Jensen, vice president of operations for Heating and Plumbing Engineers, Inc., Colorado Springs, CO, expounded on the virtues of 3D CADD at the 1999 SMACNA convention, held here recently. One of the speakers at the industrial contractors’ forum, Jensen detailed the pros and cons of hand detailing and 2D CADD, but noted that “3D CADD is light years ahead.”
“3D CADD does everything 2D CADD does, plus helps decrease hours by enabling designs that call for less fittings and duct,” said Jensen. “It also provides a vertical model of a building, making it easier to route duct, check clearances, draw obstructions, and perform collision checks.”
Regarding hand detailingNot too long ago, there was only one way to coordinate a job and that was for a foreman to take charge, said Jensen. The foreman coordinated the rough location with other trades and was responsible for drawing on, or over, contract drawings. Among his duties when hand detailing, the foreman created takeoffs from the contract drawings for easy areas, “maybe 50% of ductwork.”
The advantages to hand detailing, according to Jensen, is the direct line of responsibility for all work done.
“Especially in remodel work where there are poor as-built drawings or no information available, the foreman can gather the data and make the initial drawings himself,” said Jensen. “This type of activity actually helps a foreman develop the ability to visualize and detail projects.”
There are, however, plenty of disadvantages to the process, he said.
“Today, many jobs have specifications calling for job coordination and as-built drawings to be handled electronically,” he said. “If you don’t have the capability to comply with those requirements, you’re out of the running as far as winning the job goes.”
Other disadvantages to hand detailing Jensen listed include:
- Â The foreman can spend a lot of time detailing and creating takeoff, which doesn’t allow the foreman to assist in installation as necessary and keeps the foreman from other necessary tasks.
- Â The hand approach can cause an increase in shop hours due to the necessity of creating non-standard fittings, inconsistent duct orders, and increased data entry. “In other words,” he said, “your costs can go up.”
- Â Increased material waste and transportation costs, plus “it takes longer to put duct together on site.”
“Hand-detailed plans often lack proper dimensions, lead to more connections being needed, and plenty of loose ends,” said Jensen.
Enter 2D CADDWhen CADD surfaced, Jensen said the foreman began to see answers to some of the problems associated with hand detailing. Because everything moved into the realm of the electronic, CADD enabled the computerized coordination of duct system location with other trades.
Some of the other advantages of 2D CADD, per Jensen:
- Â Meets most job coordination requirements listed in job specifications.
- Â CADD designers allow the foreman to concentrate on other tasks.
- Â CADD drawings go through a review process to check for errors.
- Â Drawings done on CADD are cleaner and easier to read, and are easier and faster to modify.
But not all is perfect with 2D, he said.
“One of the biggest (disadvantages) is its inability to provide a vertical model of a building,” he said, adding it can be difficult to route duct, it provides no collision checks, and sometimes “obstructions are overlooked.”
“These types of drawings tend to be cluttered with a lot of notes, plus the foreman and detailer must review structural data to truly understand the building,” he said.
In the end, he said, 2D CADD programs sometimes require separate, hand detailed take-offs, which, again, take away from a foreman’s time.
And the winner is ...With 3D CADD now upon us, Jensen can list many benefits to this process.
“For the hvac and sheet metal contractor, this provides a much-needed link to structural designers and architects who use 3D CADD to design and model the buildings they build,” he said.
In this scenario, the drafter and the foreman are responsible for job coordination, duct fabrication, and as-built drawings. CADD allows for coordination with other trades, he said. It also provides an “audit trail” of fitting downloads, duct accessories, and materials for the foreman to alter or approve.
These last capabilities are what enables the fabrication shop to cut fittings and duct directly from drawings that are downloaded to plasma cutters. The foreman verifies the final connections and as-builts almost simultaneously, said Jensen.
Other advantages to 3D CADD, per Jensen:
- Â It exceeds most job coordination requirements;
- Â Accuracy, in that it provides field plans that have all the fabricated pieces numbered, and can produce 3D isometric drawings of an area for depth, height, and width accuracy;
- Â Decrease in shop hours;
- Â An improved image of your firm’s ability at the beginning of a project; and
- Â Increases potential for a lower total job cost than hand detailing or 2D CADD.
With the good, however, is the bad. The biggest disadvantage to 3D CADD is its initial cost, admitted Jensen. He said his firm’s upfront cost was approximately $40,000.
“Yes, it can be expensive,” he said, “but with 3D CADD you have 3D knowledge. And, in the end, that can save you a lot of time and money.”
Before closing, Jensen went through several of his firm’s projects, noting how 3D CADD paid for itself in the information it provided.