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A Review of CAMWorks for Solid Edge

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by L. Stephen Wolfe, P.E.

Here’s a look at the features and capabilities of version 1.05 of Solid Edge.

CAMWorks was first published as an add-in application for numerically controlled (NC) tool programming in SolidWorks in 1997. In June 2013, Geometric Software released a version of CAMWorks integrated with Solid Edge, the value priced CAD system from Siemens PLM Software. Although seven computer-aided manufacturing (CAM) software products have achieved so-called Gold Partner integration with SolidWorks, CAMWorks is the first such software to be seamlessly embedded within Solid Edge.

CAMWorks
CAMWorks appears as just another tab in the Solid Edge menu.

CAMWorks for Solid Edge allows programmers to open a part file in native format and begin making a numerically controlled tool program immediately. There is no need to export software to another format and import it into an NC programming tool. When complete, tool paths and other CAM information are stored in the Solid Edge model.

Changes made to Solid Edge parts are immediately reflected in NC programs produced by CAMWorks. CAM systems that are not integrated with CAD require revised parts to be re-exported, and in most cases updates to geometry must be made interactively.

CAMWorks-machinable-features
Examples of machinable features recognized by CAMWorks.

In its first release, CAMWorks for Solid Edge lacks some of the capabilities of CAMWorks for SolidWorks. Missing features include:

• Ability to machine parts in assembly models
• Simultaneous 4- and 5-axis milling
• Mill-turn machine operations
• Wire EDM
• Full machine simulation

These capabilities are planned for the last quarter of 2013. The ability to work with assembly models will enable tool-path simulation along with parts of the machine itself, such as the table and work-holding fixtures. The software will be able to check for collisions with the machine and fixtures if desired. Assembly model support also permits rough stock models (such as castings) to be imported as Solid Edge models. In the first release, rough stock models must be converted to the faceted STL format employed by 3D printing systems.

Knowledge capture and continuous improvement
What sets CAMWorks apart from most other graphics-based NC programming systems is its ability to capture knowledge of customers’ manufacturing processes in ways that can be re-used easily. This knowledge capture enables customers to continuously improve their machining processes, thereby improving product quality and reducing costs.

CAMWorks-machinable-features-list
A list of machinable features.

CAMWorks uses two key technologies to capture knowledge of machining processes. The first is the ability to recognize more than 20 manufacturing features as distinct from the dimension-driven design features native to CAD systems such as SolidWorks and Solid Edge. Manufacturing features include drilled, countersunk, counter-bored, and tapped holes; irregular, rectangular, and cylindrical pockets; irregular and cylindrical bosses; faces; grooves; curves; and engravings.

CAMWorks does not require these features to be defined in the CAD model. It identifies them based purely on the solid model geometry. Consequently, CAMWorks can identify features in featureless solid models that have been imported in Parasolid, STEP, IGES, or proprietary translator formats.

CAMWorks-machinable-features-list-operations
Operations plans associated with each feature.

The second technology for capturing data is the Technology Database, which contains operational plans for machining various types of features. For example, the operations for producing a counter-bored hole might include center drilling, drilling of the through-hole, and milling the counterbore. The operational parameters include tool characteristics, feeds, speeds, entry or lead-in strategies, tool changes, and other variables that the NC programmer might want to control. Tools may be selected from a comprehensive tool library included in the database.

CAMWorks pairs operational procedures with the various feature types and the sizes of features it recognizes. For example, a small hole might be matched with a drilling operation whereas a larger hole might be milled.

Of course CAMWorks is not yet capable of automatically recognizing every feature in a part. So customers also have the ability to select part faces and classify them as manufacturing features. These can then be associated with manufacturing operations in the Technology Database that enable the feature to be turned or milled. Manufacturing operations include hole-making operations such as drilling, center drilling, and boring; rough and contour milling; and various three-axis milling operations such as z-level, flat-area milling, and pencil milling.

CAMWorks-machinable-features-list-operations
Operations plans associated with each feature.

The ability to combine manufacturing features with predefined operations enables programmers to generate NC code much faster than is possible with more conventional graphics-based systems. Instead of specifying each tool path individually, CAMWorks enables complete operations such as roughing and finishing to be implemented in a single step. CAMWorks automatically traverses the manufacturing feature tree and generates operational plans for each manufacturing feature. Then it generates a tool path for each operation.

Programmers can simulate the tool path and compare it with the original part shape to identify undercuts and overcuts. When the toolpath is correct, CAMWorks generates NC code for the appropriate NC tool controller that will be used to make the physical part.

The Technology Database contains a variety of controller types, and CAMWorks and its dealers can customize these for most commercial tool controllers. CAMWorks uses the same library of controller models and post-processors for both the Solid Edge and SolidWorks versions of the software. Consequently, even though CAMWorks for Solid Edge is new, it benefits from the rich history of a mature CAM product.

