Who Needs 2-D Drawings?
Modern 3-D CAD applications can create rich, 3-D, total product definitions, and software applications can now expose this data to downstream operations-eliminating the need for redundant, ambiguous and expensive 2-D drawings.
Few people would argue that the revolution in drafting-from 2-D to 3-D product definition-has yielded incredible benefits for manufacturers. Digital drafting tools and 3-D modeling enable accelerated time to market, reduce development costs, and yield higher-quality products, even as products have become smaller, more complicated and more difficult to manufacture.
To varying degrees, it has been possible since the mid-80s to create a “digital product definition” that encompasses critical aspects of a design. More recently, through the use of dimensioning and tolerancing tools found in modern CAD packages and the ability for these tools to create 2-D drawings, manufacturers have been able to define and capture all aspects of a product’s design characteristics-in essence, creating a total product definition.
CAD-generated 2-D drawings have been an effective medium for communicating a design’s product definition, but it has been obvious for several years that: 2-D drawings restate much of the information that is already captured in a 3-D model that can be ambiguous as to the designers original intent; are prone to quality errors; and are expensive to generate and regenerate when the design changes.
In a quest to eliminate unnecessary 2-D drawings, many manufacturers have turned to model-based definition (MBD) practices, which seek to add all of the important product definition data typically found in a 2-D drawing, back into the original 3-D model. Special manufacturing notes, definition of block tolerances, special material treatments, and structural considerations are all examples of 2-D drawing data that are being added to the 3-D model.
Eliminating redundant design steps and expensive, non-value added activities may be driven by quality initiatives, however, eliminating these factors as expenses may ultimately serve as a differentiator between successful and unsuccessful OEMs.
While it has been possible for some time to define all aspects of a product through the use of CAD modeling tools, annotations, etc., effective reuse of 3-D CAD and embedded 3-D MBD data for downstream manufacturing process has been elusive for the following reasons:
- OEMs and prime contractors use different 3-D CAD authoring tools (like CATIA, UG/NX or Pro/E) that store their parts and assembly designs in proprietary CAD formats. This requires downstream manufacturing organizations to purchase and become experts in each of the native CAD software systems in order to make effective use of the 3-D designs and MBD information.
- OEMs and prime contractors assign MBD information to parts and assemblies (such as dimensions, tolerances, surface finish symbols and manufacturing attributes) using different techniques and nomenclature (schemas). The lack of a standard schema makes interacting with and interpreting MBD data difficult, inconsistent and hard to find within the native 3-D part or assembly.
- 3-D CAD assemblies are usually too heavy and too complex for normal downstream manufacturing operations, which then require labor intensive manual simplification in the native CAD system to make the 3-D data fit for purpose. It should be no surprise that 3-D CAD systems are great for creating complex parts and assemblies, but are often poor at simplifying these parts and assemblies to make them usable for a given manufacturing, inspection or assembly operation. Activities like this can drive PLM black belts insane: Is the simplified model a configuration of the original model? What revision
- Requiring people to use a native CAD application to view MBD data such as part tolerance, imposes a significant learning curve to learn the software. In addition, MBD is usually too detailed and too hard to find or interpret for typical manufacturing and inspection operations. The abundance of data makes it hard to isolate critical part dimensions and tolerances from the hundreds, if not thousands, of tolerances embedded within the 3-D parts or assemblies.
- CAD and PLM software vendors have been hesitant to aggressively embrace open standards or to promote open access to their 3-D CAD and MBD formats for fear of losing a lock on the customers’ CAD data. Preventing CAD and MBD data from being accurately represented in non-native formats is driven by fear of customers switching to other 3-D CAD vendors or losing market share to best-of-breed 3-D software technologies provided by other 3rd party developers.
- CAD and PLM software vendors promote their complete line of downstream manufacturing PLM software tools based upon the ability to accurately represent their own native 3-D CAD and MBD formats within same-brand applications. These systems do not typically offer best-of-breed technology. And, if they do, they typically do not work well with CAD and MBD formats from other vendors. This lack of interoperability typically forces the customer to maintain a plethora of different products for each CAD format. People that work in heterogeneous CAD environments readily agree that maintaining two proprietary CAD formats within a single project or operation is worse than dealing with a single proprietary CAD format. Most large companies use multiple CAD and PLM products, and suffer with sub-optimal design to manufacturing practices as a result.
