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Navigating the Inspection Challenges in Sheet Metal Manufacturing
Manufacturing sheet metal for the automotive industry is a complex and precise task. Due to stringent safety and quality standards, rigorous inspections are mandatory to ensure components are crafted to exact dimensions. This involves checking length, width, surface profile, and overall shape, ensuring that parts can endure stress and fatigue over a vehicle’s lifetime.
The Importance of Quality Inspection
Quality inspection in sheet metal manufacturing not only guarantees safety but also meets consumer visual standards. This involves ensuring the best possible flush (height alignment) and the smallest gaps (width of a strip between components) in assembled parts, such as doors and chassis.
This blog explores the inspection challenges in sheet metal manufacturing. If you aim to enhance the quality of your sheet metal parts, balance thorough inspections with cost and time efficiency, and gain tips to stay ahead of the competition, read on.
Popular Sheet Metal Manufacturing Techniques
Stamping and Laser Cutting are the most commonly used methods in the automotive industry, each requiring dimensional inspection to ensure parts meet specified dimensions and tolerances.
Stamping
Stamping uses a press to transform flat sheet metal into a net shape, producing high-volume parts like frames, hoods, doors, and panels. Inspections focus on dimensions of features like holes, flanges, bends, and overall part geometry due to the high volume and precision required.
Laser Cutting
Laser cutting creates precise shapes in metal, typically for intricate components requiring high accuracy. Inspections here focus on cut dimensions, edge quality, and the position of features like holes or cutouts.
Various tools and instruments are used for these inspections, including callipers, micrometres, coordinate measuring machines (CMMs), and laser scanning tools.
The choice depends on part complexity, required precision, and production volume. Laser 3D scanning, for example, is beneficial for complex shapes and detailed features.
Key Features to Inspect on Sheet Metal Parts
Overall Shape
Objective: Detect warping or distortion during manufacturing.
- Flatness: Ensures surfaces lie within two parallel planes.
- Profile of a Surface: Ensures the entire geometry conforms to the part’s shape, creating a 3D tolerance envelope.
Edges and Corners
Objective: Detect deformities and irregularities from cutting and shaping.
- Sharp Edges: Common in laser-cut or stamped parts, requiring deburring to ensure safety.
- Hemmed Edges: Found in areas prone to injury, like car door contours, requiring inspection for position, angle, and straightness.
Holes, Oblongs, and Cut-Outs
Objective: Ensure correct size and positioning for alignment with other components.
Flanges and Tabs
Objective: Ensure precise dimensions and angles for proper assembly fitment.
Which sheet metal parts are more challenging to inspect?
Certain parts pose more inspection challenges than others. Here are a few examples:
Roof
The roof of a car plays a vital role in ensuring passenger safety, which is why inspecting it is of utmost importance. However, due to its large size, measuring specific points directly on the assembly line can pose accessibility problems, requiring adapted tools. Therefore, when choosing the right inspection method, it’s not only the part itself that must be considered but also the condition in which the part is inspected. This is particularly important in an automated quality control (AQC) context or for troubleshooting purposes.
Doors and Fenders
Parts that have structural rigidity once assembled, such as doors, do not need to be physically conformed before inspection. However, other parts, like front and rear fenders, that do not have structural rigidity, must be conformed. Conforming a part can be easy if the appropriate checking fixture is available. (Checking fixtures are typically designed for a specific part.) However, in today’s manufacturing world, production is shifting from Low Mix-High Volume to High Mix-Low Volume. This shift demands more checking fixtures, which in turn adds extra costs to the manufacturing and inspection processes.
Holding fixtures are, however, more versatile than checking fixtures. They can be used on multiple parts, which reduces costs and saves storage space. Therefore, holding fixtures to which we add a fast measuring tool can significantly accelerate the conformation process.
Car Body
During the body in white (BIW) stage in which the car body’s frame is joined together, quality control is critical because it involves ensuring the quality of the vehicle’s metal framework before other components like the engine, chassis subassemblies, electronics, and interior trim are integrated into the structure. When inspecting large parts like the car body, pay close attention to the volumetric accuracy of the measuring tool used.
Since the measurement deviation increases by a few microns per meter, the cumulative error of scanning a larger part is higher. Such deviations cannot be ignored, and scanning methods have been developed to reduce errors, such as using markers like passive or active targets and photogrammetry.
Next step: Understanding the technology that is available for inspecting sheet metal
Selecting suitable measuring technology is crucial to address the inspection challenges in sheet metal manufacturing. By understanding the advantages and disadvantages of different measurement solutions, manufacturers can ensure parts meet high standards of quality and safety, reduce waste, minimise rework, and ultimately lower production costs, staying competitive in the automotive market.
To find out more about the different measurement solutions available, take a look at a recent blog that compares 3D Measurement Tools.
