Micro-Epsilon Systems Technology Division expands
The System Technology division of Micro-Epsilon has now moved into larger premises on June 15, 2010. With a floor area of 1,300m2, this provides the System Technology division ...
Draw-wire sensors under pressure
Displacement measurement in a hydraulic cylinder is a challenging task since a reasonable solution cannot often be easily found. For example, for truck-mounted cranes a load torque limiter ...
Robot positioning in seam welding
In the bodywork shop at the BMW AG factory in Leipzig, the roof panel and side frames are welded together. In order to permanently seal this weld against ...
The System Technology division of Micro-Epsilon has now moved into larger premises on June 15, 2010. With a floor area of 1,300m2, this provides the System Technology division with sufficient space for six large offices and a good-sized assembly area. Due to outstanding growth and development, the department reached full capacity in its previous premises. The building, designated as Werk II, is located in the centre of Ortenburg. There are currently twelve employees in the Systems Division at Ortenburg who are involved in planning, project planning, installation and sales.
Micro-Epsilon’s System Technology concentrates on seven different sectors, whereby process control of production and quality assurance processes. In addition to the automotive and tyres/rubber sectors, the sheet metal, film extrusion, aerospace and defence, glass and semiconductors, are also supported with special measurement and inspection systems.
Today, the Systems group comprises three locations with specific core competences. Austrian company ATENSOR in Steyr is involved with robotics. In particularly, this division is concerned with automatic track generation for robot-automated production of small batch sizes based on the dimensional measurement of the object to be machined. Settled in the automotive sector with core competences in dimensional measurement technology of tyres and rubber production, the company ME-Inspection SK whose head office is in Pressburg, Slovakia, also belongs to the Systems group. The System Technology business area of the Micro-Epsilon Group has approximately 40 employees in total across its three sites.
Cables are often sheathed with different materials because they are exposed to many different loads. The sheathing with different banding materials is performed in a banding machine where optoNCDT sensors from Micro-Epsilon are installed. The cables can be banded with Kapton, Teflon, mica, polyester, copper or glass fibre yarn.
The uninsulated wire is fed into the banding machine from one side. The banding units consist of a receiver for the banding material which is wound on a roll. The receiver is also called a bobbin. There is a case around the bobbin, also called head, which takes over the guidance of the tape. The wire runs in the centre of this unit. When the wire is moving through the machine, the bobbin and head are constantly rotating in order to band the wire with the inserted material. This is possible because the head and bobbin can rotate separately from each other and therefore achieve different tensile forces and angles.
The laser sensor is mounted in the machine next to the drum. It continuously measures the current diameter of the drum from this position. The measurement data obtained are transmitted to a winding processor which calculates the desired torque of the bobbin drive from this. The problem in this application is the different materials ranging from shiny to transparent which can be located on the drum. Shiny metals present a problem for many laser sensors due to the direct reflection. The tapes used have a thickness of about 0.1 mm and are 6 to 8 mm wide. The optoNCDT 1401 with a measuring range of 200 mm competently performs this measurement. The laser spot reflects onto the coil surface and makes a clear statement about the diameter of the coil possible. For the data acquisition, it must be noted that the head has many vertical cross members for the tape guide. These stays continuously cross the measuring range of the sensor and must be suppressed on the software side so that only the diameter value remains as the measurement result.
In the bodywork shop at the BMW AG factory in Leipzig, the roof panel and side frames are welded together. In order to permanently seal this weld against ingress of moisture etc., seam welding is carried out prior to the filler coat being applied to the vehicle body.
The application of the adhesive beading is performed using a robot positioned on either side of the production line. Two optoNCDT 1700 laser sensors from Micro-Epsilon are used for precise positioning of these robots. The sensor and nozzle for applying the adhesive beading are located on the end effector. The sensors measure the position of the roof channel on the vehicle body. Using the calculated data, the nozzle is positioned precisely over the weld seam, enabling error-free application of the PVC seam.
Due to its fast exposure regulation RTSC (Real-Time Surface Compensation) the optoNCDT sensor is used here. The steep transition into and out of the roof channel is measured reliably and without errors using RTSC. As the maximum load capacity of the robots is almost reached with the applicator alone, the sensor must be as compact and lightweight as possible, with high measurement performance and low space requirements. This combination of installation size, weight, accuracy and price were decisive factors in this application.
Applications by .
When it comes to large, high capital cost machines such as a soft coal excavator, it is more economical to repair any worn parts than to replace the worn components with brand new ones. A chain link on an excavator is a good example here. After approximately four years of harsh, continuous operation, these steel parts are worn so much that several centimetres of steel are missing in the affected areas.
