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The Role of Drawings in the CAD Process

Drawings with the highest corporate value are found within the modeling and analysis environment using higher end CAD tools. These models require a geometric (vector) database in order to enable functions such as stress analysis, NC programming, parametric or variational modeling, automated mapping, and/or facilities planning.

There are different ways a drawing can be represented in CAD. The most common use of a revised drawing is a 2-D digital picture without computer readable intelligence. Geometry is for visualization only, and modifications are usually made to the drawings using erase and redraw methods.

Typical scanned drawings (picture based CAD) do not convey the complete part definition as a modeling system can. Scanned drawings may introduce part definition conflicts and discrepancies. The goal is to enable tools and technology that permit use of raster drawings in their "native" raster format, as well as convert raster drawings to intelligent CAD models for use in company critical engineering applications.

The archived drawing.

It is common for many companies to have large quantities of designs which must be preserved throughout the life cycle of the product or service. Even though this archived information may only be needed for reference or contractual purposes, it is highly valuable. Archived documentation often exceeds the quantity of active information. At any time, a drawing can become active due to maintenance of an older design, or a new design may reuse information created in the past.

Drawing distribution.

Circulation of active drawings within the conceptual or production cycle is often accomplished with physical hardcopy and digital CAD or raster data. The emergence of viewing software, internet and intranet services, e-mail, and EDM/PDM systems offers tremendous potential for companies to accelerate critical information throughout the enterprise.

Legacy CAD and paper drawings can easily be enabled into this process making them universally available to the user community. Since some of today's electronic distribution tools rely on a raster or vector only environment, it is common to only convert raster to vector or vector to raster. The result is increased value of both CAD designs and paper drawings.

The revised drawing.

As companies move towards a digital archive and drawings evolve to CAD, the distribution advantages of EDM/PDM tools become available. Drawings within the revision cycle represent active changes or work in process. Integrating these older designs into CAD creates two potential editing solutions: hybrid raster CAD and vector CAD.

Newer designs are typically modified within the proven environment of CAD; however, a large portion of drawings are still based on paper archives and modified manually due to the initial costs associated with getting drawings into CAD. With today's tools, these drawings may now be updated and maintained within the CAD environment. One such tool is hybrid raster vector. This tool allows both raster and vector data to be maintained within the same drawing file. This hybrid raster vector environment offers significant payback to users who must revise drawings but only require a digital picture or archive. Selected areas of scanned drawings can be converted to vector for ease of updating and editing. The result is increased value from legacy drawings and CAD without the need for total conversion to vector.

When the requirement is for a true CAD model with precise geometry, a critically important revision must be made to a scanned drawing. That critical revision includes not only the conversion of geometry from raster to vector, but also the update of those vectors from hand drawn precision (typically +/- 1/32) to CAD accuracy. Parametric CAD and Variational Geometry, discussed below, provide excellent tools for this purpose.

Intelligence at last.

Engineering models are established when geometry and attribute relationships are contained in application readable form. This can be either 2-D or 3-D. More advanced CAD systems offer parametric and variational geometry models. These offer truly intelligent environments where engineers can analytically and dimensionally drive design concepts.

A picture is worth 1000 words but a model is worth 1000 pictures.

When updating a drawing in an environment in which a true model is not required, hybrid raster vector editing is effective. However, when intelligence of a model is required, all geometric data must be transformed into vector form. This process has often been called raster to vector conversion or vectorization. This technology helps to move beyond the unintelligent picture or raster role into a more intelligent vector drawing and editing environment.

2-D Parametric CAD.

The classic 2-D CAD model consists of geometry, dimensions and notes. In Parametric CAD, the dimensions and geometric elements are "associated". Changes made to a dimension will update the associated geometric element, but do not update elements of the drawing not associated to the dimension.

Parametric CAD is an excellent aid for updating CAD drawings. For example, it is easy to update a circle from its'.300 as-drawn radius to its' intended .500 radius. Although effective, it requires that the shape be changed element by element. Let us next consider a technology to ease the process.

2-D Variational CAD.

A Variational Geometry model allows for the establishment of relationships (tangency, mutual relimit, etc.) between geometric elements. When a geometric element is updated, the figure will "hold shape" by maintaining those relationships.

After these relationships are applied to scanned and converted drawings, the update of just a few dimensions can bring all geometric elements of a shape to the desired CAD precision.

2 1/2-D Variational CAD.

2 1/2-D CAD, which may also be parametric and variational, contains view intelligence that understands the relationship between Front, Top, Right, and other views. Although a 2 1/2-D model does not contain an internal 3-D solids representation, it contains the 3-D intelligence to allow easy generation of a 3-D solid when the model is,transferred to a 3-D system.

