By Paul Johnston, Senior Application Engineer Consultant, Mentor Graphics Corp.
While design engineers labor to produce the most efficient signal routing and grounding schemes for their vehicle wiring harnesses, product engineers strive to ensure that the harnesses can be manufactured at a competitive and well-understood cost. This is a difficult challenge because project time scales and margins are continually squeezed, while variables such as design content and copper prices can change rapidly. And it is a task whose dynamics exceed the grasp of manual record-keeping methods.
Are there any credible software solutions available to help OEMs and suppliers perform wire harness costing expediently? Does the problem call for in-house tools, or something purchased commercially?
Many design and manufacturing operations, mid-size and larger, turn to the common spreadsheet in spite of its limitations for costing work. It is perceived as inexpensive to purchase and run even though the hourly cost of a spreadsheet user is the same as that spent on more value-added tasks. Spreadsheets are readily available and familiar to millions of users. Other harness makers turn to custom-written costing solutions. Inevitably these tools are expensive and are limited in their own way.
The optimal tool for the job would be one that truly automates the costing regime, delivering accurate figures to departments that urgently need the cost information. The tool would be purpose-built but not custom-built, well supported, and readily adaptable to a wide range of processes and policies. This ideal automated solution would accept design data directly, apply rules, and calculate harness costs in minutes.
Time and Risk vs. Cost
The global wire harness market is not just a prediction—it has emerged. Many suppliers of harnesses work under stringent annual cost reduction targets enforced by their clients, while product and market requirements allow no compromise on quality and durability. The industry strives constantly to reduce labor costs and other expenses.
The task of designing and producing wire harnesses often involves a blizzard of engineering changes swirling through to manufacturing. Doing the job without a detailed cost paradigm pre-negotiated between participants introduces risk, which consumes resources. Too often it is necessary to spend one’s way out of trouble when risks become realities. The winners in the wiring harness industry are those who are able to quote competitively and produce high-quality products.
“Simple” Wiring Assemblies Have Hidden Complexities
A wiring harness may look like a simple assembly to the unschooled eye. It is not. Its individual parts are numerous and diverse, and the assembly operations applied to these diverse parts are equally varied. It all adds up to many tiers of data complexity, and these may be further complicated by choices relating to the degree of assembly automation.
Profit margins for industrial production of wiring harnesses are slim. A costing miscalculation bites immediately into the bottom line and may impact the prospects for commercial success. The pressure to “get it right the first time” is intense, especially in high-volume jobs. Care and thoroughness are necessities, but can result in slow progress toward certainty. Without the help of automated tools, it may be impossible to get timely, correct answers.
An engineer tasked with producing an accurate cost prediction for wiring assemblies is at the end of a long chain of colleagues: design and manufacturing engineers, customers, sales people, production planning staff and others. There is an equally long chain of software tools and computer systems involved, from electrical and mechanical CAD packages to product lifecycle management systems and more.
The resulting volume of data can be overwhelming. Some enterprises are fortunate enough to employ costing professionals to hold back the chaos. More often, perhaps, the chains’ links are imperfect and it becomes necessary to bid the lowest price on a complex project in the absence of accurate, detailed inputs. It is a strategy fraught with risk.
Costing must consider both internal systemic demands and external market pressures. Astute cost modeling must join other modeling and planning tools in the harness design kit. To carry on doing things the same old way while complexity and pressures mount up is an admission that defeat will come sooner or later.
Choosing An Approach That Delivers the Goods
Today there are several approaches that draw on information technology (IT) concepts to automate harness costing. Three approaches are prevalent, though it is common to assemble a hybrid solution incorporating elements from more than one of the architectures. Figure 1 (above) summarizes these differing architectures.
“In-House”
The In-House solution is based on the practices of a single enterprise, led by its own internal IT group. The development team works with internal data sources and adapts data descriptions meant for engineering use, adding cost and price elements and then integrating this into a workable whole.
The end product is a completely custom solution which usually has high up-front development costs and a heavy ongoing maintenance burden. Nevertheless, the In-House solution is very common. Every formula in every spreadsheet cell is deliberately chosen for its role in decision support, customer price quoting, or validation. And some in-house expert knows the whereabouts of all these formulae.
The best In-House solutions achieve a degree of costing accuracy, and most manage to eliminate some estimating uncertainties. But sometimes this approach inadvertently enshrines “the way we do things now,” perpetuating outdated systems and processes.
“Standard Compliant”
The Standard Compliant solution is tied to a superset model built from the experiences of many companies. These platforms drive toward costing automation based on an industry-developed universal standard model for harnesses. The solution design may come from either in-house resources or commercial software developers.
The solutions themselves are not “industry standard” (there is no such thing) but they incorporate standardized elements which will, it is hoped, evolve toward industry acceptance. Enterprises that pursue this approach are not spoilt for choice. The ProSTEP organization’s AP212 standard is perhaps the most prominent example, using the KBL harness listing format.
