Flatness and Level measurment methods
Measuring Flatness and level in general:
We must firstly distinguish between flatness and level. In mathematics, the flatness of a surface is the degree to which it approximates a mathematical plane. We call this plane level if it is on average orthogonal (at right angles) to gravity. (Sometimes called “in water”) So we only talk about something being level if it is also very flat.
To measure flatness we require a reference plane. To measure level we require a reference to gravity. Typically we measure a matrix of points or angles and interpolate between these discrete measurements.
Specification and Mechanical adaptaion.
In engineering applications we measure and sometimes correct the flatness of machine components. In flatness and straightness measurements the mechanical adaptation has a dramatic effect on what we measure. It is important to consider the flatness specification in detail in order to choose an appropriate method.A flatness can state that all points on the surface shall lie between two parallel planes separated by "X" distance, where "X" is the flatness tolerance. It can specify a tolerable wave over a specific area. Alternatively it can specify the variance of the deviation for a best fit plane. Often the specification will define explicitly or inexplicitly how the measurement must be performed.
The size of the plane and accuracy required and the length of time required for that measurement method are usually the defining factors.
The best method for you depends on the following:
a) What exactly are we measuring? (Dimensions, accessibility, environment)b) What is the required spec? (tilt, roll, line deviation, waviness etc )
c) What provisions (adjustment screws) are available to correct the deviations?
d) Who is doing the work and how much time does he/she have?
e) What kind of a report is required? (For whom?)
f) What’s your budget?
Status Pro offers the following techniques and technologies.
We list them in order of what we think is a mix of value for money, speed in alignment, documentation and above all ease of use. Starting with the best.
ProLevel
ProLevel is a "Reference Laser plane + active target" solution.The reference plane is generated by the precision rotation laser T330. The beam is rotated at ca 10Hz. The self-levelling mechanism continuously ajusts the laser plane to keep it in the desired position. The receiver R310 is used then to measure the deviation of the plane from the laser reference. All the results are logged to the Display unit. This solution is most suitable for machine assembly people looking to measure surfaces from 1x1m to 20x20m with an accuracy of <= 0,1mm.
Advantages: Very quick and very easy to use. Good documentation and good value for money.
Disadvantages: Medium range accuracy +/- 0,05 depending on the size of the surface.
µlevel
µLevel is an "Electronic Spirit-Level" solution.The use of spirit-levels for measuring flatness and level is common in machine tool assembly. It is used in applications where the measurement object is very straight (<0.1mm/m) from the outset.
The method is the same as the straightness measurement where usually a matrix of straightness measurements are connected. Clearly we must distinguish between the overall inclination and local deviations caused by "non-straightness". Often 2 µLevel units are used together where one remains stationary and serves as a reference for the other, which is moved incrementally along the object.
Advantages : Everybody knows what a spirit level is. µLevels are very versatile and training is minimal.
Disadvantages: The measurement takes a very very long time. Spirit-Levels only measure in the vertical plane. So the object must be very level to start with. The basis is very small. Errors will be cumulated along the way in a straightness measurement.