A Reminder About Parameters

As you know, many CNC manufacturers design their controls to be used on a wide variety of machines. One machining center control model, for example, can be used by any number of machine tool builders for all machining centers in their product line.

Control parameters are used to handle the differences from one CNC machine to another. Maximum spindle speed, rapid rate, pitch error compensation, communications protocol and backlash compensation are among the countless functions specified by parameters. Note that the parameters from one machine to another will be different, even for otherwise identical CNC machines. As the CNC user, it is imperative that you keep a backup copy of your parameters in case of control failure. Do not depend on the machine tool builder, control manufacturer, distributor, importer or anyone else for this extremely important task.

If the control fails and a service person must repair it, it is not uncommon for all information to be lost including CNC programs, offset settings and parameters. Once the machine is repaired, the parameters must be reloaded. One control manufacturer that has claimed that they have downtime of less than five percent says that the bulk of this time is spent trying to get the machine parameters back to their former state because the CNC user has not kept a backup copy.

While most machine tool builders do supply the parameter settings with the machine's documentation, remember that these are factory settings and may not be helpful if your machine goes down. Most CNC users must change parameters from their original setting on a relatively regular basis. Functions such as communications protocol, backlash compensation, how canned cycles behave, initialized states, and even pitch error compensation are among the many functions a CNC user will commonly change. Of course, whenever parameters are changed, you must remember to update your backup copy of parameters.

Admittedly, this has been the topic for a previous CNC Tech Talk column. But judging by the number of attendees in my CNC seminars who have never backed up their parameters, there are many CNC users that have not been exposed to the importance of doing so.

With most controls, the parameters can be transferred via your distributed numerical control (DNC) system in the same manner that CNC programs are transferred. Check your control manufacturer's documentation to find out how to execute the procedure. If you don't have a DNC system, write down all of your parameter settings. Though this may sound tedious and time consuming, it is time well spent when you consider the downtime it will save should you ever have a control failure.

Important note: Most CNC machines have a programmable controller (commonly referred to as the PC ladder) that has its own set of parameters. These parameters are not backed up with the control parameters, yet can also cause headaches should they be dumped during machine repair. Unfortunately, the only way to back up these parameters with many controls is to manually record them. But again, this is time well spent. Contact your machine tool builder to determine what volatile data must be backed up and get their recommendations for how this should be done.