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Straightness ApplicationStraighness Measurement of linear guides

Straightness Measurement


Traditionally with a wire and a spirit level, in fact the wire and the spirit level are two very different measurements, they measure different characteristics of a guide. Here the wire measurements are absolute measurements where the spirit level measurements are incremental. Additional we measure an angle with the spirit levels and calculate the hight. So there can be large differences between spirit level measurements and laser based or granite stone based measurements.

The advantage of our ProLine system is here that we measure both axis simultaneously and absolute!

Sketch of Straighness Measurements

Straightness according to the Norm DIN ISO 1101 is defined as follows: The tolerance zone is defined by two parallel lines drawn above and below the best fit of the measured data. The lines are separated by the tolerance (t). Naturally, a line is defined by the shortest distance between two points. If we have 20 points then the “best fit” line is the line through these points where the sum of the errors is a minimum. The tolerance lines are drawn parallel to this best fit line.

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.

Laserquelle T250

The best method for you depends on the following:

  • What exactly are we measuring? (Dimensions, accessibility, environment)
  • What is the required spec? (tilt, roll, line deviation, waviness etc )
  • What provisions (adjustment screws) are available to correct the deviations?
  • Who is doing the work and how much time does he/she have?
  • What kind of a report is required? (For whom?)
  • What’s your budget?