1. Using Completed 3D Models of a Part with no Bends
This is probably the most basic issue we see. Sheet metal is flat and must be bent, formed, cut, lased, and sometimes cajoled into its final shape. It’s a very hands-on process. If you design your sheet metal part as a solid object, it’s important that you send us a CAD file that appears folded, but shows where bends should go. Related to this, because the raw materials are single sheets of metal, the entire part must have the same material thickness throughout. For example, if you create a part that uses 0.125 in. (3.175mm) thick aluminum, your entire part will need to be that same thickness.
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2. Placing Features too Close to Bend Lines
A quick way to create difficulties during manufacturing is to place holes, tabs, or other features too close to a bend. So, how close can you get? Just follow the 4T rule. Keep all features at least 4x material thickness away from bend lines. So, if your design tells us to use 0.050 in. (1.27mm) copper, give your feature at least 0.200 in. (5.08mm) of clearance. If you don’t, the part will deform awkwardly in the press brake, and no one wants that.
3. Designing Perfectly Perpendicular Sheet Metal Corners
When you bend sheet metal in a press brake, the resulting bend doesn’t form a perfect 90-degree angle. Instead, the tool has a rounded tip that adds a radius to the bend. If you measure the length of that bent area and divide it by two, you’ll get the bend radius, a figure that is defined by the tool that made it. If the size of that curve is important to you, make sure you specify it in your model.
The most common internal bend radius (and our default) is 0.030 in. (0.762mm). An important consideration to remember is that the external bend radius—the one formed on the die side of the press brake toolset—is equal to the material thickness plus the internal bend radius.
Some designers like to get fancy and create different radii for each bend in a part. Want to save some money? Use the same radius for all of the bends. When your manufacturer doesn’t have to change tooling that saves you on labor costs.
4. Forgetting to Include Detailed Hardware Specs in your CAD File
Do you know of anyone who wants longer lead times? Probably not. Always remember to let your manufacturer know what kind of hardware you want to use by including the details in your top level assembly information. Whether it’s a self-clinching nut like CLS-440-2, flush-head stud like FHS-M5-15, or other hardware, this guarantees that you’ll get exactly what you want placed in the location you expect it. To save yourself time and trouble, download and use the PEM clinch hardware models.
5. Picking the Wrong Finish (or Not Using One When You Need One)
Generally, finishes serve two purposes. They can protect your part or they can make it look better. Some do both. Aesthetic finishes—ones that focus on looks—don’t focus on corrosion protection. Still, powder coating does offer some protection (unless a scratch reaches to the metal beneath). Silk screening, on the other hand, is used to add text and images to parts and offers no protection at all.
Chemical conversion finishes are meant to protect your parts by altering the properties of the outermost layers. For example, if you want to use steel in a corrosive environment, consider choosing galvanized or galvannealed metal, which already has a protective zinc coating. Watch out, though! We can’t weld galvannealed steel due to the dangerous toxins it would give off. Instead, we can make the parts out of steel and add a zinc coating after welding.
Chromate conversion can give your part electrical connectivity and provides a primer layer to your part if you want to paint. Anodizing can add a pop of metallic color to your parts while also protecting them. Think of that colorful, small flashlight you own.
Here’s a helpful summary of the most common finishes for sheet metal.
6. Selecting the Wrong Sheet Metal for the Job
Imagine making hundreds of parts out of unfinished steel that are destined for installation in a salty, marine environment. Amazingly, we’ve seen quotes that request just that. Save yourself the grief of the customer complaints you’ll get when your parts corrode and consider these factors when selecting the right sheet metal:
- Expected wear on your part from daily use
- Corrosion protection
- Manufacturability
- Cosmetic appearance
- Mechanical properties (tensile strength, yield strength, ductility, etc.)
- Conductivity (for electrical applications)
This handy chart can help.
7. Failing to Consider U-Channel Strength
When designing U channels, always think about the strength of the material you’re using and how easily it can bend. At Protolabs, narrower doesn’t work for us because of our tooling. If we had narrower tooling, we could manufacture narrower U channels. The bottom line is that it is best practice when working with us to maintain at least a 2:1 width-to-height ratio for your U channels. If you need a narrower channel, consider a welded or riveted assembly.
8. Designing Unrealistic Weld Requirements
Have you ever tried welding a seam inside a closed box? Nope? Neither have we. Make sure that your weld requirements are realistically achievable. It’s important to remember that if a welding torch can’t access a seam, the weld can’t happen. We strongly recommend designing so all welds are done on the outside of the part.
