With automated saws and auto-jigging tables, what remains is automated material handling, and that’s what we find at Builders FirstSource’s (BFS) Austin plant. House of Design’s (HoD) robotic roof line there extends the floor truss pre-plating methodology found at their Atlanta plant (see The Last Word on the Promise of Robotics from August 2022) to the varied geometry of roof trusses. Beginning last April, Area Manager John Hansen and GM Jay Schroder worked with HoD technicians installing robotics on a new double-sided gantry line and they continue to improve uptime and output. These BFS initiatives continue their quest to gain a competitive advantage with automation, which is how they entered the truss business 30 years ago by buying leading-edge computerized saws and laser setups.
The HoD roof system again borrows from Professor Tuomo Poutanen’s patent (see The Last Word on Pre-Plating from November 2022), though it is not yet integrated with a saw. Currently Austin’s cutting is processed through an ALS and is staged manually in the sequence directed by the HoD software. Special attention is required to properly orient the end-cuts of each piece “up or down” and “leading or trailing” to match the display at the infeed to the table. While the picking process adds manual labor, this extra cost is somewhat offset by the reduction in lumber waste from optimization at the ALS.
From the cutting staging area, each part is manually fed into a trough-like track and is conveyed to a station at which the bottom side of chords and the top side of the webs are pre-plated hydraulically by a robot. Plates are located very accurately and fully embedded prior to assembly in the impressive four step process shown in the images. This increased accuracy enables a reduction in fabrication tolerance during truss design. Per ANSI/TPI 1–2014 Commentary, the “most commonly used fabrication tolerance has been 20 percent.” With HoD pre-plating, this tolerance may be reduced to 10%, effectively reducing plate sizes by 10% and decreasing truss cost accordingly. (Note that the fabrication tolerance still needs to account for the incidence of flattened or ineffective teeth due to lumber defects.) [For images, See PDF or View in Full Issue.]
The truss perimeter is preset on the table with automated pucks, and the chords are taken first from the track and set against the pucks by the robot. To provide for lumber tolerances, the pucks are initially offset approximately one-half inch from the outside perimeter. Since the pucks are only effective in controlling vertical dimensions, trusses with end verticals may require horizontal stops to be manually installed. Then the webs are placed in proper locations, with each end set on top of the plates that were affixed to the bottom face of the chords. When all pieces are in place, the pucks are tightened to close joint gaps.
The final assembly step is the manual adjustment of any out-of-place parts and the setting of plates by the roller press operator(s). As Hansen notes, this involves nearly a reversal of their former assembly techniques. Finally, with all pieces in place, the operator(s) returns to the gantry platform, traverses the gantry across the truss, and engages the truss lifters just as is done in a manual operation.
The result is a good, safe coordination of robotic material handling with proven automated truss setup. The advantage is the elimination of handling of all materials during assembly, both plates and lumber, which constitutes the bulk of labor cost. Yet this is a pioneering effort requiring the continual onsite support of two HoD technicians, just as BFS’s early adoption of computerized saws required the diligence of onsite engineer Michael Fuss. Once this operation proves itself, BFS plans to integrate the cutting and stacking in Austin, and to install similar systems in several other locations.