Transcript
Geometric precision improves Equipment performances, technical developments and examples from the PRUFTECHNIK daily life. Author Pascal Locoge PARALIGN & Machinery Service Manager Tel: +49 89 99616-250 Mob: +49 151 19569 251 Mail:
[email protected] Co-Author Dr. Edwin Becker Head of Service Center Tel: +49 89 99616-340 Mob: +49 160 97883209 Mail:
[email protected] Adress PRÜFTECHNIK Condition Monitoring GmbH Oskar-Messter-Str. 19-21, 85737 Ismaning, Germany
1. Introduction In addition to dimensional tolerances, geometrical- and bearing tolerances from rollers, plays a crucial role in the reliability process of the equipment. Furthermore, rollers and machine components in the production plant shall be coupled and adjusted so that no constraints and additional forces between the machine components and/or rollers appear at the high speeds and under varying production loads. In any case the production process should not be impacted negatively by the assets components. The use of advance technologies such as inertial measurement, laser-based alignment and vibration measurement provide efficient ways to increase quantitatively the asset performance and their service life. As the inventor of laser shaft alignment and inertial measuring equipment for rolls, PRUFTECHNIK DB has developed such technologies early on and is acting successfully also as service provider for more than 10 years in this field.
We will describe practical techniques and developed techniques using the following technologies: • • • • •
Precise rolls parallelism using inertial ring laser gyroscope technology Flatness and straightness accurately measured over long distances using accurate self-leveled rotating Laser (up to 0,05 mrad) Measuring rolls parallelism to machine reference axe with rotating laser technology, Determination of runout, axial position and level of roll with targeted fine balancing operation (without rollers disassembly), Laser optical alignment to reduce the potential excitation to the rolls and the asset, with target optimisation
2. Inertial ring laser gyroscope technology to measure the parallelism of rolls a. Description of the technology The device using this technology is PARALIGN®. PARALIGN® is a different approach employing aerospace technology. How it is possible to use aerospace technology for roll alignment, and what are the advantages? It is the highly precise angular measurement by ring laser gyroscopes. Such gyroscopes measure the angle around their centre of rotation with a resolution of 4 µm/m. By placing three of such gyroscopes perpendicular to each other (see Picture 1), we indicate our three dimensional coordinate system (x,y,z) and the so created inertial measurement unit can learn about their position in space. By this technology aircrafts navigate and even the space shuttle finds its way back to the earth.
Picture 1: The left picture shows the inertial unit and its gyroscopes in blue. Each gyroscope measures around its rotation axis shown in red. The right picture shows the measurement process of a roll. The inertial measurement unit is placed on the roll’s surface. By moving the device along a circle on the roll, the geometrical position of the roll are measured. Unlike traditional systems the PARALIGN does not need any line of sight to or between the rolls.
By placing the inertial measurement unit on a roll and move it along a circle on the roll’s surface, the geometrical properties of the roll are recorded and the rotation axis of the roll is calculated automatically. By measuring several rolls, their axes can be compared regarding roll parallelism. No mechanical or optical connection to or between the rolls is needed to perform the survey. In addition, this inertial system is calibrated before each measurement during 5 minutes with the earth rotation (15,04105°/hours). Such a measurement is incomparably fast. No peripheral devices like mirrors or prisms are needed any more. Only a physical contact between the PARALIGN and the roll is necessary. The measuring accuracy of 50 µm/m can be reached for every roll, independent from its position in the machine or the actual temperature gradient. Frames, housings or multi-layer setups do not influence the accuracy any more. So every production line can be improved with the inertial method regarding its availability and product quality. b. Need for aligned roll All kinds of production lines containing rolls are influenced by the rolls’ parallelism the one or the other way. The reason is shown in Picture 2. One effect caused by non-parallel rolls is the non-symmetric web extension. Even if it does not affect the production directly, the winding will be non-symmetric as well, what causes troubles in the following production step. Another, most awkward effect is the transversal force on the web. This force is perpendicular to the production line. Whatever this force is doing to the web or web carrying fabrics, it is most unwanted in all kinds of productions and affects the production quality and quantity negatively.
Picture 2: The effect in case of non-parallel rolls. Not only that the web is extended non-symmetrically, also a transversal force is brought on the web.
c. Example in the metal industry Picture 3 shows a PARALIGN® survey protocol (side view) of a galvanizing line (cut out). Your point of view is the operator side of the machine, represented by the green circles while the red ones represent the machine side. The lower supporting roll (blue) is chosen as a reference, it is perpendicular to the plane of projection.
Picture 3: Cut-out of a PARALIGN® protocol of a galvanization line. The picture shows a four-high mill stand and two pairs of S-rolls. The offsets of the S-rolls to the chosen reference (blue) can be seen clearly. Additionally an offset between the S-rolls themselves can be found.
The correction can be easily perform, using the feet values in vertical and horizontal. The Picture 4 shown the alignment after performing corrections. The improvements in roll parallelism can be seen clearly.
Picture 4: PARALIGN® protocol of the galvanization line after corrections.
d. Example in the packaging industry A whole module of the laminator (picture 5) was mounted non-parallel to the existing machine. When running the laminator after the reconstruction, too many folds occurred, so the waste production increased drastically. In only one day of measurement the whole laminator was surveyed and the inertial technology device PARALIGN® detected in short time (a windows of 4 to 6 hours are far enough) the reason for the quality problems.
