With the invention of integrated production methods, one of the greatest evolutions has been the electronic transfer of information from the truss designs to the computerized equipment, eliminating human error and translation issues. Automatic puck systems, lasers, ink jet marking, or shop drawings projected onto large screens [for photo, See PDF or View in Full Issue] positioned directly behind the production line have created some major improvements and opportunities for today’s fabricator.
Often this automation makes it easier to lay out and fabricate difficult items, because the important information is right at hand. This photo [for photo, See PDF or View in Full Issue] is an example of a complicated joint made easier with modern technology. The parts have been cut with a linear saw from downloaded information and marked by its ink jet printer with the plate information and location of joints, making it (nearly) ready for plating. While the information is not always completely accurate, it is a great approximation that helps the table make the right decisions. In this end detail, almost all of the information is printed on the lumber — but unfortunately not everything is present nor is it reasonable to expect everything in such a complicated situation. As shown in the next illustration of a simpler example [See PDF or View in Full Issue], there can be variations with ink-jetting parts, and the marks may not be exactly where they should be.
Causes of variations from design vs. ink jet
- Calibration issues
- Variations in web lengths
- Fluctuating widths of lumber
- Flipping members end of end
- Mixing parts of the same batch
This simple joint will probably be plated correctly, if the truss builders are trained on how to understand truss designs and have these designs available to them. In other words, they need to understand that this joint requires the plate to be centered on the joint. They should disregard the marks on the bottom chord.
In the next photo [See PDF or View in Full Issue], the truss builders were not aware of design standards nor did they have a truss drawing to refer to for more information. They did have a truss drawing projected on a large screen, but unfortunately it was not large enough or clear enough to show the detail necessary. They tried to follow the ink jet marking, but they failed to understand the required positioning of the connector — resulting in a failed plate placement which could have resulted in a truss failure if it had not been caught. For these reasons, if paper shop drawings are not provided, giving the truss builder offset dimensions, coded plate placement information, and for that matter heel to peak information, then we are taking chances on getting the design correct at the table. At a recent plant visit where a shop utilizes a puck system integrated with a laser and ink-jetted parts, they were still having problems getting the joints to pass the drawing and ANSI/TPI 1 requirements.
Rock, paper, scissors?
While the convenience of electronic information is undeniable, there is no substitute for training and access to correct and complete information. Automation can never completely eliminate the (critical) human involvement in the process. Also, machines and calibration need to be maintained. When comparing methods in the truss plant, paper continues to play an important role. The shop drawing still has a wealth of information that the builder needs to do his job correctly.
An ANSI/TPI 1 3rd Party Quality Assurance Authorized Agent covering the Southeastern United States, Glenn Traylor is an independent consultant with almost four decades of experience in the structural building components industry. Glenn serves as a trainer-evaluator-auditor covering sales, design, PM, QA, customer service, and production elements of the truss industry. He also provides project management specifically pertaining to structural building components, including on-site inspections and ANSI/TPI 1 compliance assessments. Glenn provides new plant and retrofit designs, equipment evaluations, ROI, capacity analysis, and CPM analysis.