Spindles: Center, set, go

Centering spindles no longer requires dismounting guide bushings, collets, or tools if machine operators use Wibemo SA’s Mowidec-TT spindle centering system. Designed to reduce setup time and save on tooling – especially for single-spindle Swiss-type automatic lathes – the system also eases use on machining centers, multi-spindle rotary transfers machines, milling machine, and multi-spindle lathes.

“The spindle centering process is done without any complicated equipment or operator training. It’s a very intuitive system that allows users to start centering as soon as it’s connected,” says Emil Rustempasic, owner of Phoenix, Arizona-based Toolnet Int’l and the U.S. distributor of the Mowidec-TT. “The system is designed to help companies get the most out of their machines while saving tooling costs because spindles are aligned and running correctly; the system improves the life of cutting tools, delivers increased precision in machining, and fits easily into the machine setup process.”

The inspiration behind the system’s development is that it’s not a measuring device, it’s a system that makes a comparison between points, Rustempasic explains. Depending on the distance to the probe, the diameter of the cutting tool, and the sensor used, measurements can vary. The Mowidec-TT system considers all these parameters and provides comparative measurement of several points to reach optimal alignment.

Users receive a case containing the digital readout display unit, sensor, cables, and a set of color-coded rings for each diameter. Once the power supply is connected, the electronic proximity sensor connects via a USB port. Next, the operator attaches the display unit – provided with magnetic pads on the back – to the machine’s housing. Once the adapter ring is fitted to the guide bushing, the alignment process can start. Readout is available in inches or millimeters.

Set up, ready to run

Operators use the machine’s control to bring the tool into working position by moving the spindle to its theoretical reference value. Once in position, the operator adjusts the probe so it’s within a few tenths of a millimeter from the tool body.

The display unit starts displaying values, indicating that the probe is now in the workspace. The operator then positions the probe on its vertical axis, parallel to that of the tool holder, and resets the readout to zero. Once reset, the guide bushing holder is manually rotated by 180°, allowing the probe to compare the distance between the top and bottom of the tool with respect to the exact center of the machine guide bushing. This value shown is twice the real centering error of the tool on its vertical axis, so it must be corrected by half using the machine’s control. Once corrected, operators check that this value is the same at the beginning and end of the 180° rotation.

The vertical axis has now been centered so the operator moves the probe 90° to check the centering of the horizontal axis. The value displayed is now the real error value. Using this value, the operation now repositions along the horizontal axis – either manually or with the machine’s control.

Wrapping up the alignment process, the operator does a final check to make sure the sensing device does not vary by more than the minimum along the probe’s 180° travel.

Rustempasic says, “Users should note that when the horizontal axis is set using a mechanical system, the vertical axis may be affected and should be corrected again following the same steps.”

A similar process is used to align in counter-headstock and counter-operation tool centering. First, the operator will assemble the corresponding ring on the counter-headstock, making sure a few millimeters of material is visible through the guide bushing. Once the counter-headstock is in position, the probe is adjusted to within a few tenths of a millimeter from the material and the display unit begins showing values. Next, the counter-headstock spindle is manually rotated 180° so the probe can compare the distance between the top and bottom of the material with respect to the exact center of the machine guide bushing. This value is twice the real centering error of the counter-headstock on its vertical axis, so it must be corrected by half. Then, the operator will check that this value is the same at the beginning and end of the 180° rotation.

Now that the vertical axis is centered, the probe needs moved by 90° to check the horizontal axis.

This value displayed is now the real error value. Using this, reposition along the horizontal axis and to finish, check that the sensing device does not vary by more than the minimum along the probe’s 180° travel. Once the counter-headstock is centered, with respect to the guide bushing, move it to the counter-operation position and repeat the centering steps. Note, that for the vertical axis it’s the counter-headstock axis that is moved and for the horizontal axis, in most cases, it’s a mechanical axis.

“By following the above steps, users get an accurate reading. It’s easy to install and set up, fits positions impossible for traditional indicators, is quick to transfer from main- to sub-spindle, and checks for error and runout,” Rustempasic explains.

Continuing advancements

While the system was originally designed for use on Swiss machines, expansion of the line with the Mowi-TS measuring head allows it to fit on any machine’s tool holder and collet chuck. Built with the smallest size to reduce required space, it is a solution for center front toolholders as it can be adjusted into the guide bushing, areas where there’s not enough space to install a lever-type dial test indicator. The system gives high accuracy readouts without any special tooling or adaption required.

Toolnet Int’l
http://toolnetinternational.com/

About the author: Elizabeth Engler Modic is editor of Today’s Medical Developments and can be reached at 216.393.0264 or emodic@gie.net.