Design Aspects of Generating a Long Life of AISI 316 Stainless Steel with the Modification of Tool Geometry:
Present Status
Pratik Oza Dr. J.P. Mehta D. D. Kundaliya
Department of Mechanical Engineering Professor, Department of Mechanical Engineering
Assistant professor, Department of Mechanical Engineering V.V.P. Engineering College, Rajkot V.V.P. Engineering College, Rajkot V.V.P. Engineering College, Rajkot
Gujarat Technological University Gujarat Technological University Gujarat Technological University [email protected] [email protected] [email protected]
Abstract: This paper investigates the different aspects of AISI 316 to increase the life of the twist drilling tool of stainless steel. No one has represented the work on modeling and modification of the tool geometry to generate the long life of twist drill of AISI 316 stainless steel. Many researchers have worked on effect produced by changing the cutting parameters as well as coating material for the same. The work has also been presented to find the Torque, Power and Thrust at the different feed, different material hardness and material factor for AISI 316 stainless steel material. Rigorous analysis is going to be carried out to decide a proper tool geometry for stainless steel tool with the help of experimental analysis and software.
Keywords: Drilling tool, stainless steel, drill geometry, Angles of tool, Drill point geometry
I. INTRODUCTION
The drilling involves [1] the creation of holes that are right circular cylinders. This is accomplished most typically by using a twist drill. Drilling is a process of producing round holes in a solid material with the use of multi point tooth cutting tool called drills or drill bit. Various cutting tools are available for drilling, but the most common is the twist drill.
Cutting tools have been used in metal machine shops since the late 19th century and manufacturers are continuing to evolve these mechanisms to become more efficient within the industry. Cutting tools become into contact with the raw material, cutes, removes debris and chips from the material and helps to create the end piece. Cutting tools started off as tools made from high carbon steel, to high speed steel, cobalt, carbide and even diamond and ceramic.
In order for cutting tools[1] to work effectively, the tool must be made of a material harder than the material it is going to cut through. A few types of cutting tools include: broach, a metal working tool with chisel points mounted on a piece of steal; end mill, a tool used in industrial milling applications;
reamers make existing holes dimensionally more accurate and improves the finish of the surface material in metalworking;
drill bits, which are used to create cylindrical holes by
rotation; countersink, a tool used to make a conical hole;
diamond blade, which is often found as a circular saw blade used for cutting hard materials; and diamond tools, which contains diamond segments that help to cut through non- ferrous materials, or metal materials containing no iron.
These cutting tools can cut through wood, plastic, composite and metal, depending on what tool you’re using and what size and shape of hole you desire.
Fig. 1. Stainless Steel Cutting Tool
A.)Types of cutting tool 1. High-speed steel cutting tool, 2. Carbide tipped cutting tool, 3. Solid carbide cutting tool, 4. Diamond related cutting tool, 5. Leather Cutting tool,
6. Metal Cutting tool, 7. Glass Cutters cutting tool.
II. LITERATURE SURVEY
S. Dolinsek[2] represented the effect of work – hardening in the drilling of austenitic stainless steel mainly for specific properties arising from their structure( high toughness, work Harding, low heat conductivity) as austenitic stainless steel belong to the group of materials that are difficult to machine.
It has been related the chip transformation process on the cutting edge using quick stop of drilling process as the basis to establish a real cutting tool model for the drilling austenitic
stainless steel and then geometrical solution of the drill was established and recommendations were made for selection of the parameters to drill austenitic steel in the region of a minimal degree of work Harding to increase the life.
J. Paulo Davim et al.[3] represented the finite element modeling of machining of AISI 316 steel: Numerical simulation and experimental validation paper is to modeling the thermo mechanical behavior when machining a stainless steel (AISI 316) and to determine the influence of the friction coefficient in the tool-chip interface on cutting and feed forces, cutting temperature, plastic strain, plastic strain rate, maximum shear stress and residual stresses. All the numerical simulations that were made, it is possible to withdraw that the friction coefficient greatly influences the cutting and feed forces, cutting power, maximum cutting temperature and plastic strain. Unfortunately, friction coefficient cannot be measured with precision and it needs to be iterated. Using the experimentation tests, a Coulomb friction coefficient was found for each case of study and this value was the starting point to simulate the machining operations.
