Never Waste Another Minute Due to CNC Machine Inaccuracy

According to the American Society of Mechanical Engineers (ASME) there are nominally 35 measurements which need to be taken to fully measure and qualify a machine. The exact number of measurements depend on the machine, variables such as the number of axes, setup and positioning of the axes, and performance abilities of the machine. All these effect what measurements should be taken. While there are many products on the market which can perform any number of these measurements, Automated Precision is the only company that offers a solution for every measurement, and has also optimized tools for making the measurement process as easy and quick as possible.

Baseline Measurements

Vibrations of the machine spindle as a result of environmental factors.

The first set of measurements to take are the baseline
measurements. These three measurements describe the machine tools relationship to the environment it is working in. this set of measurements are environmental temperature variations,
vibrations of the machine shop, and position deviations under
force. The XD LaserTM provides a solution for hysteresis measurements, while the Spindle Analyzer offers the ability to measure machine vibrations as well as temperature variations, which completes the baseline measurements.

Geometric Error

MTH_2The next 13 recommended measurements fully describe a machines geometry and accuracy. This is where the numbers become less exact, not every machine has parallelism to measure, while others need parallelism and can have up to 6 squareness measurements to perform (including axes of rotation and measuring the Z and W axes). The XD is the ideal solution for many of these measurements. Not only does it take 6 measurements at once per linear axis, the squareness and parallelism measurements become much easier by taking advantage of the XD’s ability of extrapolating a linear measurement in these calculations. Our products will also provide a full analysis
of the data based on the ASME as well as a number of other standards, and will
also create a compensation table.

The 21 error of a 3 axis machine are Roll, Pitch, Yaw, X, Y, and Z for each axis, plus 3 squareness errors.

The Swivelcheck is a unique solution offered by API for rotary axis evaluation. There is no other product on the market which can so easily measure the positioning accuracy of an A or B axis. For these measurements, the Swivelcheck is used as a standalone product, and there are no optics involved. For the C axis, the Swivelcheck is paired with an XD to complete the measurement process.

Also measured are backlash, periodic error, and repeatability, which is calculated by the software, and requires no extra setup or measurements, when using API products.


Spindle Health

Position error due to bore error can be captured with a Spindle Analyzer.

The next set of 5 or 6 measurements are performed with the Spindle Analyzer. Spindle health is often over looked by machine tool users, which is unfortunate. The most often replaced part of the machine is the spindle, which is not a surprise considering it is also the part of the machine which is under the most stress. No other machine tool health provider offers a spindle analyzing device. The spindle analyzer is used in five measurements, with the spindle off, in feed hold, emergency stop, then in stability mode, then used while turning the machine manually. These readings are then compared to analyze what components of your spindle may need to be replaced, if any.

Thermal Stability

MTH_5The next three measurements are of thermal stability. A machine will deform due to temperature changes, and a machine heats up while it is running. The spindle, while machining, will run at several thousand, often tens of thousands of RPM. This creates an intense amount of heat during the machining process. The Spindle Analyzer is the optimal tool for measuring spindle error motion as a function of temperature. Linear and rotary axes also heat up as they are used, but not to as large of a degree. The deviations of these axes can be measured with an XD and Swivelcheck, respectively.


The last set of measurements are performance measurements, there are about seven. Most of these measurements revolve around the spindle feed rate, and are measured with the XD. The measurements include measuring the largest step size, fastest accurate feed rate, velocity and acceleration measurements, and diagonal measurements. The Swivelcheck can be used to evaluate the rotary feed rate and minimum block execution. The Ballbar is used to evaluate servo error including servo mismatch, stick-slip, vibrations, and servo lag.

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