HSM is a powerful machining method that combines high feed rates with high spindle speeds, specific tools and specific tool motion

1. MACHINE TOOL STRUCTURES FOR
HIGH SPEED MACHINING
Suresh Lal S R
Assistant Professor
Department of Mechanical Engineering
Government Engineering College, Wayanad

2. DEFINITIONS
• High cutting speed machining
• High rotational speed machining
• High feed machining
• High speed and feed machining
• High productive machining
Finally,
“HSM is a powerful machining method that combines high
feed rates with high spindle speeds, specific tools and
specific tool motion.”

3. EXTREME PARAMETERS
High Spindle Speeds
• 20,000 to 50,000 rpm
High Feed Rates
• 10 to 20 m/min
High Acceleration/ Deceleration
• Up to 2g

4. • First tries were made in early twenties of the past century.
• The first definition of HSM was proposed by Carl Salomon in
1931.
• He has assumed that at a certain cutting speed which is 5 –10
times higher then in conventional machining, the chip tool
interface temperature will start to decrease.
History Of HSM:-

5. Salomon’s curve

6. Effect of cutting speed on cutting force

7. HIGH SPEED
MACHINING
ACCURACY
EFFICIENCY
REDUCED
MACHINING TIME
QUALITY OF
WORKPIECES
DECREASED
COSTS
High Speed machining leads to -

8. Comparison between Conventional Machining and High
Speed Machining

9. REQUIREMENTS OF HSM
 High speed machines should have higher structural rigidity
to withstand higher cutting forces and vibrations.
 It should be employed with efficient damping methods.
 It should be light in weight.
 The rotating spindle must be dynamically balanced.
 Bearing should properly designed for their life and
capacity.
 Dimensional and geometrical stability
 Low coefficient of thermal expansion
 Low cost

10. DESIGN TASKS
Light Weight Structures
- Composites, thin wall steel, aluminium
High Speed Spindles
• Air, magnetic, hybrid angular ball bearings
Guide ways
• Ball, roller, hydrostatic
Feed Drives, Controls
• High torque motors, feed forward and cross controls
Fast NC Controllers
• 1 msec block, 0.1 msec loop closing

11. CONVENTIONAL STRUCTURAL MATERIALS
Grey cast iron and steel
Advantages
• Manufacturing flexibility
• Low cost
• Better damping
• Static stiffness

12. Limitations
• Exhibits either static stiffness or damping
• Conventional steel moving frames of machine tools operates
with maximum feed rate of 0.2 – 0.8 m/s and maximum
acceleration of 0.2 – 2.1 m/s2.
• The high speed machines are required to have feed rate of 2m/s
and acceleration of 14m/s2.
• These high transfer speeds are hard to be realized if massive
steel moving frames are employed.
• Furthermore, machine tool structures vibrate creating problems
during machining at these high speeds.
• Results in poor surface quality.
CONVENTIONAL STRUCTURAL MATERIALS

13. STRUCTURES FOR HSM

14. REQUIREMENTS OF MACHINE TOOL STRUCTURES
 For high speed operation with accuracy, machine
tool structures should be designed with light
moving frames.
 High stiffness and damping properties are
required to increase the fundamental natural
frequencies and decrease the vibration induced.

15. 1. COMPOSITE MATERIALS
Composite materials replacing cast iron
• Ferro cement
• Polymer concrete
• Epoxy granite
• Fiber based polymer matrix composites
• Glass epoxy
• Kelvar epoxy
• Carbon epoxy

16. EPOXY GRANITE
• particular type of polymer prepared with fine granular
particles of granite material as the filler and the epoxy
resin as binder.
• High damping and compressive strength
• High strength
• Reduced deformation due to creep
• High cost

17. FIBER REINFORCED POLYMER COMPOSITES
• The requirement of high specific stiffness with high
damping for high speed machine tool structures can be
satisfied by employing fiber reinforced polymer
composite materials.
• Since the fiber reinforced composite materials consist of
reinforcing fibers with very high specific stiffness and
matrix with high damping, the resulting material
characteristics of composite materials reflect the best
characteristics of each material, i.e., high specific
stiffness with high damping.