CAMWorks-tooltab
The tool tab shows properties of the selected cutting tool for an operation in the technology database.

The integration of CAMWorks with CAD software further improves productivity by updating NC tool programs when changes are made to the associated CAD model. Toolpath data is stored with the CAD model so it can’t get lost.

CAD integration also enables families of similar parts to be programmed quickly by saving part models with new file names and changing the part geometry. The associated NC programs automatically update with the new part.

Even more powerful is CAMWorks’s ability to reuse machining processes for individual part features in parts that are otherwise dissimilar in shape. For example, two different shaped parts may contain round holes, irregular packets and bosses, slots, and fillets that use similar manufacturing processes. Such parts can be programmed much faster than would be possible with more conventional CAM software.

Labor savings are easy to measure, but CAMWorks can help produce even greater savings by enabling consistency and continuous improvement in a company’s machining processes. With conventional graphics-based systems, programmers have a great deal of flexibility in how they program each part. The same programmer may use different techniques and strategies on similar parts. Different programmers may employ even more widely varying strategies.

CAMWorks-toolpath-simulation
CAMWorks toolpath simulation.

CAMWorks enables companies to standardize processes by storing knowledge about them in its Technology Database. This practice ensures that similar processes— tool choices, feeds and speeds, and milling strategies, for example—are used across similar features in all parts being produced. When improvements are made to a process on one part, standardization ensures that similar improvements will be used on all future part programs. For example, if the choice of a different tool or machining strategy leads to longer tool life or reduced machine time when cutting a new alloy, the new tool can be employed to reduce costs in all future part designs.

Continuous improvement also improves product quality. It enables, for example, better machine finishes to be developed, reducing the cost of hand polishing and the attendant human error. Computer-controlled processes and machinery also are consistent, ensuring less variability among parts in a production run. This consistency can produce near-zero defect rates when combined with statistical monitoring of machine adjustments and tool wear.

Another benefit of CAMWorks is the ability to store a company’s current good practices in a form that can be easily shared with new workers. When skilled and experienced NC programmers leave a company for another job or for well-deserved retirement, their knowledge of good machining practices often leaves with them. With conventional CAM software, new workers hired to replace them have a nearly impossible time inferring these good practices from existing programs.

With CAMWorks, new workers need only learn which types of features should be applied to the types of geometry that are not automatically recognized. With the right features in place, good machining practices are automatically used.

The use of application programming interfaces (APIs) for CAD software combined with CAMWorks APIs has enabled some CAMWorks customers to completely automate the design and manufacture of custom products. For example, CP-Carrillo of Irvine, Calif., makes custom pistons for a variety of automotive and marine racing engines. Customers speak with application engineers about their requirements, and the engineers enter appropriate values into a SolidWorks CAD application that generates the design for a set of pistons and connecting rods.

When the piston and connecting rod models are complete, the NC programs to mill them are automatically generated using CAMWorks. The entire process is automated. Engineers don’t interact with the piston design or CAMWorks.

Another company in Sanford, Fla., named .decimal (pronounced dot-decimal) uses CAMWorks to automatically mill custom filters for radiation therapy in brass, aluminum, and copper. Beginning with CT-scan data, .decimal’s custom software generates the appropriate surfaces to be milled from a standard blank designed to fit most radiation treatment machines. CAMWorks then automatically generates the program to mill each blank into a patient-specific device. As with CP-Carrillo, .decimal’s entire milling process is automated. No human interaction is required. In this case, speed is critical to minimize delay between diagnosis and treatment.

Custom-IMRT-filter
Example of a custom IMRT filter produced by .decimal.
cad-piston-milling
On the left, an example of a CP-Carrillo piston designed automatically and an example of a piston partially milled with CAMWorks is on the right.

Operational considerations of knowledge-based machining
Effective use of CAMWorks requires developing a Technology Database that matches each company’s production requirements. Elements to be included in the Technology Database are:

• The capabilities of each machine tool and its controller
• Tool-path post-processors for each machine
• A tool library that matches each customer’s tool crib
• A set of operations matched to the features, feature sizes, and materials typically used by the customer

The Technology Database is accessible from a button on the CAMWorks ribbon bar. From the main dialog box, customers can define mills, lathes, and the operations associated with them. They can also define tools in the tool library, including special tools with unique cross sections. And the Tech DB allows feeds and speeds for different machine types to be associated with materials of varying strength and hardness such as mild steel, tool steel, and various grades of aluminum.

CAMWorks-Technology-database-top-level
The top-level menu of the Technology Database.

Most of the information in the Technology Database can be entered or modified from dialog boxes with parameter fields or pull-down menus. There is no need to write scripts or define data tables. Geometric Technologies has taken care of all this administration.

The Technical Database menus are three levels deep with multiple tabs at the lowest level. The multitude of options gives customers a lot of control over how their parts will be machined.

