Control technology / Motion control
Automated to the folding rule in 16 stations
No household or construction site can do without a meter stick or folding rule - yet this practical measuring instrument usually receives little attention. However, its production is quite complex in terms of automation technology.
Since 1922, the Czech wooden goods manufacturer Metrie has specialized in folding rulers - and thus in a very demanding product: after all, a folding rule - as it is officially called - consists of 48 individual parts. Nevertheless, the length deviation between the many thousands of pieces is no more than 0.7 mm.
The largely automated production requires a total of 16 work steps. Recently, an older, cam-controlled machine was to be replaced by a modern system with synchronized motion sequences in order to increase productivity and make the process more stable.
The production of folding rules with a total of 48 individual parts is largely automated.
© CNC TechnologyThis task was taken on by the Czech specialist machine manufacturer Vúts, based in Liberec in the border triangle of the Czech Republic, Poland and Germany. The solution from the Vúts designers arranges a total of 16 stations around a central, 360° rotating carousel turning station. Several processing steps, such as drilling and milling, can be carried out in parallel in the stations. Further stations are used for loading and unloading the machine and for measuring processes for quality assurance. The particular advantage of this concept is that the machine does not have to be mechanically retooled when the product is changed. Instead, the required parameters can be easily set via the HMI control panel. The machine achieves a total cycle rate of 60 cycles per minute.
Both the control of the complex, synchronized motion sequences and the drive of the carousel turning station and a further 20 axes are carried out via the MP3200 machine controller from Yaskawa as well as via servo drives from the Sigma-5 series and V1000 frequency inverters from the same manufacturer. The latter, with their highly dynamic current vector control (Open Loop Vector), are designed for both asynchronous and permanent magnet synchronous motors in the 100 W to 15 kW power range.
As far as the aforementioned machine controller is concerned, the MP3200iec is also available as a variant specifically for the European market. With its IEC development interface, this enables simple and clear programming in accordance with the 61131-3 standard. As the CPU size and the base unit can be freely selected, the performance can be increased as required for future expansions. Depending on the application, several base units with three, five or nine slots are available for input and output modules, as well as the option for cross-rack expansion. In total, up to 62 axes can be controlled with this controller.
Set up via auto-tuning
Two of the aforementioned Sigma 5 servo drives are used in the machine, each consisting of a servo motor, servo amplifier and Sigma Win+ commissioning software. The latter does not require any manual settings or special expertise from the user. The auto-tuning algorithm allows, for example, two axes to be set up in high-performance machines in less than two hours - instead of the usual eight. The software also has an automatic filter function for vibration suppression, so that the drives run quietly and with low vibration even at low speeds. This is also used, for example, in plasma cutting, which results in better or cleaner cutting. At the same time, machine wear is reduced.
The machine's carousel is moved precisely by a single-axis motor with an output of 4.4 kW. In the machining stations themselves, 20 additional 400-watt servo systems move 20 individual axes, which are controlled by a total of ten frequency inverters. These move the drilling and milling spindles in the five processing stations, each with two processing units - one for the top and one for the bottom surface of the wooden workpiece - with a positioning accuracy of less than one micrometer.
Drilling and milling, which take place in parallel here, are just two of several work steps.
© CNC TechnologyIn this specific case, the frequency inverters were integrated into the drive via the Mechatrolink-III interface; further modular interfaces to Ethercat, CANopen, Powerlink and Mechatrolink-II are available as options.
In addition to its compact dimensions of 140 mm × 254 mm × 140 mm, the V1000 frequency inverter allows side-by-side mounting, i.e. the installation of several devices directly next to each other. This means that the inverters require even less space in the control cabinet. A patented hybrid heat sink made of a special alloy compensates for the reduced ventilation effect and thus prevents the inverters from overheating.
An integrated dual-rating function allows the inverter to operate with 120 % overload in normal-duty mode for applications requiring low overload. This means that a comparatively smaller frequency inverter can perform the work that would otherwise require a larger one. The braking resistor also reduces the deceleration time by 50 %. Ultimately, Metrie was able to increase its productivity by over 50% with the new system compared to the mechanically controlled predecessor machine. A second, comparable machine is already being planned.
Author:
Markus Schoenefeld is Manager Distribution Channel Drives & Motion Division at Yaskawa Europe.
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