1. from research .… to market
Integrated analysis of
machine tools and cutting
process
Marco Leonesio
marco.leonesio@itia.cnr.it
Milan, 14th of February 2011

2. Contents
• Machine tools specifications for heavy machining
• Objectives of machine tools Virtual Prototyping
• Integrated Modeling Approach: structure, control and
cutting process
• Ongoing research developments
• Conclusions
2

3. Machine tools specifications for heavy machining
Aluminium rib Titanium impeller
In some components for aerospace industry up to 90% of the material is removed from
the workpiece during cutting, therefore Material Removal Rate (MRR) is typically an
important machine tool performance.
On the other side, some machine tools are designed and built aiming at specific
machining operations (or even parts) that should be performed with an acceptable
quality …
Specifications in terms
of machining Machine design
operations
3

4. Machine tools specifications for heavy machining
Two main needs arise from this situaution:
To decrease the risk of requirements
To avoid the costs due to
mismatching (above all when the
over-sizing
prototype cost is unaffordable)
Focus the design on
specific cutting Increase analysis
operations efforts to anticipate
problems
•Identification of an independent
set of cutting operations relevant
for MT design;
Virtual Prototyping
•Synthesis of the static and
dynamic behaviour sutited to the
required operations.
4

5. Objectives of machine tools Virtual Prototyping
The adoption of rich numerical modeling of the designed product
(a.k.a. Virtual Prototyping) allows the NPD to close a new and much
faster loop, compared to the “testing stream”.
In order to emulate physical validation tests, the models should be
predictive…
5

6. Objectives of machine tools Virtual Prototyping
structure
components
process
control
6

7. Integrated Modeling Approach
Machine modeling for
N.C. performance prediction
drives
measured
displac.
motor motors sensors
torques transmis- structure
sions guideways
workpiece
spindle and tool quality
tool
cutting motion
cutting process
forces
cutting
param.
7

8. Integrated Modeling Approach
Components libraries have been developed in Matlkab/Simulink environment enabling frequency
domain analysis and functional simulations of the whole machine during cutting.
Tool Center Pos(1x1x 1 vector )
ChipThickness [mm]
processo
milling Vel mandrino 360 [rpm]1
RPM*2*pi/(60)
Vel mandrino 360 [rpm]
di taglio Force on tool (x,y ,z)
D o Cut [mm]
process Lavorazione LINEA (vel x = 18.24 mm/s)
b
D o Cut [mm]
fresatura
forze i74340.02WorkPX
o74340.02WorkPX
o74340.03WorkPY spost
-K- i74340.03WorkPY o74340.01WorkPZ
-4 o74341.02ToolX
Spost
azionamenti i74340.01WorkPZ o74341.03ToolY Rel
axis drives MeccAzTandemUnitsV1FIG.mdl
o74341.01ToolZ
processo
tandem i74341.02ToolX
o74338.25VMotX1R
o74338.26VMotX2L
PosRef i74341.03ToolY
Pos Com Motor1 Force [Xdata]
o74338.05PMotX1R
Vel Com GotoX1
AccLimRamp 1 Meas AX Pos Motor mass [kg] o74338.06PMotX2L OutX1
i74341.01ToolZ
- Mot1 vel
Motor2 Force
Meas Mot1 Pos o74302.02LinEncX
[Xdata]
Mot2 vel Response1
F_Xdata i74338.05MotX1R o74339.24VMotY1R
Meas Mot2 Pos
Excitation input Response2
o74339.26VMotY2L
Siemens Reg TandemCont X
1 [Ydata ]
i74338.06MotX2L o74339.04PMotY1R
Pos Com GotoY1
Motor1 Force
Vel Com o74339.06PMotY2L OutY1
1 Meas AX Pos Motor mass [kg] i74339.04MotY1R
o74302.03LinEncY
Mot1 vel
-1 Motor2 Force
Meas Mot1 Pos o74337.24VMotZ1R
[Ydata ]
Mot2 vel Response1 i74339.06MotY2L
F_Ydata
Meas Mot2 Pos
Excitation input Response2
i74337.04MotZ1R
o74337
o74337
.25VMotZ2L
.04PMotZ1R [Zdata]
reduced
struttura
Siemens Reg TandemCont Y
1 GotoZ1
Pos Com
Vel Com
Motor1 Force
o74337.05PMotZ2L OutZ1 FE
FEM
i74337.05MotZ2L o74302.01LinEncZ
1
-2
Meas AX Pos
Mot1 vel
Motor mass [kg]
Motor2 Force
model
ridotto
Meas Mot1 Pos
[Zdata] M_VINCOLATO_TERRA _RMod
Mot2 vel
F_Zdata Response1 INPUTSN, Nm
:
Meas Mot2 Pos OUTPUTSmm, rad
:
Excitation input Response2
Siemens Reg TandemCont Z
1
8

