Machine builders and other manufacturers can now acquire a ready-to-go, preprogrammed, modular screw-driving machine, the Viper MBC fromVisumatic Industrial Products, Lexington, Ky. And though it’s said to be the fastest screw-driving module available, installing up to six screws in 5 sec, it can also install nuts, bolts, pins, clips, brass rings, and barbed darts.
Viper uses a Visumatic 94 feeder to deliver screws and other fasteners directly to the tooling tip. Other screw-installing robots fall in the pick-andplace category. This means the robotic arm spends time getting the fastener and then returning to the work area. Viper eliminates this wasted time.
Viper uses a SCARA robot to handle motion because, as its full name suggests (Selective Compliant Assembly Robot Arm), it is selectively compliant. So it is stiff in the vertical direction, which helps when installing screws and pushing parts together, but a bit compliant in the horizontal plane, which lets it compensate for less-than-perfect alignments between the tooling tip and the hole for the screw.
The Viper also features zero-offset mounting for the screw-driving portion. This is a change from conventional designs where mounting points are located beyond the extreme end of the robot, which creates an exaggerated cantilever effect. This means screw-tightening torque transfers directly to the robot’s extended joints, and the tooling payload is magnified by the moment arm and applied to the joints as well. With the Viper, joints three and four do not see any tightening forces, and they carry only one-third the weight of the tooling. This leads to faster motions, lon- This is one serious screwdriver ger robot life, and repeatable assembly with consistent quality. The lack of offset also simplifies setup by eliminating complex calculations to account for any offset.
The Viper has a working envelope of at least 7,000 in.3, and an NST traceable axis.
