theory of cutting – tool wear - Ústav technologie...
TRANSCRIPT
![Page 1: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/1.jpg)
Theory of cutting – Tool wear
Technology II – Jan Tomíček
![Page 2: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/2.jpg)
Tool wear
Cutting tools undergone wear during the cutting. The wear means that the tool loses its volume and geometrical properties.
There are different mechanisms of tool wear
![Page 3: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/3.jpg)
Tool wear mechanisms
1) Simple wear
o Abrasive wear
o Adhesive wear
o Diffusion wear
o Chemical wear
2) Plastic deformation
3) Fracture
![Page 4: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/4.jpg)
Abrasive wear- Related to hardness
- Caused by hard particles in workpiece material
- Caused by particles of the built-up-edge
- Caused by the transformed surface (hardened)
1.simple wear
![Page 5: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/5.jpg)
Adhesive wear
Appears at low cutting temperatures (or cutting speeds)
High pressure causes pressure welds on tops of the surface irregularities.
1.simple wear
![Page 6: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/6.jpg)
Diffusion wear
•For diffusion is necessary certain temperature approx. 600°C
•NO Diffusion using carbon steels and HSS steel (low temperature)
•Diffusion using SC, ceramics, PCD and CBN.
•Diffusion is exchange of chemical elements between tool and material
1.simple wear
![Page 7: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/7.jpg)
Diffusion wear
• Chemical affinity of materials
* SC vs. steel
1.simple wear
![Page 8: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/8.jpg)
Chemical wear
• New comounds or composition of surafce layer is created
(Oxidation, cuttig fuild reaction etc.)
1.simple wear
![Page 9: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/9.jpg)
Plastic deformation
All cutting tools, all materials – after some amountof tool wear the contact surface is too large
- Massive heat generation leeds to rapid temperature increase
- The hardness of material decreases (limitingtemperature)
- The high cutting force load leeds to loss ofgeometry and appearance of plasticdeformation(usually together with rapid wear ofcombined thermo-mechanical load)
![Page 10: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/10.jpg)
Hardness to temperature rel.
![Page 11: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/11.jpg)
Fracture• Usually from overloading the tool – heavy
forces from heavy cutting condition
• Hard particles, particles with high strength
• Increase of cutting forces due to tool wear
![Page 12: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/12.jpg)
Important tool properties
Property Abrasion Adhesion Difusion ChemicalPlasticdef.
Fracture
Hardness X X X
Strength/toughness
X X X
Chemicalstability
X X
Thermalconductivity
X X X
Thermalexpansion
X X X
Melting point X X
Surfaceinertivity
X
![Page 13: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/13.jpg)
Tool wear forms
Basic mechanisms are combined to create a tool wear form for different cutting cases.
Flank wear
Crater wear
![Page 14: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/14.jpg)
Tool wear forms• Complex tool wear forms
– Notch(groove) wear
– Thermal cracks
– Plastic deformation
– Fracture
– chipping
![Page 15: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/15.jpg)
Tool wear forms
• Notch type wear
• Comb cracks on the edge
• Fatigue cracks
• Chipping
![Page 16: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/16.jpg)
Tool wear types
![Page 17: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/17.jpg)
![Page 18: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/18.jpg)
Notch type wear
• Caused by hard surface
![Page 19: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/19.jpg)
Thermal cracking
• Thermal expansion due to temperature change (discontinual cutting e.g.milling)
![Page 20: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/20.jpg)
Chipping
• Special type of fracture – small particles (ceramics)
![Page 21: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/21.jpg)
Tool wear – flank wear(notch)
• Specified by „Average wear-area width“ (VB)
![Page 22: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/22.jpg)
Tool wear – flank wear(notch)
• Three regions
– AB – initial tool wear(rapid but decreasing)
– BC – uniform wear(uniform, slower)
– CD – rapid wear (fast and increasing)
![Page 23: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/23.jpg)
Tool wear – crater wear
• Characterised by „Depth of crater (KT) in mm
![Page 24: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/24.jpg)
Tool life
• Defined tool property!!!„Cutting time required to reach tool-life criterion(definite tool
wear)
There is relation between the tool life and cutting speed Taylor‘s Equation
T…Tool life (min)Vc…cutting speed(m.min-1)n…empirical exponent(tool material effect)Cvc…empirical constant
![Page 25: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/25.jpg)
Tool life
Equation in log scale
straight line
Tg α…values
0,2….HSS steel
0,3….carbides
0,45….ceramics
![Page 26: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/26.jpg)
Tool life
Experimental measurement
Changing cutting speed – VB measurement
![Page 27: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/27.jpg)
Tool wear vs. cutting speed
Left – typical relationship
Right – effect of built-up edge (wear of BUE instead ofthe tool) irregular!!! Out of normaly used range of Vc
![Page 28: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/28.jpg)
Taylor‘s equation – general form
Cv…emipirical constatn
x,y…empirical exponents
typical values (x=0,15, y=0,5, n=0,3) for SC cutting
Influeace:
highest – cutting speed, feed, depth of cut -- lowest
![Page 29: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/29.jpg)
Tool wear measurement• Direct – measuring the lost tool material
– Weight
– Isotopes method
– Resistance layer method
– Micrometric etc.
• Indirect – measuring the effects related to wear– Glossy ring method
– optical reflection
– Force measurement
– Temperature
– Vibration or sound measurement
– Roughness measurement
– Acoustic emission (ultrasonic) etc.
![Page 30: Theory of cutting – Tool wear - Ústav technologie ...utopm.fsid.cvut.cz/podklady/TE2/Lectures/Lecture_no_3_Tool_wear.pdf · Tool wear Cutting tools undergone wear during the cutting](https://reader031.vdocuments.mx/reader031/viewer/2022021504/5afcb28e7f8b9aa34d8c7bc2/html5/thumbnails/30.jpg)
Literature:
• BRINKSMEIER, E. : Monitoring of grinding wheel wear , Ananals of the CIRP, vol,1/1992, pp. 373
• GIUSTI, F. - SANTOCHI , M. – TANTUSSI, G.: On line sensing of flank and crater wear of cutting tools, CIRP, 1/1987, pp. 41
• GOMES DE OLIVEIRA , J.F. – DORNFELD, D.A. - WINTER , B.:Dimensionalcharacterization of grinding wheel surface through acoustic emission, Ananals of the CIRP, vol, 1/1994, p. 291
• ISO 3685 : 1990. Tool Life Testing With Single Point Turning Tools. 1990