Gantry
pick and place robots, although primarily used in palletizing
applications, lend themselves to a variety of tasks. Among these
are palletizing, packaging, welding, glueing, painting and moving heavy
parts. Because the gantry system is mounted primarily overhead, it
uses little floor space. A gantry system has a very large work
envelope and repeatability in the range of 0.1 to 1 mm, which is good
considering the large size of the work area. A gantry system can
lift small payloads up to very large ones. Payloads can vary from
a few pounds up to 2000 lbs. Gantry systems do have larger masses
to move and therefore are generally slower in both acceleration and
deceleration than other types of robotic systems.
Gantry robots come in various shapes and sizes. Typically when someone refers to a gantry robot, what they really mean is a robot that hangs upside down and travels along either an 'X' or 'X' / 'Y' path to get to its pickup/putdown points. Pictured
to the left is a Fanuc robot with an 'X' directional gantry travel. If the beam that the robot is mounted on were also to travel the robot would be capable of 'Y' directional travel as well as 'X'. This type of configuration is well suited for stacking multiple pallet positions. So, for instance, a distribution center could have an
Order Fullfillment System or OFS that has 20 products that come in as 1 product per pallet. The DC needs to stack mixed pallets for distribution to their "customer". Customer in this context could refer to a sales location of the same company. So, this order fullfillment system could de-palletize product from the "pure" pallets that come in and re-palletize the product into a "mixed" pallet for shipment to the customer. There could also be any number of "output" positions.
The
unit to the right uses a robotic arm placed on an overhead structure, a gantry, to achieve four-axis movement. The arm has three prismatic joints, whose axes are coincident with a Cartesian coordinator. The arm or end effector is mounted to a bridge that moves above the loads. The arm can be a suction cup, gripper or hybrid combination of the two. This palletizer is ideal for palletizing
8 to 60 pallets at a time. If more speed is required two or more bridges with arms can be place on the
same gantry.