Effective Implementation of DFM WHITE PAPER
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Contents Abstract... 4 Introduction... 4 Current Practices and Issues in DFM Implementation... 4 Existing process of DFM implementation for this rule will involve... 5 Methodology for Effective Implementation of DFM... 6 1. Knowledge Capture system or Rule Engine... 6 2. Manufacturing Feature Operations Recognition... 7 3. Validation and Feedback Mechanism... 7 Example 1... 7 1. Knowledge Capture... 7 2. Manufacturing Operation Recognition... 7 3. Validation and Feedback Mechanism... 7 Example 2... 8 1. Knowledge Capture... 8 2. Manufacturing Operation Recognition... 8 3. Validation and Feedback Mechanism... 8 Conclusion... 9 Acknowledgement... 9 References... 9 Author... 9 About Geometric... 10 3
Abstract Design for Manufacturing (DFM) comprises of a set of tools and associated knowledgebase that help design engineers to evaluate manufacturability of their designs in simple and cost effective steps without compromising on design intent and functionality. Effective implementation of DFM in actual practices has somewhat lagged behind in making use of the latest software technologies and the power of automation. This paper highlights the increasing importance of automation in effective DFM implementation. In today s context, where Design Anywhere, Manufacture Anywhere concept is becoming more popular, need is more acute. Paper also discusses the required framework and related technologies in CAD CAM which can facilitate the automation and rigorous application of DFM in design and manufacturing practices. Introduction Design for Manufacturing (DFM) involves upstream validation of design for manufacturing related issues. It involves identifying manufacturing constraints and also cost multipliers during design phase itself. DFM, as we know, comprises of a set of tools and associated knowledgebase that help design engineers to evaluate manufacturability of their designs and making required changes in design without compromising on design intent and functionality. Knowledge of DFM has been continuously updated to keep pace with changes in manufacturing technology. Current Practices and Issues in DFM Implementation Most companies implement DFM in the form of checklists for manual review process and/or cover DFM in periodic training programs for their design engineers conducted by manufacturing experts [2]. Other commonly followed practice is calling manufacturing expert for design review from manufacturability point of view. Both these methods need very close interaction between design engineer and manufacturing experts. Increasing geographical distance between design engineer and manufacturing engineer is presenting new challenges in implementation of DFM. Following examples will highlight the issues faced in existing DFM implementation practices: Example 1 Design hole features are typically manufactured using machining drill operations. DFM guidelines state that hole feature dimensions should confirm with standard drill size parameters and those available within organization. 4
Figure 1: Design to be analyzed for standard hole dimensions Existing process of DFM implementation for this rule will involve Training design engineers on the standard drill tool parameters and those currently available within organization. Next step in DFM conformance for this rule would involve manual review of entire design to actually validate all hole feature parameters for their conformance with the documented standards provided by manufacturing department. This may be time consuming manual process and can be error prone as manual review may miss on few violations. If a violation of the rule is slipped in review process, then issue gets discovered downstream. Here manufacturing engineer would either send it back to design department pointing out the issue for correction or attempt to manufacture it with additional steps and costs. Both these options would cause losses to organization in terms of lost time and/or increased costs. Example 2 DFM guidelines recommend avoiding sharp internal corners inside pockets when it is to be manufactured using milling process. Figure 2: Reviewing design for sharp internal corners To follow this DFM guideline, following precautions are typically taken Educating design engineers on reasons for having such rule and imparting them regular training. 5
Manual verification of design to find out existence of sharp internal corners within pockets of the design. However, this may be very time consuming task for complex geometries and reviewer may miss out a few violations if only visual inspection is relied upon. When design with missed issues reaches manufacturing shop, manufacturing would need to add extra number of processes to achieve sharp internal corners which would be time consuming as well as costly. Above examples highlight key issues faced in existing DFM implementation practices, which can be summarized as: Dependency on manual interactions in implementation and need of close proximity between design engineers and manufacturing engineers. Implementation processes lacking common characteristics of automatic processes like consistency, predictability and repeatability. Need of training and continuous retraining of design engineers to keep them updated on evolving DFM guidelines. Time consuming and costly iterations of design between design engineer and manufacturing engineer for reviews and updates. Concept of Design Anywhere, Manufacture Anywhere is gaining wider acceptance, resulting in increased isolation between design and manufacturing engineers. This scenario is further aggravating challenges in implementation of DFM throughout organizations. Methodology for Effective Implementation of DFM CAD and CAM technologies have today revolutionized design and manufacturing fields through use of computer enabled technologies. Application of DFM in actual practices has somewhat lagged behind in taking advantage of latest technologies and the power of automation. Today there are not many software systems which can facilitate automation of DFM in the true sense. Effective implementation of DFM would greatly facilitate, if review of design against an organization s set of DFM guidelines is automated and interactive feedback for design engineers is generated to take immediate corrective actions, all this within design process itself. Key technologies which can facilitate automation in DFM implementation would be: 1. Knowledge Capture system or Rule Engine As DFM primarily deals with manufacturing process knowledge to review design for manufacturability, a good knowledge management system is mandatory which can help to capture this knowledge in suitable format for digital usage independent of people who contributed to such knowledge. 6
