Drive Diagnostics and Your Maintenance Tasks

I want to open our New Year by pointing out that I will be addressing topics of interest to three groups during 2011 – namely, programmers, operators and maintenance personnel. If you have any comments or questions about your particular interaction with CNC, I would be happy to answer them, or make them the topic for future columns.

CNC drive and motor diagnostics have always been maintenance nightmares. Traditionally, the set-up time for a routine check-up alone was a production slowdown that often necessitated changing machines to run certain jobs and resulted in all the attendant problems that often causes.

In the new CNC operating systems on the market today, drive diagnostics have been simplified to a visual set-up on a single screen, with a menu of “stoplight” graphics and easy check-mark validation of axis parameters.

That’s not all. The feedback and harmonic problems often encountered in the past with older systems can now be more easily identified because of the advancements in electronic nameplating in the quick-connect devices and external encoders on the motor assemblies. Does anyone remember how long it once took to refit and reprogram an integral encoder?

Think about having all of the rpm, temperature, pressure, speed, position, setpoint, absolute value and overrides preconfigured and available immediately after a quick connection of the motor online . . . and all of it on a single screen. It doesn’t stop there. Because the system features auto-tuning, there is no more hit-or-miss trial and error procedure in the set-up or status checking.

The process becomes nearly goof-proof as it allows a perfectly consistent, tight and dynamic alignment of the communication hardware, resulting in accurate data appearing onscreen immediately. This is a troubleshooter’s dream scenario.

Maintenance personnel using such new drive diagnostics have often reported the reduction in procedures from a full day down to twenty minutes. No kidding! Even the more elaborate spindle tests for vibration, temperature, stiffness, proper timing, sequentials, harmonics and other factors can now be accomplished in an hour or less, with the proper training.

Even when a motor must be changed out, the set-up and test time can take less than the installation time.

This type of maintenance procedure can be accomplished on a machine tool, regardless of the axes of motion onboard. If your machines are PC-based – and this applies to many types of machine tools, including metalforming equipment and other non-chip cutting systems – the same drive diagnostics capabilities can be found on the market today.

New absolute encoders can return absolute position values with the machine in motion and can be parameterized for a variety of applications. All values are recognized for a motor and presets are immediately interpreted on the CNC.

Next month we’ll address the reporting procedure and how to save or transmit reports in ways you may have never thought possible. Trust me, they are possible and can be done in half the time it takes you to do them right now.