Previously, in order to repair these worn areas, the eroded material was welded on again manually, which took several hours. The welder has to manually weld on several parallel webs in order to restore the chain link to its original form.
As soon as this is done, he checks the shape conformance using templates and a calliper gauge.
Mabotic has developed a completely automatic method for RWE to completely automate this repair process.
In the first stage, the surface of the defective area is scanned with a scanCONTROL 2700 – 100. For this, the scanCONTROL is moved over the surface by a robot. The 3D data of the worn area together with the position data of the robot are obtained. The outstanding quality of the sensor data on different types of surfaces means that surface pre-treatment is not required.
In a second stage, 64,000 measuring points per second are obtained in the CAD target model of the chain link. Therefore, the difference in volume between the high resolution measured values and the target contour is obtained.
In the next stage, the optimum welding lines for welding the eroded material in this differential volume are calculated.
This entire process is completed in less than 3 minutes. Finally, the calculated welding lines are transmitted to the robot controller and the welding process can start.
Mabotic is also applying the system to other applications, partly due to the flexibility of the scanCONTROL range, which provides measuring ranges from 10 to 100mm with measuring point rates of 64,000 to 256,000.
Applications by .
Displacement measurement in a hydraulic cylinder is a challenging task since a reasonable solution cannot often be easily found. For example, for truck-mounted cranes a load torque limiter is required in order to comply with health and safety regulations. Previously, the crane could only be operated when the hydraulic supports were fully extended. Today, a displacement measurement on the hydraulic cylinder can enable dynamic load torque limitation. Previously, this measurement could only be resolved reliably with some reservations. Micro-Epsilon Messtechnik has provided a completely new approach to displacement measurement of hydraulic cylinders.
The selection was previously restricted to three different methods for measuring the stroke movements of hydraulic cylinders. If the displacement measurement was already considered during the design, a magnetostrictive sensor could be integrated in the cylinder. For subsequent attachment outside on the cylinder, draw-wire sensors or magnetic or optical measuring rods or tape measures could be selected.
Previous methods
Magnetostrictive sensors are designed so that the measuring element is in a tubular sensor housing. This is always somewhat longer than the respective measuring range. The evaluation electronics are located on or in the cylinder base at the rear end of the sensor. For magnetostrictive sensors, a magnet in the piston is used as the position transmitter.
As these sensors are designed to be pressure-proof, they can be integrated in the cylinder. Adjusting the sensor for the application is fairly straightforward, for example, by modifying the bar length. However, a bore in the piston rod that the sensor tube can be immersed in is required for operation. The greater the stroke movement of the cylinder, the deeper this bore has to be. In the case of large cylinders, for example for hall gates, this means that a bore in the metre size range may be necessary. Vertically boring a cylinder piston in this size range and without tilting is a major challenge.
Rather than an integrated displacement measurement, a draw-wire sensor can be mounted on the outside of the cylinder. This method can be easily achieved, providing measuring ranges of up to a few metres. However, in harsh environments in which cylinders are frequently used, the draw-wire sensor can only be used with caution as dirt and mechanical loads may destroy the sensor over the long term. This limitation also applies when using optical or magnetic measuring rods. Here, the measuring rod is also installed on the outside of the cylinder. A grid applied to the bar is scanned optically or inductively. As this sensor is also outside on the cylinder, it is susceptible to soiling.
Due to these limitations , the two companies Sensor-Technik Wiedemann from Kaufbeuren and Micro-Epsilon from Ortenburg have developed an alternative solution. Both companies have many years of experience in the field of sensor systems.
Integrated draw-wire sensors
During development, particular attention was paid to the sensor being suitable for harsh environments and that no significant extra costs are incurred for the integration of the sensor to larger cylinders.
The co-developed solution is based on the draw-wire sensor, which is integrated inside the cylinder. Here, the sensor is completely protected from external influences. The sensor is positioned at the bottom of the cylinder and the measuring wire is attached to the bottom of the piston. A particular challenge here is the design of the sensor and the signal routing to the outside, as a bore hole in the cylinder hosuing is always a weak point. With pressures of up to 600bar in the cylinder, leakage is a risk that must be prevented.
As well as the housing, the essential elements of a conventional draw-wire sensor are the spring, the drum, the measuring wire and a protractor as sensor element. A housing for the sensor can be dispensed with in this application, as the cylinder takes over this function.
Each movement of the piston causes a rotation of the wire drum. The rotation movement is divided using a gearbox onto two shafts with different rotation speeds. A magnet is positioned on each shaft at the bottom of the cylinder, whose positions can be measured by external, magnetic angle sensors. Using a suitable gearbox, each combination of the magnet positions only occurs once across the complete measuring range. The sensor therefore shows the characteristics of an absolute encoder. Micro-Epsilon was able to contribute a lot of expertise to the development of the sensor design and function of a draw-wire sensor.
