Flashcards in Chapter 15 Deck (16):
Name the three material removal processes
Machining - sharp cutting tool
Abrasive process - Hard abrasive particles like grinding
Nontraditional process - Energy forms
Benefits of Machining (3)
Accurate round holes
Very straight edges and surfaces
Disadvantages of machining (2)
Wasteful of material
Time consuming relative to another shaping process
Explain turning. What moves what does it form
Single point cutting tool
rotate workpiece to form a cylindrical shape. Move tool.
Explain drilling. What moves what does it form
Rotate toolpiece. Move tool.
Creates round holes with two cutting edges
Explain milling. What moves what does it form
Rotate multiple-cutting-edge tool. Move piece.
Cut a plane or straight face.
Explain single-point tools vs multiple cutting edge tools.
One dominant edge. Point rounded to form a nose.
More than one cutting edge.
Describe the three dimensions of machining.
State the Material removal rate formula Rmr
Cutting speed v - Primary motion
Feed f - secondary motion
Depth of cut d - penetration of tool below work surface
Rmr = v f d
Roughing vs finishing
Roughing - High feeds and depths; low speed
Finishing - Low feeds and depths; high cutting speed
State the three functions in machining
Positions tool relative to work
Provides power at determined speed, feed, and depth
State the Chip thickness ration r
r = to / tc
to - depth of cut
tc - chip thickness
Ratio always less than 1
State the four basic types of chips (3)
Discontinuous - Brittle work. Low cutting speed. Large feed and depth of cut. High tool-chip friction
Continuous - Ductile. High cutting speed. Small f and d. Low tool-chip friction
Continuous with Built-up edge - Ductile. Low to med v. Tool-chip friction causes portions of chip to adhere to rake face. Built-up edge forms and breaks off cyclically
Serrated - Difficult-to-machine metals. High cutting speed. Cyclical chip forms with alternating high shear strain then low shear strain.
State the merchant equation for minimizing the energy thru shear plane angle phi. What does it say? (3)
phi = 45 + alpha/2 - beta/2
Phi is angle from surface to chip shear plane.
Alpha is orthogonal angle to tool face.
Beta is orthogonal angle b/w resultant force of tool to face of chip.
In order to increase shear plane angle increase rake angle and/or reduce the friction angle (reduce coefficient of friction).
Larger shear angle, smaller shear plane which lowers shear force, cutting forces, power, and temp
State the Power to perform machining formula
Pc = Fc v
HPc = Fc v / 33,000
Pc - cutting power
Fc - cutting force
v - cutting speed
Problems with high cutting temp (3)
Reduce tool life
Produce hot chips = safety hazard
Cause inaccuracies from thermal expansion of work material