The Hidden Perils in Sheet Metal Design and Manufacturing
The Hidden Perils in Sheet Metal Design and Manufacturing
Date：2024-02-19 16:10
Sheet metal manufacturing can hide defects in its designs. What appear to be solid blueprints can harbor engineering errors. And these mistakes, often ignored in the design-stage review, contribute to some lamentable production and product outcomes—too slow, too expensive, not durable enough, or altogether unsatisfactory. Every sheet metal designer has faced the payback from design indiscretions in one form or another, and novices are witnessing firsthand how paying attention to sheet metal design principles can safeguard against what would otherwise be costly and time-consuming oversights. A basic principle that must be safeguarded against in sheet metal design is the failure to consider the attributes of the basic material it’s using—which really comes down to a failure to understand basic material science.
In sheet metal fabrication, bending is the balance of taking the material to the point just before it breaks, and then stopping. When designers attempt to go beyond the limits of flexibility, by specifying bending radii that are smaller than the material thickness, they are courting disaster. Such dangerously tight bends can and most probably will take the metal past its "stretch" point. Once it passes this point, it can no longer hold its shape. If it doesn't break, it will be so close to breaking that the excessive internal stresses set up by the tight bend will be the next best thing to an outright failure. By using almost poetic language, the author notes how serious an issue this is; it's. "Ingenuity should ensure that failed attempts at sophistication—making an item appear or act along with something that it is not, such as a cardboard cutout of a human that's only meant to be seen from a distance—will not compromise the component's strength."
Understanding the complexities of welding design can mean the difference between a working structure and a failed one. Weld shrinkage and the heat-affected zone are two important factors that can't be overlooked. Shrinkage occurs when the weld pool cools and solidifies. Hot metal tends to want to curl up, and the hotter it gets, the more it tends to want to curl. That's why consistent penetration of the weld into the joint it is trying to join is so important. To achieve that requires controlling the heat—that of the welding tool and the heat of the metal being joined. The designer has to remember that both the welder and the metal have a certain amount of "wiggle" when they're hot.
Too often, the art of assembly gets lost in the excitement of design, the sheer rush to innovate overshadowing any consideration for practicality. Designs that make assembly difficult serve only to complicate and inflate production costs. Assembly ought to be a prime consideration for any product, but it rarely gets discussed or taught. When assembly comes up in conversation, it's usually in terms of what to do when something goes wrong, a situation in which all the ease-of-use problems tend to manifest. What is not said is that the appearance of a product (the "look") and the means by which it accomplishes its primary function (the "work") ought to be the two central concerns for any designer—that and the absence of undue reliance on fasteners, which always, in the end, add weight, cost, and dampened efficiency.
When we talk of errors or risks, we generally think of them as single, manageable problems. When you stack tolerances, however, you create a risk that is no longer just a problem but an error waiting to unfold. A poorly controlled stacked-tolerance situation leads to assembly problems or mechanical interference; if you don't pay attention to the details, you have a situation that's bound to "come to light." The reinvention of the wheel in sheet-metal design—that is, pursuing uniqueness in parts that don't need to be unique—leads to inflated complexity and unnecessary production costs. The sheet-metal part we used in a test rig last year was never in our design conversation; it was plain to see that using a "noisy" part in place of a standard component was something we should have avoided because it didn't make sense.
In sheet metal fabrication, bending is the balance of taking the material to the point just before it breaks, and then stopping. When designers attempt to go beyond the limits of flexibility, by specifying bending radii that are smaller than the material thickness, they are courting disaster. Such dangerously tight bends can and most probably will take the metal past its "stretch" point. Once it passes this point, it can no longer hold its shape. If it doesn't break, it will be so close to breaking that the excessive internal stresses set up by the tight bend will be the next best thing to an outright failure. By using almost poetic language, the author notes how serious an issue this is; it's. "Ingenuity should ensure that failed attempts at sophistication—making an item appear or act along with something that it is not, such as a cardboard cutout of a human that's only meant to be seen from a distance—will not compromise the component's strength."
Understanding the complexities of welding design can mean the difference between a working structure and a failed one. Weld shrinkage and the heat-affected zone are two important factors that can't be overlooked. Shrinkage occurs when the weld pool cools and solidifies. Hot metal tends to want to curl up, and the hotter it gets, the more it tends to want to curl. That's why consistent penetration of the weld into the joint it is trying to join is so important. To achieve that requires controlling the heat—that of the welding tool and the heat of the metal being joined. The designer has to remember that both the welder and the metal have a certain amount of "wiggle" when they're hot.
Too often, the art of assembly gets lost in the excitement of design, the sheer rush to innovate overshadowing any consideration for practicality. Designs that make assembly difficult serve only to complicate and inflate production costs. Assembly ought to be a prime consideration for any product, but it rarely gets discussed or taught. When assembly comes up in conversation, it's usually in terms of what to do when something goes wrong, a situation in which all the ease-of-use problems tend to manifest. What is not said is that the appearance of a product (the "look") and the means by which it accomplishes its primary function (the "work") ought to be the two central concerns for any designer—that and the absence of undue reliance on fasteners, which always, in the end, add weight, cost, and dampened efficiency.
When we talk of errors or risks, we generally think of them as single, manageable problems. When you stack tolerances, however, you create a risk that is no longer just a problem but an error waiting to unfold. A poorly controlled stacked-tolerance situation leads to assembly problems or mechanical interference; if you don't pay attention to the details, you have a situation that's bound to "come to light." The reinvention of the wheel in sheet-metal design—that is, pursuing uniqueness in parts that don't need to be unique—leads to inflated complexity and unnecessary production costs. The sheet-metal part we used in a test rig last year was never in our design conversation; it was plain to see that using a "noisy" part in place of a standard component was something we should have avoided because it didn't make sense.
Surface Treatment: The Forgotten Final Touch
Surface treatment is the final flourish on a product, yet it's often an afterthought during the design phase. Overlooking requirements for painting, plating, or anodizing can lead to poor outcomes if the material or design is incompatible with the desired finish. It underscores the importance of holistic design thinking that anticipates the product's journey right through to the end user's hands.
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