A comprehensive tool-wear/tool-life performance model in the ...

884
ARTICLE IN PRESS
P.W. Marksberry, I.S. Jawahir / International Journal of Machine Tools & Manufacture 48 (2008) 878–886
ASTMD 5619 Tapping Torque (N-cm)
550
500
450
400
350
300
250
Straight Oil
5.55-mm Reamed Hole
(Lubricity)
5.48-mm Reamed Hole
(Cooling)
Soluble Oil Semisynthetic
Oil
Synthetic Oil
MWF Type
Fig. 4. ASTM tapping torque results varying MWF type and reamed
holes.
6. Discussion
Tool-life/tool-wear modeling using mist spray applications
can be successfully and more accurately predicted
than using dry machining equations for NDM. Fig. 5
shows that predicted tool-wear values mostly fall within
actual 95% machining confidence intervals for actual
results while varying MWF type and rate. Table 6 indicates
that significant improvements in tool-wear (over 400%)
can be achieved using NDM compared to dry machining.
This study emphasis that models developed for dry
machining conditions cannot accurately predict NDM
performance. Equation accuracy over a broad range of
MWFs, nozzle position(s) and MWF volumetric flow rates
was observed to be less than 10% on the average.
Linearization of MWF rate and type effect factors
simplified model calculations, yet provided to be fairly
accurate for shop-floor use. Modification of the tool
coating effect factor allowed the Taylor equation to be
extended without deteriorating chip groove or tool coating
factor accuracy.
Table 6
MWF rate and type effect factors for MWFs primary used for lubrication
Dominant tool
wear pattern
Nozzle position
MWF type
MWF rate
( 10 4 ) M ZX ( 10 4 ) M ZY
effect factor effect factor
W BL R (rake face) 25.6 2.7
F (flank face) 1.3 6.2
C (chip) 5.1 18.9
Table 7
MWF rate and type effect factors for MWFs primary used for cooling
Dominant tool
wear pattern
Nozzle position
MWF type
MWF rate
( 10 4 ), M ZX ( 10 4 ), M ZY
effect factor effect factor
W BL R (rake face) 23.4 10.4
F (flank face) 6.6 7.5
C (chip) 5.7 8.3
7. Conclusion
It has been observed that the selection of ‘‘mist spray’’
delivery parameters represents an essential element in
minimizing tool-wear/tool-life. The following is a summary
of findings from the present work:
A new tool-wear/tool-life relationship has been developed
for NDM with coated grooved tools by extending
the Taylor-type equation to include mist spray
delivery parameters by modifying the tool coating effect
factor.
More accurate and consistent estimates of tool-wear are
made by using the new predictive model for NDM
compared to dry machining models.
The G mapping function allows users of the empiricalbased
model to customize the equation to consider a
wide variety of mist-spray delivery parameters, including
nozzle position, MWF volumetric flow rate and
MWF type.
Table 8
MWF rate and type effect factors for MWFs primary used for cooling
MWF
type
New tool coating for mist
factor (n mist )
NDM total effect factor
(NDM)
Predicted tool-wear
W BL (mm)
Actual test tool-wear
W BL (mm)
Error
%
Improvement % over dry
machining
Straight 0.078 0.140 0.88 0.91 3.30 102
Soluble 0.060 0.135 0.77 0.74 4.05 125
Semisynthetic
0.055 0.126 0.55 0.59 6.78 157
Synthetic 0.065 0.138 0.22 0.23 4.35 402
Dominant tool-wear pattern: W BL ; nozzle position: rake face; MWF volumetric flow rate: 180 ml/h; chip-groove effect factor (W g ): 0.89; tool coating effect
factor (n c ): 0.56; empirical constants: k ¼ 0.32, m ¼ 1 for turning, n 1 ¼ 0.230, n 2 ¼ 0.642.