grinding and other
TRANSCRIPT
![Page 1: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/1.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 1/24
ENMF417
SP
Lect. 9: Abrasive MaterialRemoval
Dr. Simon Park
![Page 2: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/2.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 2/24
ENMF417
SP
Announcements
![Page 3: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/3.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 3/24
ENMF417
SP
Learning Objectives• Fundamental Cutting Operations
– Machinability
– Tool Materials
– Chatter
– Abrasive Methods - Grinding
• Video: SME – Tool Material, PM,Grinding (if time permitted)
![Page 4: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/4.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 4/24
ENMF417
SP
Machinability• a measure of relative ease of
machining operations
• longer tool life, lower force, bettersurface finish, easier chip disposal,higher MRR means Good Machinability
• Ex.AISI 1112 steel: MR (Machinability rating) = 1
Titanium: MR=0.2 (poor machinability)
Aluminum: MR = 2 (good machinability)
![Page 5: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/5.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 5/24
ENMF417
SP
Tool MaterialsImportant properties
• Toughness – avoid fracture
• Hot (high temp) hardness – resistabrasion
• Wear resistance
![Page 6: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/6.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 6/24
ENMF417
SP
• High Speed Steel (HSS)
• Carbides (the most common)
![Page 7: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/7.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 7/24
ENMF417
SP
• Ceramics/Cermets (Ceramic and metal)
• Diamond (Polycrystalline Diamond – PCD)
• Cubic Boron Nitride (CBN)
![Page 8: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/8.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 8/24
![Page 9: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/9.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 9/24
ENMF417
SP
Chatter (self-excited vibration)
E
![Page 10: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/10.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 10/24
ENMF417
SP
How to Avoid Chatter?
ENMF417
![Page 11: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/11.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 11/24
ENMF417
SP
Chatter Simulation
ENMF417
![Page 12: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/12.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 12/24
ENMF417
SPStability Lobes
Example (Modern Chatter Theory) in milling
– Controlling spindle speed so that it matches with chatter frequency (~wn)
• Wn = 2000 Hz
• 2 Fluted Cutter
• Chatter free speed: 2000 Hz / 2 flute x 60 sec/min = 60,000 rpm
• RUN the machine at 60,000 rpm, 30,000 rpm, 20,000 rpm, ….
ENMF417
![Page 13: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/13.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 13/24
ENMF417
SP
Selection of Cutting Conditions• Cutting Conditions:
– Speed, feed, depth of cut, and cutting fluids– Machining Handbook or Tool Catalogs’Recommendations
• Limitations:– Horsepower and torque
– Machine tool and rigidity– Strength of cutting tool– Chatter– Tolerances
• Selection of Feed and Speed – Select Cutting the Depth and Speed – minimize
chatter vibration– Select Feed – roughing or finishing– While maintain good MRR
ENMF417
![Page 14: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/14.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 14/24
ENMF417
SP
Surface Integrity1. Strain hardening of a surface
2. Cracks formed in low speed cutting
3. Phase transition due to high temp.
4. Residual stress
ENMF417
![Page 15: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/15.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 15/24
ENMF417
SP
Abrasive Machining
ENMF417
![Page 16: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/16.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 16/24
ENMF417
SP
Abrasive Machining • Material removal by abrasive particles
– Grinding is the most common abrasivemachining– (others ex: honing, lapping, buffing)
• Reasons for grinding are:1. The material is too hard to be machined
economically. (The material may have beenhardened in order to produce a low-wear finish,such as that in a bearing raceway.)
2. Tolerances required preclude machining.Grinding can produce flatness tolerances ofless than±0.0025 mm (±0.0001 in)
3. Machining removes excessive material.
ENMF417
![Page 17: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/17.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 17/24
ENMF417
SP
Abrasive Machining (Different thanMilling)
• Cutting speeds are higher
• Higher negative rake angle
• Self-sharpening as each abrasive fallsoff
ENMF417
![Page 18: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/18.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 18/24
ENMF417
SP
Grinding MechanismSpecific Energy is greater
than machining
• Size effects (small chipsize causes energy toremove each unit volume)
• Extremely negative rakeangles (low shear plane
angles and high shearstrains)• Part of grits is engaged in
cutting• Shearing (knife), plowing
(plastic and elastic
deformation), and rubbing(friction)
ENMF417
![Page 19: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/19.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 19/24
ENMF417
SP
Honing
• For internal holes or bores
ENMF417
![Page 20: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/20.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 20/24
ENMF417
SP
Lapping• Lapping is a loose abrasive machining
process to form a slurry to form anabrasive film between the plate and theparts to be lapped.
ENMF417
![Page 21: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/21.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 21/24
ENMF417
SP
Polishing/Buffing
Before After
Toyota MR2 Intake Manifold
ENMF417
![Page 22: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/22.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 22/24
ENMF417
SP
Abrasive types• Aluminum oxide
• Silicon Carbide
• CBN
• Diamond
ENMF417
![Page 23: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/23.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 23/24
ENMF417
SP
Dressing• Dressing is…
– Conditioning worn grains by producing sharpnew edges
– Truing – producing a true circle on a wheel
– Usually uses a diamond point tool
ENMF417
![Page 24: Grinding and Other](https://reader030.vdocument.in/reader030/viewer/2022020810/577cd1361a28ab9e7893e007/html5/thumbnails/24.jpg)
7/27/2019 Grinding and Other
http://slidepdf.com/reader/full/grinding-and-other 24/24
ENMF 7