Three straightness measurment methods
What does measuring straightness mean?
A line is a straight curve. We measure the "not straightness" or the curvature of something which looks straight from a distance. In engineering applications we measure and correct the straightness of machine components.
Typically we are dealing with a mixture of all of following deviations: Horizontal curvature, vertical curvature, Roll, Screw and Surface discontinuities. Depending on the measurement method chosen these deviations will be more or less visible and more or less separable. The chosen mechanical adaptation is often as important as the measurement technology. We are looking for practical methods and procedures for measuring, correcting and documenting the not straightness of long machine components like linear guides.
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) Whats 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.
ProLine
ProLine is a "Rerefence Laser + active target" solution.The position of the laser is measured directly by the 2D target with a µm resolution and sent to the Display unit. The distance travelled along the guide is logged by a Disto whos data is also sent to the Display unit. This solution is most suitable for machine assembly people. Looking to align linear guides to <= 0,05mm over distances of between 1 and 15 metres.
Advantages: Very rapid setup and measurement, very easy to use especially if the object must also be aligned and not just measured, very good documentation and good value for money.
Disadvantages: Medium range accuracy +/- 0,01. The distance Z is only logged and not measured accuratey.
µLine
µLine is an Interferometer solution. Ideal for the calibration of machine tools. The distance Z is measured with nm accuracy whereby the x and y axes are measured with a PSD as in Proline. This solution is most suitable for quality control people. Especially for machine tool calibration.
Advantages: Superb accuracy, good software support and very good documentation. Also good value for money.
Disadvantages: It“s an interferometer, so the setup must be done carefully. Don“t interrupt the beam or you start again! so its not as good as ProLine for the alignment process.
µlevel
µLevel is an "Electronic Spirit-Level" solution.The use of spirit-levels for measuring straightness is common in machine tool assembly. It is used in applications where the measurement object is very straight (<0.1mm/m) from the outset. 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: Spirit-Levels only measure in the vertical plane. We need something else to measure the horizontal plane. The base is very small. Errors will be added along the way in a straightness measurement.