1-Lean Manufacturing (Old)
A production strategy
in which all parts of the production system are focused on eliminating waste
while continuously increasing the percentage of value-added work. Methodologies
include designing assembly and fabrication for short flows, creating kits of
details and subassemblies, and preventing in-process defects.
(Black,J., Lean Production Implementing A world-Class
System, pg.179, Industrial Press, Inc., 2008)
Lean Manufacturing(New and Better) (Manufacturing Type)
In a modern manufacturing environment, companies must be
responsive to the needs of the customers and their specific requirements and to
fluctuating global market demands. At the same time , manufacturing enterprise
must be conducted with a minimum amount of wasted resources to ensure
competitiveness. This realization has lead to learn production or lean
manufacturing strategies.
Lean manufacturing is a systematic approach to identifying
and eliminating waste ( that is , non-value-added activities) in every area of
manufacturing—through continuous improvement and by emphasizing product flow in
a pull system. When applied on a large scale, lean manufacturing generally is
referred to as agile manufacturing. Lean production requires that a
manufacturer examine all of its activities from the viewpoint of the customer
and optimize processes to maximize added value. This viewpoint is critically
important, because it helps identify whether or not an activity:
·
Clearly adds value
·
Adds no value but cannot be avoided
·
Adds no value but can be avoided
·
(Kalpakjian S.,
Schmid S.R.,Manufacturing Engineering and
Technology, 5th Edition, pg.1227)
2-Control numerical
control (CNC) (Old)
First implemented in the early 1950s, this is a method of
controlling the movements of machine components by direct insertion of coded
instructions in the form of numerical data.
(Kalpakjian S. , Schmid S.R. , Manufacturing Engineering and
Technology, p. 34)
CNC ( Computer
Numerical Control) (New and better) (Control)
Computer Numerical Control (CNC) is a computer-assisted
process to control general-purpose machines from instructions generated by a
processor and stored in a memory system or storage media ( tape, disk, chip,
etc.) for present use as well as future use. Numerical Control means precisely
what the term implies—control by numbers. Controlling machines by numerical
command has brought about a revolution in manufacturing. CNC can be adapted to any kind of machine or
process that requires direction by human intelligence.
CNC is a specific form of control system where position is
the principal controlled variable. Numerical values, representing desired
positions of tools and symbolic information corresponding to secondary
functions, are recorded in some form ( tape, disk, network, etc.) where the
information can be stored and revised indefinetely. Hard Drives, Tape Readers,
and other converters transform this information into signals that ultimately
operate servo-mechanisms on each axis of the machine whose motions are to be
controlled.
CNC was originally applied to metalworking machinery: Mills,
Drills, Boring Machines, and Punch Presses. It has expanded to other areas of
metalworking includinf applications in Robotics, on cutoff machines, tube
benders, grinders of many types, gear cutters, broaching machines,
electromechanical machining, flame cutting, and welding. CNC is also used for
inspection, drafting systems, electronics assembly macihnes, laser cutting and
bonding processes, automatic testing systems, printing machinery, woodworking
machinery, step-and-repeat photography, and garment-cutting equipment. Today,
32-and 64-bit-bus microprocessors directly coupled with production machine
control systems are expanding both the application and the basic definition of
numerical control.
(Madison James G. CNC
machining handbook: basic theory, production data, and machining procedures , pg.5)
3-Lost Foam Casting (Old)
The lost foam casting process origineated in 1958. The lost
foam process consists of first making a foam pattern are created from
polystrene beads , similar in s,ze and shape to sand granules , expanded to the
desired shape using aluminiun toolnig. More complex shapes can be created by gluing
a number of patterns together. The assemblies are then attached to a central
foam piece or tree. ,Depending on size multiple a patterns can be produced on a
single tree. (Workshop Processes, Practices and Materials ; Bruce J. Black ,
pg. 286 )
Loast Foam Casting(Old)
The lost foam casting process consists of first making a
foam pattern having the shape of the finished metal part. The foam patterns are
created from polystyrene beads, similar in size and shaped to sand granules,
expanded to the desired shape using aluminium tooling. More complex shapes can
be created by gluing a number of patterns together. The assemblies are then
attached to a central foam piece or tree.
After short stabilising period, the completed pattern is
strengthened by dipping in a refractory material which coats the foam pattern
leaving a thin heat-resistant layer which is then air dried. This ceramic
coating also provides good surface finish for the finished casting.
After compaction, molten material is poured into the mould
causing the foam to burn up and vaporise as the molten metal replaces the foam
pattern, exactly duplicating all the features of the original pattern.
After solidification, the container is tipped over and the
unbounded sand flows out together with the castings. Because there are no
binders or other additives the sand is reclaimable.