CAMWorks-Technology-database-features-dialog
The Features and Operations dialog allows customers to define machining strategies for various types of features.

However, learning what all the options mean, let alone which choices are optimal for a given situation, takes considerable time and experience.

For many machine shops, setting up the Technical Database may become the biggest cost of their CAMWorks investment. Defining all the right options and processes and securing the right post-processing software may require not only staff time, but time from dealer’s consultants or application engineers as well. The costs of this investment can be recouped by future labor savings, quality improvements, and machine time-savings that accrue from the practice of continuous improvement.

CAMWorks-Technology-database-operational-parameters
The Operational Parameters dialog box for the Contour Milling operation strategies for various types of features.

Fortunately, customers need not set up the entire technical database from scratch to begin improving productivity with CAMWorks. The software comes with a rich set of processes out of the box. These processes can be modified by tool programmers as they are used and saved as new manufacturing strategies in the course of normal work. Consequently improvements to the Technical Database can be made gradually over time.

Reprint info >>

Siemens
www.plm.automation.siemens.com

Is CAD Becoming More Portable?

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For years now I’ve been writing on the topic of CAD software running on mobile devices. As more and more of engineering and manufacturing tasks become distributed among various partners and suppliers in ever-expanding supply chains, having a way to access drawings and models on mobile devices (tablets, smartphones, etc.) has become more important.

Obstacles Abound

Critics—for myriads of technical reasons—don’t believe that mobile CAD is anything but a pipe dream of vendors looking for additional ways to deliver software as well as the potential of a new revenue stream for their products. Though most of the apps are free, as the market grows and demand increases, there is always the possibility that users will eventually be willing to pay for mobility. There are also concerns regarding security as mobile devices can’t be regulated and managed by IT in the same manner as desktop computers.

The Current State of Portable CAD

Autodesk was the first vendor to jump into the not-yet-tested waters, offering AutoCAD WS (now called AutoCAD 360), a free drawing and drafting app that enables users to view, edit and share AutoCAD drawings on the go. Available for free on both on the Apple store and Google Store, AutoCAD 360 has been downloaded five million times, though how that equates to the number of actual users is not completely clear.

Ralph Grabowski, an industry analyst, follows the portable CAD market closely and has just released his State of Portable CAD in 2013 report, featured in his weekly upFront.ezine. One of the drawbacks he sees with portable CAD—and one quickly identified with early critics—is the reality that CAD is very hardware-intensive and the portable devices don’t yet have the computing horsepower to run it effectively.

With limited RAM capacity on mobile devices, it’s difficult to cram the operating system, CAD program, and all the drawing data into .5 GB of RAM. On the graphics side is another lingering issue, as users can’t simply swap in a faster, CAD-friendly graphics board. For developers, another issue revolves around the question of how to write apps for iOS with Apple’s secrecy (most hardware specs are unknown), while writing for Android is also tricky because of device targeting.

Have no fear; the hardware problems will resolve themselves, as developers are already upping available RAM and GPU specs are on the upswing. Quad-core CPUs running at 1.5 GHz or faster are now common, while units with a whopping 8 cores of processing power and/or with speeds of over 2.5 GHz are beginning to ship.

How do vendors make money selling CAD apps?

Technical issues aside, there is also the lingering question of exactly how vendors would make money selling portable apps as nearly all of them are free, especially after Apple takes its 30% cut. So this begs the question: how do CAD vendors pay for the cost of developing apps when most of them aren’t charging for them?

There are exceptions. Autodesk is charging for its AutoCAD Pro and Pro Plus apps ($49 and $99/year respectively). IMSI/Design, developer of TurboViewer, is also charging for its higher-end TurboViewer X, TurboViewer Pro, and TurboReview ($6.99, $29.99 and $49.99, respectively) though special pricing of those packages is available.

AutoCAD 360
AutoCAD 360 is a free drawing and drafting mobile app that allows users to edit, view and share AutoCAD drawings from anywhere.

An alternative pricing model ties the mobile apps to desktop software, making the free mobile app useless unless the user is paying for the desktop version. Vendors trying out this pricing structure include Geometric, with its Glovius software, Simens PLM Software with its Solid Edge Mobile, Nemetschek Vectorworks with its Nomad software, and Vizerra with its Revizto Viewer.

The bottom line

Though some of the pricing quoted here may have changed, it’s a good landscape to view the general market for mobile CAD applications. While most vendors understand that there is a need for portable CAD, finding out how to actually make money at it in the short run might prove problematic.

We’ll certainly keep an eye on this emerging new market and hope to see progress—both on the technical side and the business side—so designers and engineers will have the CAD apps they need to become increasingly productive when they are out of the office or on the road.

The failed promise of parametric CAD, final chapter: A viable solution

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Model reuseWhat is the failed promise of parametric CAD? In short, model reuse.