The use of a 2 1/2-D CAD system to create a precise CAD model from your 2-D paper drawings provides more than an upgrade from 2-D paper to a 2-D CAD model. Changes made in one view are reflected through all other views. An avenue is created to move from paper to solids and a significant step towards an accurate 3-D CAD model.

How Does It Work

With the emergence of cost-effective scanning hardware, services, and standards for storing drawings in raster format, the raster environment came of age in the early 1990s. Today there are a number of methods you can use to get your paper archives or "BC" (Before CAD) designs into the design and drafting environment of your CAD system.

Deteriorated drawings can be scanned, cleaned up, and stored in raster. Modifications can be made to the drawing in raster or areas of the drawing can be converted into CAD vectors as it becomes necessary. This combination of raster and vector can be plotted as well as stored within more advanced EDM/PDM systems.

Raster drafting.

Raster editing or drafting is the simplest and most productive way to modify scanned paper drawings. This is supported by the availability of advanced clean-up and editing features contained in some of today's products. Raster drafting works best when simple updates are required in non-dimensioned or unintelligent picture oriented drawings.

There is significant differentiation within the available software products in features, functionality, and positioning. The more advanced products are capable of working with raster "entities" just like vector CAD entities. Complex entity oriented changes can be made while preserving the integrity of other intersecting geometry. New additions can be made using your present CAD system and added or "burned" into the drawing with ease. This process is called rasterization or vector to raster conversion.

Hybrid process.

A fully hybrid approach is one where raster and vector CAD data co-exist within a drawing. The term hybrid in this case means a combination of both raster (scanned) and vector (CAD) data within a drawing. Hybrid editing means using both raster data and vector data simultaneously. Changes can be made within either environment. Information can be exchanged back and forth between the two distinctive formats. This approach offers the most efficient method for modifying the old within the new.

Two approaches exist for managing the hybrid databases. One approach separates the raster and vector models. It then introduces a third calibration file to define positioning, scaling and orientation of the imbedded object. This approach introduces more management burden on the user.

A more integrated approach treats the scanned raster data or multiple images as a CAD drawing. No additional management or operator burden is required.
Working in a hybrid environment allows use of the scanned drawings immediately. Decisions to modify, plot, or vectorize can be made as needed. Investing time and money to convert existing drawings can be done on a "just in time" basis.

Conversion: Raster to vector.

Drawings within Analysis and Modeling systems have the greatest corporate value. These need to be in a fully vectorized CAD format. Some examples: a company may need to develop a 3D model from an old drawing and run FEM or interference checks within the model; or variational and parametric modeling is required to test various design concepts for a complex part or assembly. Both situations require vector CAD models in their purest form, and consequently require full conversion to vector.

The process of automatically converting the scanned image into a CAD drawing is called raster-to-vector conversion, or vectorization. Conversion software will not produce an unattended 100 percent conversion. It is best used as a component of the conversion process rather than a total solution.

The tools used to vectorize are:

Overlay Tracing.

This is often referred to as heads-up digitizing. A scanned image is loaded into the CAD system as a backdrop and the image is "traced" over with CAD entities. This is very similar to the idea of digitizing but a digitizer table is not needed.

Automatic Vectorization.

Conversion of scanned drawings to intelligent CAD models has long been the desire of companies. There are numerous approaches presented by products found in the market.

Batch Conversion.

Batch tools work with a set of predefined rules to recognize unique settings such as text classification, width separations, and geometrics. This works best when drawing quality is very good, drawings are consistent, and the desired result is basic primitives. Results of batch systems will often require clean-up to ensure the converted drawing meets the needs of the user.

Selective or Interactive Conversion.

This is the most effective of the CAD conversion techniques. It combines the intuitive knowledge of the user with an interactive line-following or selective conversion process. These tools allow an operator to isolate selected geometry and text, then work within the limiting factors of the technology.

As an example, a manufacturing firm needs to make modifications to a part design. Advances in new materials and related cost savings demand that the part be redesigned to meet new structural requirements. Variational modeling is needed to optimize the design process. Rather than convert the entire drawing, only the appropriate geometry is selectively converted. The resulting relationships are defined, making future parameter driven design easy and in a sense, automatic.

Integrating Paper with EDM and PDM

Implementing task-oriented tools like CAD or word processing have improved individual productivity gains; similarly, scanning paper assets and implementing EDM/PDM enhances the business process. Reduced product cycle times, ISO 9000 support, and lower cost of goods represent the kind of measurable issues impacted by implementing EDM/PDM systems.