2. Manufacturing Feature Operations Recognition Ability to analyze design geometry and automatically extract various manufacturing features /operations from it, is first step to facilitate any kind of automation in DFM implementation. This recognition needs to be independent of the way the geometry may have been modeled. For example, design engineer can model hole design feature as circle which is cut extruded or rectangle sketch revolved around its side or as a special hole library feature. But manufacturing operation recognition of this geometry consistently needs to be as drill manufacturing operation. 3. Validation and Feedback Mechanism This stage brings together historic knowledge repository and recognized manufacturing feature or operations parameters to automatically verify design for any DFM related violations. Using knowledge repository. It can also offer interactive feedback to design engineer on the reason and exact locations of violations and possible steps for corrections. Applying these technologies and framework to same examples, automation of DFM knowledge repository and ability to provide interactive feedback to design engineers within their design system can be achieved as explained below. Example 1 DFM guideline states hole feature or drill operation parameters should confirm with standard drill sizes available within organization. Applying this new framework: 1. Knowledge Capture There are two sets of information about this rule which needs to get captured in knowledge repository. First relates to knowledge about which parameters of hole or drill feature need to be associated with standards and second relates to current organizational standard data about currently permissible values of these parameters. Knowledge part of this rule can be captured in knowledge repository system along with associated data. This data needs to be regularly updated or linked with central data server within organization for relevant information. 2. Manufacturing Operation Recognition Given any design, ability to automatically recognize all drill operations on it and value of parameters is required. its 3. Validation and Feedback Mechanism This mechanism will now associate recognized drill operation parameters with parameters defined in knowledge repository and associated data to verify DFM guideline implementation. In case of any violation, system would highlight parameter in fault on design, so that design engineer can take corrective action. 7
Figure 3 illustrate such mechanism in action for above mentioned rule. Figure 3: Automated DFM rule validation and interactive feedback for Hole rule (4) Example 2 It is recommended to avoid sharp internal corners inside pockets to be manufactured using milling process. Again, applying the new framework: 1. Knowledge Capture Knowledge part about this rule comprises of the pockets to be milled and that they should not have sharp internal corners, needs to be stored in knowledge repository system. 2. Manufacturing Operation Recognition Given any design, ability to automatically recognize all pockets which would need to be machined is required. 3. Validation and Feedback Mechanism All internal corners of recognized pockets in step 2 above needs to be done one by one. Using recognized parameters, system can verify angle between side faces and if they are forming sharp corners. If any sharp corners are detected, feedback needs be given to design engineer by pointing such sharp corners in the design system and suggesting steps to correct violation. Outcome of automated DFM validation and interactive feedback mechanism for the design engineer is illustrated in the figure 4. 8
Figure 4: Automated DFM rule validation and interactive feedback for sharp internal corner rule (4) Conclusion By bringing in automation in DFM implementation, effectiveness of the process would greatly increase by achieving consistency, reliability and predictability independent of the people involved. Need for location proximity and iterations of design between design and manufacturing engineers is minimized. DFM related knowledge gets captured in reusable systematic format and it also establishes mechanism for its scalable expansion. Automated DFM validation will not only improve quality of designs and reduce issues in manufacturing for organizations; it will also result in big savings in terms of manufacturing costs and shorter design and manufacturing cycles. Acknowledgement Sincerely thanks to Geometric Software Solutions Co. Ltd. for allowing use of the product DFMPro for presenting the concept of automated DFM reviews. I would also like to thank Dr. Vinay Kulkarni, for providing valuable inputs and guidance in writing this paper. References 1. Manufacturing Feature Recognition (http://feature.geometricglobal.com) 2. Design For Manufacturability, Kenneth Crow (DRM Associates) 3. Manufacturing Feature Recognition from Solid Models: A Status Report Author Sameer Kondejkar marketing@geometricglobal.com 9
About Geometric Geometric is a specialist in the domain of engineering solutions, services and technologies. Its portfolio of Global Engineering services and Digital Technology solutions for Product Lifecycle Management (PLM), enables companies to formulate, implement, and execute global engineering and manufacturing strategies aimed at achieving greater efficiencies in the product realization lifecycle. Geometric was incorporated in 1994 and is headquartered in Mumbai, India. It is listed on the Bombay Stock Exchange (BSE: 532312) and the National Stock Exchange (NSE: GEOMETRIC) in India. For its consolidated operations for the year ending March 2007, the company recorded revenues of 3.95 Billion Rupees (85 Million US Dollars), with market capitalization of 6.2 Billion Rupees (142 Million US Dollars) as on 31 March 2007. The company has two main business subsidiaries. Geometric Engineering, Inc., formerly Modern Engineering, Inc., headquartered in Rochester Hills MI, provides product engineering and manufacturing engineering solutions to the automotive and industrial sectors. Geometric Technologies, Inc., formerly TekSoft, Inc., headquartered in Phoenix AZ, develops and supplies cutting edge productivity solutions for manufacturing operations. Geometric employs over 3000 people delivering solutions from 10 global delivery locations in the US, France, Romania, India, and China. The company is assessed at SEI CMMI Level 5 for its software services and the engineering operations are ISO 9001:2000 certified. Geometric has a joint venture with Dassault Systèmes, 3D PLM Software Solutions Ltd., which was set up in 2002 with an equity participation of 70% and 30% respectively. For further details about Geometric, please visit www.geometricglobal.com 10