18. Comparison of mechanical
properties of conventional
and stone based alternative
materials used in machine
tool structures.
Mechanical properties of
fiber based alternative
materials used in machine
tool structures

19. 2. HYBRID MACHINE TOOL STRUCTURE
Photograph of a high speed milling machine tool structure (F500, Daewoo heavy industries & Machinery Ltd.,
Korea).
1Adapted from Design and
manufacture of composite high speed
machine tool structures Dai Gil Lee *,
Jung Do Suh, Hak Sung Kim, Jong
Min Kim

20. Photograph of the hybrid X-slide and composite
reinforcements
Photograph of the hybrid Y-slide and composite
reinforcements
X-slide and the Y-slide composed of composite sandwich structures adhesively
bonded to welded steel structures.
High strength carbon epoxy composite and glass fiber epoxy were mainly used
for the faces of sandwich beams and reinforcing plates for the X and Y-slides.

21. Section views of vertical columns of the X-slide: (a) reference of section view; (b) hybrid; (c)
conventional.
1Adapted from Design and
manufacture of composite high speed
machine tool structures Dai Gil Lee *,
Jung Do Suh, Hak Sung Kim, Jong
Min Kim

23. • The mass reductions of the hybrid X-slide and the Y-slide were
26% and 34%, respectively, compared to those of conventional steel
structures without sacrificing any bending stiffness.
• The damping factors of the hybrid X-slide and the Y-slide
increased 1.5–5.7 times compared to those of the conventional
structures.
• Furthermore, the machine tool structure equipped with the hybrid
X-slide showed large damping capacity through a wide range of
frequencies.

24. 3. DESIGN MODIFICATION PROCESS
Geometry Modification
In order to increase the structure’s rigidity, the
column cross section geometry of the structure was
modified in this step.
Material Modification
Cast iron has higher inherent damping, better sliding and low
cost manufacturing. Steel has superior strength under static and
dynamic loading, as well as unit rigidity under tensile, torsional
and bending loads.
Therefore, the combination of steel and cast iron is the best
solution in this case. The beam material selected is made from
welded steel as it is not complicated to manufacture, while the
two columns were cast using cast iron.
7Ahmed A. D. Sarhan et al.,
Improvement on a CNC
Gantry Machine Structure
Design for Higher
Machining Speed
Capability

25. The dynamic analysis of the final gantry
structure
The dynamic analysis of the initial gantry
structure design
7Ahmed A. D. Sarhan et al., Improvement on a CNC Gantry Machine Structure
Design for Higher Machining Speed Capability

26. 4. NEW DYNAMIC MACHINE TOOL CONCEPT
A new active mechatronic concept of extreme lightweight design is to split the moment
of inertia of a heavy feed-drive axis to avoid the disadvantages.
For a high dynamic performance when cutting, the small axis is moved locally with high
accelerations whereas the heavy axis is realising the main motion over longer periods.
This concept, known as redundancy, principles for the splitting of necessary motions
4R. Neugebauer et al.,
New high-speed
machine tool structure
by holistic mechatronic
systems design

27. SPINDLE AND BEARING

28. HSM SPINDLES
• High cutting speed is ensured by motor spindles with
roller bearings
• In the bearings of high-speed spindle assemblies of
machine tools, very complex states of internal tension
take place.
• Centrifugal forces acting on spinning elements of
bearings cause deformations of spinning elements,
which have a great influence on values and directions of
forces in bearings, as well as axial displacements of the
spindle

29. REQUIREMENTS OF SPINDLE
• High rotational speed
• High stiffness
• Lowest possible axial displacement.
• Spindle material should have a low thermal
expansion of coefficient.

