Error-proofing is not high tech, but integrating the various parts can be challenging.

When the product arrives at the station, the controller displays an image of the assembly on the screen, showing the fastening locations in white circles. When the tool is correctly positioned, the circle turns blue. Photo courtesy WSP Technologies

Any line that relies on manual assembly requires error-proofing technology, particularly if the product has multiple configurations or equipment options.

The product arrives at a station, and a bar code is scanned. A flat-panel display indicates where to install some bolts, and the tool automatically configures itself to apply the right torque. If all the bolts are tightened correctly, a PLC triggers an actuator to release the product to the next station. If a bolt is omitted or cross-threaded, a signal lamp flashes red, and the product stays put.

Although this is hardly cutting-edge technology, integrating the various components can be challenging. Now, WSP Technologies (Shelby Township, MI) has made the process of setting up error-proof assembly stations easier.

WSP’s Station Master controllers help engineers integrate assembly stations involving fastening tools, vision systems, sensors or electrical testing. Equipped with a 15-inch touch-screen LCD, these plug-and-play controllers do not require special programming or software development. Engineers are guided through a series of menus that define the control logic, sensing locations and operation sequence.

“We wanted to take some of the design engineering out of the equation,” says Ray Ormachea, president of WSP Technologies.

The F Series controllers for fastening operations are a good example. The controllers are compatible with any pneumatic or DC electric tool. They also interface with manually operated torque wrenches. The engineer simply plugs the tool’s controller into the Station Master, along with a code reader, light stack, proximity sensor, printer and other I/O devices. The Station Master also interfaces with the plant network, so it can communicate with PLCs, radio frequency identification systems and manufacturing execution systems.

Some models interface with tools mounted to torque-reaction arms, so the assembler can only position the tool within the limits of the arm. Feedback devices, such as proximity switches and encoders, are integrated into the arm to tell the controller the position of the tool in the X, Y and Z axes. With an encoder, the system has a positional resolution of ±2 millimeters.

Other models allow complete freedom of movement of the tool. The tool is equipped with a wireless sensor that reports the position of the tool in X, Y, Z, roll, pitch and yaw. These systems have a positional resolution of ±5 millimeters.

A vision system can also be integrated with the controller. This is helpful for large parts, such as aircraft assemblies, which may not arrive at the station in the same location and orientation every time.

Programming the controller is akin to how a robot is programmed with a teach pendant. The engineer moves the tool to each fastening location to tell the system where each point is in space. At the same time, these locations can be identified on a digital image of the assembly that’s been uploaded to the controller. Engineers can even set the order in which fasteners should be installed.

In practice, when the product arrives at the station, the controller displays an image of the assembly on the screen, showing the fastening locations in white circles. When the tool is correctly positioned, the circle turns blue. If the tool is in the wrong spot, it cannot be activated. If the fastener has been tightened correctly, the circle turns green. If the torque is low, it turns yellow. If it’s high, the circle turns red. The controller collects fastening data and sends it upstream to the shopfloor network.

The company’s other specialty controllers work in much the same way. For example, the V series controller for machine vision applications is supplied with VisionPro software from Cognex Corp. (Natick, MA). Up to four “dumb” cameras can be connected to the controller via FireWire. Programming is done through the touch screen by cycling through a series of menus.

For more information, call 586-247-9400 or