Assembly in Action: Automated System Assembles Window Valves
March 23, 2009
WIN Products GmbH (Frankenburg, Austria) manufactures an innovative window system that allows the window to automatically close after it has been opened to air out a room, without using either batteries or electricity.
At the heart of each system is a throttle valve attached via a cord to the window frame. By opening the window and pulling on the cord, the user also pulls against a pre-tightened spring inside a cylinder, creating a vacuum. As air flows in through the open window, its also flows into the throttle valve where it eventually balances out the vacuum, relieving the pressure on the spring and closing the window again. Depending on how quickly the air streams in, the window will close in anywhere from five minutes to five hours after opening.
To ensure that each valve functions as it should, WIN Products uses an automated, six-station assembly system built by screwdriving and automation equipment manufacturer DEPRAG Inc. (Lewisville, TX). The system is critical to the success of the product, because of the precision required and the volumes involved-up to 2.5 million units per year.
In the first station, an operator inserts a valve end piece in a fixture, and the system confirms that the piece has been correctly clamped in place. When the operator clears the light curtain, the rotary table indexes to the next station.
At the second station, an automatically fed X-ring is picked up by a vacuum gripper and placed into a predetermined end-piece slot with the help of a two-axis handling system. A pneumatic cylinder then positions the X-ring to a precisely defined height. The height placement needs to be extremely accurate, so that the X-ring will be able to seal the valve correctly.
In station three, the system presses a threaded insert into the valve’s tilting end-piece and then verifies that it has been correctly placed through the use of a depth sensor. In station four, a dedicated gripper installs an O-ring and a second depth sensor verifies that this part has been correctly installed as well.
Station five includes a valve-stem blow feeder and a Micromat-E EC-electric screwdriver, which installs the valve to a torque setting of 0.15 newton-meter and then reverses the valve to a preset angle. This final step is critical, because the resulting gap determines the specific airflow properties of the valve: the greater the gap, the greater the airflow, the sooner the valve will close the window.
A depth sensor verifies the presence of the valve stem at the end of this assembly step. If required, the system can record both torque settings and final valve angles.
Once all of these processing steps have been successfully completed, a two-axis gripper removes the part from station six and places it onto a chute for packaging. Defective parts automatically continue on to station one, where the operator removes them manually.
In the hands of an adept operator, cycle times for the machine are as low as three seconds per part. The total footprint for the system is 1.92 by 2.08 meters. Working at 85 percent capacity over two shifts, the system produces about 16,000 valves each day. A safety light-curtain with a red and green LED display ensures safe access when bad parts are removed and new end pieces are loaded.
For more on screwdriving and automated assembly, call 800-433-7724 or visit www.depragusa.com.