Part III: Table Presses
More CMs are “doing it right the first time” via vertical presses, taking advantage of their flexibility and the quality of their production. But few realize that some of the most successful plants in our industry started with table presses. These presses have always had the following key advantages over roller gantry systems:
- Eliminating hammering of truss plates
- Reducing assembly time and effort
- Embedding truss plates uniformly
- Fewer bent teeth in SBCA QC inspections
- Finishing truss in a single process
- Reducing “touches”
- Multiple table widths
- Minimizing material handling distances
- Less working on top of table
Few operated the table press as well as Trussway in the 1970s in their (still-prosperous) Houston plant. Their Gang-Nail Mark V presses cranked out completed trusses in less than 2 minutes. They took advantage of the unique structure of the Mark V tables: a light but durable LVL surface with Uni-Strut jigging channels. Because the press had lower and upper platens, the table could be supported by wooden kick legs, and its width could be varied. While the press head traversed the table much slower than a roller gantry, the time lost pressing plates was nearly recovered by the time saved not hammering them. And each cycle resulted in a finished truss that was stacked in an orderly manner, eliminating downstream processes. In other words, doing it “right” the first time. Today this process continues to be effective at Shelter Systems Limited in Maryland with Auto 8 and Auto 14 Presses.
The Mark V had a feature not yet available on any roller gantry: automatic travel and pressing. This was accomplished during setup by the insertion of drift pins in a floor track below each joint. After the press was started to the right [See PDF for diagram or View in Full Issue], a limit switch on the press head engaged each pin and began the pressing cycle. When the fifth pressing cycle was completed (at the right heel), the head returned to the starting position. During this time, the build crew shifted to the left jig station to assemble another truss.
Building small trusses or jacks is the forte of the vertical press. An 8’ or 10’ wide table is easily accessed by truss builders, and completed trusses can be properly stacked and banded adjacent to the table. With the addition of automated jigging, complex truss profiles are rapidly set up. To accommodate increasingly complex trusses, jigging channels may be located closer together than the customary 24” on center.
Most table presses, like roller gantries, can build long span trusses. That explains the preference for Mark Vs at Trussway in Houston, which specialized in apartment trusses. Contrast that with Trussway-Barnes’ Glide-Away operating on Lombardy Lane in Dallas, building repetitive Fox & Jacobs’ single family trusses. These two highly successful plants exemplified the state-of-the-art hydraulic press production in the 1970s and 1980s.
Roller Gantries Take Over