Thin Sheetmetal Stampings are Palletized Automatically

A major manufacturer of commercial air conditioning units needed to handle large but thin sheet metal parts directly from press to pallet. The parts would vary in width, length and thickness. After being punched with rows of louvers, parts would be shuttled onto a conveyor and presented to a pick and place mechanism. Easy machine configuration from one size to the next was necessary. The height of the conveyor was 45.5 inches and the pallet height was 22.5 inches. A 20 inch high stack of parts would be loaded onto a pallet and then that pallet would shuttle over to allow for removal. As the full pallet shuttled over, an empty pallet shuttled into place. After the full pallet was removed, an empty pallet would be set in its place.

To meet these requirements, a machine capable of stacking 1 panel every 7.0 seconds was designed. This equates to 8.5 panels per minute or 510 per hour or 4,080 per 8-hour shift at 100% efficiency (3,672 at 90%).

The machine consists of a 2-axis pick-and-place mechanism. It runs automatically without an operator. The machine automatically accepts a stamped panel from the press via a short section of conveyor. The panel activates two sensors, which initiates the pick-and-place cycle.

When the cycle starts, a pneumatic z-axis slide lowers to grip the panel using permanent magnets. The slide is self adjustable, able to place a panel within a range of 25 inches. The gripper has 8 magnets mounted on spring loaded plungers. The outer magnets are placed on rails, so they can easily be moved to two different positions (in and out) to fit different panel lengths. The panel is raised slightly. The panel is then shuttled using a programmable slide unit to a fixed position over the pallet. The programmable slide positions the panel to one position on the pallet. When in position over the pallet, the panel is lowered and the permanent magnet release mechanism allows the part to be placed onto the pallet. The panels are always placed in the same position on the pallet. On the conveyor they will stop with their front in the same position, but due to different lengths, the middle of the panel will be in various positions. That is the reason why a programmable slide is necessary to pick them up.

When a pallet stack is complete, a dual position pallet shuttle moves an empty pallet into position. Complete cycle time of the unit is approximately 7 seconds. The unit is controlled using a PLC. Panel guides are used for feeding the panel away from the press and gripping the panel. The panel guides are manually adjustable for different sizes.

The press stacker is located adjacent to the press and has a footprint of approximately 15 x 12 feet.

The machine is capable of loading one 42" wide steel pallet at a time. The pallet shuttle is configured to accept 2 sizes of steel pallets 42" wide x 51" long and 42" wide x 66" long. The machine is configured to accept stamped panels varying in width from 23" to 40" and in length from 27" to 64". They range in thickness from 0.026" to 0.034".

Automatic operations are controlled using an Allen Bradley SLC-5/02 programmable logic controller (PLC). The PLC has all the required imbedded inputs and outputs. The PLC capacity is sized to provide an adequate amount of inputs and outputs plus at least 15 percent expansion capability. The PLC is capable of controlling all inputs, outputs and additional control functions through a single system.

The PLC, power supply and all other control system components are neatly mounted on a panel housed in a NEMA 12 rated electrical enclosure that is mounted on the equipment. Input pushbuttons for emergency stop and power reset functions are separately mounted in an enclosure and positioned on the machine within reach of maintenance and operating personnel. System operating status is signaled using a stackable indicating light tower.

All electrical components are easily accessed with all wiring, lines and cable neatly arranged and labeled. All labels are machine generated. All control wiring is 24 VDC.

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