Customer References - Hewlett-Packard BMO

BRIDGING THE GAP BETWEEN CAD AND CAM

Written by Ulrich Sendler in May 93, translated by Siegmar Siegel

Part 1: SheetAdvisor ensures design-for-manufacturability, shorter development cycles and minimized prototyping.

Hot from the presses, so to speak, Hewlett-Packard's new sheet metal application is more than a cut above the conventional competition. HP's SheetAdvisor is a development born of hands-on experience in meeting real requirements. It is the brainchild of engineers in Böblingen, Germany, where HP has production facilities for sheet-metal parts. The Böblingen plant has cut time-to-production for parts such as computer housings by a significant margin.

The brief called for a design tool that would automatically permit online access to all manufacturing-related data and constraints. Design for manufacturability was the keynote of the project. The underlying philosophy and the advantages benefiting production are discussed in this first part of the article. The second part deals with the new horizons opened up by this CAD/CAM application, show how users operate the system, and outline the significant progress in sheet metal-working that has already been achieved.

Is the requisite tool available? Operatorless sheet metal working means putting a great deal of knowledge into design.


Visitors to the Böblingen plant soon realize that there is more involved here than the mere bending of sheet metal. Horizons have been expanded beyond the target component and its functionality. It is an accepted fact that 80 percent of production costs are fixed during the concept and design phases. Everyone concerned should therefore gain a new perspective of the overall process, from design through prototyping and production, right on up to recycling and environmental issues. The shorter the life-cycle of an individual product, the more important it is for industry to gain this perspective.

Obviously, it is crucial to have all the requisite information where it is needed in each phase of product development. That was the idea motivating the designers of SheetAdvisor. Conventional standard programs have seldom offered much more than a drawing board transposed to the monitor. For SheetAdvisor, the aim was to use the computer to bridge the gap between design and manufacturing.

Analyses revealed the possibility of dispensing with approximately 30 percent of all prototype runs. Every third prototype exhibits defects that could have been avoided if the designer had been able to consider and allow for manufacturing rules and constraints by applying comprehensive know-how up-front. The new system was designed to help avoid unnecessary process loops.

In the Böblingen plant, all processes are continuously scrutinized in the cause of ongoing optimization. Would another material or a thinner sheet be just as good or even better for the intended purpose? This was another problem that SheetAdvisor would help to solve.

In the past, optimization on this scale meant redesigning from scratch to allow for the new conditions. SheetAdvisor, in contrast, is clever enough to automate a great deal of the design modification process. Whenever intervention on the part of the designer is necessary, SheetAdvisor presents the various alternatives.

Yet another major consideration spurred on the in-house designers: efforts to optimize production underscored again and again and with ever-increasing clarity the differences between noncritical and critical products. The former are suitable for completely automated production, while the latter are not. Obviously, the benefits would be enormous if designers could go straight for "noncritical" designs.

The system knows the machine pool, the tools and the material stocks. Its proposals cover all these aspects at the earliest stage of development.


The bottom line in these considerations was to achieve the highest possible degree of standardization. This applied to the tools, the material and the finished products. That meant pooling the experience of everyone involved and creating the software to make it accessible.

SheetAdvisor earns its name by its ability to fully link the geometric data of the solid modeler with the engineering data of a sheet metal CAM application. SheetAdvisor is an object-oriented solution written in C and C++. It applies the principle of feature modeling (in other words: using geometric features instead of primitive solids).

SheetAdvisor wraps itself like a shell around the component being designed. It works largely in the background. When a working title was assigned to the development project, the name chosen derived from the German word for "onlooker", because that is what SheetAdvisor does - it looks on over the designer's shoulder. It lets the designer known if rules of design practice are being violated. It draws attention to boundary conditions. It remembers every single step in the design process.

At no time, however, does SheetAdvisor overstep the mark that the user can draw. On the contrary, bending rules is encouraged if the result improves the process. Since all actions are automatically logged, individual steps in the development process can be retraced even long after the design is completed. The designers had more or less given up on an earlier attempt to achieve much the same end with the help of design libraries. Quite simply, there was too much outlay involved in after-the-fact recording and archiving this type of information on product development.

If the designer pursues this course, a production problem will result. SheetAdvisor presents a graphic illustration of the problem and proposes alternatives.


