University College Dublin
Mechanical Engineering
Laser Assisted Machining
P. Mitchell, Prof. G. Byrne and R. Byrne
Email: [email protected]
Abstract
Laser Assisted Machining (LAM) allows difficult-to-cut materials to be machined by conventional cutting tools with
greater ease. During LAM, a laser beam tracks ahead of the cutting tool selectively heating the workpiece
material, reducing its shear strength in a localised region. The heated material is then removed in chip form by
the tool. The most suitable LAM workpiece materials are hardened steels, titanium and nickel based alloys and
ceramics. Benefits of the process include reduced cutting forces, increased material removal rates, machining
without lubrication and the use of more economic cutting tools. Recent increases in the power capability of HighPower Diode Lasers (HPDL) have made them suitable for materials processing. The HPDL is compact, cost
effective and efficient when compared to the traditional materials processing lasers (CO2 and Nd:YAG). It also has
a unique Top-Hat by Gaussian beam profile. An analytical 3D thermal model of the laser heating process has been
developed. This model shows the temperature profile generated in the workpiece due to the laser beam. A 3kW
HPDL has been integrated into an ultra precision CNC turning centre. The laser is mounted on a unique
positioning system that allows the optimum LAM process parameters (laser-tool lead distance, laser power, beam
profile orientation and dimensions and machining parameters) to be established. LAM experiments are being
conducted on hardened steel (AISI 4340 at 53HRC) at a range of laser powers. Initial results show significant
cutting force reduction for LAM compared to conventional machining of hardened steel (AISI4340 at 53 HRC).
Experimental Set Up
Principle
Laser Beam
Chip
Tool
Laser
Heated Area
Chuck
Cutting
Tool
Vc
Primary Shear
Zone
Dynamometer
High Power Diode Laser
Workpiece
Initial Results
Gaussian
Distribution
Cutting force reduction for LAM compared to
conventional machining (CM) of Hardened Steel
(AISI4340 at 53 HRC)
500
Top-hat
Distribution
Force (N)
HPDL Unit
(Courtesy of Laserline)
HPDL Beam Profile
(Courtesy of Laserline)
Thermal Model
1  
r 2U  r
T(x, y, z) T0 
I
(
x

r
,
y
)
e
a
  Ur0
r2  z2

T(x,y,z) = Temperature at position (x,y,z) (K)

T0= Initial Workpiece Temperature (K)

 = Thermal Conductivity (W/mK)

 = Thermal Diffusivity (W/m2)

U = Constant Velocity of Translation in X Direction
(m/s)
CM
400
LAM
300
200
100
r2 z2 

dr
0
10:50
-100
10:50
10:51
10:52
10:53
10:53
10:54
Time (min)
Machining Parameters: f = 0.15mm, ap= 0.2mm
vc= 150 m/min