9. Integrated Modeling Approach: structure & control
Gear
Belt transmission
transmission spindle
bearing
Nut
Vipromwiki,
Drives business model
1
ELEMENTS
NOV 22 2007
17:37:57
carriages
9

10. Integrated Modeling Approach: structure & control
The virtual machine tool prototyping
platform allows the designer to rapidly build
a complex model but today a proper
accuracy is not always assured: further
research is needed.
Cedevolezza dinamica al naso mandrino
experimental Simulata
Sperimentale
-7
10
mod [m/N]
-8
10
-9
10
numerical
-10
10 machine+ spindle
1 2
10
hz
10
modes
VELOCITA' SU RIFERIMENTO DI COPPIA, ASSE X ANELLO APERTO experimental
50 NUMERICO VELOCITA' SU RIFERIMENTO DI VELOCITA' ANELLO CHIUSO, kvel=400
SPERIMENTALE
FEM
ACCELEROMETER
ACCELEROMETRO
45
40 experimental 0
35
-5
30
NUMERICO
SPERIMENTALE
25
DB
-10
DB
20
MARTELLOnumerical
INSTRUMENTED
STRUMENTATO
HAMMER
15
-15
10
5 numerical SPINDLE
FLANGIA TOOL
NASO
-20
FIXACTION
MANDRINO ATTACHMENT
MANDRINO
0
1 2 1 2 3
10 10 10 10 10
HZ HZ
Function response frequency of a machine tool, dynamic behavior 10

11. Integrated Modeling Approach: cutting process
Cutting process
modeling and simulation
(milling and turning)
 Force model: F=f(actual chip section).
Different models implemented
 Variable Spindle Speed supported
 Run-outs effects
 Rountines for model parameters Lav01 (ATI Porcupine) - D=63mm - Z=4 - Ap=8mm - Ar=12.5mm - Sp=253rpm
identifications (cutting coefficients, 1000
Fx fitting
run-outs,…)
[N]
0
-1000
650 700 750 800 850 900 950 1000
Displacement force 2000
Fy fitting
0
[N]
-2000
-4000
650 700 750 800 850 900 950 1000
Samples
Results:
- predict chatter occurrence
- estimate surface finish
- predict realistic spindle torques and axes forces
- test special chatter suppression techniques (Spindle Speed Variations)
11

12. Integrated Modeling Approach: cutting process
Steel face-milling
8 teeth inserted endmill
D=80mm
Width of cut: 50mm
Depth of cut: 5mm
Virtual prototyping allows the
designer to investigate the machine
behavior in operational conditions
12

13. Ongoing reseach developments
Chatter is a complex phenomenon: even if it is an old problem, some
scientific challenges are still open.
DASM group does reasearch on the following topics, in co-operation with
MUSP (a consortium of POLITECNICO of Milan):
Spindle Speed Variation: In order to suppress chatter, one of the possible
strategies is to continuously vary the spindle speed during the cutting
process in order to break the regenerative process.
Process damping: At low spindle speed, chatter stability limit is often
increased by a phenomenon called process damping. A satisfactory
predictive model of process damping is not available in literature.
Experimental stability Lobes
6 6
Bubble diameter is proportional
5 5
to acceleration RMS 7 (in feed
Depth of(mm) [mm]
direction) measured on spindle
Depth of Cut (mm)
6
housing.
passata Cut
4 4 5
4
3 3
3
2
2 2
1
0
1 1
0 500 1000 1500 2000 2500
600 600
800 800
1000 1000
1200 12001400 14001600 1600
1800 1800
2000 2000
Spindle Speed (RPM)
velocità mandrino(RPM)
velocità mandrino(RPM)
Spindle Speed
13

14. Ongoing research developments: process damping
Process damping mechanism
•Tool Vibration
•Surface Waviness
*zoom (x100)
Variables:
Micro-Geometry
Force
Coatings Output:
Cutting speed Force
Vibration Temperature
Deformation
Wear
Ksp = F/V
Compressed Volume
FEM simulation are performed aiming at:
•Support the prediction of lobes diagram modeling process damping
•Tool Design
14

15. Ongoing research developments: grinding
A model of grinding process is being developed, based on removal
specific energy, enabling chatter occurrence simulation.
Chatter in grinding y, dy/dt
x, dx/dt
dFt
dFn
15

16. Conclusions
Virtual prototyping of machine tools with cutting process can be the key to
tackle successfully the design of machine tools with high Material Removal
capabilities.
Nevertheless, in order to make Virtual Prototyping efficient and
economically feasible, new co-operation models have to be developed
enhancing the synergies between machine tools manufacturers and
component suppliers, with the support of knowledge provider (Universities
and research centres).
As virtual prototypes must be predictive, a relevant amount of research has
to be still carried out in order to refine the estimation of chatter stability
limit and machine tool static and dynamic behaviour.
16

17. from research .… to market
Thanks for the attention!
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