One of the spectacular features of the new system is that it does not simply copy from the rule-book to the hard disk. In other words, SheetAdvisor does not passively present knowledge, data and rules. Instead, it automatically flashes the practical information the user needs onto the screen at exactly the right moment. It can even specify which step is next in design and check progress to date.

SheetAdvisor also lists all the cost data generated in design. Even before the detail design stage, a developer can estimate with reasonable accuracy how much the finished product is going to cost for which production batch quantity. Potential buyers of the application will probably be interested to know that SheetAdvisor has already been in use for over a year on more than 1,000 workstations. Not one sheet-metal part is designed by HP in Germany or the US without the Advisor's assistance. The designers draw on the resources of a database in Palo Alto, California, via enterprise-wide networking. The database contains all information on tools, materials and resources available in the individual production facilities. Hewlett-Packard sees this as extending the principle of "virtual source" - it is of no consequence to the customer which factory produces which part. Customers receive products from HP plants as if there were a single production site.

Over the last three years, HP has virtually doubled sheet-metal throughput in Boeblingen without any change in capacity and with the same manpower. There can be no doubt that the new software has contributed significantly to this success. Undeniably, SheetAdvisor makes it easier than ever before to design for manufacturability.

Part 2: Day-to-day work with SheetAdvisor: HP designers cut design times by up to 50 percent. Error rates are virtually zero.

HP's PE/SheetAdvisor, its underlying philosophy and the hands-on input from the Boeblingen production facilities that went into its making were the topics discussed in part 1 of this article. Part 2 describes how the system is used, the new opportunities it uncovers in CAD/CAM, and the effect it can have on production.

Before the designer puts pen to screen, the system wants to know where the finished product is to be manufactured. A central database in Palo Alto, California, contains descriptions of all HP plants in Germany and the US (including those of an external company), so the company knows which engineering and cost-related boundary conditions apply.

The various company sites are interconnected by a dedicated satellite link and Ethernet. The database can be updated at any time. Shared-X sessions enable designers to view and discuss the same CAD drawing from the convenience of their own desks on either side of the Atlantic.

Once it has been informed of the intended production facility, the system overlays a filter on the data. This filter ensures that the designer is offered a choice of preferred materials (in a green field). The aim is to avoid the use of additional sheet materials for new designs. In this way, SheetAdvisor reduces stock variety to a minimum.

The designer can also request a choice of other raw stock (presented on a red background). This option could be used, for example, for parts already in current production. Alternatively, users can impose their own judgment and select a completely different sheet material. SheetAdvisor, remember, is not restrictive. Instead, its purpose is to provide practical support in standardizing production.

Tools are presented in much the same way. Designers intending to rule out problems in manufacturing and, even more importantly, to achieve automated production of the sheet-metal parts, must give full consideration to the tools that will be used. This implies that the parameters of production plant such as punching machines plus associated tools - need to be incorporated in the design concept.

Just like real life: the 3-D model of the finished sheet metal part is virtually a photographic image of design output.


The machines used in Böblingen include two of different generations. A record of the total strokes per year executed by the tools on the older machine revealed that approximately 80 percent of parts were machined with approximately 20 percent of all tools. The total number of tools was cut by more than half, and the new machine was ordered with only a small set of tools.

To maximize flexibility, SheetAdvisor offers a choice of preferred tools - those used by both machines. The next level on the hierarchy is reserved for tools and dies used on only one of the machines. Picking one of these tools is tantamount to reserving the corresponding machine for the production process.

Here again, designers can exercise their own discretion and use entirely new tools. This decision means special production or a special order. The system knows this, so the special tool in question can be ordered immediately and in advance. Tooling mechanics no longer stare in puzzlement at the machine and claim (never saw a tool like that before in my life). When the designer wants to bend a sheet, he or she is offered a choice of those bending radii that are feasible for the combination of selected sheet material, available tools and applicable machine forces and moments. At the touch of a button, however, SheetAdvisor flashes the alternatives onto the screen with color highlighting for distinction.

Warning: If positioned as shown, the slot may cause the sheet metal to tear; minimum distance from edge: 3.2 mm.