It’s a lot more difficult than it ought to be, for a variety of reasons. Several months back, I wrote a series of articles discussing those reasons, as well as some of the solutions that have come up over the years.  What was missing from the series was a final chapter; a detailed description of what could prove to be a viable solution to problems with model reuse: the resilient modeling strategy.

The resilient modeling strategy (RMS) is the brainchild of Richard “Dick” Gebhard. I wrote about Dick last June, in the article A Resilient Modeling Strategy. He’s a low-key guy with deep experience and serious expertise in the practical use of MCAD software. Over his career in CAD, he’s been a reseller for CADKEY, Pro/E, and most recently, Solid Edge.

RMS is a best practice for creating CAD models that are stable and easily reusable (even by inexperienced users.)  It can be learned and easily used by typical CAD users, it preserves design intent in models, and provides a mechanism by which managers or checkers can quickly validate a model’s quality.

Resilient Modeling Strategy

When Dick first started thinking about the concepts that make up the resilient modeling strategy, it was natural that it was in the context of showing the advantages of Synchronous Technology (The Siemens PLM brand name for its version of direct modeling.) In our discussions about RMS over the last year or so, I pointed out that, while I thought that RMS did indeed demonstrate the benefits of hybrid history/direct modeling in Solid Edge, for it to be taken seriously, and not be unfairly dismissed as a marketing initiative for Solid Edge, it needed to work with a wide variety of MCAD tools. I think Dick got where I was coming from, because he’s continued to refine and generalize RMS, with feedback from users of a number of MCAD systems.

In its current incarnation, RMS works particularly well with Solid Edge, as might be expected, but also works very well with Creo, NX, CATIA, and IronCAD (all of which are hybrid history/direct systems.) Further, with a few modifications, it can provide compelling value with SolidWorks, Inventor, and Pro/E (all of which are primarily history-oriented systems.)

It’s significant that RMS is also free to use. While Dick is available to provide presentations, seminars, and training, he has not attempted to patent, or keep as trade secrets, the underlying concepts of RMS. (He does claim a trademark on the term “Resilient Modeling Strategy,” which means that organizations offering commercial training on RMS will need to get Dick’s OK to use the term.)

Dick has posted an introductory presentation on RMS at resilientmodeling.com. While the entire presentation is 20 minutes long, the first 3-1/2 minutes cover the problems that people invariably experience when reusing or editing history-based CAD models. Watching that much will likely convince you to watch the rest.

On Wednesday, November 20, at 10:00 AM PST, Dick will be hosting a webinar on RMS. It’s scheduled to last just 30 minutes, with the emphasis on content, not hype. If you’re a serious CAD user or a CAD manager (or, for that matter, you work for an MCAD developer), it’ll be well worth your time to attend.

TL;DR: Resilient Modeling Strategy is a best practice for creating high quality reusable 3D MCAD models. It works with many CAD systems, it’s easy to learn and use, and it’s free. Big payoff for MCAD users. 

Presentation at resilientmodeling.com

Register for Nov 20 webinar on Resilient Modeling

 

 

 

Siemens Extends Monthly Subscription Options with 3D Editing Tool

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After 20 years of covering the CAD industry, I’ve seen many changes and advances in the technology offered in the various systems. One thing that has remained constant, however, is that CAD is expensive. For many years, even so-called “mid-range” CAD systems would set an engineer back $5,000, and that’s just to get started and doesn’t include any associated hardware, training or support costs. To rectify this cost barrier, a growing number of CAD vendors are offering their software on a monthly subscription basis. This fits rather well with the needs of smaller companies and those whose business is cyclical in nature, meaning they don’t use the CAD tool on a daily basis.

Following in this trend, Siemens began offering its Solid Edge 3D CAD software by subscription in August. Yesterday, Siemens announced that it is now offering a new monthly subscription option as well as a free 45-day trial for its 3DSync software, a 3D editing tool based on the company’s proprietary synchronous technology, which is offered in both of its CAD applications, NX and Solid Edge. The company reports that the tool has been shown to increase the productivity by a factor of ten or more when working with imported CAD data, a common activity for engineers in today’s multi-CAD world. The new subscription option is initially available online in the US, Canada, UK, and Ireland. The free 45-day trial is available globally.

The 3DSync software is a much-needed tool in today’s product development environment in which engineers must collaborate among multiple companies (suppliers, partners, and customers). Inconsistent data formats among the various CAD systems create headaches, bottlenecks, errors and often time-consuming rework. The design intent built into CAD models created in parametric CAD systems is often lost during the translation process, making the resulting model difficult to work with and often requires the engineer to fix, or worse, recreate it. Synchronous technology enables users to interrogate imported 3D models, recognize design intent, and automatically apply appropriate design parameters. Using a tool like 3DSync will extend these benefits to users of any commercially available CAD system. Certainly a step in the right direction towards eliminating the headaches engineers suffer as a result of having to work with imported CAD models.