A) Material
High-speed steels[4] cut four times faster than the carbon steels they replaced. There are over 30 grades of high-speed steel, in three main categories: tungsten, molybdenum, and molybdenum-cobalt based grades. Cemented carbide is a powder metal product consisting of fine carbide particles cemented together with a binder of cobalt. The major categories of hard carbide include tungsten carbide, titanium carbide, tantalum carbide, and niobium carbide. Each type of carbide affects the cutting tool’s characteristics differently[6]. Carbide is a compound composed carbon[4] and a less electronegative element, for example, calcium carbide and tungsten carbide. Each uses in key industrial application or carbon compound with a non-metal (such as boron, calcium or silicon) or metal (such as in cobalt, titanium, tungsten, or vanadium). Metal carbides are characterized by their extreme hardness and resistance to high temperature and are used as abrasive and in cutting, drilling, grinding and polishing tools.
Stainless steel[4] is the universal name for a number of different steel used in primarily for their anti-corrosive element. It has been developed to resist a no. of corrosive environments. Stainless steels are iron alloys with a minimum of 10.5% chromium. Other alloying elements are added to enhance their alloying elements are added to enhance their structure and properties such as formability, strength and cryogenic toughness. Such as, Nickel, Molybdenum, Titanium, Copper.
III. REQUIREMENT OF DRILLING TOOL
The geometry of a cutting element is defined by certain basic tool angles and thus precise definitions of these angles are
essential. There are mainly the different types of the tools and basic tool angles.
Fig. 2. Angles of Tool Geometry
Rake Angle
The rake angles[5] are defined in the corresponding planes of measurement. The rake angle is the angle between the reference plane and the intersection line formed by the plane of measurement considered and the tool rake plane. The rake angle depends mainly on the flute helix angle, point angle and the radius at which it is measured. The variation of rake angle along the cutting edge.
Fig. 3. Rake Angle
tan ϒx = (rx/r) * (tan λ/sin(ρ/2))
where ϒx = rake angle at any considered point r = radius of the drill
λ = helix angle ρ = point angle rx = radius of point Helix angle
The helix angle[5] of the twist drill is the equivalent of the rake angle on other cutting tools and is established during manufacture. Helix angle[5] practically determines the rake angle at cutting edge of the drill. As the helix angle
decreases, the rake angle also decreases and makes the cutting edge stronger.
Fig. 4. Helix Angle
Table 1. Recommended helix angle of drill Range of diameters (d) mm Recommended helix angle
Over up to
For normal material
For hard and brittle material
For soft material
- 0.60 16˚ ± 3˚
0.60 1.0 18˚ ± 3˚
1.0 3.20 20˚ ± 3˚ 10˚ ± 2˚ 35˚ ± 3˚
3.20 5.0 22˚ ± 3˚ 12˚ ± 3˚ 35˚ ± 5˚
5.0 10.0 25˚ ± 3˚ 13˚ ± 3˚ 40˚ ± 5˚
10.0 - 30˚ ± 5˚ 13˚ ± 3˚ 40˚ ± 5˚
Point angle
The most commonly used point angle[5] is 118˚. Reducing the point angle leads to an increase in the width of cut, and generally it is adopted for brittle materials. By increasing the point angle, the width of cut is reduced and thicker chips are produced for the same feed rate.