A Perfect Storm
Despite these hurdles, strategic planning by Adobe, long hours spent in standards committees, hard lobbying by customers to PLM vendors and other recent developments, have all converged to create a “perfect storm” that will finally allow manufacturers to create and share rich product manufacturing data without requiring end users to purchase expensive and proprietary CAD applications to support every format they receive.
Among the benefits are:
- Widely accepted, potable, secure data container and viewing platform (Adobe PDF platform);
- Open standards for model-based definition (JT, STEP, PRC);
- Well-disciplined standard modeling practices; and
- Easy-to-use, cost-effective, best-of-breed, off-the-shelf software provided by independent and aggressive 3rd party software vendors.
Adobe’s PDF format has evolved and matured since its introduction in 1993 and gained the ability to embed true 3-D CAD geometry in version 8.1 with the introduction of the PRC format. The beauty of the PDF format is that it can encapsulate just about any type of media and structured data into an electronic document that can be opened on most PCs around the world using a free Adobe Reader. In fact, the PDF format is ideal for downstream manufacturing processes because a single PDF document can contain a combination of 3-D geometry, dimensions and tolerances, manufacturing notes, process steps, 2-D pictures and animation-all the information required to completely and effectively capture the manufacturing, inspection or assembly processes.
Equally important, Adobe has created a vibrant ecosystem around the PDF platform (a published ISO standard) to facilitate document distribution and collaboration.
Importance of Open Standards
Since the early 80s, a plethora of CAD tools have been developed to meet product development and manufacturing requirements. However, as is often the case in large, distributed manufacturing and supply chains, organizations are often faced with difficult interoperability issues stemming from multiple CAD tools from multiple CAD vendors-with data locked away in multiple incompatible CAD formats. Several open and standards-driven data exchange formats and numerous CAD translation solutions have been painstakingly developed and refined over the years to capitalize on the move toward capturing the complete product definition and 3-D MBD initiatives.
Because of recent breakthroughs in the standard definition of MBD based data sets, it is now possible to faithfully, and with unparalleled quality, to translate dimensions, tolerances and other manufacturing annotations into the STEP AP203-E2, JT and PRC open standard formats.
In addition to the advent of 3-D CAD modeling software tools, it is impossible to overstate the importance of defining and implementing standard CAD modeling practices for modeling tools used within manufacturing organizations. Implementing standard practices for defining product views, placement of dimensions and tolerances and schemas (standard methods for defining related product MBD data), drives consistency up and down the supply chain, and enables manufacturing application development based upon fixed product definitions that were defined early in the design process.
The Army Research Lab, in conjunction with several of its contractors, has made great strides in defining a standard modeling practices for the United States Army. The document encompasses best practices, schema definition, and ASME Y14.41 standards for digital product definition and data practices. These 3-D CAD modeling and MBD techniques are encompassed within a standard data schema that can be implemented by anyone designing products for the U.S. Army.
By implementing standard practices and data schemas, it will be possible to create a total product definition that combines 3-D design and manufacturing information-in essence, all the information required to completely define how military equipment should be manufactured, repaired and maintained. Once embedded into rich 3-D PDF documents, the data will be accessible to any Army facility or supplier in the world, using Adobe Reader.
Cost-Effective COTS Software
Through the use of commercial off the shelf (COTS) software provided by 3rd party software companies, engineers can deploy an effective, low-cost and efficient process for transforming heavy 3-D CAD and MBD data into lightweight, standard 3-D PDF manufacturing documents which can be used for such things as:
- 3-D Inspection Instruction
- 3-D Tooling Instruction
- 3-D Request for Quote Documents
- 3-D Digital Work Instruction
- 3-D Technical Data Package
Once documents are created, they can be easily deployed inside the enterprise, and outside the firewall to partners and suppliers for little or no cost using Adobe Reader. Adobe has constructed a compelling feature-set and ecosystem around the PDF platform, which allows just about anyone to share, comment, review and view PDF documents. Documents also can be encrypted, password protected and distributed through standard e-mail.
Modern 3-D CAD applications can now create rich, 3-D total product definitions, and software applications can now expose this data to downstream operations, eliminating the need for redundant, ambiguous and expensive 2-D drawings.
However, only recently has it been possible to cost-effectively share high-quality total product definitions across an extended enterprise-thanks to a widely deployed, viewing platform such as Adobe Reader; MBD oriented data-exchange standards like STEP AP203-E2; disciplined modeling techniques and standard MBD practices like those developed by the Army Research Lab; and easily deployable, off-the-shelf, 3rd party software applications that can automatically create fit-for-purpose, lightweight, 3-D PDF manufacturing documents.
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