To sign up to receive 3DSynch on a monthly basis, go to: http://store.plm.automation.siemens.com/store/siplm1/en_US/pd/productID.288669500.

Or give the tool a free 45-day test drive by signing up here:
http://www.plm.automation.siemens.com/en_us/products/velocity/3dsync/free-3dsync.shtml

Barb Schmitz
bschmitz@wtwhmedia.com

The failed promise of parametric CAD part 5: A resilient modeling strategy

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bamboo-gardenThe model brittleness problem inherent with parametric feature-based modeling is a really big deal. And it’s something, honestly, that I don’t have a great answer for. I’ve even asked a few power users who I know, and their answers seemed to involve a bit of hand-waving, and a reference to having lots of experience.

While best practices are a potentially good step forward, they need to be straightforward enough that mere mortals (as opposed to power users) can follow them.

Around Christmas last year, I got a call from Richard Gebhard, an engineer’s engineer, who has made his living selling CAD, and training people to use it (including more than his fair share of power users), for longer than he would like me to admit. (I’m pretty sure I’ve been in the CAD industry longer than him, though.) Richard told me he had something he wanted to show me, and if I’d take the time to meet him, he’d buy me lunch.

What Richard showed me was a way of creating and structuring CAD models that made a lot of sense. It not only reduced parent-child dependencies, but it made them more predictable. And, more importantly, it made it a lot easier for a mere mortals to scan through the feature tree, and see if there were any grues (it’s a technical term. Feel free to look it up.)

Over the next several months, we had lunch several times. I made suggestions. He rejected some, accepted some, and thought about others. At the same time, he was bouncing his ideas off several of his best power users (including his son). By a couple of months ago, he had refined his system to the place where it would work impressively well with nearly any parametric feature-based CAD system. So, he went to work finalizing his presentation.

I had mentioned that Delphi, by patenting some of the elements of horizontal modeling, limited the number of people who could benefit from it. (Worse for them, they patented it, then filed bankruptcy. That didn’t help much.) Richard’s goal wasn’t to monetize his process. His goal was to evangelize it. To help CAD users—both power users and mere mortals—to get their jobs done better.

Richard and I had talked, over time, about what he should call this process. At first, I liked the word “robust.” In computer science, it is the ability of a system to cope with errors during execution. In economics, it is the ability of a model to remain valid under different assumptions, parameters and initial conditions. Those are good connotations. But, then I thought of one of my favorite examples of robustness. The first time I visited Russia, I noticed that the apartment buildings were built of thick poured concrete. Very robust. And nearly impossible to remodel.

Richard’s system wasn’t robust. It was resilient. So, he has named it the Resilient Modeling Strategy. RMS.

So far, I’ve written over 2,600 words, to provide some background on the problems of parametric modeling, and some of the solutions that have been offered over the years. But, after all that, I’m not going to tell you anything more about RMS. At least, not yet.

Tomorrow, Wednesday, June 26, Richard will present RMS for the first time ever, at Solid Edge University, in Cincinnati, Ohio. His presentation will start at 9:00AM local time, and will be in room 6 of the convention center. If you’re there, put it on your calendar. If not, you’ll need to wait until Richard gets back to Phoenix, and I publish a follow-up post.

RMS is not anything difficult, or fundamentally new. It’s just an elegant distillation of best practices, designed to work with nearly any parametric CAD system, and simple enough that it doesn’t get in the way.  It’ll help you make better CAD models faster.

The failed promise of parametric CAD part 4: Going horizontal

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In the early 90s, Ron Andrews, a senior product designer at Dephi’s Saginaw Steering Systems Division, became fed-up with the difficulties of editing parametric CAD models. So, he and a team of his colleagues, including Pravin Khurana, Kevin Marseilles, and Diane Landers, took on a challenge of trying to find a solution.

They came up with an interesting concept that they called horizontal modeling. Here’s a description of it from their patent abstract:

“Disclosed is a horizontal structure method of CAD/CAM manufacturing where a base feature is provided and one or more form features added to it to form a model. The form features are added in an associative relationship with the base feature, preferable a parent child relationship, but are added in a way as to have substantially no associative relationships with each other. The result is a horizontally-structured Master Process Model where any one form feature can be altered or deleted without affecting the rest of the model. Extracts are then made of the Master Process Model to show the construction of the model feature by feature over time. These extracts are then used to generate manufacturing instructions that are used to machine a real-world part from a blank shaped like the base feature.”

Here’s a picture that makes it clearer:

Horizontal Modeling

The simplest explanation I can give for it is this: You create a base feature, and bunch of datum (working) planes. You attach all the child features to those datum planes. Viola: no parent-child problems.

