Software helps cut design time for air-handling system enclosures

July 11, 2000
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Automated design software that works in conjunction with AutoCAD has reduced the time required to design commercial air-handling system enclosures by more than 60%.

The software has also improved manufacturing quality by improving the consistency and understandability of manufacturing documentation.

Based on operator-entered specifications, the software uses precoded design rules to automatically generate 3-D designs, including bills of material for sheet metal panels needed to enclose roof-mounted systems.

Developed by the Professional Services Group of Avatech Solutions, Des Moines, Iowa, the automated design tool has made it possible for existing design staff to handle a 35% increase in volume.

Old process

The air-handling units designed by the software incorporate fans, filters, and coils, and are designed to handle up to 60,000 cfm.

In the past, these enclosures presented a significant design challenge. Several years of experience were required to learn the design rules needed in order to produce a satisfactory design.

Typically, the designer would start with the specific equipment that fit inside the enclosure and the building openings that needed to be connected to the enclosure. Then they would go into AutoCAD and generate a quick, 2-D proposal drawing.

When the order was received, the designer then had to generate the detailed drawings needed to manufacture the enclosure. Commonly, 25 different drawings are required to provide the information needed to fabricate each panel and stiffener and to assemble the enclosure.

The basic problem with the old approach was that it took too long and did not produce drawings of the desired quality. About 8 hrs were required to produce the documentation required to build an enclosure.

A large number of engineering judgments had to be made for each design, limiting the task to people with considerable experience in structural engineering. In spite of that fact, mistakes requiring rework were frequently made, which had a significant impact on manufacturing expenses.

In order to save time, no effort was made to produce drawings to scale. Instead, dimensions were attached to symbols that were taken from a library. To further avoid delays, all of the drawings were done in two dimensions.

These factors made it relatively difficult to understand the drawings, increasing the skill level required for the assembly process and also the rate of human error.

Custom solution

An air-handling system supplier’s management wondered if it would be possible to automate the design process.

They first considered an existing software package developed for the design of enclosures. This program, however, was not capable of designing enclosures according to their standards and also could not be customized to meet their needs.

They began looking for an integrator capable of developing a custom AutoCAD application specifically for air handlers. They soon heard about Avatech Solutions, which has developed a number of custom AutoCAD applications, including several for hvac design applications.

Avatech consultants informed the air-handling system vendor’s management of the advantages of ObjectARX, the recently introduced programming environment for AutoCAD that offers a much higher level of power and flexibility than has been available in the past.

Prior AutoCAD procedural or interpreted application programming interfaces, such as AutoCAD Development System and AutoLISP, made it possible for developers to write programs to automate tasks and customize existing features.

ObjectARX, introduced as AutoCAD Release 14, offers a leap forward by creating applications that transform lines, arcs, and circles into intelligent design objects that behave according to the specific properties by which they are used in the real world.

These objects become first-order objects in the AutoCAD database with the ability to respond directly to editing commands, display according to their inherent display characteristics, and interoperate among themselves.

Practical considerations

The air-handling system vendor asked Avatech to develop an initial working release of their application within three months from the time that they were given the assignment.

Avatech consultants began by meeting with managers and designers in an effort to capture the objectives of the design process and knowledge possessed by the designers so that both could be incorporated into code. This knowledge was encapsulated directly into panel and stiffener objects that know, for example, how many stiffeners are required to support an enclosure of a given length with a certain amount of cutaways.

A key aspect of the application is that designers interact with it in the same 2-D format that they are already familiar with, while the model itself is created in three dimensions.

Generating a 3-D-model database provides many advantages, such as being able to create all plan and section views from a common model, ensuring consistency, and also being able to generate perspective drawings that are much easier for manufacturing personnel to understand.

The user interface is based on the 2-D proposal drawings that are already an inherent part of the design process, minimizing the need for changes to the air-handling system vendor’s design procedures.

The program begins by prompting the operator for the overall size of the enclosure. It then determines the number of panels that will be required. The program then asks the operator to specify the placement of panels on the enclosure.

For each panel specified by the operator, s/he is asked to define the cutaways required to accommodate equipment and building openings. The operator is asked to input information required for the bills of material, such as type of finish required.

The program then internally builds a 3-D model of the panel and creates a flat sheet layout of the panel, as well as bills of material, ready for presentation to the fabrication shop.

When each panel has been processed, the program creates assembly drawings that include perspective views that are much easier to comprehend than conventional blueprints.

The air-handling system vendor’s management said that the first iteration exceeded their expectations. After they had gained some experience with it, management developed ideas for further improvements.

The resulting program now automates nearly every aspect of the enclosure design process, allowing the operator to produce all required enclosure documentation in 3 hrs, a 63% reduction from the time required in the past.

Because the program encapsulates much of the skill of an experienced enclosure designer, far less experience is required to perform this task.

Documentation quality

Just as important, the quality of the documentation has been dramatically improved. The fact that manufacturing documentation is based on a single 3-D model eliminates the possibility of inconsistencies between different 2-D drawings that caused problems in the past.

Stiffener placement is based on established design rules, preventing the possibility of judgment errors. All drawings are now produced to scale and perspective views are included with the result that the documentation has become much easier to understand, so that manufacturing rework has been noticeably reduced.

The time savings and quality improvements have substantially improved the competitive position of the air-handling system vendor. Management says the key to the success of the new system was that it was built around the way they operate, eliminating the need to change their operating methods to fit a different system.

The use of the latest ObjectARX object-oriented technology made it possible to incorporate intelligent objects into the system that encapsulate design rules specified by the company, ensuring that designs are consistent and minimizing the loss that would be caused by staff turnover.

As a final advantage, the object-oriented nature of the database will make it relatively easy to provide future enhancements. Avatech consultants are currently developing an interface to business applications that will automatically enter bill of material information into the company’s job costing system.

For further information on the design software, contact Avatech Solutions at 410-581-8080; 410-581-8088 (fax); www.avat.com (Web site).

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