Non-contact signal transmission
Due to the high pressures, the cylinder walls consist of relatively thick metal. A magnetic signal transmission through these thick walls is not suitable for measurement requirements. Due to the experience of Sensor-Technik Wiedemann in pressure measurement technology, a solution was found for this without having to weaken the design of the cylinder. At those points where the two gearshafts reach the bottom of the cylinder, the steel is tapered and a special membrane is welded on. A magnetic signal transmission with sufficient quality is achieved using this membrane. Using FEM calculations, the minimum possible wall thickness was determined.
The electronics on the outside were designed extremely flat and can easily be attached to the bottom of the cylinder. The electronics are available with cable or connector output. 4–20mA or a CAN interface are provided as output variants.
Application areas
Due to the draw-wire sensor, the system can easily be adapted to different cylinder lengths and diameters and to many different operating conditions.
The new wireSENSOR WDS-TZ10 is ideal for cylinders with a lifting height from 0.5m up to approx. 15m. The lubricating oil in the cylinder surrounds the draw-wire sensor. This functions as a lubricator for the sensor and provides a longer service life. This method is also suitable for cylinders without piston rods due to the hooking of the measuring wire. Cylinders with this type of displacement measurement are ideally suited to harsh environments and in mobile machines.
The TZ10 is an appropriate supplement to the magnetostrictive method for short cylinder strokes.
Applications Measurement by .
Every type of test rig today represents a complex interaction of mechatronic disciplines. These consist of the mechanical design and the complete software for the control of the test rig and measurement technology or sensors. The measurement technology itself always contributes significantly to the expertise of a test rig. In other words, the performance of the test rig depends on the precision of the sensors. This is why eddy current sensors are frequently used on test rigs. These sensors often originate from Ortenburg, the head office of measurement technology company Micro-Epsilon.
Eddy current displacement sensors are used in many different applications, yet the requirements are often very similar. Typically, requirements are for nanometre resolution with the sensor as compact as possible and which is resistant to external influences. In addition, the sensor often needs to be easily adapted and integrated with other components or system parts, as the target is usually found inside the test rig. The measurement task itself could be gap measurement, distance or displacement measurement.
The requirements outlined above are satisfied very well by eddy current sensors. Compared to the test rig, the sensor itself is a very small component; currently the smallest sensor in the world has an external diameter of just 2mm. Nevertheless, the component has an extremely important task. So how does an eddy current sensor work?
Measuring via eddy current is based on the extraction of energy from an oscillating circuit. This energy is required for the induction of eddy currents in electrically conductive materials. Here, a coil is supplied with alternating current whereby a magnetic field forms around the coil. If an electrically conducting object is present in this magnetic field, eddy currents are produced in it. According to the Lenz Rule, the field of these eddy currents is opposed to the field of the coil, which causes a change in the coil impedance. This distance-dependent impedance change can be captured at the controller as a measurable factor using the change in the amplitude of the sensor coil.
The principle can be used for all electrically conductive materials. As eddy current penetrates insulators, even metal behind an insulating layer can be used as a measuring object. A special coil winding enables very compact sensor designs, which can even be used in high temperatures up to 320°C. All eddy current sensors are insensitive to dirt, dust, moisture, oil and pressure. This means they are ideally suited to harsh industrial environments.
The eddy current sensors of the eddyNCDT series cover measuring ranges between 0.4mm and 80mm whereby the sensor geometry is directly dependent on the measuring range. A measurement channel can achieve a maximum resolution of 0.09nm.
Controlled welding
A fully automatic test rig has been set up at the Technical University of Brunswick, which establishes the quality of the seam during the welding process when the seam flanks are continuously moving. The test rig simulates dual-axis stressing of the weld sample. Special attention is paid to the acquisition of the weld edge movement of the sample plate, because the reliable acquisition of this controlled variable is critical to the success of the welding. The fact that displacement measurement is not influenced by external factors such as dirt, smoke and electromagnetic fields, was therefore key to selecting a suitable measurement system. Due to its very high robustness, the displacement measurement system from Micro-Epsilon is used. The eddyNCDT series sensor has a measurement range of 4mm and provides micrometre accuracy for a controlled sequence of the weld edge movement. The non-contact technology also ensures a longer, maintenance-free operational period in the test rig. The stability of Micro-Epsilon’s eddy current sensors with respect to high temperatures was a decisive advantage in this particular application.
