User-friendly loading and unloading system for machine tools
19. June 2019
An enormous savings potential lies in automatic loading. Those at corporate headquarters are well aware of that, as are the management bodies of small- and medium-sized enterprises. Reductions in downtimes, increased flexibility and autonomy extending as far as unmanned shifts – all trigger an urge to exploit the last remaining rationalization potential.
Nevertheless, special robotics solutions are often not exactly user-friendly, as well as being expensive and lacking flexibility. They may also complicate the processes and detract from system availability, in the worst-case scenario with a negative influence on overall cost-effectiveness. It is precisely for this reason that Peter Kösters, Manager of Kösters Maschinenbau, came up with a special solution.
He sums up the main concerns of the experienced mechanical engineers: “We wanted a fully automatic loading solution with six-axis robots that could be operated without any kind of prior robotics experience. At the same time, the robot cell should facilitate a far greater degree of flexibility that permits the processing of even the smallest batch sizes, in turn requiring only the shortest setup times.”
An early agreement was reached on one of the main prerequisites for putting this into practice. The user should not come into contact with the robotics, i.e. teaching and programming should be unnecessary. His tasks should be limited to the simplest operating steps, the supply of blanks and shipping of the finished parts.
Pilot application in plastics processing
The first prototype cell, installed at renowned plastics specialist ISO-TECH Kunststoff in Ahaus, is representative of how Kösters Maschinenbau implemented these requirements in a practical application. The company is among the leading manufacturers and processors of thermoplastic materials. Its product portfolio consists of sheet materials and finished parts, including gear wheels, rollers, bushings, rings, sleeves and similar.
In finished part production the robot cell handles the fully automatic loading of a Spinner machining centre, on which a variety of plastic parts are milled. Batch sizes range from a dozen to a small series of several thousand units; the number of variants is virtually unlimited.
What immediately grabs the eye is the sturdy execution and professional design of the robot cell, with rounded edges and a convincing design language that bears the hallmark of a knowledgeable industrial designer. System loading is particularly ergonomic and simple: the operator deposits the individual blanks randomly on one of three workpiece loaders and pushes the full loader in the working area of the robot.
From here on a YASKAWA MOTOMAN MH24 six-axis robot assumes the fully automatic loading and unloading of the machining centre. The reason why this robot manages without programming and teaching on the part of the user is to be found in the cell ceiling, where a high-performance 2D image processing system is mounted. The latter communicates with the YASKAWA robot via the process control, developed in-house. In this way the robot receives the precise position data of the blanks and can automatically pick up the parts in a predetermined sequence.
This compelling solution was one of several decisive reasons for the selection of a YASKAWA six-axis robot: “To ensure smooth communication and data transmission between image processing and robot we had to intervene deeply into the control unit of the MH24. In the case of robots of other manufacturers this would have been either impossible or extremely complicated. With the DX200 controller, YASKAWA offers all options that make our work a whole lot easier,” says Kösters.
But let us go back to the workflow: with a gripped plastic part the MH24 passes through the open loading door of the machining centre to the workpiece holder. Here the six-axis robot removes a completely machined part with its finished part gripper; the gripper system then rotates 180 degrees and places an unfinished workpiece in the holder. The MH24 deposits the finished part and fetches a further blank from the workpiece drawer. During this processing cycle, the system operator can fill the two other drawers of the loading cell while the machining is in process.
Set-up in record time
The speed in which the system can be retooled in practical operation at ISO-TECH is demonstrated every time a version change is due. “The operator only needs to enter the dimensions of the new part variant in the graphic display of the system control and mechanically set the gripper jaws of the raw and finished part gripper to the corresponding dimensions. Thanks to a quick clamping mechanism, this setting can be completed within a few minutes,” Kösters points out.
This impressive flexibility, that can be realised with simple means, enables ISO-TECH to economically handle batch sizes as small as a dozen or even less parts. A setup time of less than ten minutes makes this possible.
ISO-TECH as a user and Kösters as the manufacturer of the robot loading cell are equally pleased with the high availability of the prototype cell. So far there have been no downtimes, so that there is actually no need for the anticipated amendments. Nevertheless, minor optimizations will take place before this system is launched on the market as the standard cell.
In future standard cells it is planned to replace the MOTOMAN MH24 with the newer MOTOMAN GP25. All YASKAWA robots are the first choice for use in the robot cells: “The new GP25 is also perfectly suited to use on machine tools. Thanks to its slim design and media lines inside the arm, the six-axis robot performs well in a confined space. Furthermore, the wrist is optimally protected against the penetration of shavings. And high availability has always been one of YASKAWA’s strengths,” says Kösters.
With the pilot cell that passed the acid test at Iso-Tech with flying colours, Kösters Maschinenbau has established a new business sector. “We are convinced that with this trailblazing standard cell we have introduced a perfect loading solution for machine tools and machining centres. The main advantage of our cell is its unique flexibility and easy operation that requires no knowledge of robotics,” says Kösters.
Text: Ralf Högel / Pictures: YASKAWA
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