Lecture 2 - HVM + Machine Processes Review Flashcards
What is the majority of UK manufacturing
manufacturing of finished goods
What is HVM
strategy of UK government to develop UK manufacturing technology and systems High value manufacturing
application of leading edge technical knowledge and expertise to the creation of products, production processes and associated services which have potential to bring sustainable growth and high economic value
What does HVM mean in practice
UK never compete on volume, but can compete by adding value to manufactured goods through technological improvement
What demands on manufacturing are emphasised in HVM
Decrease product quantity
increase in customer expectations
use new or better materials
maintaining variety on smaller scale by developing new or better processes
Does HVM lose jobs
no, generates jobs as required new processes to be developed and enables supply chains to be brought closer to production facilities
local level yes but overall just relocation
HVM facilities examples
rolls royce, boeing, mclaren factories in sheffield
JLR plant in wolverhampton
Catapults - uni based industrial research centres e.g. AMRC
After HVM what is next
Industry 4.0, applying emerging digital technologies to manufacturing to
improve productivity
improve quality
reduce costs
What are the potential benefits of 4IR
factory floor and production systems - autonomous systems, flexible machines
use of AM techniques
digital assisted assembly and 3D visualisation
Whats the difference between HVM and 4IR
4IR will impact small and medium enterprises
HVM is mostly large companies and unis
4IR tech becoming cheaper and easier to implement quickly
What is the key part of HVM
production process - making the basic shape, making the final shape attaching everything together
Types of casting
Making basic shape
traditional - disposable mould casting (sand and investment)
more recently - permanent mould casting (die), continuous, powder metallurgy, sintering, AM (SLS, SLM, EBM)
Types of machining
making final shape
Traditional - turning, milling, shaping
more recently - high speed machining, grinding (for bulk material removal)
What have been the main developments of machining with HVM
where most of focus has gone
Greatly improving efficiency, removal of lot of cost, removal of whole processes in manufacturing, techniques to deal with very hard materials e.g. electrical discharge machining
Types of joining
Traditional - Fusion welding (oxy-feul and arc), brazing and soldering, mechanical fastening
more recently - fusion welding (electron/laser beam), resistance spot welding, solid state (small heat affected zone)
What is machining
process of removing unwanted material from a work piece in the form of chips
Why is metal cutting a complex process
large variety of inputs machine tool cutting tool property and parameters of workpiece cutting parameters workpiece holding fixtures
Types of machine tools
manual lathes and milling machines
multiple axis cutting machining centres
What are the types of cutting tools
one piece (solid tools more traditional) HSS two piece (insert + body) expensive insert that can rotate for fresh edge cheap body
Why do modern machines use two piece tools
cheaper (only worn out tips)
tough material for body/hard material for insert
inserts can last longer as indexable
can use more exotic materials (as smaller)
Why are cutting tools so important
usually only spend <10% manufacturing cost, have much higher of the success of the machining process
Mechanical of chip formation
tool move along shear plane at cutting speed V
Relief/clearence angle exists to minimise contact between tool and workpiece
shearing occurs at shear plane
material under shear plane is not deformed, everything above converted to chips
What is chip thickness a function of
tc=f(depth of cut to, rake angle alhpa, shear angle theta)
HVM modify model for max efficiency
and push to the limit
What is speed in machining
primary cutting motion, velocity of cutting tool relative to surface of a workpiece
What is feed rate in machining
secondary cutting motion, velocity perpendicular to the speed and is usally expressed per revolution or per tooth
What is depth of cut in machining
third motion that represents how far tool penetrates per cut
What is the material removal rate equation
for single point tools
MRR = speed x feed x depth of cut
for multi point tools
MRR = cross sectional area of cut x feed
What are the four types of chips
continuous
serrated
discontinous
built up edge
What are continuous chips
ductile materials, high cutting speed and/or rake angles
deformation around primary shear zone
good surface finish but chips wrap around machine parts - need chip breakers (extra cost)
What are serrated chips
semi continuous chips with zones of low and high shear strain
chips have a saw tooth like appearance
work piece low thermal conductivity and strength that decrease sharply with temperature (titanium)
What are discontinuous chips
segments that may be firmly or loosely attatched to each
brittle workpiece (cannot undergo high shear strain, will happen anyway how do you make better)
very low/high cutting speed, depth of cut
worse surface finish and accuracy
What type of chips are used by some tools
build up edge, give protection to tool, reduces surface finish, but where unimportant increases tool life
What are built up edge chips
formed at tip of tool during cutting
consists of layers of material from workpiece gradually building up on the tool, then break off
poor surface finish, work hardening of surface, poor geometrical control but small life increase