Metal melts under high temperature, so you need material thicknesses that can manage the extreme heat. The minimal material thickness for welding is 0.040 in. (1.016mm) to ensure that the weld doesn’t end up an unholy mess of melted metal.
Finally, in your models, always indicate the need for welds using a welding function or nomenclature. Never box corners to indicate welding.
No single design tip can cover all the sheet metal mistakes we’ve seen, but this “best of” collection is a start. Take a look at our sheet metal design guidelines to keep you moving in the right direction.
For additional help, feel free to contact a Protolabs applications engineer at 877-479- or [ protected]. To get your next design project started today, simply upload a 3D CAD model for an interactive quote within hours.
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Sheet metal fabrication is an essential process in manufacturing, where it’s all about precision and accuracy. At Rapid Axis, we understand that achieving high precision in sheet metal custom fabrication is crucial for ensuring the quality and functionality of the final product. Whether it’s for aerospace, automotive, medical, or other industries, our experts utilize advanced techniques and best practices to deliver exceptional results.
In this article, we’ll explore the key methods we employ to achieve precision sheet metal fabrication and maintain the highest standards of quality control.
#1: Accurate Material Selection
The foundation of precision sheet metal fabricating starts with selecting the right materials. Different projects require specific material properties such as strength, flexibility, and corrosion resistance. Our team at Rapid Axis carefully considers these factors and selects materials like aluminum, stainless steel, and mild steel, ensuring they meet the required specifications for the project. Not sure what material you need? Tell us some specifics about your project and we can help you make the decision.
This attention to detail helps minimize material-related deviations and enhances the overall precision of the fabrication process.
#2: Advanced CAD/CAM Software Utilization
Precision in sheet metal custom fabrication begins with precise design. We leverage advanced Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) software to create detailed and accurate models of the desired components.
This software enables us to plan and simulate the fabrication process, identify potential issues, and optimize your design before production begins. By utilizing CAD/CAM software, we ensure that every aspect of the design is meticulously planned, leading to higher precision in the final product.
#3: State-of-the-Art CNC Machining
CNC (Computer Numerical Control) machining is a cornerstone of precision sheet metal fabrication. At Rapid Axis, our state-of-the-art CNC machines offer unparalleled accuracy and repeatability.
These machines follow programmed instructions with extreme precision, allowing us to create complex shapes and intricate details with minimal tolerances. The use of CNC machining not only enhances precision but also improves efficiency, reducing lead times and ensuring consistent quality across multiple parts.
#4: Laser Cutting and Waterjet Cutting Techniques
For achieving high precision in sheet metal fabrication, cutting techniques play a vital role. We employ advanced laser cutting and waterjet cutting technologies to achieve clean, precise cuts. Laser cutting provides exceptional accuracy and is ideal for intricate designs and thin materials.
Waterjet cutting is versatile and can cut through a wide range of materials without generating heat, preventing material distortion. These cutting techniques enable us to produce parts with tight tolerances and smooth edges.
#5: Precision Forming and Bending
Bending and forming are critical processes in sheet metal custom fabrication. Our experts utilize precision press brakes and other forming equipment to achieve accurate bends and angles.
We employ techniques such as air bending, bottom bending, and coining to ensure that the bends are consistent and within specified tolerances. Additionally, our experienced technicians carefully monitor the forming process to prevent defects such as warping or cracking, ensuring the highest quality in the final product.
#6: Stringent Quality Control Measures
At Rapid Axis, quality control is at the heart of our precision sheet metal fabrication process. We implement rigorous inspection and testing protocols at every stage of production. Our quality control team uses advanced measurement tools, such as coordinate measuring machines (CMMs), to verify the dimensions and tolerances of each component.
We also conduct visual inspections and functional tests to ensure that the parts meet the required specifications. These stringent quality control measures guarantee that our customers receive products that are both precise and reliable.
#7: Expertise and Continuous Improvement
Our commitment to achieving high precision in sheet metal fabrication is helped by the expertise of our skilled professionals. Our team continually hones their skills and stays updated with the latest industry advancements.
We invest in ongoing training and development, ensuring that our technicians are proficient in the latest fabrication techniques and technologies. This dedication to continuous improvement allows us to consistently deliver top-notch precision sheet metal fabrication services to our clients.
Conclusion
At Rapid Axis, precision sheet metal fabrication is more than just a process—it’s a commitment to excellence. By implementing best practices and utilizing advanced technologies, we ensure that every project we undertake meets the highest standards of accuracy and quality. From accurate material selection to state-of-the-art CNC machining and rigorous quality control measures, our approach to sheet metal custom fabrication is designed to deliver exceptional results.
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