Automated design tools can rapidly select and validate the complete configuration of wires, connectors, terminals, and cavity seals–with minimal interaction by the engineer.
BY JOHN WILSON
Electrical systems in cars, trucks, and other large machinery are becoming increasingly complex. Gone are the days when an electrical cable harness was composed of 30 or 40 wires. Today, electrical harnesses have wire counts measured in hundreds or even thousands of wires. This is causing big problems for some small and medium sized harness makers who are still using design technology tools better suited to the simple harnesses of 10 years ago.
 FIGURE 1. Intelligent connector and wire part definitions support automated configuration. |
It is not uncommon for harness makers to still be using simple drawing tools to capture the complex interdependencies found in electrical harness design. Simple drawing tools are fine for capturing the decisions made by a design engineer when designing a simple harness. But even with a simple harness, there are many interdependencies to consider, including: the suitability of a particular terminal for a particular connector cavity; the compatibility between a selected terminal and a range of wire sizes; the compatibility between a particular wire size, a particular wire seal, and a particular cavity.
These interdependencies can cause many problems for the designer as even a small change can have a cascade effect on the specification of other design entities. When the wire counts increase from scores, to hundreds, the design process becomes immensely difficult and time-consuming.
Automated harness design software tools (such as Mentor’s Capital Harness) have been used by large harness makers for many years. More recently, lower-cost versions of these tools, such as VeSys, have come within the reach of smaller harness makers. Theseautomated design tools are able to rapidly select and validate the complete configuration of wires, connectors, terminals, cavity seals, and other items–with minimal interaction by the engineer–providing correct validated designs within minutes rather than days.
Bundle system
With VeSys, the harness designer lays out the harness bundle sections using a “bundle” entity to define the branch network–either unscaled for a harness schematic, or scaled for a formboard.
Placing a “bundle” entity is as simple as placing a line on a regular CAD system, but the “bundle” entity has intelligence that allows it to validate the continuity of the bundle network, understand which wires it contains, calculate its diameter, and know what components define its covering (tubes, tapes, labels, and so on).
Connectors are placed where required. Placement is as simple as placing a rectangle in a regular CAD system; yet, like the bundle, the connector has intelligence. Other components, such as grommets, clips, and labels, are also intelligent.
Once the basic layout is defined, the designer can import wires into the design–typically, from a spreadsheet definition, although data can even be input automatically from a wiring schematic. The wire import process is automatic; the intelligence built into the initial harness layout interacts with the incoming wires to correctly route and terminate each wire, saving a huge amount of manual design work and eliminating the possibility of introducing errors.
A key part of the intelligence and automation built in to the VeSys harness design tool is the data contained in the parts library. Conventional parts libraries will typically list part numbers, part specifications, and other important details. The VeSys parts library extends this information with configuration data that defines how each part can interact with other related parts. So, a connector will define the compatible terminals, wire seals, and cavity plugs; and a terminal will describe which wires are compatible.
 FIGURE 2. Automated configuration tools can generate a wide variety of reports at the touch of a button |
These specifications will contain many common attributes, such as part-number, cost, supplier-name, and weight; plus specialized attributes for each type of part.
With the configuration data in the parts library (Figure 2), the VeSys automated design rules can process the wiring information with the harness layout:
- Each wire is processed–The from-to information defines the start and end connectors, and the harness layout routing defines the initial length.
- Each wire end is processed–The cavity of the connector is “asked” to provide its list of available terminals, and each terminal is ”asked” for its range of compatible wire sizes until a suitable terminal is found for the wire. The connector cavity is then “asked” for its range of compatible wire seals until a suitable wire seal is found for both the wire and connector. Finally, the terminal and connector parts are “asked” for their add-on/knock-off values to define the precise cut and strip length for the wire. Cavity plugs are automatically added, as required, to the connectors to complete the task.
That’s your problem
The result of this process is typically a long list of problems–connectors that don’t have any suitable terminals, wires that cannot be sealed, wires that don’t fit the connector, and so on. VeSys does not attempt to fix these problems; they are engineering design problems that require resolution between the harness designer and the customer.
Fixing these problems may require changes in connector specification, or sometimes even a redesign of the harness. While this is part of the normal harness design process, the key difference with VeSys is that the computer discovers these problems within seconds rather than waiting days, which is commonly required when designing a harness manually.
Once the harness design is complete and correct, harness designers usually need to translate the definition into a series of reports and drawings to support the purchasing and manufacturing process. Creating this information is laborious, time-consuming, and yet another place where errors can creep in. A significant proportion of these reports and drawings, however, are automatically generated by VeSys.
The reports provide significantly more information than is typically available, which are designed to help the designer better understand the design configuration and identify opportunities for driving down cost, including:
- Costed bill of materials;
- Wire cutting lists;
- Splicing instructions;
- Cost summary;
- Operations summary;
- Assembly instructions for connectors, hand termination, tubes, sleeves, etc.
- Program files for Komax andother machines.
Improved efficiencies
Simplicity and ease-of-use are key reasons why a large number of companies are beginning to embrace this technology. The familiar graphical design process found in simple design tools is still there, but the power of the automated configuration rules underpins the process. And this automation is applied with a single key stroke–comparable to how a word-processor can perform spelling and grammar checks. This is helping to drive improved efficiencies in cost and design turnaround, benefiting the bottom line for both the OEM and the harness maker. CS
JOHN WILSON is business development manager at Mentor Graphics’ (www.mentor.com) Integrated Electrical Systems Division.