There is nothing new about machining rules of this nature. Every shop has its documents and catalogs where operators can find this information. There is, of course, a certain degree of risk, because the information may not be up to date. Then again, the information might not be available when and where it is needed. And yet another proviso - a designer in a hurry will still have to make time to find out just exactly what is wanted.

The maybes are many and varied when productivity depends on a library of printed matter. This is precisely where SheetAdvisor comes into its own. No need for the operator to ask what the standard states for this radius and that material. This information is on screen just when it is needed. The gaps in cross-departmental communication, long thought to be unbridgeable, are spanned with ease.

If that were all there was to SheetAdvisor, however, much would still be lacking. Certainly, it is an excellent source of information and a superb option browsing tool. The total capabilities of SheetAdvisor are only apparent when the designer settles down to work.

The CAD basis of the system is HP's PE/ME30. Future versions will also support PE/SolidDesigner. Broadly speaking, however, the computing basis is fully transparent to the user. There are no cumbersome standard commands, no models to be structured from primitive solids using complex computations, nothing to disrupt the flow of work. These functions are discharged by the software automatically and in the background.

SheetAdvisor generates design elements known as features. The advantages of feature modeling are that, once generated, a model can be modified at will. This remains true even if a manipulation yields a fundamentally different geometry. The new software proves its worth in each individual design step. HP's vast experience in sheet-metal production has gone into its making. This is an expert system offering its knowledge pool to the designer.

The following example will illustrate the principle of design support. The designer wants to position a stamped boss. The program is aware of the geometry of the tool and die, so it can calculate the minimum clearance between the intended boss and an existing radius. It therefore displays this distance with the boss before the designer positions it.

Displaying warnings and design alternatives, SheetAdvisor also offers preferred tools (green menu) for punching a hole: this way SheetAdvisor supports designers throughout the design phase.

If the designer ignores this advice, the system issues a warning. Depending on the gravity of the "error", the warning is yellow, green or red. The designer has the choice of ignoring the warning, suppressing it entirely for subsequent steps, or aborting the current operation. Or of course, the designer can accept the advice and correct the design. The SheetAdvisor tenet is to inform without forcing the user to conform. Many major developments would never have come to pass if their originators had not chanced bending the rules.

This supportive role is played by SheetAdvisor alongside each and every user action. To ensure that the sheet does not tear, the program checks that a hole is not placed too close to an edge. It allows adequate space between two stamp features, so that the blank holder will not cause damage. If the designer wants to produce a rectangular hole, the program checks whether the appropriate tools are available. Last but not least, it examines all punching and stamping operations in the finished design to ensure that the directions are optimized for the machine shop.

Manufacturability is what the program advises on in every single step in the design process. Once the product is modeled, SheetAdvisor issues a list with all the rule violations it has discovered. This is, so to speak, the last chance for the designer to check whether these violations are necessary. At the same time, it provides the designer with valuable information for subsequent modifications.

So much for design support, but SheetAdvisor also sources information for administration, purchasing and production engineering. Any data generated during the design phase is made available to other upstream and downstream areas without delay. This includes parts lists, dimensions of finished parts and semi-finished products, surface finishes, material numbers, processes involved, estimated time requirement and even production batch costs.

Time and cost calculations vs. batch size can be called up at the touch of a button.


Hewlett-Packard has seen that the system boosts productivity by a considerable margin. In the design department alone, cycle times have been cut by some 50 percent. An interesting side effect is the significantly improved acceptance of the 3D application. Design errors are now a rarity. Last but not least, the degree to which the installation and introduction of the system encouraged everyone involved to think about the overall process of product development vastly exceeded all expectations.

SheetAdvisor already boasts a proven track record. Certain adjustments are needed, of course, before the system can be used by other companies. The knowledge database, for example, has to be filled with company-specific data. Even at that early stage, however, the program can have a productive effect by stimulating new ideas. The methods currently available and - even more importantly - those not yet implemented come under close scrutiny. Standard components and special designs take on new significance. Expectations in the manufacture of sheet metal parts can be turned into automation accomplishment.

About the author:

Dipl.-Ing. Ulrich Sendler, born 1951, trained as tool-and-die maker and NC programmer before studying precision engineering. Worked in CAD software development and in trade publications, freelance journalist and management consultant since 1989.