Burr Reduction in Drilling Titanium using Drills with Peripheral Slits

Abstract

Drilling of titanium alloy results in considerable burrs at the exit surface of a hole. The burrs deteriorate quality of hole surfaces and can cause misalignment during assembly. Therefore, burr minimization while drilling is necessary. In this study, innovative chamfered drills with slits have been developed to reduce the burr height and thrust forces. Dry drilling experiments were conducted using chamfered drills without slits and with slits (CWS) having four different point angles. Drilling performance was measured in terms of burr height, thrust forces, and chips morphology. A finite element method-based model was developed to simulate drilling of Ti6Al4V alloy using the drills without and with slits. The results show that the maximum burr height for CWS drills was reduced by 48.5% as compared to the conventional drills. The thrust forces were reduced by 5.5% and were in a fair agreement with the simulation results. For most of the cases, the simulated forces were within 10% of their experimental counterparts.

Appendix

With the regression analysis, the obtained response surfaces models for the burr height using CWOS and CWS at four different drill point angle are given in Appendix (Eqs. 8–15).

$$ h_{{{\text{\_wos}}}} = 475.41 - \left( {4412.25*f} \right) + \left( {15943.75*f^{2} } \right)\quad {\text{for}}\;\theta _{1} = 120 $$

(8)

$$ h_{{{\text{\_wos}}}} = 1101.14 - \left( {8702.75*f} \right) + \left( {15943.75*f^{2} } \right)\quad {\text{for}}\;\theta _{2} = 130 $$

(9)

$$ h_{{{\text{\_wos}}}} = 1011.26 - \left( {9754.5*f} \right) + \left( {15943.75*f^{2} } \right)\quad {\text{for}}\;\theta _{3} = 140 $$

(10)

$$ h_{{{\text{\_wos}}}} = 509.65 - \left( {6396.16*f} \right) + \left( {15943.75*f^{2} } \right)\quad {\text{for}}\;\theta _{4} = 150 $$

(11)

$$ h_{{{\text{\_ws}}}} = 449.23 - \left( {4459.8*f} \right) + \left( {15955*f^{2} } \right)\quad {\text{for}}\;\theta _{1} = 120 $$

(12)

$$ h_{{{\text{\_ws}}}} = 952.16 - \left( {7582.55*f} \right) + \left( {15955*f^{2} } \right)\quad {\text{for}}\;\theta _{2} = 130 $$

(13)

$$ h_{{{\text{\_ws}}}} = 895.86 - \left( {8780.55*f} \right) + \left( {15955*f^{2} } \right)\quad {\text{for}}\;\theta _{3} = 140 $$

(14)

$$ h_{{{\text{\_ws}}}} = 435.90 - \left( {5622.55*f} \right) + \left( {15955*f^{2} } \right)\quad {\text{for}}\;\theta _{4} = 150 $$

(15)

where h_{_wos} and h_{_ws} represent the burr height for CWOS and CWS, respectively, and f denotes the feed.

With the regression analysis, the obtained response surfaces models for the thrust force using CWOS and CWS at four different drill point angle are given in Appendix (Eqs. 16–23).

$$ F_{{{\text{t\_wos}}}} = 59.50 + \left( {4116.85*f} \right) - \left( {14297.5*f^{2} } \right)\quad {\text{for}}\;\theta _{1} = 120 $$

(16)

$$ F_{{{\text{t\_wos}}}} = 99.39 + \left( {3576.85*f} \right) - \left( {14297.5*f^{2} } \right)\quad {\text{for}}\;\theta _{2} = 130 $$

(17)

$$ F_{{{\text{t\_wos}}}} = 77.20 + \left( {4015.8*f} \right) - \left( {14297.5*f^{2} } \right)\quad {\text{for}}\;\theta _{3} = 140 $$

(18)

$$ F_{{{\text{t\_wos}}}} = 63.51 + \left( {4558.6*f} \right) - \left( {14297.5*f^{2} } \right)\quad {\text{for}}\;\theta _{4} = 150 $$

(19)

$$ F_{{{\text{t\_ws}}}} = 13.74 + \left( {4830.05*f} \right) - \left( {18117.5*f^{2} } \right)\quad {\text{for}}\;\theta _{1} = 120 $$

(20)

$$ F_{{{\text{t\_ws}}}} = 56.35 + \left( {4244.55*f} \right) - \left( {18117.5*f^{2} } \right)\quad {\text{for}}\;\theta _{2} = 130 $$

(21)

$$ F_{{{\text{t\_ws}}}} = 85.55 + \left( {4018.8*f} \right){\mkern 1mu} - \left( {18117.5*f^{2} } \right)\quad {\text{for}}\;\theta _{3} = 140 $$

(22)

$$ F_{{{\text{t\_ws}}}} = 29.29 + \left( {5072.3*f} \right){\mkern 1mu} - \left( {1817.5*f^{2} } \right)\quad {\text{for}}\;\theta _{4} = 150 $$

(23)

where $F_{{{\text{t\_wos}}}}$ and $F_{{{\text{t\_ws}}}}$ represent the thrust force for CWOS and CWS, respectively, and f denotes the feed (Tables 11, 12).

Table 11 ANOVA for the thrust force of chamfered drill without slits (CWOS)

Table 12 ANOVA for the thrust force of chamfered drill with slits (CWS)