The Standard Compliant approach, too, brings with it a maintenance and programming burden for the IT staff. This can evolve into a fixation on the mechanics of the XML language and style sheets, causing a loss of focus on real cost estimation issues.
“COTS”
The Commercial Off-the-Shelf method commonly known COTS as is derived from a superset model built from the experiences of many companies. COTS offers an advantage innate in most credible commercial products: it is fully designed, tested, supported, and presumably in stock on an actual “shelf.” A COTS solution from a trusted vendor is the most expedient way to automate harness costing. Ideally this vendor should be an established industry presence and should offer:
* A costing solution that is an equal “partner” in a suite of tools that span the engineering process
* Regularly updated software that leverages new technologies and improves over time
* Technical and account representatives in convenient geographic locations
* Training, consulting and ongoing support
Some vendors of wiring design and harness manufacturing software do not spotlight their costing capabilities; others have never included costing in their commercial offerings; yet others embed some costing capability but don’t promote it. But costing tools need to be on the checklist when buying harness design solutions. Overlooking the requirement is unwise, entailing additional expense. The software architecture behind the cost calculations and the data schemas is proprietary to each vendor’s products.
Seeking the Best Fit for the Needs at Hand
Some decision-makers are nervous about using off-the-shelf solutions for cost calculation. Labor and material cost rules, which the system must know in order to do its work, are highly sensitive proprietary information. The burden is on the costing tool (and its maker) to provide a secure framework for enterprise-specific trade secrets while capturing and recording all the necessary rules. At the same time there is an obligation on the enterprise to ask the right questions about data security, protection against unwanted access, and of course the ability to integrate and manage the whole gamut of costing rules.
The task of finding a good fit for one’s needs may seem daunting. One common shortcut is to build a system that focuses on the changes to the harness product between engineering releases. Essentially it costs the “delta” (the amount of change) and applies that to the original quote or cost data. Using the “cost the delta” approach makes the process a hostage to the past. Is that a valid baseline, or is there new information that might make the original harness costs obsolete? And it can be rather difficult to recognize what the delta really is. A design change at the top level can easily have an unseen trickle-down effect on the Bill of Materials (BOM)—particularly if the design involves multi-configuration harnesses (also known as composite or modular design). For example the cost of adding just one wire is easy to predict but it might necessitate different, more expensive connectors or terminals in the harness.
Modern computing platforms can handle the costing details like this, and do it efficiently. But it is still too easy to select automated tools that lack features that can eliminate uncertainty. In the long term a comprehensive choice is the choice that works.
The comprehensive solution is one that can recognize all of the many operations that take place in the assembly of the harness, and can handle the applicable time and cost standards. Flexibility is critical. A flexible costing system can encompass “what-if” scenarios, labor rate changes, and fluctuating prices for harness constituents such as copper wiring. In a recent four-year span copper prices varied from approximately $1.50 to $4.00/pound. Costing tools must be able to adapt quickly to changes such as these.
The object of a comprehensive solution is not to “future proof” the costing process; that is the province of software upgrades that can integrate future advancements when they arrive. Realistically the goal is to fully embrace the policies that are in place now. Today’s needs are challenging enough!
Can the costing tool determine how many connector cavities exist at a particular harness location? How many cavities contain wire ends? Only when variables like these are known is it possible to determine the applicable labor standards and fold them into the costing. Fortunately, modern COTS wire harness costing software can automatically model such variables.
Cost calculation is the culmination of many peoples’ efforts. Knowing more about product cost earlier in the design cycle is the goal, not only for engineers but also for harness sales executives. COTS solutions for electrical interconnect designs, harness definition and manufacturing are not the drawing packages of ten years ago. Design tools now encompass the entire process with end-to-end coverage. Some of these tools have become virtually one-stop solutions built around database-centered storage and incorporating modern graphical engines to support drawing tasks. Today’s offerings have Mechanical CAD integration central to their functionality. PDM system interoperability and advanced library management features, too, are integral. And the platforms are extensible as new features or methods become available.
Today’s COTS costing systems can derive cost information from prototype BOMs, architectural studies and similar early-cycle sources, as well as the normal engineering data. Figure 2 summarizes these sources and outputs. They provide actionable intelligence that was little more than sketchy guesswork just a few years ago. If a design begins to stray from its cost targets, one part of the tool can isolate the cause and another can correct the problem. Now costing professionals have the opportunity to remedy cost overruns early or better yet, prevent them from happening in the first place. Prevention saves even more money than cure.
Harness Costing: Automated At Last
Timely details about costs can change the direction of a design project. Engineers empowered with modern automated costing tools are equipped with the right knowledge to do this.
Automation takes the discipline of costing to its logical conclusion. The speed of an automated costing process allows more time for cost studies as the physical design evolves, ensuring that the most cost-effective design will emerge. Its accuracy eliminates misquotes and errors. The models in the toolset embody the expertise of users and apply best practices consistently. A well-designed costing system can apply changes in variables as diverse as copper price, manufacturing location and freight charges.
With modern automated tools and a properly designed process, today it is possible to cost a complex harness design in minutes, with complete accuracy.
