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The production of noncircular glass moulds

A machine concept for an efficient production of noncircular glass moulds was presented. The production process is mainly limited by the dynamic behaviour of the feed drive system. A prototype of a highly dynamic feed drive system was developed based on the latest technology in linear motor drives. To avoid excitation an active mass compensation for the feed drive system was developed.

The main spindle has a great impact on the capabilities of the new machine tool. The required velocity and acceleration rates of feed drive depend upon the complexity of the bottle shape and the rotational speed of the workpiece. The prototype of the main spindle is based on a water cooled built-in direct drive. To generate minimum flutter of the rotational speed at low number of revolutions the main spindle is fitted with an angular measurement system that provides a high resolution.

To design a computer aided design/numerical control (CAD/NC) coupling for the production process of noncircular glass moulds a new CAD/NC postprocessor was developed. It generates NC turning programs for noncircular workpieces directly from the CAD system. For optimal adaptation of the processed NC program to the capabilities of the machine, a user interface is implemented in the postprocessor to simplify the input of the technology data.

As machine control a Siemens 840D computer numerical control (CNC) was tested. To adapt the synchronous linear motors of the developed feed drive system to the digital servo amplifiers several modifications had to be made. Linear servo motors can then be controlled by Siemens CNC without any restrictions. Therefore a closed loop control structure for the machine has been achieved.

The results of the project can be exploited in a wide range of application fields, such as the design of machine tools for high speed cutting.

Reported by

University of Hannover
30159 Hannover
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