Viewing and redlining tools play an important role within this environment as they allow for quick and easy visual access and commenting (redlining) of the drawings. The ultimate viewer is one that supports your native CAD modeling format, raster formats and common office formats (word processing, spreadsheets, etc.), and is tightly integrated with your EDM/PDM Vault.

Tightly Integrated CAD/EDM/PDM.
A tightly integrated system is one in which the revision, release, and review cycles are all controlled from a common database environment of EDM or PDM. Drawings earmarked for update are flagged for check-out and launched into the appropriate editing tool.

Scanned drawings, now electronic files, can be managed and edited by the same tools used for vector files. More advanced CAD tools allow you to work on these electronic archives in their scanned raster format. This makes it possible to use a single editing environment for all drawing revisions, both in CAD and raster. Managing these raster or hybrid files is easiest with systems that store the raster files as part of a CAD drawing file.

Redefining the ECO Cycle.
Tightly integrated systems also link the viewing tool and its' redlining capabilities. These systems can concurrently allow viewing and simultaneous redlining of drawings throughout the enterprise.

As the drawing approaches approval, all redlines can be consolidated into a single approved file that can make its way into CAD. The resulting raster or vector drawing is updated and a final electronic comparison performed to verify completion of the task.

Cost-Benefit Analysis

Creating an open environment for drawing archives requires a one-time cost for scanning paper drawings into an electronic environment. Once implemented, savings are realized throughout all phases of the product life cycle.

Considering that the amount of technical information grows exponentially throughout each successive phase of a product life cycle, the savings can easily accumulate. This can provide a substantial return for the maintenance, archiving, and revision of paper assets.

With reduced labor costs and improved usage of CAD, the benefits of revising drawings electronically are clear. What may not be clear is the trade-off between investing in the upfront conversion to raw vector CAD, conversion to intelligent variational models, or taking advantage of lower cost hybrid raster CAD system.

Revision Life-Cycle Cost Savings.
The costs associated with revising drawings are dependent on the method and solution used. The methods presented here include manual, CAD digitize, hybrid raster CAD, full vectorization, or conversion to intelligent models.

Costs are incurred with each individual revision and include the cost associated with capturing the document to a digital form unless the manual method was used. Therefore, the true cost is calculated by combining labor rate and time spent projected on each revision plus the digital transformation expense.

In an article first appearing in Document Management Magazine, the inherent costs to recreate and revise a complex drawing, using each of the methods we have discussed, were compared. The comparison considered both the initial capture time, various labor rates, and the time associated with making revisions to the drawing once it had been captured.

The hybrid raster/vector approach, which eliminates the redraw, cleanup, and verification processes, offers the greatest immediate cost benefit for non-model oriented drawings. Drawings required in a vector CAD environment are best served by full conversion to intelligent variational modeling systems.

Business Reinvestment.
Companies already spend 7-10% of their expenditures on manual document management processes. A business reinvestment strategy involving the technology presented here can help reduce the incurred costs of managing, revising, and distributing information.

Market/Lead Time Benefits.
Manufacturing companies often survive based on getting quality products to market sooner than its competition. Doing so helps increase mind share and hence market share.

Project oriented companies, such as utility and construction companies develop a product at a greater scale. Contracts are awarded based on accurate and detailed proposals which must include cost and time estimates. A paper-enabled and intelligent modeling system at the front end yields faster design times and more accurate bidding efforts.

Other Benefits.
The direct benefits of integrating paper within EDM/PDM and CAD can be attributed to labor savings in the revision cycle. However, there are many other benefits:

• An increase in the value of CAD by eliminating its use for tedious redraw. CAD can now be used for productive design and analysis functions.
• Improved product quality. Getting it right the first time reduces downstream costs significantly.
• A common electronic database.
• Reduced retrieval and print times for documents with a document management solution.
• Improved information flow with workflow and E-mail tools.
• Improved conformance to the ISO 9000 or OSHA regulations by instituting better document control procedures.
• Increased value of paper drawings through integration with CAD and EDM/PDM tools.
• Fewer lost, damaged, and misfiled documents.
• Immediate availability of accurate information.
• Streamlining of the change process.
• Improvement in the time to market.

A simple cost-benefit example in which a company has 100 drawings with 20 ECO's to perform each month illustrates some of the measurable benefits of the raster-enabled approach presented in this paper. Various labor rates are used for each discipline. Actual numbers should be determined for individual organizations.

Selecting Vendors

When purchasing software, a relationship is established with the manufacturers and their resellers. Here are some points to consider when selecting a business partner:

Historical Longevity:

Market experience helps to ensure that your software manufacturer can deliver the best tools.

Investments in Research and Development:

Look for a consistent history of investment in the development of technology.

Integration Services:

Companies with strong integration services can assure full implementation of their technology with investments you have already made into databases and applications software.

