When we talk about tolerances and adjustments to suit the manufacturing process, we acknowledge that building a metal plate connected wood truss is part art, part skill, and mostly perseverance. Plate embedment is very dependent on that process, and we are very dependent on plate embedment for the successful performance of our products.
Some manufacturing methods are more reliable than others. Plate placement can be simplified by settings in your software or utilizing lasers or ink jet marking. While increasing fabrication tolerances will provide more room for defects, rotation, or variations to location, one type of defect is not tolerable, has no tolerance, and is totally unacceptable. It’s the missing connector.
What does it say to your customer when they receive their product missing connectors? I was pleased to see several companies at the recent BCMC show that are trying to address this ugly occurrence with some automation. But until there is a reasonable, cost-effective, and reliable method, what can we do to help prevent missing connectors from occurring?
- Perform 100% visual verification that all plates are installed
- There are several methods for workers to accomplish this after the truss is through the finish roller.
- Vertically stacking trusses will allow your truss stacker the opportunity to look at each joint as the trusses as stacked.
- If trusses are horizontally stacked, I have seen methods where a worker on a rolling cart (similar to the creepers used to work under vehicles) rolls under the outfeed rollers.
- Pits are an exceptionally reliable method to back plate and survey a truss. While very few plants use this method, the plants that do have an impeccable track record of catching missing connectors.
- Polished metal mirrors placed under trusses as they exit the finish roller are effective (and metal is better than glass because glass mirrors are easily broken).
- Economical web cameras can be installed to monitor trusses exiting the finish roller. As with all of these methods, the workers in these positions must be attentive to the trusses before or during their exit from the building.
- Improve gantry press table operations
- Close walk-through tables to provide a solid surface counter gantry roller.
- Twice a year, re-level gantry tables with an optical laser. Tables over time become soft or low from repeated pressing. Normally the front of the table requires the most adjustment. Non-lever tables create the perfect opportunity to lose a connector on the back side of the truss, preventing it from being properly pre-pressed.
- Nothing beats a simple hydraulic press system. Plates can still be missed, but that’s extremely rare.
- Carefully monitor connector counts
- Pre-count connectors. When the count comes up wrong, investigate the problem.
- Keep the floor area under outfeed rollers clean, so when a plate falls off, it’s seen and can be immediately addressed.
- A qualified in-house inspection program will help you monitor if your manufacturing process is effectively preventing missing connectors.
- Field inspections are the worst time to find missing connectors, but if one is discovered, notify everyone involved, and then make prevention a shared priority.
The Bottom Line
Missing connectors should never reach the customer. Preventing them requires consistent inspection, dependable equipment, accurate connector counts, and accountability throughout production. Whether a problem is found in the plant, during a field inspection, or through a customer call, use it to identify the cause, communicate the lesson, and strengthen the process. A disciplined approach protects product quality, worker safety, and customer confidence.
An ANSI/TPI 1 3rd Party Quality Assurance Authorized Agent covering the Southeastern United States, Glenn Traylor is an independent consultant with over 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, expert witness and ANSI/TPI 1 compliance assessments. Glenn provides new plant and retrofit designs, equipment evaluations, ROI, capacity analysis, and CPM analysis.