Chapter 9
162
UM10349_PCNC1100_Manual_0916A
Maintenance
9.3 Advanced Maintenance
9.3.1 Overview
Each PCNC is tuned at the factory to meet or exceed certain precision metrics. These metrics are
indicated on the Cercate of Inspecon that is included with each mill, along with the actual
values measured for each metric as part of Tormach’s Quality Assurance program. The following
advanced maintenance procedures may become necessary over the ownership lifeme to maintain
the original factory precision:
• Gib adjustment
• Angular contact bearing preload adjustment
• Geometry adjustment (tram)
These adjustments are generally used to address component wear-in over me, but may also be
needed to correct misalignment resulng from misuse, a hard crash of the system, or when some
components are removed or replaced due to damage. The frequency of these procedures depends
on both how the mill is used and how oen.
The adjustments in this secon should not be considered lightly as a wrong adjustment can adversely
aect mill precision. Before making any of the adjustments in this secon ask:
• Why am I making this adjustment?
• How will I measure the eect of this adjustment?
• What unintended consequences may result from this adjustment?
If you do decide to make an adjustment, do not assume where the error is from. The error could
be aributed to a specic problem, or from the combined eect of several problems. Mistakenly
making the wrong adjustment can make maers worse. As a praccal example, if the Z-axis gib is
too loose, it will cause the spindle head to lt slightly downwards, toward the column. It would
be fairly easy to incorrectly assume that the issue is with the column and base connecon (oen
referred to as tram), and make an adjustment by inserng shims between the column and base.
Instead of correcng the real issue, this adjustment causes the column to slant back to correct for
the head leaning down. Now, the mill is running in a slight parallelogram in addion to a loose head.
9.3.2 Definitions
The following denions are important to the advanced maintenance discussion.
Lost moon: the dierence between commanded moon and observed moon. This is somemes
referred to as apparent backlash. There are a number of components of lost moon, including
convenonal backlash, bearing compressibility, sliding fricon, and thermal expansion.
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