TouchSensor Technologies LLC (Wheaton, IL) manufactures nonmechanical control interfaces for appliances, fitness equipment, vending machines and beverage-dispensing machines. The company keeps a watchful eye on quality. "Our outgoing product quality is critical," explains Bob Campbell, vice president of operations at TouchSensor. "One of our points of differentiation is an ultrareliable product. It is critical that it meets every specification before leaving our factory."

To meet that demand, TouchSensor hired Sibos Prime Inc. (Rockford, IL) to develop an automated system for testing the control panels. The company chose Sibos Prime because of its experience in building flexible automated test and assembly cells for quality-sensitive applications, such as cell phones and hearing aids. TouchSensor needed a system that would be flexible enough to accommodate a wide variety of panel sizes and an almost infinite number of possible sensor locations. Because TouchSensor’s panels are produced with both curved and flat surfaces, the test cell also had to accommodate test points at varying heights. A final requirement was growth: The test cell had to be able to support future expansion of TouchSensor’s technology.

TouchSensor’s panels do not use what we normally consider "buttons." A traditional button or switch consists of a base, spring, body and contacts. TouchSensor’s panels are different. Each button is replaced by a single, solid-state sensor pad activated by human touch. This technology is unlike the membrane-covered, mechanical switches found on many cooking ranges and fitness equipment. Sensing through decorated glass or formed plastic, TouchSensor’s switch has no moving parts to wear and potentially fail, and there is no membrane to tear, crack or degrade over time. These pad sensors are completely sealed within a rigid, laminated substrate that is impervious to many challenging environments.

Testing these pads requires more than simply verifying that the device turns on and off. The test process also must check the pads’ sensitivity, which can be specified by the customer without software. In addition, TouchSensor’s keypads can be used in safety circuits, which means the test process must be particularly robust. "It is also important that the user’s perception of the sensitivity is consistent from pad to pad and panel to panel," adds Campbell. "The Sibos solution allows us to confirm this, as well as objectively capture data for process control."

TouchSensor’s wide range of control panels—each of which may have its own individual specifications—presents a unique challenge to the testing process. Using a person’s finger to test each sensor pad’s "feel" brings up appreciable logistics and cost issues, not to mention concerns about repeatability, calibration and standardization.

TouchSensor needed a test cell capable of inspecting multiple panels with multiple button configurations on both flat and curved panels. The cell also had to test various keypad sequences. The solution was Sibos Prime’s NexGen robotic workcell.

The NexGen is based on Sibos Prime’s FirstGen workcell. The company built more than 80 FirstGen workcells for a major cell phone manufacturer, which used the machines to test phones.

The NexGen is a predesigned robot and chassis that easily integrates with various material handing equipment. The cell has six, heavy-duty drawers to provide easy access and ample room for test instruments and PCs.

The NexGen test cell designed for TouchSensor includes an Epson SCARA robot located between two, semiautomatic operator stations. The robot is located in the middle of the cell, with a dial table on either side of it. Two operators remove tested panels and place untested panels onto test fixtures on each dial. The test fixtures are then independently and automatically presented to the robot for testing. The operators work in opposite phase of one another, so that one panel is being tested while the other is changed out.

Multiple test probes are gripped by the robot in various configurations to test the sensitivity of the pads. These probes can be straight for testing flat panels or angled to test curved panels. Different sensors can be tested to different standards without interrupting the test cycle. The robot simply swaps out probes during the testing sequence.

The robot tests each panel in a predetermined sequence. But, this sequence is not without flexibility. Based on the results of presenting a probe to the button, the robot can retest the pad with the same probe or a different one. The robot can then be used as a statistical feedback tool to not only pass or fail the button or panel, but provide valuable feedback for optimizing the manufacturing process.

For more information about automated test cells, call 815-229-3800 or visit