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ROBOTIC RESOURCES

Robotic Press Loading Made Easy – Using Vision to Identify Blank Orientation

by Peter Stephen, Program Manager for Stamping and Sheet Metal
FANUC America Corporation

You know the expression: ‘‘A picture is worth a thousand words.’‘ How about a new one: ‘‘Vision systems have saved me thousands of dollars.’‘ Yes, thousands of dollars can be saved with the use of a tried and true press loading package that encompasses a robot, an integrated vision system and some basic part transfers and tooling.

All too often a stack of blanks is brought to the press in an orientation that will not allow it to be correctly loaded onto the die. The parts may be skewed right to left or in an angular orientation coming off the stacks. Often, parts are transferred through a lubricator and/or washed prior to loading, which also makes maintaining part orientation difficult. In the past, manufacturers wanted to use automation to load parts directly from a stack into the first die, but could not.  A centering system was needed to accommodate part varieties.

Over the years, many types of systems have been used to orient blanks, including belt transfers, stops, back stops, and side pushers. The stops, back stops, and side pushers usually require setup for each part type, and to run smoothly, the parts must be correctly orientated. Many of the previous systems used manual labor for setup using ball screws, hand-wheels, and scales to reduce the overall cost of the centering system. Other more expensive types of systems use servo controls and motors to automatically set up the centering operation. Each of these systems involve many (and expensive) ‘‘one of a kind’‘ steps to accommodate various blank sizes and the unique conditions of the production line.  

Centering systems for large transfer or tandem line presses have been engineered to accommodate a wide variety of parts -- small and large pieces. However, the more comprehensive systems are very complex, and require a significant investment for the engineering and build.

Many operations require that the centering system be able to orient blanks for double, unattached parts. Running two parts on a larger capacity press line is very common today because it is more cost effective and quicker to process two parts at once. Using two robots to handle parts makes it easy to accommodate larger part capacities.
 
Vision systems have introduced ‘‘intelligence’‘ into many manufacturing processes.  Vision is popularly used to inspect, capture manufacturing conditions, and determine optimum part orientation for proper loading. Whether the product is gears, bottle labels, sacks or blanks, a vision system, along with the practical use of a robot are becoming very popular.

A typical two dimensional robotic vision system (for both large and small capacity robots) contains the following: Robot, robot control, camera mounted on or off the robot tool, the part handling tool, a PC, frame grabber, lighting on or off the tool, an interface, and some software.  A complete system includes a belt transfer to take parts to the robot’s work envelope.  A robotic solution allows manufacturers to orient virtually every part run in the press, eliminating the cost and downtime associated with traditional centering systems used for part orientation.  

When 2-D is not enough, ‘‘intelligent’‘ robots with 3-D laser vision sensors are available.  A 3-D system consists of a standard robot, and a 3-D laser vision sensor package (includes sensor assembly, lens, connection cables, PCI frame grabber, I/O board, safety unit, and software). The production system requires a customer-supplied PC running Microsoft Windows 2000 or XP operating system.  A 3-D laser vision sensor system is engineered for 3-D robot guidance applications including racking and de-racking of flat panels, rails and beams, pick-up of discrete parts from a pile, tray or bin, and 3-D assembly. Single or dual overhead camera options are available for bin picking type applications.

The use of robots for press tending operations has helped numerous manufacturers remain viable and competitive.  The benefits of a robotic blank loading system with vision include increased productivity, and reduced costs associated with traditional methods. 

Peter H. Stephan is the Program Manager for Stamping and Sheet Metal for FANUC Robotics America, Inc., Rochester Hills, Michigan. Stephan has been involved with the application of robots for the metal forming industry that include de-stacking, press load and unload, and end of line material handling. FANUC Robotics America, Inc . is the world’s leading supplier of robots and provides robotic based process solutions for many industries.

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