MCHE 3920 TEST STUDY GUIDE
What is machining used for? - ANSWER Used extensively to:
Create parts from stock material
Perform secondary operations on parts shaped by another principle
Make molds or dies to be used in other operations
Deliver a desired surface finish
Form Freedom? - ANSWER virtually unlimited
what materials can be machined? - ANSWER nearly all (ex: metal, plastic, wood, glass,
ceramic)
production volume? - ANSWER very large range
Leading edge of the tool moves how?
Tool is? - ANSWER moves with constant speed through a solid slab of material at a fixed
depth
wedge shaped with an internal "contour angle"
relief and rake angle? - ANSWER the position relative to the material
90= relief + contour + rake angle
how does machining happen? - ANSWER Machining is process of plastic deformation
Deformation localized in a "shear zone" just ahead of cutting tool
Material is quickly sheared away by the tool
Friction heats the material rapidly
For isotropic materials, yield stress is about 50-60% of tensile stress
A tool applies a force? - ANSWER in two directions
horizontal force- allows the tool to cut in a horizontal direction
vertical force- helps keep the tool from "climbing" out of the material
higher rake angle = - ANSWER higher the required Fv
relief angle prevents - ANSWER excessive friction in the region behind the part
, typical rake angles Fh=1.5kt - ANSWER k = shear yield stress
t = cutting depth
Fh = force per unit depth of cut
Machining generates heat from - ANSWER the plastic deformation and the friction
between the cutting tool and the part
about 80% of heat ends up in chip
cooling fluid is used to - ANSWER remove heat, wash away chips and lubricate the tool
and machining surfaces
problems with cooling fluid - ANSWER hazardous in work environments and pose
environmental issues associated with disposal
alloys are used in machining to - ANSWER speed up machining
lead and sulfur promote the formation of inclusions
inclusions are - ANSWER detrimental to material properties, but promote weakness in
the shear zone
results in required cutting forces
avoid applying forces in - ANSWER torsion and bending because they produce larger
deformation then forces in compression or tension
deformation considerations dictate what - ANSWER order in which the machining tasks
are completed
reduce tool deformation by - ANSWER reduce the required cutting force by making
shallower cuts and reducing tool size
high speed machining - ANSWER tool speed is increased, in order to maintain
productivity
vibration is an issue at high speeds
what creates repeating surface pattern roughness - ANSWER cutting is done in passes,
and there is overlap between the passes
also caused by part and tool vibration
burns are created when - ANSWER the tool "runs out" across the edge of the material
lay patterns are created - ANSWER when the tool creates repetitive impressions on the
part
lathe is.. - ANSWER most common turning machine
What is machining used for? - ANSWER Used extensively to:
Create parts from stock material
Perform secondary operations on parts shaped by another principle
Make molds or dies to be used in other operations
Deliver a desired surface finish
Form Freedom? - ANSWER virtually unlimited
what materials can be machined? - ANSWER nearly all (ex: metal, plastic, wood, glass,
ceramic)
production volume? - ANSWER very large range
Leading edge of the tool moves how?
Tool is? - ANSWER moves with constant speed through a solid slab of material at a fixed
depth
wedge shaped with an internal "contour angle"
relief and rake angle? - ANSWER the position relative to the material
90= relief + contour + rake angle
how does machining happen? - ANSWER Machining is process of plastic deformation
Deformation localized in a "shear zone" just ahead of cutting tool
Material is quickly sheared away by the tool
Friction heats the material rapidly
For isotropic materials, yield stress is about 50-60% of tensile stress
A tool applies a force? - ANSWER in two directions
horizontal force- allows the tool to cut in a horizontal direction
vertical force- helps keep the tool from "climbing" out of the material
higher rake angle = - ANSWER higher the required Fv
relief angle prevents - ANSWER excessive friction in the region behind the part
, typical rake angles Fh=1.5kt - ANSWER k = shear yield stress
t = cutting depth
Fh = force per unit depth of cut
Machining generates heat from - ANSWER the plastic deformation and the friction
between the cutting tool and the part
about 80% of heat ends up in chip
cooling fluid is used to - ANSWER remove heat, wash away chips and lubricate the tool
and machining surfaces
problems with cooling fluid - ANSWER hazardous in work environments and pose
environmental issues associated with disposal
alloys are used in machining to - ANSWER speed up machining
lead and sulfur promote the formation of inclusions
inclusions are - ANSWER detrimental to material properties, but promote weakness in
the shear zone
results in required cutting forces
avoid applying forces in - ANSWER torsion and bending because they produce larger
deformation then forces in compression or tension
deformation considerations dictate what - ANSWER order in which the machining tasks
are completed
reduce tool deformation by - ANSWER reduce the required cutting force by making
shallower cuts and reducing tool size
high speed machining - ANSWER tool speed is increased, in order to maintain
productivity
vibration is an issue at high speeds
what creates repeating surface pattern roughness - ANSWER cutting is done in passes,
and there is overlap between the passes
also caused by part and tool vibration
burns are created when - ANSWER the tool "runs out" across the edge of the material
lay patterns are created - ANSWER when the tool creates repetitive impressions on the
part
lathe is.. - ANSWER most common turning machine