30. BEARINGS FOR HIGH SPEED SPINDLES
• Air bearings
• Magnetic bearings
• Hydrostatic bearings
• Hydrodynamic bearings
• Angular bearings

31. BEARING REQUIREMENTS
Bearings used in the high speed spindles should have
improved performance in terms of
• Thermal stability
• Stiffness
• Lubrication
• Load carrying capacity
• Life

32. AIR BEARING
• Air acts as the lubricant
• Low friction
• Wearability
• Maintenance free
• Low heat generation

33. MAGNETIC BEARING
• Uses magnetic levitation
• No physical contact
• Low friction
• No much wear
• Mostly uses electromagnets

34. HYDROSTATIC BEARINGS
• Works on hydrostatic lubrication; external source of pressurized fluid forces
lubricant between two surfaces
• Supports large loads
• Long life
• Large stiffness
• High damping coefficient
• Excellent for exact positioning & control.

35. HYDRODYNAMIC BEARINGS
• Works on hydrodynamic
lubrication
• Load is transferred through
a lubricant in sliding
contact.
• Suited for high rotating
speeds
• Cheaper than ball or roller
bearings

36. ANGULAR CONTACT BEARING
• Uses axially asymmetric races
• Designed for combined loads
(radial & axial)
• Larger the contact angle , higher
the axial load supported
Angular contact bearings are commonly used in high speed spindles because they
provide the precision , load carrying capacity & speed required for cutting.

37. Speed ranges of bearings.
Bearings Approximately maximum
speed (DN*)
Steel bearings 1000000
Ceramic bearings 2000000
Hydrostatic /hydrodynamic
bearings
1000000
Air bearings 4400000
Magnetic bearings 4500000
* Top speed alone is not enough to describe a bearing. A better measure is the product of
bearing diameter in mm (D) and top speed in rpm (N), which is DN number.

38. GUIDE WAYS

39. GUIDEWAYS
The main function of the guideway is to make sure that the cutting tool
or machine tool operative element moves along predetermined path
Requirements
• High rigidity
• High accurate & surface finish for the guideway surface.
• High travel accuracy
• Durability
• Minimum friction
• Good damping properties

40. Types
Ball guideways
Roller guideways

41. BALL GUIDEWAYS
• Uses balls as the force
transmission interface
between a rail & a block
• Enable unbounded back
and forth rolling
movement
• High speed & accuracy
• High rigidity &
positioning accuracy

42. ROLLER GUIDEWAYS
• Uses balls as the
force transmission
interface between a
rail & a block
• High positioning
accuracy
• High rigidity

43. REFERENCES
1. Dai Gil Lee et al., Design and manufacture of composite high speed machine tool structures, Composites
Science and Technology 64 (2004), pp 1523–1530
2. Hongqi Li and Yung C. Shin, Analysis of bearing configuration effects on high speed spindles using an
integrated dynamic thermo-mechanical spindle model, International Journal of Machine Tools &
Manufacture 44 (2004) pp 347–364
3. Masatsugu MORI and Takuji KOBAYASHI, High-Speed Tapered Roller Bearing for Machine Tool Main
Spindles, NTN TECHNICAL REVIEW No.74 (2006) Technical Paper, pp 16-23
4. R. Neugebauer et al., New high-speed machine tool structure by holistic mechatronic systems design, 5th
CIRP Conference on High Performance Cutting 2012, pp 307-312
5. N.Mahendrakumar et al., Study of Alternative Structural Materials for Machine Tools, 5th International
& 26th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014)
December 12th–14th, 2014, IIT Guwahati, Assam, India, 645-1 to 645-6
6. Jerzy JEDRZEJEWSKI and Wojciech KWASNY, DEVELOPMENT OF MACHINE TOOL
OPERATIONAL PROPERTIES, Journal of Machine Engineering, Vol. 15, No.1, 2015 pp 5-24
7. Ahmed A. D. Sarhan et al., Improvement on a CNC Gantry Machine Structure Design for Higher
Machining Speed Capability, World Academy of Science, Engineering and Technology, International
Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering Vol:9, No:4,
2015, pp 572-576
8. Burak Sencer and Shingo Tajima, Frequency Optimal Feed Motion Planning in Computer Numerical
Controlled Machine Tools for Vibration Avoidance, Journal of Manufacturing Science and Engineering
JANUARY 2016, Vol. 139, Copyright VC 2016 by ASME, pp 011006-1 to 011006-13

44. Thank you