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Starting point / Task definition |
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| After the blow molding process, plastic parts have to have pieces cut out of them accurately, and often have to have holes drilled in them. The objective was to find an efficient automation solution for these tasks. The desired combination of a robot and a cutter was previously not possible for this application, since robots could only carry out exactly the path motion they were programmed with, and were not able to respond if the plastic part shrank or expanded. Rotating tools, on the other hand, would generate toxic fumes and considerable quantities of dust and fouling. For these reasons, a entirely new tool had to be found. | |
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Implementation / Solution |
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 | | Deburring of plastic engine covers |
The answer was found by KUKA system partner Cosytronic, which developed a patented, float-mounted tool unit, which can accommodate various cutter blades, for example straight, concave and convex cutters for various radii. In order to make the cuts without creating burrs, the blade must always maintain the correct cutting angle and a constant cutting pressure. This is ensured by a KUKA KR 125 robot, which cuts pieces out of the parts and drills mounting holes in a single operation. The first user of this solution is Illbruck, which uses a robotic cell to manufacture sound-proofing components for the engine compartment of the VW Golf. A workpiece carrier of milled aluminum, the shape of which is a negative image of the blow mold, holds the plastic parts in place by means of suction cups, while at the same time absorbing the forces of the robot. The blow molds are placed manually on two workpiece carriers. While the KR 125 is processing one of the sound-proofing components, at the other mold an operator exchanges the finished part for a new one. These coordinated sequences mean that the robot can carry out cutting and drilling continuously, thus making optimal use of its time. The workpiece is clamped at a single point. The controller then uses sensors to query the cell for the presence of the vacuum suction necessary to hold the workpiece in place. The robot always begins cutting at a point defined by the clamping fixture; after that, the motion of the cutter is adapted to the contour to be cut. The speed of the drilling and milling unit is controlled independently by the KR 125 via the controller. | |
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System components / Scope of supply |
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- KUKA KR 125 robot
- PC-based KUKA robot controller, including control panel with
Windows interface
- Patented cutter
- Turntable
- Two workpiece carriers, whose shape is a negative image of the blow mold
- Robot programming
- User software
- Commissioning
The robotic cell was supplied by KUKA system partner Cosytronic
Computer-System-Electronic GmbH in Wissen, Germany. | |
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Results / Success |
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- High flexibility
It is their flexibility which makes robots ideally suited for this application; to process a different mold all that is necessary is to exchange the tool and to select the appropriate program using the control panel of the robot controller. The long reach of the KR 125 contributes further to the flexibility of the robotic cell. While the current workpiece measures only 1000 mm x 800 mm, one with nearly double these dimensions is already in the concept phase. The robot is also more flexible than a stamping press, which would be tied to a single workpiece form, and would also be more expensive. The higher speed of stamping presses is not relevant here, since the blow-molding process is longer than the cycle of the robotic cell. The cycle time of the robot is 64 s, of which 49 s are required for cutting and 15 s for drilling.
- Greater cost-effectiveness
The robot combines steps which are normally separate, thus saving the user space, time, and ultimately money. That the robotic cell is also very cost-effective compared to a purely manual process can be seen from the short time needed for it to pay for itself: about one year. The cutters are also notable for their high cost-effectiveness; their service life in three-shift operation is about four weeks. Furthermore, blunted cutters can be resharpened.
- Convenient programming
Cosytronic programmed the robot using the teaching method. To do this, the company guided the KR 125 through all of the required continuous-path and point motions on the component and workpiece carrier, saving the corresponding coordinates. The values were then transferred to the second workpiece carrier.
- Better working conditions
Previously, operators had to use force to manually cut the plastic flash off the sound-proofing components. This heavy work is no longer necessary. | |
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| Further information |
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| Video |
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