Work Impossible for Humans to Fulfill

Robots carry out work that would be impossible for humans to do. Robots provide the required quality, precision, speed and traceability which cannot be achieved manually. Please find examples below:

Wittmann, Austria - IFR-Partner

Multi-component molding, styled throughout for zero error

December 2011

The central piece of all the system components is the central operating position.

The objective of this project was to realize the cost-efficient manufacture of safety relevant automobile components in continuous communication with the TRW line computer system. For this purpose, the PLC-based components needed for complex injection molding processing were first assembled. All these had to be connected up in a complex control unit in order to map the complete system of a 100% monitored production line within the line concept.

The component to be produced is an overmolded detonator which must trigger the initial ignition of the airbag gas generator with absolute reliability. A safety relevant component that saves life.

It is therefore essential to produce by the zero error method, to monitor the production in its whole fabrication depth and to document it immediately.

Production, monitoring and documentation

In semi-automated production, however, this can only be achieved by frequent and costly controls which further slow down the production process and increase the manufacturing costs.

Experience has shown that automation is greatly superior to manual production here. The monitoring and documentation of every operation taking place in a production cell can be ensured.

Errors can be reported to the module controller in real time and the necessary correction can be initiated. In this way it is guaranteed ? by automation ? that 100% of parts detected as faulty are ejected from the production process and only serviceable parts are processed in the further course of production.

The following operations had to be handled by the system described here:

  • Orienting the detonator
  • Orienting the closure piece
  • Automatically placing the pieces in the mold
  • Overmolding of the detonator units
  • Unloading the mold
  • Cavity-based separation of good/bad parts

The required cycle time had to be realized with a very fast control unit and with the help of multi-functional, intelligent software.

Advantages of professional project management

Regardless of the technical requirements mentioned, it is of fundamental importance that, for the planning and implementation of such a system, a professional project management be demanded by the client and be applied by the supplier. This management bears the responsibility from preparation of the tender to the production, test run, delivery, commissioning and final acceptance. Björn Dünfelder, WITTMANN Key Account Manager, acted in the course of the project described here as a link between WITTMANN Construction or Production and the corresponding departments at TRW. "For the success of such a complex solution, a clear assignment of responsibilities and smooth cooperation within the project team are indispensable," states Rainer Watzka, Technical Manager at WITTMANN Robot Systeme in Germany. Here, high-performance software is an essential tool for employees who, in their function as Key Account Managers, have to support such extensive automation projects.

Module computer connects system parts

Two systems from WITTMANN Robot Systeme GmbH which could do full justice to these highly complex requirements started operations at TRW at the beginning of this year, one of which produces the detonator unit for airbags. The closure piece for the driver and passenger airbags is produced on the other system. The jigs required for the feed, separation and positioning of the parts increase the complexity of this system. It was possible to realize the assembly, unloading and packing of the three parts within the overall cycle time specified at the start of the project.

Both systems have the same basic structure. Each production cell comprises a WITTMANN BATTENFELD vertical injection molding machine with a rotary table and a WITTMANN Series 7 tandem linear robot system. In addition, the systems share the use of the main module computer, which brings together all the control units of the individual system components. The computer monitors and documents the operating status and issues error messages in clear text, indicating the location and type of the error.

The production cycle

Highly automated production unit at TRW Airbag Systems in Aschau, Germany: On a servo-motorized rotary axis, 50 motion modules are integrated in a gripper system. Through linkage in a complex control system, a complete system is created for a 100% monitored production line. The result is the zero error production of high quality parts.Production planning generates the production order and passes it to the line computer, which is connected with the modules on the production line via a TCP/IP Ethernet interface. One of the stations comprises the granulate store, which provides the material intended for the production of a specific part. The corresponding material data are mapped on the touch panel of the module computer, which releases the correct material.

The operator makes the connection of the WITTMANN DRYMAX with the material hopper. When the material has reached the degree of dryness necessary, i.e. the required processing quality, the hopper releases the material flow to the injection molding machine. After the correct quality related data has been reported back by the process monitoring system and the injection molding machine has reached all its specified values, the automatic cycle of the processing machine is entered on the operating panel.

System 1 positions the pyrotechnic detonator correctly. The corresponding discs are oriented and positioned by the second handling unit. Before this assembly step, the positions and orientation of the detonator and discs are checked. The gripper of the robot picks up the two part sets from the part centering unit and places them in the lower half of the empty mold, from which the unloader gripper has first removed the finished parts. In order to achieve absolute, reproducible precision here, the gripper is set to "float", i.e. its power is switched off, just before the insertion operation by means of a special device.

The second machine produces overmolded closure pieces. Here, the parts fed in (detonator and cover cap) are laid on a rotary table, from which a SCARA robot removes the parts, orients them correctly and puts them in position.

For the specified use of the system in Aschau, two further essential conditions were fulfilled. Firstly, the automation cell is located in the Class 1.4 safety area of the production unit, meaning that all machine parts which touch the product are ESD protected. Secondly, the module control system monitors and documents the entire production sequence.

 

Author: Walter Klaus