Tormach PCNC 440 - Gib Adjustment

Chapter 9
164
UM10372_PCNC440_Manual_0221A
MAiNTENANCE
9.3.3 Gib Adjustment
9.3.3.1 Overview
PCNC mills use dovetail-
gibbed ways to guide the
X-, Y-, and Z-axis moon.
Over me, the dovetail
ways and gibs wear from
sliding fricon and it may be
necessary to ghten the gib
to reduce axis backlash. To
compensate for wear, the
design of a dovetail-gibbed
way allows for the posion
of the gib to be adjusted
to maintain an appropriate
sliding clearance.
A properly adjusted gib minimizes lost moon by balancing convenonal backlash and sliding
fricon. A gib that is too loose results in excessive convenonal backlash; a gib that is too ght
cannot adequately support an oil lm resulng in excessive sliding fricon.
The posion of the tapered gib plate is controlled by two screws on either end of the gib that
capture the posion of the gib with respect to the saddle. These screws can be adjusted (as a pair)
to tune the ghtness and sliding fricon of the dovetail way for each axis. The Y-axis gib mechanical
detail is shown in Figure 9.2; both the X- and Z-axis have similar detail.
9.3.3.2 Adjustment Procedure
The gib ghtening adjustment procedure for each linear axis is detailed in the table below.
Gib Plate Tighten
1
Notes
X-axis Le screw clockwise/right screw counterclockwise No cover removal required
Y-axis Front screw clockwise/rear screw counterclockwise
Remove front and rear way covers
to access gib screws
Z-axis Upper screw clockwise/lower screw counterclockwise
Support spindle head with wooden
block on table
1
To loosen, reverse rotaon direcon indicated in table.
NOTE: It is dicult to assess the correct clearance for the gib, as a very small adjustment can create a
dramac change in sliding fricon.
Figure 9.2
Gib for X slide
Counterclockwise on
screw loosens slide
Clockwise on screw
tightens slide
Thick end of gib
Tapered gib