Fig. 5. Point Angle
Table 2. Recommended Point Angle of drill Material of Work Piece Tensile
strength Kgf/mm2
Brinell hardness
BHN
Tool type
Point angle
±3˚
Steel and cast steel 40 -70 115 - 205 N 118˚
(alloyed and unalloyed 70 – 120 205 – 350 N 130˚
Stainless steel N 140˚
Austenitic steel H 140˚
Cast iron 140-200 N 118˚
200-240 N 118˚
Over 240 N(H) 118˚
Malleable cast iron N 118˚
Brass with copper up to 58%
N 118˚
Brass with copper up to 58%
N 118˚
German silver N 118˚
Copper up to 30 mm drill diameter
S(N) 140˚
Copper over 30 mm drill diameter
N 140˚
Aluminium alloys long chip type
S(N) 140˚
Aluminium alloys short chip type
N 140˚
Magnesium alloys H(N) 140˚
Nickel N 118˚
Zinc alloy S(N) 118˚
White metal S(N) 118˚
Moulded plastic (thickness < drill diameter)
H 80˚
Moulded plastic (thickness > drill diameter)
S 80˚
Laminated plastic H(N) 80˚
Celluloid S(N) 140˚
Hard rubber and thin plastic material
H(N) 80˚
Marble, slate and carbon
H 80˚
Chisel-edge angle
The angle between the chisel edge[8] and cutting lip, as viewed from the end of the drill, as shown in fig. 3. The angle generally varies from 130˚ to 145˚. Since bigger relief angles are recommended for small diameter drills, larger values of chisel edge angle are preferred.
Clearance angle
Clearance angle at any point[8] on the lip is the angle between the tangent to the flank and tangent to the surface of revolution at that point. The actual value of the relief angle during drilling also depends on feed.
The working clearance angle, α w = α - µ
IV. EXPERIMENTAL PROCEDURE
In this work the experiment has been conducted using the VMC. The work piece material is stainless steel and with the coating material Tin used for cutting tool and with the use of VMC and PROFILE PROJECTOR the different angles and lengths and many different cutting parameters were measured.
For the experiment different cutting parameters like cutting speed(Vc), feed(f), diameter(d) and depth of cut(D) were selected.
From above parameters one can find out the other value of parameters like number of revolution(N), feed rate (fr), time to drill of one hole and tool life.
According to the previous work, the range of cutting condition chosen are 45 m/min ≤ Vc ≤ 60 m/min, 0.12 mm/rev. ≤ f ≤ 0.20mm/rev., and diameter is 12mm and depth of cut is 30 mm to use.
Fig. 6. Measured Helix Angle with the Use of Profile Projector
Fig. 7. Measured Point Angle with the Use of Profile Projector
There are two sets of cutting parameters to use for different experiments on it and then to increasing the tool life.
Table 3. Geometry
Geometry Old New
Core diameter 35% 30%
Helix angle 30˚ 32˚
Rake angle 10˚ 15˚
Flute open angle 90˚ 95˚
Margin width 5% 4-3%
K-land width 3.5% 3.5%
k-land angle 15˚ 15˚
Leap angle 13˚ 15˚
Point angle 140˚ 138˚
Gas angle 30˚ 45˚
Thin web 0.050~0.075 0.050~0.075
Table 4. Cutting parameters
Cutting parameter Old New
Cutting Speed Vc (m/min) 45 60
Depth of cut ap (mm) 30 30
Tool diameter(mm) 12 12
Spindle revolution (rpm) 1200 1600
Feed fr 0.12 0.20
Coolant yes Yes
Fig. 8. Measured Relieve and Chisel Angle with the Use of Profile Projector
Table 5. Material factors k1 for Drilling and Reaming Work material BHN UTS, kgf/mm2 Material factor k1
Free machining steel 167 59.9 1.03
183 63.0 1.42
Mild steel 121 44.1 1.07
160 56.7 1.22
Medium-carbon steel 152 55.1 1.15
197 67.7 1.45
Alloys steel 163 58.3 2.02
174 61.4 2.10
Tool steel 229 78.8 2.10
241 81.9 2.32
Stainless steel 187 64.6 1.56
269 92.6 2.41
Cast iron 177 21.3 1.00
Grey, ductile 198 28.4 1.50
Malleable 224 35.1 2.03
Aluminium alloys - - 0.55
Copper alloys - - 0.55
Magnesium alloys - - 0.45
V. RESULT AND ANALYSIS
While in drilling, the drill is subjected to the action of the cutting force, which can be conventionally resolved in to the three components: a tangential component, a radial component, and axial component which is commonly referred to a thrust force.
Various empirical formulae exist for calculation of the torque and thrust. The following equation can be used for reliable computation of torque and thrust.
