Robotics Case Studies
Robotic System Speeds Aluminum Wheel Handling
by Sally Fairchild
Provide flexible robotic system to accurately locate and handle cast aluminum wheels that weigh approx. 40-45 lbs. and nominally measure 14", 15", 16", and 17" in diameter, each with up to five widths.
Locate wheels to avoid flashing lines during clamping and also when wheels are chucked in lathes.
Minimal manual changeover.
Meet required cycle time of 60 seconds per wheel.
Improve productivity and safety — reduce injuries and workmen’s compensation claims arising from repetitive movement of heavy wheels.
Motoman provided a highly flexible robotic system solution, including:
- SK120 robot with MRC controller.
- Off-the-shelf mechanical dual parallel wheel gripper with customized details.
- Two Allen-Bradley SLC 5/04 PLCs. One controls infeed conveyor, integration with lathes and robot information. The other controls outfeed conveyor and elevator.
- Four remote PLC racks – one per lathe, one on infeed conveyor, plus MARIO card in MRC.
- Two customer-supplied lathes. Lathe #1 turns back edge of the wheels and lathe #2 turns front edge.
- 8-ft gravity roller reject conveyor.
- 8-ft belt-driven live roller (BDLR) infeed conveyor with three zones. Includes pneumatic stops, toggle escapement lever arms, cam followers to stop wheels, centering grippers, lift and rotate device, ultrasonic sensor to detect wheel tabs, and photo eye sensors to check wheel presence.
- 100-ft of ceiling-mounted Hytrol EZ Logic sensor-activated, zone-powered, BDLR conveyor — in curved and straight sections.
- Vertical conveyor (elevator) at end of outfeed conveyor that discharges wheels in opposite direction.
- Integrated work cell protection, including 8-ft high wire fencing, two interlocked gates, photo eyes, and light curtains on elevator.
Motoman provided end-of-arm tooling, consisting of an off-the-shelf mechanical dual parallel wheel gripper body with customized details, including eight sets of roller details (two rollers per gripper finger).
Motoman also provided pneumatic fixtures on the infeed conveyor that are used to stop, locate, center, lift and rotate wheels for orientation purposes. A continuous ultrasonic frequency sensor at the load station locates a tab common to each wheel casting.
This flexible system is used to load aluminum wheel castings into two lathes for wheel edge turning operations.
The system then transfers the completed wheels out of the cell via a ceiling-mounted zone-powered outfeed roller conveyor. A vertical conveyor (parts elevator) at the end of the conveyor transfers the wheels to the next operation.
Parts enter the cell on a belt-driven powered roller conveyor. Zone 1 acts as an escapement to allow only one wheel at a time to pass. If Zone 3 is full, and Zone 2 photoeyes detect the presence of a wheel, a signal is sent to the PLC to stop the conveyor.
When the wheel reaches Zone 3, two cam followers stop it, then pneumatic centering grippers move in from both sides. A 3-pronged pneumatic pop-up arm lifts the wheel and rotates it until a tab on the casting is detected by an ultrasonic frequency sensor. Knowing the location of this tab allows the robot to avoid the flashing lines when it grasps the wheel and places it in the lathe chucks.
If sensor does not detect a tab, the SK120 robot grips the wheel using its outside diameter and places it on a gravity reject conveyor.
Lathe Loading Sequence
If the tab is detected, the robot grips the wheel using the outside diameter, and moves to Lathe #1. The robot first removes the finished part from the previous cycle, rotates the gripper 180°, and then places the new part into the chuck.
The SK120 robot then moves to Lathe #2, where it again removes the finished part, rotates the gripper 180°, and places the new part into the chuck.
Conveyor Loading Sequence
The SK120 robot moves to the conveyor load station, rotates the gripper, and transfers the finished part onto the outfeed conveyor. The gripper rotates again and the robot returns to its home position.
Photo sensors along the conveyor detect part presence and activate the rollers in the next zone only. A vertical elevator at the far end of the 100-ft conveyor lowers parts for manual unloading to the next operation.
Above sequence repeats to continue production.
Manual changeover of locating pins on the 3-pronged pop-up arm and of the chucks on the lathes is required. The chucks and some related tools are housed in the tool boxes located behind each lathe.
Cycle time achieved 56 seconds, which is >6% faster than 60-second requirement.
Estimated Return on Investment (ROI) of approximately 4 years.If the Zone 3 load station is empty, photo eyes in Zone 2 allow a wheel to pass from Zone 1, through Zone 2, and into Zone 3. Toggle flippers allow only one wheel at a time to pass. Locating pins on the pop-up device require manual changeover between wheel sizes, as do the chucks on the lathes.