Editor's CommentaryFrom the monthly column: CNC Tech Talk
Companies strive to maintain compatibility and consistency regarding the methods they use throughout their manufacturing environments. Consistent procedures minimize exceptions and provide one method of accomplishing a task that will work in all cases. This, in turn, minimizes potential for mistakes because employees don’t have to remember or deal with multiple exceptions. Unfortunately, sometimes it can be difficult to balance compatibility and consistency with achieving the most efficient ways of doing things in the majority of—let alone all—situations.
Consider, for example, this somewhat far-fetched example that stresses the point:
You know that toolholders require pull studs to secure in the spindle and possibly the automatic toolchanger magazine. The machine will clamp on to the pull stud, keeping the tool locked in the spindle/magazine. You probably also know that pull studs vary among machine tool builders. If you have machines made by different builders, and if toolholders are shared among machines, your employees must constantly be concerned with having the appropriate pull stud on the toolholder before it is loaded into a machine. (We recommend color-coding your pull studs to minimize the potential for mistakes.) However, if you limit your machine purchases to one machine tool builder, you can maintain compatibility among the pull studs used on your machines, eliminating the potential for mistakes and the related problems.
Hopefully you agree that it would be silly to base your machining center purchase decisions solely on ensuring compatibility of pull studs. You must, of course, buy machines that work best for your company. While maintaining consistency is important, it should be but one of the many important criteria you use to make your buying decision.
CNC programming and machine usage methods are riddled with these kind of choices. Should you maintain consistency or utilize a unique feature that provides a special benefit? Sometimes it boils down more to personal choice than to any clear advantage of one method over another. In these cases, consistency should easily win out.
Consider the two ways of using cutter radius compensation. With one method, the programmer specifies the cutter centerline path, and the setup person enters the related offset value as the deviation from the planned cutter size to the actual cutter size being used. With the other method, the programmer specifies the work surface path, and the setup person enters the cutter’s radius (or diameter on some machines) into the offset register.
While programmers may disagree with regard to which method is better, the benefits related to consistency will outweigh the minimal benefit one method has over the other; so pick one method and use it for all of your machines.
In other cases, it makes more sense to take advantage of a unique (possibly new) feature on one or just a few of your machines, even though it means that new methods will be required. Machine tool builders and control manufacturers are constantly improving, and coming up with features that make their machines better. The difficulty lies in determining whether the feature provides enough benefits to forego consistency.
A few classic examples include:
• Using fixture offsets (machining centers) and geometry offsets (turning centers) for program zero assignment, over assigning program zero in the program with G92 (machining centers) and G50 (turning centers).
• Using decimal-point programming over fixed format.
• Designating the size of circular arcs with an “R” word as opposed to using directional vectors.
• Using spindle probes (machining centers) and tool touch-off probes (turning centers) to assign program zero instead of manually measuring and entering program zero values.
In all of these cases, there are times when the advantages of using a (new) unique feature outweigh the benefits of maintaining consistency among (usually older) machines.
As stated, it can be difficult to strike a good balance. You have to decide whether it is more important to maintain consistency or to take advantage of newer or better features. Like machine tool builders and control manufacturers, CNC users must also strive to get better. So you must be careful and make wise decisions. You must avoid the potential of becoming stagnant by maintaining older, lesser efficient methods just for the sake of consistency. On the other hand, you must not get caught up in utilizing all of the latest and greatest new things just because they are possible.
Let your decisions be benefit-driven. New and unique features must provide clear and measurable benefits in order to win out over maintaining consistent methods.blog comments powered by Disqus