Torque
M/d3HB = 0.03(s0.8/d1.2) * [1-k2/(1+k)0.2 + 3.2k1.8] Where,
M = torque kgf cm d = diameter of drill, mm
HB
= hardness of material, Brinell hardness as per the table s = feed mm/rev
k = c/d = ratio of chisel edge length c to drill diameter d Given data
k = c/d = 6/12 =0.5 s = 0.12 mm/rev d = 12 mm HB = 187
M/d3HB = 0.03(s0.8/d1.2) * [1-k2/(1+k)0.2 + 3.2k1.8]
M/(12)3*187 = 0.03[(0.12)0.8/(12)1.2)*[{1-(0.5)2/(1+0.5)0.2}+
{3.2(0.5)1.8}]
M = 145.1461 kgf cm
Table 6. Measuring a different Torque for different feed with use of material hardness
Feed Hardness of material (HB)=187 Hardness of material (HB) = 269
Torque (kgf cm) Torque (kgf cm)
0.12 145.1461 208.7931
0.14 164.1961 236.1966
0.16 182.7076 262.8253
0.18 200.7606 288.7947
0.20 218.4160 314.1920
Power
Drilling KW = 1.25d2 k1n (0.056 + 1.5 s)/105 Where,
k1 = material factor as per table d = drill diameter in mm s = feed, mm/rev n = rpm of drill
Power = 1.25*d2*k1*n*(0.056 + 1.5s)/105
Power = 1.25*(12)2*1.56*1200*(0.056+1.5*(0.12))/105 Power = 0.79 KW
Table 7. Measuring a different Power for different feed with use of material factor
Feed Material factor(k1) = 1.56 Material factor(k2) =2.41
Power (KW) Power (KW)
0.12 0.7952 1.6380
0.14 0.8963 1.8463
0.16 0.9974 2.0545
0.18 1.0985 2.2627
0.20 1.1996 2.4709
Fig. 9. Graph of Power (Material Factor k1)
Fig. 10. Graph of Power (Material Factor k2)
Thrust
Drill thrust, kgf T = 1.16k1d(100s)0.85 Where,
k1 = material factor d = drill diameter, mm s = feed, mm/rev
T = 1.16 k1*d*(100*s)0.85
T = 1.16*(1.56)*(12)*(100*0.12)0.85 T = 277.3067 kgf
Table 8. Measuring a different Thrust for different feed with use of material factor
Feed Material factor(k1) = 1.56 Material factor(k2) =2.41 Thrust (kgf) Thrust (kgf)
0.12 179.5014 277.3067
0.14 204.6316 316.1296
0.16 229.2270 354.1264
0.18 253.6343 391.4154
0.20 277.3066 428.0867
Fig. 11. Graph of Thrust (Material factor k1)
Fig. 12. Graph of Thrust (Material factor k2)
VI. CONCLUSION
In this cutting tool geometry the main work is to design a proper tool geometry for increasing tool life. For designing the tool geometry the different design parameters like cutting speed, feed, tool diameter, spindle revolution etc. were considered. We can find out Thrust, Power, and Torque at different feeds with the use of MATLAB software. The generated graph can be useful to find out the Thrust for the same diameter tool and it can be apply for further modelling and analysis. After that I will calculating the tool life for AISI 316 stainless steel drilling tool as per use of Taylor’s tool life equation.
REFERENCES [1] Chapter 4 Drilling Machines - General information
[2] S. Dolinsek “Work-hardening in the drilling of austenitic stainless Steel”
Journal of Materials Processing Technology 133 (2003) 63–70
[3] C. Maranhão, J. Paulo Davim, “Finite element modeling of machining of AISI 316 steel: Numerical simulation and experimental validation”
International Journal of Machine Tools & Manufacture 65 (2012) 98 – 105
[4] Cutting tool material - King Fahd University of Petroleum and Minerals - MET-276 Machining Technology
[5] Central Machine Tool Institute, Machine Tool Design Handbook Tata McGraw Hill Publishing Company
[6] V.B.Bhandari, Design of machine elements 3rd edition, Tata McGraw Hill Publishing Company
[7] PSG design Data book
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