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Ultra Autocollimator – Simultaneous 2-Axis Measurement

Thursday, August 20, 2015

High accuracy, wide measurement range and built-in analysis software make the new ultra autocollimator ideal for machine tool slideway straightness measurements

Application: parallelism, 2-axis straightness, squareness 𠊊nd twist measurement of machine tool slides

  • Simultaneous two axis straightness measurements
  • Typically 5 minutes to measure a 10 metre slideway
  • 1800 measuring range with 0.2 seconds accuracy
  • Analysis software preloaded and ready to use

Among the large number of applications possible with the Taylor Hobson ULTRA Dual Axis Autocollimator, the most common is the simultaneous two axis straightness measurement of machine tool slideways.

Measurements are automatically collected for both X and Y directions simultaneously at each measuring position along the slideway. Typically a ten metre slide can be checked in approximately five minutes - a considerable reduction in the amount of time taken compared with more conventional methods. With the addition of the Talyvel Electronic Level, twist or roll can also be measured – and with an Optical Square, parallelism and squareness can be set and checked.

The ULTRA Autocollimator has a large measuring range and comes with a laser sighting aid to assist initial setting. Instrument control is via a notepad (PC) incorporating a large visual display readable from several metres. The notepad also has Taylor Hobson applications software pre-loaded at no extra cost, for computerised measurement of straightness, parallelism, squareness and twist with printouts of measured results.

Measuring procedure:

Due to the high sensitivity of the autocollimator and the high accuracy with which measurements are made, the autocollimator is usually mounted directly onto the machine slideway. This is best accomplished using a bracket, rigidly bolted to the end of the slide. If this is not possible the autocollimator can be placed directly on the slide (although this method will occupy approximately 300mm of the slideway, which hence cannot be measured).

When small slideways are to be measured and no attachment holes are available, the autocollimator can be mounted on a separate stand or tripod, taking care that no relative movement occurs between the autocollimator and the slideway.

The reflector to be used in conjunction with the autocollimator is mounted onto a carriage, specifically designed for dual axis measurement.

The steps must be of equal distance therefore the number of steps to be taken will depend on the base length of the reflector carriage and the length of the slideway. When slideways of different lengths are to be measured, an adjustable length base can be used.

Once the step length has been established it is good practice to mark the slideway accordingly.

The reflector carriage is now moved along the slideway in equidistant steps. Any out-of-straightness in either of the two surfaces (side and top of the slide) will cause the carriage to change angle with respect to the autocollimator, and it is these changes which are measured and computed automatically to determine the error in straightness.

The built-in software is intuitive to use and available in a range of languages, enabling inexperienced personnel to carry out measurements. Each stage of measurement is prompted by the software, which also indicates when any error of operation has occurred.

The out of straightness is the maximum peak to valley and can be calculated using either the ends zero, least squares or minimum zone method (selectable within the software).

In addition, the slope of the slideway with respect to the autocollimator line of sight is displayed as a gradient (ie mm per m or 0.001 in per inch). This is derived from a least squares mean line calculated from the data. This slope can be particularly valuable when measuring parallelism and squareness between slideways.

The results display also offers the operator the option to graphically display plots of dual axis measurement.

A Talyvel Electronic Level is used in conjunction with the ULTRA Autocollimator to measure the twist or roll of the slideway and an optical square is used for parallelism and squareness checks.

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