I admit that I’m not going to do justice to horizontal modeling in this conversation. There’s actually quite a bit to it, and it makes a lot of sense when coupled with computer-aided process planning (CAPP.)

Horizontal modeling has a handful of problems. First, it does a pretty good job of killing the possibility of having design intent expressed in the feature tree. Next, it works better with some CAD systems than others. (When horizontal modeling was in the news, SolidWorks had a problem managing the normals on datum planes, so it didn’t work too well.) The deadliest problem is that Delphi got a bunch of patents on the process, then licensed it to some training companies. From what I can see (and I may be wrong), none of these training centers offer horizontal modeling classes any more.

While, technically, you can’t use horizontal modeling without a patent license from Delphi, the concepts at its core are fairly similar to things that CAD users have been doing for years. A few years ago, Josh Mings posted on a couple of online forums that “Horizontal Modeling is just one word for it, you may also know it as Skeleton Modeling, Tier modeling, Sketch Assembly modeling, CAD
Neutral Modeling, or Body Modeling.” (It’s actually two words for it, but I get his point.)

Horizontal modeling is not a silver bullet solution for the problems inherent in parametric feature-based CAD. It’s just a best practice—a strategy for getting around the problems. It seems to be headed in the right direction, but it suffers from the complexity that comes from trying to fix too many problems at once.

Next: A Resilient Modeling Strategy

The failed promise of parametric CAD part 3: The direct solution

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Pull-PushDirect modeling—a syncretic melding of concepts pioneered by CoCreate, Trispectives, Kubotek (and many others)–has shown the most promise to cure the parametric curse.

Direct modeling is today’s hot CAD technology. PTC, Autodesk, Siemens PLM, Dassault (CATIA, but not so much SolidWorks), IronCAD, Kubotek, Bricsys, SpaceClaim (and certainly some other companies I’ve forgotten) all have their own unique implementations of it.

The common thread in direct modeling is to use standard construction techniques when modeling, and feature inferencing (or recognition) when editing. It’s easier said than done. It’s taken about 35 years of industry research to get to the place we are today—where you can click on a face of a model, and the system will recognize that you’re pointing to a feature that has some semantic value. And that’s not even considering the tremendous amount of work that has been required by legions of PhD mathematicians to develop the math that lets you push or pull on a model face, and have the system actually edit the geometry it in a useful manner.

For the CAD software, figuring out which way to edit a selection is almost a mind reading trick: A user clicks and drags on a part of a model. What would they like to happen? In some cases it’s easy: Drag once face of a rectangular block, and the system will just make it longer or shorter. But if the block is full of holes, bosses, and blends, it becomes a lot more complicated. What should the system do if you drag a face so far back that it consumes another feature, and then pull it back to where it was? Should the consumed feature be lost forever, or should the system remember it in some way, so it can be restored?

There are no right answers. It seems that no two direct modeling systems handle the decision of what is a “sensible” edit in the same way.

While direct modeling absolutely solves the model brittleness problem inherent with parametrics, it does it by simply not using parametrics. Even with hybrid parametric/direct CAD systems, the answer to the parametric curse is still to not use parametrics when you don’t need to.

The solution of “use direct modeling when you can, and learn to live with parametric hassles when you can’t” just isn’t very satisfying to me.

Next: Going horizontal

The failed promise of parametric CAD part 2: The problem is editing

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ErasermIn the previous post, I wrote about the failed promise of parametric CAD: problems such as parent-child dependencies and unwanted feature interactions, coupled with no easy way to either prevent, or check for them.

The difference between modeling and editing in a parametric CAD system is simply the difference between creating things from scratch, and modifying things you’ve already created. The distinction may seem academic, but it is only when editing that parent-child dependencies are a potential problem.

Consider a scenario, of creating a parametric part—one that you’ve worked out in your head pretty well ahead of time—where you start from scratch, modeling sequentially, and spending all your time working on the most recent feature without needing to go back to edit upstream features.

In that context, the model’s parent-child dependencies would exist, but would be benign. They’d never get in your way. That is, until you went back to edit the part.

In most cases, people don’t build models from scratch without periodically going back to adjust earlier features from time to time. In that process, they’ll catch, and be able to deal with, some of the dependencies. But not likely all, or even most, of them.

I’ve heard experienced CAD people use an interesting term for models with hidden and untested parent-child dependencies: Parts from hell. When you’re trying to modify them, you never know when a small change might cause them to completely fall apart. I think a better, more descriptive, term is brittle: Hard, but liable to break or shatter easily.

This also suggests a descriptive term for CAD models which are not liable to break or shatter easily: resilient.

I’ve only ever seen one group of users who could consistently create complex yet resilient parametric parts models from scratch: PTC application engineers from the early to mid-1990s. Of course, they could only do it during customer benchmarks, with parts they’d practiced ahead of time, where they had worked-out and memorized all the steps, and where they had a good idea of the parameter ranges. Even then, if you were to ask them to change a dimension that would cause a topological change, the models might unceremoniously blow up.

