius should always equal the metal thickness, and should not be smaller. Always note the metal thickness on sheet metal designs provided to a fabrication company.
Metal thickness will help determine the V and K-Factor for metal folding, as demonstrated in the Bending & Folding Information Needed at Kanyana Engineering.
5. Design Parts That The Tools You Have Can Fabricate
You should design metal sheet parts or components that conventional tools can work on. The kinds of tools that can work on your sheet metal design will determine how many ways it can be shaped.
An example would be press-brake tools. Press brake bending or folding is commonly used on fabricated sheet metal parts to create precision straight-line bends, allowing them to be used or fitted onto more components. Due to its adaptability, choosing conventional tools to work on sheet metal parts also lowers the project’s cost.
Another example of a conventional tool used in these applications is a punch press, which allows for the creation of round embosses, countersinks, bridge lances, extrusions, and other similar features on fabricated sheet metal.
It is important to note that precision sheet metal parts are different from machine parts. The design process of the two gives them different tolerances and manufacturing possibilities.
6. Avoid Overly Complex Designs
More complex sheet metal designs will result in higher design costs. Keep sheet metal designs as simple as possible without compromising its functionality or utility. This is a good rule of thumb to keep fabrication time and cost to a minimum.
Overcomplicating a design will unnecessarily lengthen the design process, raise costs, and potentially open up more room for design and production errors. For instance, you should try to have simple angled bends designed to have a radius equal to or greater than the sheet metal’s thickness.
This is because creating small bends on larger parts requires more precision, and more specialist knowledge. While experienced metal fabrication workshops can deliver the results you need, it’s also wise to avoid unnecessary complexity in your sheet metal designs.
7. Factor In Room For Tolerance
When designing a sheet metal part or component, you must remember to give sufficient room for the finished product’s tolerance. Tolerance refers to the acceptable shape variation between the sheet metal design and the finished sheet metal product or part.
In layman’s terms, tolerance is the acceptable margin of error that normally occurs during the creation or fabrication of the part. Different types of files and different machinery will offer different tolerances, and you’ll need to ensure you’re providing the right file type (eg. STEP file) for the results to be as accurate as possible.
Although lower or smaller tolerances will result in a more polished and snug-fitting metal sheet product, this also takes much more time and money since more tolerance callouts will result in a very stringent screening of parts. One way of mitigating expenses and keeping production yield high is by lowering the ‘tolerance callouts’. Generally, very few surfaces or sheet metal parts require such callouts — hole diameters, distances, and radii are among these.
It is advisable to only assign key tolerances to surfaces and features critical to the part’s functionality or proper utilisation. Doing so will allow for a more affordable and efficient design.
Does All Sheet Metal Design Software Do The Same Thing?
There is not much difference between CAD (Computer-Aided Design) software and other 3D modelling programs. Although they generally do the same things, you will notice very slight differences in the interface, functionality, and design. The differences usually lie in the toolsets offered by the software.
Different software will be better suited to different fabrication options. As such, there are better file types for laser cutting, laser engraving, and other specific processes.
How Much Does It Cost To Get Sheet Metal Fabricated?
The price will vary on many factors, such as the quantity to be produced, the type of metal used, and the complexity of the fabrication, among others. In addition, prices vary slightly per state, and different metal fabricating companies charge differently.
Contacting a metal fabricator for a specific quotation is the best way to estimate the costs.
Sheet Metal Design at Kanyana Engineering
If you’ve decided sheet metal design is out of your league, contact the professionals at Kanyana Engineering to take on your project! We offer top tier metal fabrication designs in Mandurah and Greater Perth. We use the latest CAD and CAM technology in-house to make sure the design process is seamless and easy.
Whether you are facing a design challenge or need a metal prototype design, Kanyana Engineering can help you. Learn more about our services on our dedicated CAD, CAM & metal prototyping page, or view our dedicated industry resources.
Contact Kanyana Engineering to get started on your metal fabrication design.
This article is published in good faith and for general informational purposes only. Kanyana Engineering does not make any warranties about the ongoing completeness and reliability of this information. Always seek specific advice on your metal fabrication project to ensure all variables are taken into consideration.
Graham Dawe is the Managing Director and Works Manager of Kanyana Engineering. With decades of experience in the metal fabrication industry, he is dedicated to keeping Kanyana at the forefront of the sector’s technological growth. Looking beyond the process itself to holistic, integrated CAD, CAM and MRP solutions, Graham believes Australian manufacturing has an enduring place on the global stage. In Kanyana Engineering’s state-of-the-art workshop in Mandurah, WA, Graham delivers an exceptional standard of work for commercial, industrial and government clients alike.