\ud83d\ude80 Table of contents <\/strong><\/p> Whether you\u2019re a CAD drafter or metal fabricator, there are many things you can do to make certain that all the details are correct and clearly illustrated.<\/p> When applied to the sheet metal fabrication process, design for manufacturing services,<\/a> or DFM, mainly focuses on a number of established rules of thumb as well as exceptions for typical fabrication techniques, including welding, cutting, bending, drilling, punching, and so forth. So long as the drawings are developed in conformity with DFM guidelines, you gain a lower chance of error and a higher level of accuracy.<\/p> The main point of DFM is to force engineers (and, by extension, the CAD drafter who produces the shop drawings) to consider fabrication-related matters when designing and illustrating sheet metal, so they can guide the fabricators accordingly. For example, a metal sheet shop drawing should specify the direction of the welding and when or where to use filler electrodes. If the metal part needs staggered welds, the drawing should also mention the length of every pitch, enabling the welder to avoid material warping. Specific tolerances for bending or notches must be clearly mentioned as well.<\/p> Given properly identified methods, tolerances, and limits, the metal fabricator can make an informed decision in every phase of the task. Remember that just like the product manufacturing process, metal fabrication also aims for a good balance between quality and cost. Accurate and clear shop drawings contribute to cost-efficiency a great deal. Armed with a professionally-made shop drawing, it\u2019s possible to reduce overheads (by not using a greater amount of raw material than what\u2019s needed), eliminate reworks (which also means no additional labor), and streamline the fabrication job of multiple parts. And at the end of the day, it improves the chances of the fabrication getting completed on time. More details about these technique-related matters are discussed below.<\/p> RELATED: Top 30 steel detailing companies for CAD drafting and engineering design services in the US<\/a><\/strong><\/p> An engineering design expert’s<\/a> plan may contain material specifications for the sheet metal parts, and it\u2019s the drafter\u2019s responsibility to translate and interpret the information for the technical shop drawing. There are numerous types of metal materials, from stainless steel and aluminum to tungsten and all sorts of alloys. In fact, each metal has a number of specific grades based on its characteristics, like tensile strength, corrosion resistance, durability, and more. A professional metal fabrication shop probably has a warehouse filled with tons of different metals, so be very specific about what types and grades to use. Thickness also matters, as it directly affects the materials\u2019 ability to cope with mechanical stresses.<\/p> Finishes, such as heat treatments or coatings, may seem like nothing but superficial details, but they do serve functional purposes. For instance, powder coating actually triggers a chemical reaction that melts the powder and forms a protective layer on the metal surface. The aesthetic improvement is in addition to this benefit.<\/p> Here are some practical tips to provide proper material specifications when working in a CAD environment:<\/p> Last but not least, maintain version control of the shop drawing to keep track of any changes in material specifications. The fabricator should only receive the already-finalized shop drawing, but version control helps you manage updates during the design process. Keeping track of revision history, such as by using a unique identifier to label each drawing, would also prove to be useful during quality checks and the audit process.<\/p> Depending on the shape and geometry of the metal part, sometimes it\u2019s just more practical to join two or more pieces together than to manipulate a single sheet, by either screwing or welding them together. Welding is a proven, reliable technique, but it does take some specialized equipment and skills to get everything within the tolerance for accuracy. If the shape is relatively intricate, welding can be labor-intensive, too. On the other hand, applying screws or fasteners of any sort is much simpler and even preferable, so long as it doesn\u2019t interfere with the metal part\u2019s geometry.<\/p> In case welding is the only feasible solution for effective fabrication, the shop drawing expert<\/a> must specify in detail the types of welds, such as groove, fillet, spot, seam, slot, or plug welds. The location and size of each weld point should also be clearly defined because they may affect the design and structural integrity of the sheet metal. If necessary, annotate the shop drawing with specific instructions such as post-weld heat treatments, temperature monitoring techniques, and quality control measures. All those factors have a major impact on the overall quality of the welds and the finished part itself.<\/p> A sheet of metal usually serves as a single component of an assembly. It must be secured to other parts using the correct types of fasteners to ensure structural integrity. It\u2019s crucial that the shop drawing includes accurate details pertaining to the location, shape, and size of each hole opening for proper assembly. Furthermore, some holes might need specific considerations such as chamfering and deburring; some designs require those edge treatments, whether for visual purposes or simply to prevent sharp edges.<\/p> Cutouts are no different. In addition to marking the direction (or shape) and length of cutouts, the shop drawing must inform the fabricators about the specific treatments (if any) required by the design intent. A sheet of metal typically undergoes shearing and punching treatments before it is ready for laser cutting.<\/p> RELATED: The 5 stages of prototyping for any new product idea for product design service companies<\/a><\/strong><\/p> The key to providing accurate bending information in a sheet metal shop drawing is, first and foremost, understanding what the bends are for to begin with. Metal will deform when exposed to a strong enough force to bend its shape. In the absence of a working knowledge of how metal materials behave under mechanical stress, it would be very difficult to control the deformation. Bending is neither an additive nor a subtractive method. It\u2019s a manipulation technique to modify the shape of metal without adding or reducing the raw material.<\/p> Every good CAD drafter has a good grasp of such concepts as k-factors and bend allowances to account for material compression and stretch during bending. The guide provided by shop drawing services<\/a> allows the fabricators to make the correct calculations (or deductions) and bend the material to produce the intended shape. This is especially important in critical bends, which must adhere to strict tolerances, as they affect the part\u2019s functionality and structural integrity a great deal. CAD software packages like SolidWorks<\/strong>, AutoCAD<\/strong>, FreeCAD<\/strong>, and Autodesk Inventor<\/strong> come with various tools to adjust (or automate) bend deductions.<\/p> A shop drawing must contain a list of all components required for the proper assembly of the sheet metal. This listing includes latches, hinges, fasteners (bolts, nuts, screws, etc.), and every other hardware item that comprises the finished product. The quantity of each item must be identified, too. A proper assembly uses all the listed items and nothing more.<\/p> Equally important is the assembly instruction to provide a concise step-by-step guide for the fabricator. An instruction informs the fabricator where and how to use the hardware items, the type of fastener for each hole position, the fastening specification or torque, and the correct tool for every step. The guide must be outlined in chronological order for labor efficiency. A detailed assembly guide enables the fabricator to produce a sheet metal that\u2019s both structurally sound and accurate to the design requirement.<\/p> A shop drawing isn\u2019t a site plan that contains an overview of an entire project seen from a bird\u2019s eye perspective. It\u2019s also not a visualization simply to showcase how the final metal parts should look when completed. When a CAD drafting expert<\/a> develops a shop drawing, the final document should consist of multiple sheets of images; each illustrates the part from a particular viewing angle.<\/p> In many cases, a single sheet of metal can look like two completely different objects when observed from a different perspective; for instance, the front appears smooth and polished, whereas the back is full of rivets. A complex sheet metal with several 90-degree bends will also look different when seen from either side. Illustrating a sheet metal part from multiple viewing angles leaves no room for guesswork. Among the most common views are:<\/p> There are several other views in shop drawings, but the aforementioned three are by far the most comprehensive and commonly used because they can effectively communicate design intent. Many companies have started adopting 3D modeling design services<\/a> to supplement the conventional CAD drawing.<\/p>
Sheet metal drawing best practices<\/h2>
Stick to DFM Guidelines<\/h4>
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<\/figure> Material specifications<\/h4>
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Joining and welding instructions<\/h4>
Holes and Cutouts<\/h4>
Bend specification<\/h4>
Assembly information<\/h4>
Arrange the view for clear communication<\/h4>
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