Over all for midterm Flashcards
(37 cards)
machining
process of removing material from a workpiece and forming chips
7 basic chip formation processes
turning, drilling, milling, grinding, sawing, shaping and planing, broaching
cutting speed
V
linear velocity that the tool passes through the workpiece or vice versa
cutting speed depend on
material of tool and whats being worked on
feed
amount od material removed per rotation or pass
machine feedlinear
linear velocity of the tool or workpiece
cutting time
time it takes to cut and made up of length of what is being cut and the allowance
details about orthogonal machining
rake angle is the angle between the vertical and the tool
clearance angle is the tool makes with the workpiece
chip thickness ratio (rc)= t/tc
where t is the uncut chip thickness/depth of cut = AB sin p
and tc us the sheared chip thickness = AB cos(p-a)
typically tc is thicker than t due to material compression
free vibration
system oscilate independently after distrbd frm eqlbrm postn and then released without any xtrnl forces on it. motion remains until energy dissipates
forced vibration
oscillatory motion of a system subject to external forces snd rewuire continuous or periodic input of energy
self excited vibratiin
sstm generates its own oscillation from its own dynamics and can sustain w/out anu external intrfrnce
chatter
in what direction respect to blade ?
an undersirable phenomnn where machnng tools make irregular vibrations while cutting and can happen from any of the 3 types of vibration but usually self excited
same direction as blade edge usually
chattter can be seen as … in machining focus
noise
tool wear
poor surface finish
when machining
how can chatter issue be resolved
increase cutting force
feed marks
parallel lines that occur because of irregular feed rate while cutting
for corner making
tool radius should be smaller than intended radius of making to not get chatter
name 6 Cutting tool materials
- High carbon steels
- Low/medium alloy steels
- High-speed steels (HSS)
- Cast cobalt alloys
- Cemented/cast/coated carbides
- Coated high speed steels
- Ceramics
- Sintered polycrystalline cubic boron nitride (CBN)
- Sintered polycrystalline diamond
- Single-crystal natural diamond
what are the requirements of cutting tools
*High hardness
*High hot hardness
*Consistent tool life
*Good thermal properties
*High toughness
*High elastic modulus (stiffness)
*Resistance to abrasion, wear, chipping
*Strength to resist bulk deformation
*Chemical stability with temperature
*Correct geometry and surface finish
tool steels (both Carbon steels and low/medium alloy steels)
If cutting temp goes above 400°F, they lose their hardness and cutting edges dull quickly.
Low temp associated with low cutting speed (V)
Sometimes referred to as silver steel or drill rod
hss
Temperature up to 1100°F, better than Tool Steel
High Alloy Steel – Contains tungsten, molybdenum, cobalt, vanadium and chromium as alloying
elements.
*Great toughness
*Easily fabricated (grinding)
*Great for complex geometries
Cast Cobalt Alloys
Cobalt rich alloy
Similar to HSS
Better heat hardness than HSS (so higher cutting speeds)
why are cast cobalt alloys being phased out
being phased out due to cost of production, and
reduction in $ of better alternatives!
what are the 2 primary grades of carbides
- Straight tungsten grades (C2)
- Grades containing major amounts of titanium, tantalum and or columbium. (C6
Carbides and thw types of tools they come as
➢Solid Carbide (usually end mills or drill bits (some taps)
➢Brazed insert tooling (good if custom profiles need to be ground, most similar to HSS usage)
➢Insert tooling – Replaceable, easy to service, multiple cutting edges, maximum tool life and
productivity.
insert is usually better than brazed insert
