Laser Cutting Robots and Heavy Part Material Handling Using Industrial Automation
A leading supplier of truck and bus frames to the automotive industry
supplies thousands of truck and bus frames to its automotive customers each
year. A key to their success is their ability to deliver small, medium and
large batch runs of many different frame configurations. Though a competitive
advantage, the complicated production process prompted the company to design
a state-of-the-art facility that incorporated a wide range of automation solutions
to solve the following challenges:
Customers provided as little as eight hours notice of a batch-run
order for frame rails.
Frame and stiffener rails have cutouts (round, square or rectangular
holes) located in one, two or all three sides. The cutouts are used either
to attach other assemblies, including cross-frames, or to route utilities
for the vehicle, such as fuel hoses, electrical cables, hydraulic lines, etc.
Truck and bus frame and stiffener rails vary in length from
eight to over 40 feet, and weigh 200 to 900 pounds each. A successful automation
solution is critical to handle this extreme range, especially with little
or no time allowed for changeover.
To solve these issues, the company designed and built a robotic automation
system that incorporated two state-of-the-art robotic laser-cutting cells
and two heavy-payload material handling articulated gantries. The laser-cutting
robots use a patented, shape generation software package. The articulated
gantries use a patent-pending approach where a single robot controller drives
two independent robot arms to function as a giant re-configurable gripper.
The automation system consists of two parallel lines, which converge
into a single manual frame assembly line. The parallel automation lines provide
the flexibility to manufacture completely different frame rails on each line,
or to increase throughput with the same type of rail on both lines.
Both automation lines begin with large CNC punch presses fed by servo-driven
pullers. The punch-press indexing slide punch and button holders are pre-loaded
with the multiple hole sizes to be punched in the frame rail. A blank frame
rail or stiffener rail is attached to the servo-puller, which positions the
rail lengthways within the press.
After leaving the press, the servo-puller delivers the rail to a FANUC
Robotics ARC Mate 120iB laser-cutting robot.
FANUC America’ Shape Generation software is used to program the ARC
Mate 120iB to cut pre-determined holes
or shapes through the vertical sides of the rail using a CO2 laser.
The servo-puller accurately positions the rail in the X axis in the laser
cell, and the robot positions the laser head in the Z and Y axes for hole
Arc Mate 120iB Laser Cutting
The rail is then conveyed into an automated material handling area where
one of three things might happen:
The rail might pass through to the frame
assembly area. This occurs if no further processing is required,
and/or there are no rails currently downstream.
The rail might be buffered (stored temporarily)
on a storage rack. When a partially assembled frame rail is still
present in the downstream frame assembly area, there is no room to receive
rails from the laser-cutting cell. If the rail were to remain on the conveyor,
it would act as a roadblock to all upstream laser cutting, and eventually
to the punch press. To prevent this roadblock, a FANUC dual-arm Toploader
(articulated gantry) robot, consisting of two R-2000iA/200T
robot arms mounted to the same overhead linear track, will remove the rail
from the conveyor and automatically place it onto a storage rack. This buffering
process allows the laser and punch-press operations to continue without interruption.
Then, when the frame assembly area can accept a new rail, the dual-arm Toploader
takes a rail from the storage rack, using FIFO (first-in, first-out) logic,
and places it onto a conveyor to assembly.
The frame rail might be combined with
a stiffener rail. Many of the assembled truck and bus frames require
a stiffener rail be added to the main frame rail. These stiffener rails are
matched to a particular frame rail (they receive the same punch-press and
laser-cutting process). An additional complication is that the frame and
stiffener rails come in left- and right-handed variations (an assembled truck
or bus frame has one left-hand and one right-hand frame rail connected by
smaller cross-frames). To ensure they are combined with the correct frame
rail, the stiffener rails are manufactured just after the matching frame rails
– the Toploader robot must then match the appropriate rails to one another.
When the frame and stiffener rails arrive in the material-handling area,
the FANUC Toploader robots match and combine the left- and right-hand rails
and stiffeners. Simultaneously, the robots align the various holes and shapes
in the frame rail with the matching holes and shapes in the stiffener rail.
To reduce expensive work in process (WIP), only blank frame and stiffener
rails are stocked. After receipt of an order, the appropriate frame rail
is manually loaded onto a conveyor in front of one of the two punch presses,
and connected to a linear servo-puller. The C-shaped frame rails are positioned
on the conveyor so that the horizontal “back” of the C is flat
against the conveyor, and the L-shaped stiffener rails are positioned as needed.
Through-hole shapes are then stamped in the rails by the CNC punch press.