Industry Partner Relationships:

A good indication of a quality software manufacturer is when their product is recommended by vendors of related technology.

Satisfied Customers:

Are there any "big name" accounts on the client list? References are always worth a check.

International Operation:

Worldwide usage can be a good indication of the maturity of a company. Foreign language versions can be helpful for your future or current applications.

Training and Support Services:

Proper training and support can be the difference between success and failure when implementing new technologies.

Market Leadership or Dominance:

Your investment in paper tools is a long term one and should be backed by a vendor with proven leadership in its field.

Evaluating the Software

Making It Work

Once you've made an implementation decision, how do you ensure the success of enabling your paper drawing archives within your CAD or EDM/PDM system?

Evaluate your Paper Trail. Evaluate and model the life of a drawing within your company. This will help you and your staff understand the areas needing improvement and helps in the justification of scanning, document management and hybrid systems.

Categorize your drawings: With the various technologies presented in this paper, it is clear that a number of options exist to modify them. Determine the modeling needs of the drawings throughout their projected life. Drawings without modeling needs can be scanned at lower resolutions and modified using hybrid raster and vector solutions. Modeling targeted drawings should be captured at slightly higher resolutions and converted to vector format.

Evaluate the quality of your drawings and determine the enhancement needs. Drawings that have excellent to moderate quality will work best. Poor quality and faded drawings can be improved with traditional photographic equipment and high end scanners but will likely result in limited benefits from the technology presented here.

Evaluate your resources and scanning urgency. This will help you to determine if scanning services or in-house resources will work best for you.

Include the user. Include your user community throughout the various phases of implementing this technology. This will improve the acceptance and the overall payback to your company.

Plan globally, invest incrementally. An incremental implementation can produce a more immediate payback and faster end user buy-in.

Convert incrementally. When considering the revision cycle and current paper archives, use the incremental conversion approach. Hybrid raster offers increased leverage of your CAD productivity while allowing the integration of paper archives. When drawings are being modeled, only convert the necessary geometry.

Quantify the benefits. Determine the strategic and practical value of the technology being introduced. Lower operating costs, time to market, and improved quality all provide benefits required to justify the investment.

Educate your staff. The benefits of the technology presented in this paper are far reaching but are only as effective as the staff and their understanding of the technology. Include product and procedural training seminars in your investments to ensure that user acceptance is maximized.

Conclusion. The value of capturing paper based drawings within a CAD system has long been acknowledged, but cost effective and practical tools and methods to accomplish this have only recently become available. Depending on the objectives of your organization, your goals may include archiving, management, distribution, and updating of your paper drawing legacy.

This white paper has described the tools and technology currently available for turning a paper legacy into today's and tomorrow's valued data asset.

A Word from the Sponsor (IBM)

You have most likely already implemented a CAD system to enhance your design process, but what are you doing with all of your engineering drawings that are on paper and aperture cards? There are many different approaches to take, but finding the right path for your organization can be difficult. This document is provided to help guide you through the tools and processes of modernizing and using your organization's paper and aperture card drawings in your CAD process.

The focus of this document is "Modernizing Your Legacy Engineering Archives", but many wider issues are also discussed, such as: integrating your legacy drawings into your CAD system, and Engineering Document Management/Product Data Management (EDM/PDM). This paper will give you an overview of your options and how to get started modernizing your legacy engineering archives.

IBM Corporation and Dassault Systemes are the world-wide leaders in CAD/CAM/CAE solutions. Our CATIA-CADAM Solutions family of products include CATIA/CADAM Drafting and CATIA/CADAM Hybrid Raster. Our software has proved to be a great choice for many CATIA-CADAM Solutions customers. "How to Modernize Your Legacy Engineering Archives" is designed to provide you information about the tools, techniques and processes available to help you and your organization make an informed decision about enhancing your engineering archives.

We welcome your comments and suggestions. Please contact us if we can be of assistance. Thank you.

IBM Corporation
Engineering Technology Solutions
1507 LBJ Freeway, Second Floor
Dallas, Texas 75234
1-800-395-3339
Web: David J. Wilson is principal of Open Archive Systems, Inc. specializing in paper-enabling consulting services and proven solutions for companies who wish to implement document management and raster/CAD systems. Clients include reseller partners, manufacturing firms, utilities, state and local government, and architectural firms who require raster enabled solutions.

Currently, Mr. Wilson works with major accounts including NYNEX, General Dynamics, GE, Cummins Engine, Southern New England Telephone, Dresser Rand, Polaroid, and others, providing consulting and technological services. He frequently lectures and writes on integrating paper within the CAD and EDM/PDM environment.

e-mail: dwilson@openarchive.com

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