2638 Chapter 22 



Partially mechanized assembly. — Multi-head automatic nailing machines 

 using bulk nails and multi-head automatic stapling machines using collated 

 staples increase productivity per man, can be set to variable nailing and stapling 

 patterns, countersink the fasteners, and can be economically justified at produc- 

 tion rates of 400 to 500 GPC pallets (fig. 22-24) per day. Two machine operators 

 should be able to produce about 400 such pallets in an 8-hour shift, i.e. , about 25 

 pallets per man-hour. 



Mechanized assembly. — Several more-or-less mechanized assembly sys- 

 tems are available that incorporate assembly jigs, multi-head nailers and sta- 

 plers, pallet turners, and pallet stackers. Most are sufficiently flexible to 

 accommodate either block or stringer designs in sizes from 30 by 30 inches up to 

 about 60 by 72 inches. 



In the system illustrated by figure 22-38 functions are as follows (refer to 

 position numbers on the figure): 



1. The jig is loaded with pallet shook, sent through the machine, and 

 nailed. The jig returns to the loading position where the first pallet is 

 lifted out, turned over, and placed in front of the jig, which is then 

 reloaded for the second pallet. 



2. The bottom boards are then placed on the first pallet and the jig is 

 indexed through the machine automatically. When the jig reaches the 

 rear of the machine, the finished pallet is released into a turnover device 

 which turns it right side up for stacking. 



3. The nail hoppers feeding the automatic nailer are divided so that short 

 nails can be driven and clinched and long nails may be driven into 

 blocks and singers. 



4. Automatic device to turn pallet over. 



5. Automatic stacker; 2 to 30 pallets per stack. ' 



6. Accumulator conveyor. 



7. Index wheel with cams that automatically position the pallet for nailing, 

 and control movement of the jig. 



With this system, two men can produce approximately 600 pallets per 8-hour 

 day, i.e., nearly 40 pallets per man-hour. 



A fully automatic assembly line was introduced in the early 1970's, in which 

 nailing machines operate on a continuous basis. The FMC Corporation's Fast- 

 line System includes two nailing machines, a pallet turner, an automatic stringer 

 loading device, and deckboard positioning hoppers for each nailing machine. 

 Stringers are automatically fed into the positioning systems. As the stringers 

 pass below the bottom deckboard hoppers, deckboards are positioned on the 

 stringers. Once positioned, the parts are nailed. The partial pallet is then turned 

 over and conveyed beneath the top deckboard hoppers. Top deckboards are then 

 nailed and the completed pallet stacked for removal. Three operators plus two 

 inspectors man the production line which produces at rates from 2,000 to 3,000 

 pallets per 8-hour day, i.e., more than 50 pallets per man-hour. 



Nelson (1975) described a simple mechanized pallet assembly line in which 

 hand staple guns are machine mounted for automatic driving. The system, 



