www.lammb.cz - Laser Adjustment & Measurement of Machine Bases

THE LATEST NEWS

10th February 2010
Renishaw company grants new Bluetooth wireless Ballbar QC20 to LAMMB systems s.r.o. for testing in operating conditions by its customers. Our company keeps at disposal another the most modern equipment for diagnostic and measurement of CNC tool machines and for preparing of case study for company Renishaw.
13th November 2009
Our company succesfully restored certificate authenticity ISO 9001 : 2008 for all activity related with diagnostic of CNC tool machines, service and machine repairs.
17th April 2007
We offer calibration of rotary axes by the Renishaw RX 10 system, which in connection with the Renishaw ML10 interferometer enables calibration of any swivelling angle of the rotary axis. The calibration can be carried out in automatic cycle – similar to measurement of position precision. The RX 10 table automatically monitors the axis motion and – by slight turning in the opposite direction – keeps the permanent measuring position of the measuring optical devices. Precision of ± 1 angle second is reached at measurement of rotary axes.

Vibration diagnostics

Vibration diagnostics or vibrodiagnostics is one of the methods of non-disassembling and non-destructive diagnostics of rotary machines and equipment. It uses vibrations generated by the running device as a source of information about the way of its operation. Vibration diagnostics is also an important instrument of modern predictive and proactive maintenance methods of machinery. Using the vibration diagnostics the machinery maintenance is planned according to the actual state while lots of unnecessary preventive repairs are eliminated. This, of course, saves a lot of spare parts as well as time needed for repairs of the machines. With regularly monitored devices the period of downtimes is extended and they can be planned well in advance, as it is clear from results of measurement which particular node is to be the subject matter of repair.

Vibration diagnostics options:

  • The basic measurement deals with finding out total vibrations generated by the device. In particular the following things are found out: mechanical states, such as non-balancing, nonalignment, mechanical loose, bent shaft, resonation, problems with belt drives, etc. This measurement is defined in standards dealing with permissible powers of oscillation on given devices (ČSN 122011 – ventilating fans, ČSN 105041 – compressors, ČSN ISO 10816 – the general standard for most of machines and equipment). The subject of measurement is a speed of vibrations in mm/sec in a range 10 – 1000 Hz in RMS detection (all the mentioned standards are referred to this method of measurement). The exception is assessment of vibration power on machine tools, where more stringent criteria are needed and where some suggested values of vibration power were found out by long-term monitoring.
  • For finding out the state of lubrication in slide bearings and rolling-contact bearings, for detection of electric problems with electric motors, examination of gearing, and lubrication in gear boxes the measurement of vibration acceleration in properly chosen frequency ranges is successfully applied.
  • For finding out the exact state of bearings some special so called “envelope technologies” of vibration acceleration have been developed. The reason why these envelope technologies are used is based on the fact that certain impacts (shocks) occur at generating process of defective part of bearing, which causes increased vibrations at the frequency of impact, and particularly at resonation frequencies (10s of kHz). The aim of envelope technologies is to filter and emphasize these signals from defects in the bearing in high-frequency area. Evaluating software can consequently distinguish which part of the bearing shows defects (outside ring, inside ring, rolling elements, cage).

When measuring the machines so called multi-parameter monitoring is used where all the given characteristics or values are sensed in various ranges and they can be completed with measurements of deviation or amplitudes – phase relations to make the results of measurement more accurate. The numeric value is saved together with vibration spectrum, in which the particular signs of defect or wear mentioned above are distinguished in detail.

Methods of vibration diagnostics:

Classification according to the way how the vibration diagnostics is carried out:

  • periodic tour of inspection diagnostics – manual measurements with a given period (monthly, quarterly), efficient system of determination of the future development of detected states.
  • single measurement of machinery state – finding out the immediate state; however prognosis on future development of detected states is difficult
  • continuous ON-LINE measurement – continuos monitoring of the state of machinery, usually led to protection and when exceeding the pre-set alarm levels for the device downtime

Activities connected with vibration diagnostics:

Today’s modern systems dealing with monitoring of the state of machinery based on their vibrations should not only detect the unsatisfactory states but they should immediately eliminate the troubles which do not require significant assembly intervention. The most frequent faults are non-balancing and nonalignment. Both these states are quickly and efficiently eliminated by operation balancing or setting. Further applications using the vibration measurement are so called “Operation oscillation shapes”.

Operation balancing:

It can be generally said that non-balancing occurs, if the geometric axis does not correspond to the motor central axis of inertia. The vibrations that come into existence shorten the service life of bearings, stress the structures and basement of devices, and they can finally cause failure cracks in buildings. The occurred non-balance can be quickly eliminated by operation balancing and the vibrations can be brought to an acceptable level.
Basic classification of balancing:

  • uni-planar (suitable for narrow rotors or overhanging rotors)
  • multi-planar (for large rotors, where moment non-balancing predominates or for rotors placed in more bearings)

The only precondition of operation balancing is the access to the balanced element (e.g. the rotary wheel of the fan – dismounting of the suction cover) and possibility of the device lowering.

Operation setting:

There can be parallel or angular nonalignment on clutches. In practice, however, it is mostly combined. Nonalignment on clutches causes significant vibrations, which in turn shorten not only the service life of bearings but that of clutches and basements as well, because the clutches have to transfer this nonalignment into basements. Nowadays modern laser systems (single-ray or double-ray) are used for fast elimination of nonalignment, which ensure setting of the device with precision in hundredths of millimetre. For setting the stainless plates manufactured for that purpose can be used.


Operation shapes of oscillation:

In other words, drawing attention to vibrations when the machine is running. The result of measurement of operation shapes of vibrations is a computer animation of motion of structures or machine parts dependent on operation revolutions. It is very efficient to carry out this measurement when finding out the weak nodes on the machine – loosened basis, resonation, insufficient rigidity of the structure, assessment of vibration influence to the stress of individual machine components, etc.