DT selected Dixon Automatic Tool Inc. (Rockford, IL) to supply the auto-fed screwdrivers.

The assembly called for three different fasteners, each of which required its own driver. The fasteners were an M8 that was 55 millimeters long, an M8 that was 90 millimeters long and a M6 that was 115 millimeters long. The two M8 screws needed to be driven to a torque value of 30 newton-meters. The M6 screws required a torque value of 20 newton-meters. The cycle time to complete the fastening operation was 6 seconds, including the four M6 screws that were used to bolt the part to the pallet.

Dixon overcame a number of challenges to meet the customer's needs. Blow feeding exceptionally long screws can produce enough force to potentially damage the receiver jaws when the screws enter the screwdriver. This causes wear to the jaws. Dixon's solution to this challenge was to provide screw brakes just ahead of the receiver jaws. Screw brakes absorb the kinetic energy developed during the blow cycle of the screwdriver.

Cycle time was also minimized by using the screw brake to stage the next screw while the drive cycle was active. Cycle time was also optimized using a "mid stroke" bit return sensor. One of the fasteners required a multitorque sequence. The additional sensor allowed the screwdriver bit to be retracted less than full stroke during the torque sequences. Each driver was also equipped with drive bit down-pressure regulation, which prevents damage to the screws or threaded holes.

For more information on automation systems, call 734-522-1900 or visit www.dtindustries.com.

For more information on screwdrivers, call 815-226-3000 or visit www.dixonautomatic.com.