Minimize the idle time of the spindle


Eliminating unnecessary interruptions to production dir […]

Eliminating unnecessary interruptions to production directly CNC Tool Holder affects machining cycle times, costs to complete each part from start-to-finish and, by extension, the ability to bid competitively. Getting more hours a day out of your spindle is key to optimizing this equation.A study by machine tool builder Makino, Mason, Ohio, provided statistics about the impact of machining capacity idle time. The most notable revelation in this study was that the average vertical machining center, even when it’s in cycle, isn’t cutting 30% of the time. Even more revealing is that the real cutting, that other 70%, is likely much slower than what’s realistically achievable with today’s technology.

According to Makino, if you factor in all the other time your machine isn’t running, such as setup, workpiece load/unload, cutting tool maintenance and clearing chips, and the typical VMC is working  of the time. Multiply all those wasted hours by your shop rate, and that’s what non-cutting time is costing you day after day, year after year.An innovator of CNC mill spindle optimization products, Fairport Harbor, Ohio-based JM Performance Products Inc.  takes a look at the goal of increasing cutting time–from the angle of toolholder expansion at the spindle.Industry wide, a major culprit of the majority of V-flange tooling issues machinists battle with on a daily basis is toolholder expansion.

A myriad of production issues arise from this factor including: vibration and chatter, increased runout, poor finishes, tolerances, repeatability, increased machine and spindle wear and tear, and increased setup times. The collective impact of these issues is directly related to the number of parts that can be produced efficiently in a given cycle.The average amount of toolholder expansion industry wide is 0.00035", or 1/7th the width of a human hair. This nominal amount of expansion is enough to inhibit complete toolholder taper-to-spindle contact and reduce tool life significantly. In essence, the lack of contact is equivalent to the motion of a bell clapper in that the holder moves randomly within the spindle.

This occurs because once the small end expands, the point of full engagement (or contact) between the toolholder and the spindle reverses from the gage line to the small end. The bottom line is that the toolholder and tool are loose in the spindle.Using V-flange tooling when CNC milling is inherently flawed by design. Notably, toolholder expansion occurs at the small end of the holder when a standard retention knob is installed. Extensive testing has proven that a standard retention knob has the potential to expand the small end of the toolholder when it is installed with as little as  of torque–with a CAT 40 toolholder beginning to expand at 15 ft./lbs. Of note, the extent of this expansion is variable, depending on the holder, the retention knob and the installation practice.