Test rig for tribology
Eddy current sensors from Micro-Epsilon are also being used in a new high-performance test rig at the Institute for Tribology and Energy Conversion Machines at the Clausthal Technical University. With this new test rig, which is currently under construction, the tribological, flow mechanics and rotor dynamics of highly loaded plain bearings at maximum circumferential speeds of the shaft will be examined. Based on many positive experiences already from using Micro-Epsilon eddy current sensors in existing test rigs for the examination of hydrodynamic radial plain bearings or plain bearings with particularly high loads, sensors from the eddyNCDT series will also be used in this new test rig. In doing so, the shaft reaches circumferential speeds of up to 200m/s; typical test rigs achieve a maximum of 120m/s.
The position of the test bearing housing and the relative movement between the rotor and the test bearing is detected in the test rig using eddy current displacement sensors. The bearing gap of the plain bearing between bearing surface and rotor is also measured using eddy current sensors. There are 22 measurement channels in the test rig. The eddyNCDT miniature sensors with a measuring range of 0.5mm are integrated directly into the design in order to enable the bearing gap to be measured with maximum precision.
Engine test stations
Eddy current sensors from Micro-Epsilon are also being used in automotive test stations. For example, the secondary movement of pistons during the different strokes is can be measured. To do this, several sensors are integrated directly with the pistons, forming a flat surface on the piston wall. The cables are routed along the connecting rod and drive shaft to the outside, via a swing arm. During operation, particularly when the engine is producing torque under load, it can be established for example, whether the piston in the cylinder has too much ‘play’ and whether this would adversely affect the service life. If, for example, the sensors are moved to another location in the crankcase, the “breathing” of the cylinder head gasket during the stroke can be tested. There are space constraints for all applications on an engine. The engine housing normally has to incorporate multiple coolant channels. Sensor integration and cable routing are therefore a challenge, since no channel can be modified or damaged. As well as being difficult to install, the sensor also has to withstand a harsh environment for sustained periods: temperatures of up to 200°C, pressures of up to 2,000bar and contact with fuels, oils or air-fuel mixtures.
The applications outlined above are examples of how sensors are being used in today’s test rigs. The integration of sensors in test rigs will continue to gain importance as, last but not least, test rigs must provide high quality measurements, which is taken for granted these days. This requirement can only be achieved with corresponding mechatronics competence for the complete system, which is often a decisive factor in this market.
Applications Measurement by .
Gear shafts with plug-in toothing, bevel gears with hypoid teeth and similar axial components can warp during manufacture. Therefore, an inspection/measurement of the run-out is necessary. The workpiece is adjusted if required. For this, the extent of the “ovality” and the direction in which it should be adjusted must be determined. Engineering company EHR has developed an optical measurement system for determining these parameters, which enables fast and extremely precise automated straightening of the workpiece.
For objective measurement of run-out characteristics, EHR uses the laser line scanner scanCONTROL 2800-25, which generates a digital 3D image of the tooth area.
The scanner is aligned with the component in such a way that the laser line is perpendicular to the teeth of the component. When rotating the clamped component, the complete tooth area is shown digitally in three dimensions. This then enables the 3D point cloud to be evaluated according to customer requirements. In order to make a comparison with tactile dislocation, computer-generated digital balls are placed between the flanks of the teeth.
A further benefit of using “digital dislocation” is that the diameter of the ball can be changed quickly and easily. All ball diameters that should pass between the gear teeth can be selected using simple configuration tools. Due to this increase in the number of evaluation results, measurement accuracy of better than 5µm is achieved, which is lower than the measurement resolution of the laser scanner.
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Micro-Epsilon has developed a completely new manufacturing technology for eddy current sensors. Using “Embedded Coil Technology” (ECT), the sensor is housed in an inorganic carrier material, which provides temperature and shape stability. Conventionally wound sensor coils are replaced by ECT; the carrier material can even hold electronic components. The technology provides more freedom in the physical design of the sensors; in the case of special operating environments, the ECT sensors can be easily adapted to the conditions. The electronics are either integrated in the sensor or are housed separately. The significant benefits of ECT technology are its high operating temperatures of up to 350°C, extreme temperature stability, high mechanical load capacity and its suitable for use in strong electromagnetic fields. Due to a hermetically sealed enclosure, the sensors can also be used in ultra high vacuums.
The new sensor technology has already proved itself in many challenging applications. Due to their high temperature stability, ECT sensors are used for the alignment of mirror segments in the latest giant reflector telescopes and for measuring the grinding gap of refiners in the paper industry due to their high mechanical load capacity. In the semiconductor industry, the sensors are ideal as they are resistant to Ultra High Vacuums and strong electromagnetic fields.
Measurement Uncategorized by .
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