Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Experience leads to success
Experience leads to success
Keywords: Metals, Plastics, Robots
MOHR (Germany), plastics and metal working company, uses Stäubli six-axis robots in fully automated cells for metal gearshaft coating and printed circuit boards, as well as in fully automated assembly cells for heated windshield wiper nozzles for the automotive industry. Six Stäubli robots - models RX130, RX90, RX90 L and RX60 - are used to tend the Demag Ergotech and Arburg injection molding machines. Another three Stäubli RX industrial robots are used for additional assembly applications (see Plate 4).
Eleven years ago, a small six-axis robot marked the beginning of the first fully automated cell at MOHR, integrating injection molding, assembly and 100 per cent quality control. The most important requirement was the ability to deliver flawless products, eliminating increased costs due to defective parts.
Plate 4The Stäubli RX industrial robots have precise positioning enabling a fast and exact pick and place of the extruded parts
From this first robotic experience, the former production supervisor Paul Bund and his team tried to solve more difficult automation problems, such as a manufacturing cell for the indicator control switch of the Audi A4/A8. For this application, a Stäubli RX130 was chosen for loading and unloading the injection-molding machine. Equipped with a multiple revolving gripper, the robot picks two metal inserts from a vibrating conveyor as well as two prefabricated printed circuit boards from a pallet. After the injection operation has ended, the finished coated parts are picked from the tool of the injection molding machine; the inserts and printed circuit boards to be extruded are inserted into the tool with an accuracy of less than 5/100mm. The finished parts are then fed to a stamping and high-voltage testing device. Afterwards they pass an optical control to detect any mold faults. Depending on the inspection results, the finished parts are finally palletized or fed to a reject conveyor. The robot's high speed fulfilled the cycle time requirement of less than 40 seconds.
The MOHR engineers tried to handle even smaller parts, which had to be positioned even more precisely. The specificity of the new manufacturing cell is a 2 x 2 tool mounted on a turntable, consisting of two pairs of cavities which extrude the sensor connectors for BMW motor control with polyphenylene at a temperature of 136°C.
A Stäubli RX90 L tends both pairs of cavities, situated inside and outside the tool.
The advantages of the Stäubli RX industrial robots lie within the highly precise positioning enabling a fast and exact pick and place of the extruded parts (see Plate 4). Furthermore, the Stäubli RX industrial robots are powered by a controller with the powerful V+ programming language which enables the control of the robot from machine tending to production control.