The linear servo-puller positions the rail lengthways under the punch press
-- positioning of the rail and the action of the press are coordinated by
a PLC to guarantee accurate and repeatable hole locations.
The servo-puller removes the rail from the punch press and moves it
down to the CO2 laser-cutting cell. At this cell,
various shapes are cut through the vertical “sides” of the frame
and stiffener rails. Under control of a PLC, the servo-puller positions the
rail within the work envelope of the FANUC America ARC Mate 120iB laser-cutting robot, and the PLC sends a signal
to the robot controller to begin the cutting process. The robot controller,
running FANUC America’ patented Shape Generation software, makes a
two-step laser cut on the rail. The first cut uses a low-power laser setting
to remove the paint along the path of the desired cut. Removing the paint
ensures a clean, efficient final cut. For the second cut, the laser power
is increased to ensure the desired shape is cut completely through the rail.
The Shape Generation software gives the robot programmer a choice of pre-determined
shapes (circle, hexagon, rectangle, slot, keyhole, or pommel), or they can
easily configure a custom shape. The Shape Generation software also supports
setting a kerf (cutting angle) to optimize the cut. As the rail is removed
from the laser-cutting cell, it is pulled through a brush to remove any small
metal particles created by the cutting process. After the laser cutting is
complete, the servo-puller releases the rail onto a conveyor for delivery
to the Toploader robots.
If the rail does not require any additional processing and the downstream
frame assembly area is clear, the rail is conveyed straight through to the
assembly area. If the frame rail has to be buffered to one of the eight adjacent
storage areas or combined with a stiffener, then a FANUC America R-2000iA/200T dual-arm Toploader robot is pressed into
action. By attaching a conventional five-axis articulated robot to a one-axis
overhead rail, FANUC was able to combine the benefits of a standard articulated
robot (including dexterity, high reliability and a spherical work envelope)
with those of an overhead linear or area gantry (extended linear reach and
overhead mounting). To handle frame rails with lengths ranging from eight
to 40 feet and weights from 200 to 900 pounds, FANUC America provided a dual-arm
R-2000iA/200T Toploader robot, powered
by a single robot controller. Each robot is capable of a payload of up to
440 pounds and is equipped with electromagnetic grippers, providing up to
16,000 pounds of lifting force in a simple, lightweight package. Short rails
(less than 15 feet long) are light enough to be lifted from the conveyor by
a single robot. However, long rails (in excess of 15 feet long) are too heavy
and cause excessive wrist loading to be handled by a single robot.
The solution uses FANUC America’ patent-pending approach, where
a single controller precisely coordinates the motion of both robots, in essence
turning them into one 12-axis servo-gripper. When a long rail enters the
work envelope of the dual-arm R-2000iA/200T,
one or both robots change position along the linear rail to ensure each robot
arm shares the load equally. The position of a robot arm, relative to the
second robot arm and also to the rail to be picked, varies considerably with
each unique rail length – this “on-the-fly” adjustment is
servo-controlled, meaning future rails of unknown lengths can be added at
Dual Arm Robot Handling Rails
After the two robot arms are positioned correctly along the rail, they
move down and pick the rail up using the electromagnetic grippers. When the
electromagnets are turned on and grip the rail, both robot arms are mechanically
“coupled,” in that they must move together to lift, move and place
the rail. The motion of both arms is perfectly synchronized by the single
robot controller, whether the robots are moving under program (automatic)
control or under jog (manual operation) control. The rail is then either
moved to the buffer location (one of eight rack storage areas) or, in a series
of pick-place motions, it is combined with a stiffener rail. A rail stored
in the buffer location will be removed by the dual-arm Toploader and placed
on the outbound conveyor when the downstream frame assembly area becomes clear.
Benefits/Advantages of the System
Applying the automated robotic laser cutting and heavy-part material
handling system has several benefits:
Ability to produce and ship complete frame rails with minimal
Eliminates storage of expensive, partially processed rails.
Flexibility to handle a large number of frame and stiffener
rails with little or no changeover.
Provides the opportunity to process new rail designs through
simple re-programming of multiple servo-controlled devices including: CNC
punch press, servo-puller, FANUC ARC Mate 120iB
and a dual-arm R-2000iA/200T Toploader
“The laser cells gave us the flexibility to run multiple numbers
of programs, and also made us process capable in terms of quality standards,”
said the facilities senior director of manufacturing. “Previously,
we combined plasma cutting and manual drilling for this operation. Since
we implemented the new FANUC robotic laser cutting system, we’ve been
able to increase throughput, eliminate overtime, and improve the safety conditions
of that workcell. In addition, the overhead robots provided a safer work
environment, higher throughput and reduced work in process.”
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