Product category:
EDM wire and diesinking, miscellaneous equipment
News Release from: Micromech | Subject: Delta Tau 'PMAC' PC motion controller
Edited by the Manufacturingtalk Editorial
Team on 06 July 2006
Massive diesinking EDM increases motion
accuracy
To enable a very large diesinking EDM meet required accuracy, the EDM control board and power supply with PC motion controller was combined to control all the motion axes and sparking.
An existing EDM machine for the manufacture of moulds for the plastics injection moulding industry had a problem The machine is 15m long and 6m high, the canterlevered Y-axis weighs 4 tonnes and carries the Z and O axis to a full-extended travel of 5.5m
This article was originally published on Manufacturingtalk on 23 Jun 2008 at 8.00am (UK)
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Due to the immense size of the machine it was not possible to get accuracy of movement required to meet the demands of the mould industry.
Uncompensated, the inherent machine accuracy was only 0.18mm and the previous Heidenhain control did not have the ability to do volumetric compensation, so Delta Tau found the solution.
The answer was to combine the EDM control board and power supply with the Delta Tau 'PMAC' PC motion controller to control all the motion axes and spark control.
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The motion board controlled the four axis of motion (X, Y, Z, and O) and compensated for the liner bearing and ball screw errors.
All the EDM control board and power supply had to do was provide the precision spark control.
The linear error was measured by a laser interferometer and the data used to build the compensation table in the PMAC.
The system still used the original Heidenhain linear encoders as position feedback and also closed the velocity loop from the motor feedback.
In addition the PMAC is able to control machine logic thus allowing for the flexibility to incorporate a complex tool changer into the upgrade.
The main features of the PMAC used to solve this application were the 2D and planar linear compensation, the spline mode for motion profile, asynchronous motion and logic control, and co-ordinate system definition.
It is a PC based motion board and has a very fast CPU calculation capability.
The result of these enhancements was to provide part finish and quality goals required by industry, achieving a final accuracy of 0.025mm.
The project cost was far less than the alternative approaches but a seventy times improvement in machine accuracy was attained when compared to old NC control, and by only using an 'off the shelf' technology from Delta Tau.
The part finish quality was met by the ability of the motion controller to perform on the fly calculations (4ms) for electrode position based on feedback from the EDM process controller.
Maximising the value of capital equipment these days is now a priority and being able to upgrade the performance of an existing machine thus saving the expense of a new machine and at a fraction of the cost is good news for the manufacturer and the customer.
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