THE PRINCIPLE
This is a digital hydraulic micropositioning system that is already being used in machine tools. The objectives are a high degree of rigidity with very high positioning accuracy, dynamics and system robustness.
The control range is approx. +/-100 µm. The short stroke allows the use of elastic membranes, which are free of frictional effects because they do not require sliding seals, and can therefore be position controlled with considerably greater accuracy. The use of digital valves for automatic control of the required position also makes the system cost-effective and robust with regard to oil purity.
FACTBOX
SYSTEM PARAMETERS
Control range: +/-100 µm, positioning accuracy < 1 µm, rigidity of the membranes (without oil) approx. 150 N/µm, rigidity when oil tensioned (without automatic control) approx. 300 N/µm, rigidity with automatic control ∞ N/µm (only limitation, the system pressure), pressure supply approx. 75 bar, friction-free system, digital hydraulic or conventional (proportional valve) possible
AUOMATIC CONTROL
Automatic control of the system takes place via conventional proportional control, which is easy to implement and maintain. Despite this simple basic rule, the required precision of 1 µm is attained. A precise eddy current sensor detects the position of the moving target. If there is a reduced accuracy requirement, the position can also be controlled by way of the pressure difference in the membranes, which leads to a further cost reduction.
SYSTEM ADVANTAGES
High degree of accuracy (< 1 µm), high dynamics, low investment costs, simple controller, easy maintenance, high degree of robustness, extremely low noise generation despite switching valves
AREAS OF APPLICATION
High-precision positioning of tool spindles, force control, clamping mechanisms with controlled clamping force, high-precision movement control as a series attachment for relatively inaccurate cylinder drives
COMPACTNESS
Thanks to the low oil requirement the system can be integrated into possible applications completely independently, without connection to a central oil supply and therefore flexibly in terms of space. A 0.16 L accumulator for a time period of over 10 minutes is sufficient for operation in the case in question. The flatness of the moving membranes allows good system integration.
OUR DEMONSTRATOR
The demonstrator is operated at a supply pressure of approx. 75 bar, a digital valve that is customary on the market (Rexroth SEC6) sets the differential pressure in the membranes, which are deformed by this and shift the movable target. The system is triggered by a commercially available HNC100 from Bosch Rexroth.
Please contact us for further information! We shall be happy to provide detailed information about the options offered by micropositioning.
Linz Center of Mechatronics GmbH | Science Park | Altenberger Straße 69 | 4040 Linz | Austria | T +43 732 2468-6002 | F +43 732 2468-6005 | office@lcm.at | www.lcm.at
