Machining and Grinding Processes Flashcards
DMM1: manufacturing Deck 4
What is the difference between Machining and Grinding processes?
Machining: cutting a desired shape out of a billet
Grinding: using abbrasion to wear away the surface of a billet into a desired shape
What are the three main types of machining processes
Single Point Cutting
Multiple point cutting
Abrasive cutting
What is turning
the workpiece is rotated and a stationary cutting tool is put in contact with it to create rounded shapes.
What are the 12 functions of a lathe?
Facing
straight turning
external grooving
drilling
boring and internal grooving
cutting(parting) off
taper turning
profiling
face grooving
tool forming
threading
kurling
what requirement are needed for turned parts?
all internal corners need a radius >0.4mm
externa corners must be deburred and chamfered
What is center drilling
drilling a hole that will act as a centre of rotation for following
drilling operation
What is reaming?
A process of finishing holes or slightly removing material from the hole to align it with tolerances
What is tapping?
a process used to crease small female threads
What is Milling?
A rotating tool i used to cut away matterial from a billet at a set depth to create complex shapes
What are the three types of vertical milling?
Face Milling
End Milling
T-slot milling
What are the 5 types of horizontal milling?
Slab/ Peripheral milling
Slotting
Slitting
Form milling
straddle milling
What are the requirements for end milling?
All internal corners have the radius of the end mill
all external edges must be deburred and chamfered
Describe the structure of abrasive machining surfaces
A porous network of abrasive grits embedding into a tough matrix that holds them together
What is Swarf?
waste chips of material cut away during machining
What is the purpose of a chip breaker?
a tool which splits chip into smaller parts so they are not long enough to be dangerous or damage equitment
What is machineability?
a materials ability to fracture under a small amount of strain as well as lower shear strength
what rake angle should be used for soft materials?
large rake angles as they increase the length of the shear zone
What is rake angle?
the angle of the cutting tools face normal to the surface of the material
What rake angle should be used for brittle materials?
small if not zero angle as this improves the surface finish on a material prone to splintering
how is the power needed for a cutting process determined?
P = (Specific energy x material removal rate)/ drive efficiency
what causes a tool to fracture or chip?
Excessive stresses from high cutting forces often due to too deep cuts or too fast feed rates
What causes tools to blunt or deform premeturely
Hard workpiece material causing high
cutting forces to be generated. Softening of tool due to lack of cooling
What causes gradual wear and erosion in tools
Friction on flank causing gradual abrasive wear. Crater
wear on tool rake face due to abrasive wear from chip.
Where is the highest temperature on the tool?
at the point of maxium friction and wear
How is tool life determined ?
VT^n = C
T -> tool life
V -> cutting speed
n,C are constants from the specific cutting conditions
What order should turning processes follow?
Facing -> turining -> Chamfering -> parting off
What is a handling cost?
the cost of time loading and unloading machines
What is machining costs
the cost associated wth the time taken to machine each part
What is tooling cost?
the cost of all the components of the machinery and tools as well as their replacements