Not to paint too bleak a picture, there are certainly CAD power users who have the skills to create resilient CAD models. I’ve met more than a few of them: true professionals, who by combining experience, insight, and education, have earned the respect of their peers. They understand how to structure CAD models to avoid any problems with brittleness.

Nah. I’m just messing with you. Power users struggle with this just like us mere mortals. It’s just that their models don’t usually fall apart until you go outside the scope of parametric changes they had anticipated. Give power user’s carefully crafted CAD model to a user who has a black thumb (I’m sure someone comes to mind), and they’ll find ways to blow it up that the power user never imagined.

Next: The direct solution

The failed promise of parametric CAD part 1: From the beginning

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The modern era of 3D CAD was born in September 1987, when Deere & Company bought the first two seats of Pro/Engineer, from the still new Parametric Technology Corporation. A couple of years later, Deere’s Jack Wiley was quoted in the Anderson Report, saying:

“Pro/ENGINEER is the best example I have seen to date of how solid modelers ought to work. The strength of the product is its mechanical features coupled with dimensional adjustability. The benefit of this combination is a much friendlier user interface plus an intelligent geometric database.”

According to Sam Geisberg, the founder of PTC:

“The goal is to create a system that would be flexible enough to encourage the engineer to easily consider a variety of designs. And the cost of making design changes ought to be as close to zero as possible. In addition, the traditional CAD/CAM software of the time unrealistically restricted low-cost changes to only the very front end of the design-engineering process.”

To say Pro/E was a success would be a terrible understatement. Within a few years PTC was winning major accounts from the old-line competitors. In 1992, on the strength of its product, PTC walked away with a 2,000 seat order from Caterpillar that Unigraphics had thought was in the bag.

The secret to Pro/E’s success was its parametric feature-based solid modeling approach to building 3D models. To companies such as Deere and Caterpillar, it offered a compelling vision. Imagine being able to build a virtual CAD model of an engine, and, by changing a few parameters, being able to alter its displacement, or even its number of cylinders. And even if that wasn’t achievable, it would be a great leap forward to just be able to rapidly create and explore design alternatives for parts and assemblies.

Yet, things were not that easy. In 1990, Steve Wolfe, one of the CAD industry’s most insightful observers, pointed out that Pro/E was incapable of making some seemingly simple parametric changes.

Pro/Engineer placed limits on the range of parameters. (A designer could not increase the dimension of L2 to point that L3 vanished.)
Pro/Engineer placed limits on the range of parameters. (A designer could not increase the dimension of L2 to point that L3 vanished.)

David Weisberg, editor of the Engineering Automation Report (and from whose book, The Engineering Design Revolution, I have liberally cribbed for this article), pointed out the fundamental problem with parametrics:

“The problem with a pure parametric design technique that is based upon regenerating the model from its history tree is that, as geometry is added, it is dependent upon geometry created earlier. This methodology has been described as a parent/child relationship, except that it can be many levels deep. If a parent level element is deleted or changed in certain ways it can have unexpected effects on child-level elements. In extreme cases (and sometimes in cases that were not particularly that extreme), the user was forced to totally recreate the model… Some people described designing with Pro/ENGINEER to be more similar to programming than to conventional engineering design.”

Weisberg barely scratches the surface of the issues that can create problems.

In 1991, Dr. Jami Shah wrote an Assessment of Features Technology, for Computer-Aided Design, a journal targeted to people doing research in the field of CAD. He identified that there were problems with features:

“There are no universally applicable methods for checking the validity of features. It is up to the person defining a feature to specify what is valid or invalid for a given feature. Typical checks that need to be done are: compatibility of parent/dependent features, limits on dimension, and inadvertent interference with other features. In a study for CAM-I, Shah et al. enumerated the following types of feature interactions:

  • interaction that makes a feature nonfunctional,
  • non-generic feature(s) obtained from two or more generic ones,
  • feature parameters rendered obsolete,
  • nonstandard topology,
  • feature deleted by subtraction of larger feature,
  • feature deleted by addition of larger feature.
  • open feature becomes closed,
  • inadvertent interactions from modifications.”

The important thing to notice here is that, not only are there multiple failure modes for features, there are also no universal methods for validating features. It’s left up to the user to figure out. And that process, as Weisberg hinted, is much too difficult.

Rebuild Error

Since the early days of Pro/E, a lot of work has been done, both by PTC and other companies in the CAD industry, to improve the reliability and usability of parametric feature-based CAD software. Yet, the problems that Weisberg and Shah identified still exist, and still get in the way of users being able to get the most from their software.

Next: The problem is editing.