Picture 5: Cut out of a laminators’ protocol after some reconstruction.
As an expert of modern alignment methods with more than 30 years of experience in different industries, we are also a professional consultant for many kinds of machine alignment such as straightness, flatness and other complex measurement tasks in fixed and moving aggregates. Our development department is also ready to discuss customized solutions which makes PRÜFTECHNIK the worldwide market leader for industrial alignment services. 3. Self-levelled rotating laser technology to measure accurately (up to 0,025 mrad) Flatness, straightness and parallelism of rolls over long distances a. Technology laser to create a reference plan in space The key technology is a self-levelled rotating laser and an accurate sensor (picture 6) with the following properties:
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The Flatness of this laser plane is better than 0,025 mm/m (all laser errors combined) An accurate receiver (better than 0,02 mm) precisely measures the position of the laser to the object/machine/surface.
Picture 6: Rotating laser in horizontal position, measuring 2 references on the floor and the perpendicularity of a roll during a new installation.
b. Rotating laser technology to measure a brass treatment band. The rotating laser (picture 7) is install in from of each cylinder and adjust on to the mark on the floor in order to measure: • •
The rotation of the roll axe, The references mark on the floor, used for all the machine.
Picture 7: Self rotating laser LEVALIGN expert is installed on a tripod and allow the measurement of the reference on the floor and the rotating axe of the roll.
The report give automatically the results after choosing a reference Roll. (Picture 8)
Picture 8: Part of the report, showing the rolls that have to be corrected.
c. Self-levelled rotating laser technology to measure the flatness off a production table The laser must be installed in a stable location and is the reference for all the surface. This is like having a Laser Marble (picture 9).
Picture 9: The rotating laser is roughly parallel to the surface and allow the measurement up to 100 m in radius. The measured table have to be corrected
4. Determination of runout, axial position and level of roll with targeted fine balancing operation (without rollers disassembly), a. Condition Monitoring tools used to improve balancing and monitor machine element movement The technologies used here are typically used in condition monitoring: • • •
Data collector FFt multi channel, Accelerometers,RPM sensors and proximity probes, continuous and synchronous measurement channels acquisition system
b. Benefit of a roll balancing perform on site While vibration analysis does not always lead to immediate improvements, vibrations can be reduced significantly by balancing the machine under operation conditions. Field balancing has many advantages: • • • •
The machine component that is to be balanced does not need to be removed and transported to the balancing bench Changes in balance condition that arise during operation can be corrected Rotors of virtually any weight and size can be balanced Field balancing takes roller bearing influences into consideration – as shown Picture 10.
Picture 10: Field balancing, take into acount the industrial environnement, Bench balancing is the basic requirement for the rotor itself, don’t take into account industrial parameters (resonnaces,..)
In addition, the norm give guide line to evaluate if a balancing is required or not (Picture 11). The vibrations coming from an unbalance are potential source of machines resonance excitation. It is very often easier and cheaper to reduce the excitation than to modify the structure or the speed of the machine to reduce resonance problem. c. Recording process parameter and machine movement on site Using a mobile synchronous measurement channels acquisition system allow to “track” any event around the asset that could reduce the efficiency of it. As example, such system allow the correlation between machine or product no quality events and transient event on the asset: • • •
Speed variation, process or misaligned cardan , Weight variation (product related), Temperature modification,
Picture 11: How to calculate the residual unbalance of a rotor and to evaluate its condition.
5. Laser optical alignment to reduce the potential excitation to the rolls and the asset, with target optimisation a. Laser technology to measure misalignment Used on a regular basis, accurate laser alignment is probably the first best action for the rotating machines in the field with the following benefits: • • • •
Reduced vibrations and noise, Reduced coupling, seal and bearing failure, Secure foundation bolts. Reduce source of machines resonance excitation.
This contribute to improve the process and extend the assets life. This technology is affordable to any maintenance department, with market price between 5 k€ and 17 k€. We use a Uni-beam laser system to be able to combine self-levelled Rotating laser and shaft alignment. b. The cardan alignment Avery often we heart that cardan don’t have to be aligned: right and wrong. To work properly, cardan need : •
A minimum offset , corresponding to a incidence angle of 2° to 3° (depend of application), a maximum offset of 15° to 25° (depend of the application)
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A good angular alignment between input and output shaft.
Depending on operating angle ß universal joints transmit power irregularly. Every 360° turn provokes 4 x load alternation of the power transmission. The second joint converts this “irregular” rotational movement of the spacer shaft into a regular movement of the driven shaft, if ß1=ß2. (Picture 12)
Picture 12: How works a cardan
The alignment of cardan on site is not complicate. 2 methods can be used (Picture 13): • •
The first with the cardan spacer in place, The second without the cardan spacer.
Depending of the situation the first or the second can be chosen. In the best case, we choose the first one, to save working time on site. The removal of the cardan is often a matter of hours.
Picture 13: left, the special bracket allowing the measurement with the spacer in place, right the method without the spacer shaft.
