Got DFM/DFA?
New 3D CAD Technologies Streamline Transition from Design to Manufacturing |
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Developing successful products in today's competitive global environment requires more than an innovative design. The most elegant, inventive design will not succeed if a company cannot manufacture, assemble, and maintain it at a profit. As most veteran designers know, the interplay between design and manufacturing — identifying and resolving manufacturing issues early, including prudent trade-offs between performance and production requirements — is critically important to a product's success.
Manufacturers used to have more flexibility to accommodate iterations between design and manufacturing: time and cost demands were less pressing, and design and manufacturing personnel were often co-located, making collaboration more efficient. Today, however, the need to accelerate time-to-market and squeeze costs out of product development, combined with greater levels of geographically removed or offshore manufacturing, has created additional challenges for spotting and addressing production issues upfront.
Fortunately, new capabilities that assess design for manufacturability/design for assembly (DFM/DFA) features in 3D CAD software can help engineers address manufacturing and assembly issues as part of design, preventing delays and cost overruns during production.
 | With COSMOSWorks Design Insight,
designers can gain insight into an optimal
design. For example, this Design Insight
plot suggests that the I-beam cross-section
and chamfered corners represent the
optimal design for this handle. |
 | SolidWorks DFMXpress allows engineers
and designers to check their designs for
turning manufacturability, such as minimum
corner radii and bore reliefs. |
 | SolidWorks DFMXpress enables engineers
and designers to check their designs for
manufacturability upfront by identifying areas
that are difficult, expensive, or impossible
to machine. |
Design for manufacturability
Manufacturing methods predominantly fall within three categories: forming, fabricating, and machining. Each process has its own characteristic production issues, and a range of 3D CAD technologies have emerged to assess DFM for each method.
Forming processes use tool - a mold, a pattern or a die - to create the part and include injection-molding, casting, forging, and stamping. Although each of these methods uses different materials and techniques, a common requirement is the need to provide sufficient draft: the minimum taper or angle given to a mold, pattern, or die to ensure the part will pull away easily and blemish-free. Instead of leaving decisions about draft and parting lines to the toolmaker, designers can now use CAD draft and parting line analysis capabilities to ensure proper extraction of the part, while still meeting the functional and aesthetic requirements of the design. Tools are also available for identifying costly undercut features that require sliders or side action, as well as for maintaining uniform wall thicknesses to prevent sink spots.
For fabrication, designers can use 3D CAD capabilities to create sheet-metal parts in both flat and bent states; first designing the bent state then automatically creating flat patterns based on bend table and K-factor information for different material types. Designers can export flat patterns directly into laser and water-jet cutting machines for cutting the flat patterns. This eliminates the time-consuming, expensive and often error-prone step of manually converting the bent sheet-metal design into a flat pattern for manufacturing.
When machining parts — whether milling, turning or drilling — designers can use new 3D CAD capabilities to assess the manufacturability of specific features. These tools help designers check for features that would be impossible or very expensive to machine, such as rounding the outside edge of a machined part to break the edge when a chamfer would be less expensive, or creating a bolt clearance hole that does not match an available machine shop drill size.
 | The SolidWorks DimXpert automatically
dimensions and tolerances 3D models. |
 | With the SolidWorks DimXpert, designers
can automatically define dimensions and
tolerances and display them in the drawing,
automating the drawing detailing process. |
 | With the SolidWorks DimXpert, designers
know that their models are fully dimensioned
by highlighting the "constrained" geometry in
green. |
Tolerances and dimensions
3D CAD tools can also save time and reduce errors by automatically applying industry-standard dimensioning and tolerancing schemes for manufacturing. Failing to define tolerances and dimensions appropriately can add costs by leaving too much to interpretation in the production of parts.
Drawings with appropriately dimensioned and toleranced parts apprise machinists of the critical dimensions and tolerances they must abide by when manufacturing parts. Tolerance stack-up analysis capabilities help engineers evaluate dimensioning and tolerancing schemes to ensure that assemblies will fit together and function properly.
Design for asembly
Design for Assembly (DFA) relates to both assembly and disassembly. In both instances, the visual nature of 3D CAD can help designers to pinpoint assembly and clearance issues upfront. For example, interference detection tools allow engineers to identify and resolve part collisions within an assembly during design. Likewise, the ability to virtually disassemble and reassemble parts in a 3D CAD system enables engineers to address clearance needs, such as providing enough room to tighten or loosen a screw, access and change a filter, or make sure components fit within a housing.
Perhaps the greatest challenge that product developers face today in developing successful products is generating designs that are as close to the final, manufacturable state as possible. New DFM/DFA CAD capabilities can provide the tools designers need to achieve this goal by identifying and addressing manufacturing issues as an integral part of product design.
Ved Narayan is Dassault Systemes SolidWorks Corp.'s Vice President, Asia Pacific Operations
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