By Mike Edwards
Commercial air conditioners are everywhere: on the top of schools, hospitals, office buildings and factories. Lennox Industries, a name synonymous with this market, turned to a pair of Canadian companies to help it mass process the foundation that anchors each of these units.
That foundation is a full perimeter base rail, providing holes to attach the air conditioner’s side panels, openings for conduit and slots for forklift truck access. The Lennox packaged rooftop units (lennoxcommercial.com) can be gas/electric or electric/electric and range in capacity from 2 to 50 tons. The base rail also “provides greater structural integrity so the unit is easier to handle when rigging and transporting,” according to Lennox.
To manufacture the base rails at its Stuttgart, Arkansas, rooftop unit production facility, Lennox approached metal rollforming specialist Samco Machinery (samco-machinery.com) of Toronto to produce the precision, fully customized equipment required. Samco in turn recruited Almac Conveyor Co. Ltd. (almac.com) of Aurora, ON, to produce the sophisticated material handling systems that transfer the rails between the process stages.
The rollforming equipment in the Arkansas plant transforms coils of galvanized steel into a wide variety of Lennox base rail profiles in precise steps, according to project leader Calin Fudulu of Samco Machinery. “Each frame is a specifically designed unit,” said Fudulu. The Samco system has to be flexible to accommodate all the different models Lennox produces, “along with future projects,” he added.
The PLC-controlled continuous feed system starts with several punch presses creating notches, holes and corner mitres for downstream assembly. “The roll former then gives the rail its profile, strength and channels, with up to 24 forming passes, before it is cut by a hydraulic press into a specific length,” said Fudulu.
Once a base rail is punched, formed and cut, it has to make its way to the hydraulically-driven Samco bender where the four-sided frame is formed – and that is where Almac Conveyor came into the picture.
“It was a complicated engineering project,” said Boris Gartsbein, project leader at Almac Conveyor (now a division of Almac Industrial Systems). The complication was to develop a system that could handle the broad range of rail lengths that Lennox required, varying from 172 to 424 in., and then handle them again as rectangular frames to be stored in stacks on a receiving table.
This meant that Almac had to design both an infeed and outfeed system. The infeed handling was initially engineered with magnetic grippers, according to Gartsbein. “That didn’t work, so we designed a system with eight PHD pneumatic grippers on a rack and pinion drive for the vertical movement of the gantry.” Two variable frequency drive motors from SEW-Eurodrive control the timing belt and sprocket-driven X-Y gantry system.
To receive a cut rail from the Samco rollformer station, an Almac roller conveyor pushes the product into a pocket, then tilts the rail for better pneumatic gripper access. Once a rail is gripped, it can be transported and deposited in the Samco bending station.
“The bender is a single unit that does all four corners,” said Fudulu. “The rail goes from being straight to a closed-in frame. Three bends are created, followed by an operation to ‘close’ the last corner.” Lennox personnel later install a fastener to complete the frame.
The Almac adjustable outfeed pick and place gantry system consists of four hooks to lift the frame from the bender and travels 396 in. in 20 s to the receiving table. For smaller product, a Numatic screw driven unit moves the hooks, while for larger product, a Duff-Norton actuator is employed.
“This is a special piece of machinery, not just an off-the-shelf set of conveyors,” said Gartsbein.
Both Samco and Almac equipment is controlled by one electrical platform, the Allen-Bradley ControlLogix PLC system over a DeviceNet I/O network, according to Gus Theoulis, electrical engineering manager at Samco. “One central processor” was necessary for such a complex project, said Theoulis.
Rockwell Automation PanelView HMIs and remote I/O drops throughout the base rail manufacturing system monitor a variety of motor encoders, proximity switches, photoelectric sensors, fibre optic sensors and limit switches. Theoulis said that one of the biggest challenges for Samco was designing a rotary embossing unit in the base rail rollforming line. The unit creates notches, permitting the finished frames to be stackable. “The pattern had to be precise and flexible, allowing for slippage in the rollforming process,” explained Theoulis. An Allen-Bradley servodrive and some creative programming kept the embosser from slowing down the continuous feed system.
Almac, founded in 1969, is involved with the designing, engineering, manufacturing, installing and commissioning of complete material handling systems.
Samco Machinery was founded in 1972, and produces rollforming equipment for applications such as the garage door, automotive, building construction, shelving and racking industries.
