As parts get more and more complex, you will see part tolerances get tighter than ever. We’ve all seen the (+ -) .0001” size on a turn or bore, but what about concentricity? Quite often, it’s a call out that’s just plain missed. Catching the spec is one thing, meeting it is another.
Here’s some helpful ideas.
First of all, concentricity starts with “round” features. Remember, you cannot check for concentricity between two journals; maybe the spec is .0003” if one of the journals has .0004” run out in itself.
Second, boring the spindle tooling while positioned in the spindle, especially for the 2nd chucking, is a must. If you’re talking .001”, probably not needed, but if the print calls for .0004” concentricity or less, bore the spindle tooling and your success rate goes up.
Third, for the most demanding concentricity specifications, machine all the critical features together. This trick is pretty well understood in this industry but be careful, it’s not a 100% guarantee. There are a lot of factors that affect concentricity, Example: Balance, tool pressure, excessive part clamping pressures, to name a few….…
It’s having the latest technological components designed into and built into the machine. This way the entire structure becomes a single harmonious entity. Plus including other factors that few builders offer, such as a collet-ready spindle for direct use of a collet (no spindle adaptation chuck), allows the workpiece to be gripped and machined as close to the spindle bearings as possible. In fact, gripping a part with a collet is the preferred method for high-precision machining. This ability further enhances the tolerance and surface finish capability and allows effective turning of hardened metals, further reducing or eliminating costly grinding operations. A high-performance machine also has features such as linear scales, unique ESA precision tooling and top plate system, Harcrete polymer composite filled in strategic areas of the cast iron base, high grade linear guides, ball screws and guide trucks. Plus the collet-ready spindle is driven by a perfectly matched motor and drive system for optimum speed and torque. High-pressure and through-spindle coolant capabilities help during the machining process to keep chips flowing away from the machining area, while maintaining proper cutting temperature.
A machine’s design should also included the latest software design platform and FEA (finite element analysis) techniques to accurately depict the structural deflection, stress levels, thermal response and vibration response of the assembled components and the assembled machine. Extreme-case loadings should also be used to verify adverse machining conditions. Every machine produced receives laser calibration to the X and Z-axis to ensure positioning accuracy and straightness. Accuracy certification is included as assurance of machine accuracy. Size repeatability, surface finish quality and thermal stability are a hallmark for Hardinge RS-Series turning centers which truly is a High-Performance turning center.
Existing machines and toolholders can be used in BIG-PLUS Spindle System machines and toolholders. When a new machine with BIG-PLUS Spindle System is introduced, existing toolholders can be used. It is not necessary to purchase all new toolholders. Therefore, it is possible to save cost to introduce simultaneous fit toolholders.
Although other simultaneous fit systems requires exclusive new accessories, BIG-PLUS Spindle System uses existing accessories such as a presetter and a toolholder fixture as it is based on a conventional steep taper shank. Therefore, no extra cost is needed.
Simultaneous fit of taper and face prevents vibration from heavy or high speed cutting and discoloration on taper (called fretting corrosion).
At high speed rotation, a machine spindle expands due to centrifugal force and heat. Then, a toolholder is pulled into the machine spindle. On the contrary, BIG-PLUS toolholder is not pulled in even at high speed rotation as the flange face fits the machine spindle nose. Then, variation of projection length in Z axis is minimized. (variation due to heat exists.)
Rigidity is enhanced by simultaneous fit of taper and face. There are excellent effects on heavy or high speed cutting, deep or large dia. boring and especially using a cutting tool with long projection length.
Since BIG-PLUS toolholder is rigidly supported on taper and face, higher repeatability at ATC can be achieved. This brings about many good effects such as higher T.I.R and stable precision of finish boring.
BIG-PLUS Spindle System is strictly controlled in dimensions of a machine spindle as well as a toolholder in order to guarantee simultaneous fit between taper and face, the dimensions are measured by a exclusive high tolerance gage and measuring devices. Full interchangeability exists between all BIG-PLUS machine spindles and BIG-PLUS toolholders.
Is your chuck-style cnc lathe not giving you the results you need? Ask about the Hardinge FlexC™ Collet System. It weighs less than a chuck so that you can take advantage faster feeds and speeds. It provides part length control and it has faster changeover time with improved concentricity. Hardened steel or emergency collet heads provide chucking diameters up to 2-9/16″
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