Vision System, Motion Control Lead Integrated Seat Assembly Operation
To help keep up with increasing commode production, systems integrator Phoenix Automation (Norcross, Ga.) recently built an automated machine that assembles up to 24,000 toilet seats every 10 hours, or 40 seats per minute. This sequential operation requires two indexing pallet conveyors.
Siemens Energy & Automation's VS710 vision system helps locate drilled holes on an automated toilet seat assembly line.
T he origins of the flush toilet may go back 4,000 years ago to the Minoans of ancient Crete. Whoever contributed to its invention would be amazed to see how popular the device has become over the years.
To help keep up with increasing commode production, systems integrator Phoenix Automation (Norcross, Ga.) recently built an automated machine that assembles up to 24,000 toilet seats every 10 hours, or 40 seats per minute. Though the assembly would seem to be a straightforward project, it was actually quite a complex challenge, especially at the production speeds involved.
Automated assembly of this particular toilet seat requires two indexing pallet conveyors that move the covers and seats through a sequential operation. Placing bumpers into predrilled holes molded into the covers and seats required vision integration with motion control.
As the covers travel down one line, the vision system locates the bumper holes using 'blob analysis' in conjunction with the system's pixel matrix. Because the holes are filled with paint, they are first re-drilled to clear out the paint. This process requires the vision system to find the holes, coordinate a servo system to locate drilling heads, and then position servo controlled grippers to place the bumpers into the re-drilled holes.
Each toilet seat moves through the drilling and sequential assembly operation on indexing pallet conveyors.
Data via Profibus network
Since a toilet seat is not a precision item, a certain amount of variance in hole placement must be taken into account by the vision system. Data for each hole coordinate are sent via a Profibus network to the control system. The data packet contains simple coordinate information that allows the motion control systems to index properly.
Each conveyor system has multiple stations that perform additional tasks, such as pounding bumpers, drilling hinge screw holes, attaching hinges, placing parts for assembly on the pallet, inspecting sub-assembly integrity, and marrying all the parts together.
The entire system has 23 servo-controlled drives, two vision systems, nine 16-valve air banks, more than 300 photocell and proximity sensor inputs, and four Siemens human-machine interfaces (HMIs), controlled by a Siemens PLC and communicating via Profibus.
The Phoenix engineering team reviewed several companies' vision systems and chose Siemens VS710 vision system, which met performance and accuracy specifications and also had a Profibus interface.
The toilet seat assembly line's motion control servo drives and air valve banks are controlled by a Siemens PLC via a Profibus network.
Control Corporation of America (CCA, Norcross, Ga.) helped to configure, specify and support the control equipment. In the project's initial stages, Phoenix requested CCA to help test the camera using sample parts. CCA, together with Siemens product specialists, was able to set up the test with an algorithm in the camera within 15 minutes.
In the same 10-hour shift, the new system produces the same number of parts with only 10 operators that used to require more than 100 assemblers working at drill presses and other workstations.
After staging the system at Phoenix Automation's facility and obtaining customer approval with a simulated production run-off, the machine was shipped to the toilet seat manufacturer's plant, where the system was installed and brought online.
Rob Trobaugh, president, Phoenix Automation (Norcross, Ga.)
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