 

How was the Mars rover Curiosity designed? With Siemens PLM software

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Last Sunday night, I watched the live video feed from NASA’s Jet Propulsion Laboratory, as the rover Curiosity descended through the Martian atmosphere, and landed on the planet’s surface.

NASA called the process of landing the Curiosity “7 minutes of terror.” The whole process was completely automated—and all that the people at JPL (or the tens of thousands of us who were watching over the web) could do was wait, helplessly, as the drama played out. When Curiosity landed safely, and sent its first pictures from Mars’ surface, cheers rang out—not just at JPL, but on Twitter and other social media sites.

One of the things I noticed immediately, when I tuned into www.nasa.gov was that the average age of the scientists and engineers shown in the feed was quite young. I’d noticed this before, in a video segment shot by PhD Comics inside the Mars Rover Test lab, where NASA engineers Chaz Morantz and Bobak Ferdowski talked about Curiosity.

It’s not your father’s NASA anymore.

The Curiosity is the largest and most advanced space exploration robot ever made. It was designed with Siemens PLM software, including TeamCenter and NX, and is almost a best-in class example using those to tools, from conceptual design, to full-system simulation. (To understand why I say “almost,” keep reading.)

Here are a few videos that discuss Siemens PLM’s involvement with the Curiosity rover project:

Here is Daren Rhoades, who works for Siemens PLM, and used to work for JPL, explaining some of the challenges in designing Curiosity:

Doug McCuiston, Director of the Mars Exploration Program, talking about the importance of Siemens PLM software in designing Curiosity:

You can watch these, and other videos here.

Almost a best-in-class example.

In the videos, NASA’s Doug McCuiston says: “The challenges of building something like that, with all the parts that are involved—all the discrete parts, all the interfaces, and all the testing, and the ability to maintain not just the documentation, but all the drawings, the test flows, the verification items, is a very complex task in itself.”

No kidding.

Yet, if NASA were to design Curiosity today, I suspect they’d want to take a serious look at a couple of advancements in Siemens PLM software could make their life quite a bit easier.

Active Workspace

The first is a product called Active Workspace. Siemens calls it “a personal environment for accessing your entire PLM system.” You can download a fact sheet for it here.

I was lucky enough to be able to Active Workspace before its public announcement, and talk to some of the key people behind its development. The product includes a lot of really valuable capabilities, incluidng product data navigation and visualization, visual reporting, shared contexts, flexible collaboration, and ridiculously powerful search (including shape search.)

But what completely surprised me was that it goes way beyond just letting you view relationships between parts. It lets you view relationships between all of your product information, including requirements, functions, logical diagrams, and systems-engineering information.

Let me put that in a different way: Active Workpace supports a systems engineering driven product development process. It is systems engineering that lets you link together all the disparate elements of a product design into an intelligent product model, which can be continuously validated. It is the key to enabling true model-based development.

Here’s Chuck Grindstaff, CEO of Siemens PLM Software, talking about systems engineering and Active Workspace:

Product and Manufacturing Information

The other advancement from Siemens PLM that NASA would benefit from isn’t entirely new, but it’s become increasingly important: PMI (Product and Manufacturing Information.)

If you watch the videos about Curiosity, you’ll notice that they talk about “drawings.” CAD drawings have been around a long time—but that doesn’t mean they’re a good thing. They’re designed for human interpretation, and are thus subject to human misinterpretation. And they create a disconnect between product design and manufacturing.

PMI can contain GD&T, weld symbols, text and dimensions, as well as the product definition and process notes. PMI can exist in 3D models in the same way that information exists on 2D drawings – using leader lines that connect the data to specific parts in the product design.

The use of PMI shortens the design cycle by enabling product teams to incorporate product and process information during the design phase. This results in better communication between design and manufacturing groups, fewer errors, streamlined design and manufacturing processes and faster change management. PMI not only reduces the need to generate 2D drawings; it also enables downstream applications to directly access this information for automating tasks such as CNC programming, tolerance stack up analysis and CMM analysis.

Here’s what Norm Crawford, of Applied Geometrics, has to say about PMI: “Through the use of 3D documentation methods (i.e., PMI), the time and cost of documenting a part can be reduced by 50 percent and make early involvement of manufacturing easier with state of the art online 3D collaboration and visualization tools. Limiting redundant annotation and views – normally created on drawings in an attempt to clarify part design requirements – leads to better communications with fewer interruption errors, improved first time quality and increased productivity.”

You can watch a video about NX PMI here.

Now, as for NASA: they may well be using PMI already. NX has supported PMI for many years. If they produced 2D drawings for the Curiosity rover, it may have been a crutch (because of some immaturity in NX’s support for PMI at the time), or it may have been just a matter of habit. (CAD people love their drawings, and don’t want to give them up.) In either case, today’s NX supports PMI well enough that there’s no reason to create 2D drawings. And many reasons not to.