Robotics Case Studies
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US Chemical Automates Case Packing With Robotics
FANUC America Corporation Posted 01/17/2006
A robotic cell that packs chemical containers into cardboard cases is eliminating repetitive manual operations at a US Chemical plant in southern Wisconsin. The system, designed by Promatech, LLC, New Berlin, Wisconsin, was integrated with the plant’s existing filling, capping and conveyor system and incorporates a six-axis robot with a series of interchangeable grippers.
US Chemical, a JohnsonDiversey Company, is the largest supplier of privately branded specialty cleaning chemicals in the nation. The company’s Watertown, Wisconsin, plant packages these cleaning products, including both liquid and powder formulas, in large plastic bottles ranging from spray bottles to quarts and gallon sizes. Typical products are used for ware washing, laundry, housekeeping and janitorial services in hospitals, hotels, universities and other institutions, commercial laundries, and the restaurant and food service industries.
Automating for Ergonomics
The newly automated packing line replaces a manual operation that was installed about eight years ago. Originally, containers were conveyed from a filling operation and manually packed four or six to a case. Operators lifted the containers from the conveyor and placed them into cardboard cases that were then closed and sealed. As the volume and variety of products and containers increased, it became necessary to add a second shift and another operator. Looking to improve adaptability, stabilize operating speeds and eliminate the potential for repetitive motion injuries, the company automated the case-packing operation with a single-arm robotic cell.
Plant Lead Robert Dourlain says, ‘‘Increased speed wasn’t really a factor, but with the operation automated, we get some consistency, and we don’t have to worry about operator fatigue setting in.’‘ The changeover was made without laying off any employees, he notes. ‘‘We were able to re-assign them to other areas where we needed extra labor and weren’t ready to automate.’‘
Robotic Cell Brings Consistency
The robotic system, which was designed and developed by Promatech engineers, went into operation in February 2005. The robot is a six-axis FANUC M-16iB™ series, articulated-arm robot. It uses several different end-of-arm grippers, designed by Promatech, to handle various container sizes and configurations.
In operation, filled containers and empty cartons approach the robotic cell on parallel conveyors. Conveyors carry the containers from the filler and labeler, and an escapement directs them onto two adjacent tracks as they enter the cell. Sensors on each side are set to detect when the product is in place on the track. When the sensors show that the correct number of containers needed to fill a case is in position, the robot picks them up and loads them into the next carton in line. The sensors then detect that no product is in position and allow the next batch to move ahead.
US Chemical sent a group of people to Promotech for training before the system was accepted. Dourlain says, ‘‘They did a dry run, and that gave them some exposure on how the machine operated. After it was in place, the operators had a good understanding of how to make it work here.’‘
The system was easy to learn, and the people who operate it had no prior experience with automated equipment. Dourlain says that they have a maintenance person check the setup if they encounter any issues, but the operators continue to learn the skills needed to perform more of the setup and changeover between containers themselves. In addition, Promatech provides around-the-clock technical support when needed.
Operators use the FANUC iPendant to program the robot and make adjustments in its operation. The color, Internet-ready teach pendant is Microsoft Windows®-based and easy for the operators to use, Dourlain notes.
The line operates two shifts per day, five days a week. ‘‘In most cases,’‘ Dourlain says, ‘‘we try to run different formulas that all use quart bottles, gallon bottles, or bottles with sprayers together to get a longer run time without changing the robot tooling.’‘ He says it takes about 10 minutes to change an end-of-arm effector but expects to cut that in half through some planned modifications to the attachments. Upstream from the robot, fillers have to be washed and labelers changed between runs as well. Run lengths vary but typically average one to two shifts per container, Dourlain reports.
Automation Engineer Corey Long, of Promatech, says, ‘‘US Chemical wanted to use a single robot to pack cases of several different types of bottles in various multiples. We often provide tool changing, but a lot of their runs don’t change often enough to justify that.’‘ Instead, Promatech designed a number of different work holders that could be changed to accommodate the varying containers. ‘‘They aren’t all uniform bottles,’‘ Long points out. ‘‘Some of them have spray handles, and there are balance issues as well. If you pick them up on center, they will tilt one way or the other, so we had to add stabilizers and other features.’‘
Another consideration was the behavior of the bottles themselves during handling. Long says, ‘‘Each program is unique to each bottle, because there are forces that act on them when you move the robot at different speeds. You have to finesse the acceleration and deceleration, because if you pick the bottles off the line and go as fast as you can, inertia and momentum will act on the bottle and its contents. This could cause them to spread out and make it difficult to position them correctly.’‘
Long says that the robotic cell was designed to fit into the line where the manual case packing had been done. ‘‘Containers come from the filler and go through the capper before coming down the line into the cell,’‘ he explains. ‘‘The box line runs parallel to the filler line, so the boxes are erected and come right in alongside the bottles. The robot reaches over the boxes to pick up the product, brings it back over the box and places it inside.’‘
‘‘At first,’‘ Long notes, ‘‘the box erector did not open the flaps fully, so US Chemical developed a box spreader to ensure that the flaps are fully open when the carton reaches the robot. The robot will go to the same point every time, but if it can’t get the containers into the box, that becomes an issue.’‘
Sensors Guide and Control
Several types of sensors are installed within the robotic cell to monitor and control the container placement, as well as to protect workers from being injured and to prevent disruption to the operation. Promatech partners with SICK, Inc., a leading manufacturer of sensors and safety systems, in these areas. For this application, SICK WT4-2P330 proximity/diffuse sensors are used to signal when products and cartons are in place and ready for loading. The doors to the cage are protected by SICK E1000SK1 Safety Key devices. When an operator needs to enter the cage, she activates a request-to-enter button, and the program pauses the robot at the next convenient point to allow her to use a special key to open the gate. The operator must take the key with her, and the robot will not start until it is re-inserted to ensure safety.