Typically, a gantry-type (also known as Cartesian, linear or transverse) top-mounted three-axis robot is used to demould injection moulded parts. Pick-and-place automation is commonly used to demould injection moulded parts. According to Fanuc Robotics programme manager for the plastics industry, Joseph Portelli, the demand for part orientation capability is increasing. However, today’s moulders are looking for automated methods to perform increasingly difficult tasks, such as demoulding complex shapes and managing upstream or downstream processes.
Dirk Schroeder, managing director of Remak Maschinenbau in Germany, says that some parts must be rotated in the mould for easy removal when they have a complicated ejection angle or must pass under or over obstacles such as tie bars and mould slides. Automation of insert loading and post-moulding activities is also increasingly necessary. Many moulders also face shorter runs and need automation that is adaptable enough to allow for quick job changeover. Considering six-axis articulated or jointed-arm robots is a good idea for all of the above reasons.
Moulders now have the option to move away from “hard” automation thanks to articulated arm robots. A more advanced robot could perform value-added tasks directly on the press. These activities could be challenging for a linear robot, depending on their complexity and the area available. As a result, some moulders will now have the opportunity to incorporate downstream processes in the moulding room.
Jim Healy, Conair’s vice president of automation, explains that six-axis robots can run numerous jobs if the cycle time is long enough, making them suitable for applications such as high-cavitation insert moulding. The robotic arm can create a wide range of inserts, pick them up, extract finished parts from the mould, position the inserts for the next cycle, degenerate the moulded parts and place them for automated inspection and packaging. For a linear robot to complete such a complex series of tasks would be extremely difficult, if not impossible. The process can be greatly improved if a single six-axis robot can perform all of these tasks before, during and after demoulding of the components.
Companies selling six-axis robots include Automated Assemblies, Conair, Geiger, Husky, Krauss-Maffei, Remak, Ventax and Yushin. The robots are purchased by system integrators, who then install the programming interface and other ancillary equipment. AEC’s sister company Sterltech Robotics has used this ‘systems integration’ strategy. System integrators purchase a six-axis robot and install the programming interface, safety devices and other ancillary equipment.
Companies specialising in plastics manufacturing are launching new models of six-axis robots. Manufacturers of six-axis robots are supplementing their floor-mounted units with platen-mounted variants and even gantry- or beam-mounted “hybrid” designs to address space constraints next to or on top of a press. These manufacturers include ABB, Adept, Fanuc Robotics, Kawasaki, Kuka, Motoman, Reis and Staubli. Suppliers point out that more user-friendly controls have been developed to accommodate the increased complexity of programming a six-axis robot, previously a difficult operation for a moulder.
Conair’s Healy explains: “We have done an application with a Fanuc robot in a pick and place operation where we used our own linear robot PLC to perform the programming and control of the robot instead of a Fanuc controller. President of Yushin America: “Cell-type automation solutions that combine a linear robot for part removal have grown tremendously. Robots and humans working together is “not unusual” in modern times, according to David Preusse, president of Wittmann Automation. His company is a system integrator for Motoman and manufactures linear robots.
Cartesian models can now be used with five or six axes thanks to the optional servomechanical movements that many linear robot suppliers have developed for their robots.
Many linear robot suppliers have developed servo wrists for their robots. Instead of having a rectilinear working area, six-axis robots have a spherical one, which increases their adaptability to tasks other than pressing.
The fixed platen of a moulding machine or a pedestal fixed to the floor are two options for mounting articulated robots. More recently, a combination of linear and articulated capabilities has been created by mounting the articulated arms on travel rails. While a shorter manufacturing cycle may limit the amount of work a robot can perform, a longer moulding cycle leaves time for downstream activities.
Other criteria that influence the acceptance of an articulated robotic solution are the payload and the required “reach” of the robot. A linear robot will always offer its maximum payload capacity during the stroke. He points out that the payload capacity of a six-axis model may vary during the stroke.
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