Workshop Processes, Practices and Materials - pg 286
Lost-Foam Casting(New and better) (Manufacturing Method)
The lost-foam casting process uses expendable polystyrene
patterns. Different versions of the basic process are called the “full-mold”
process, “evaporative pattern casting” (EPC), and “expanded polystyrene”
process. Styrofoam beads are used to form the pattern. The beads are injected
in a steam-jacketed die under low pressures and allowed to expand and fuse to
form the pattern. The surface quality of the foam pattern determines the
surface texture of the cas part. Both underaged foam patterns ( incompletely
fused beads) and overaged patterns ( partially melted beads that create
wrinkles on the surface) impair the casting’s surface quality. After ejecting
the foam pattern from the die, Gates and risers made out of foam are glued the
appropriate surfaces. A thin coat of a fine ceramic is aplied via immersion in
a slurry to cover all the surfaces of the foam pattern ( except the pouring
basin). The coating improves the casting surface finish by acting as a barrier
between the supporting sand the foam. After the coating has dried, the coated
pattern assembly is either buried in
loose, free-flowing sand or covered in lightly pazked gren sand. The coating
also provides some stability to the mold and prevents sand from caving in the
cavity created by evaporating foam, especially when the pattern is buried in
loose ( rather than packed) sand. The metal is poured, allowing the pattern to
volatilize and progressively create the mold cavity to be continuously filled
by the incoming metal. Pouring is usually assisted with a vacuum that removes
gases from the burnt foam through the semipermeable coating, thus enabling
uninterrupted metal ingress. Alternatively, pressurized lost-foam casting is
used to eliminate gas porosity to a nearly undetectable level. After
solidification, the casting is readily extracted from loose sand by robots,
thus eliminating shakeout.
(Asthana, R.,Kumar, A., Dahotre, N., Materials Science in Manufacturing,p. 74)
4-AS/RS: ( Old)
Automated
manufacturing systems such as flexible manufacturing systems can provide quick
changeovers to different part types and their cost-effective production only if
we can get the right parts, pallets, fixtures, and tools to the right place at
the right time. For this purpose an efficient system for their storage and
retrieval together with a material transportation system is required an
integrated FMS, AGVS, and AS/RS system provides an efficient production system
for manufacturing low- to medium- volume and middle- to high-variety products.
It is addressed a number of issues related to the design and analysis of
automative storage and retrieval system.
Types of
AS/RS:
1-Unit load
AS/RS
2-Miniload
AS/RS
3-Person-on-board
AS/RS
4-Deep-lane
AS/RS
5-Automated
item retrieval system
(Nanua
Singh, Computer-Integrated Design and Manufacturing, pg:277)
AS/RS : AUTOMATED STORAGE/RETRIEVAL SYSTEMS
(New) (Better)(Automation)
An automated storage/retrieval system (AS/RS)
is defined by the Materials Handling Institute as, “A combination of equipment
and controls which handles, stores and retrieves materials with precision,
accuracy and speed under a defined degree of automation”. AS/R systems are
custom-planned for each individual application, and they range in complexity
from relatively small mechanized systems that are controlled manually to very
large computer-controlled systems that are fully integrated with factory and
warehouse operations. The AS/RS consists of a series of storage aisles that are
serviced by one or more storage/ retrieval (S/R) machines, usually one S/R
machine per aisle. The aisles have storage racks for holding the materials to
be stored. The S/R machines are used to deliver materials to the storage racks
and to retrieve materials from the racks. The AS/RS has one or more input
stations where materials are delivered for entry into storage and where
materials are picked up from the system. The input/output stations are often
referred to as pickup and deposit (P&D) stations in the terminology of
AS/RS systems. The P&D stations can be manually operated or interfaced to
some form of automated handling system, such as a conveyor system or AGVS.
Basic
Components of an AS/RS All automated storage/retrieval systems consist of
certain basic building blocks. These components are: 1) Storage structure 2)
Storage/retrieval (S/R) machine 3)Storage modules (e.g., pallets for unit loads)
4) Pickup and deposit stations.
1. The
storage structure is the fabricated steel framework that supports the loads
contained in the AS/RS. The structure must possess sufficient strength and
rigidity that it does not deflect significantly due to the loads in storage or
other forces on the framework. The individual storage components in the
structure must be designed so to accept and hold the storage modules used to
contain the stored materials.
2. The S/R machine (sometimes called a crane)
is used to accomplish a storage transaction, delivering loads from the input
station into storage, or retrieving loads from storage and delivering them to
the output station. To perform these transactions, the storage/retrieval
machine must be capable of horizontal and vertical travel to align its carriage
with the storage compartment in the storage structure, and it must also pull
the load from or push the load into the storage compartment.
3. The
storage modules are the containers of the stored material. Examples of storage
modules include pallets, steel wire baskets and containers, tote pans, storage
bins, and special drawers (used in miniload AS/RS systems). These modules are
generally made to a standard base size that can be handled automatically by the
carriage shuttle of the S/R machine.
4. The
pickup and deposit stations are used to transfer loads to and from the AS/RS.
They are generally located at the end of the aisles for access by the S/R
machine and the external handling system that brings loads to the AS/RS and
takes loads away. The pickup stations and deposit stations may be located at
opposite ends of the storage aisle or combined at the same location. This
depends on the origination point of the incoming loads and the destination of
the output loads. The P&D stations must be designed so that they are
compatible with the S/R machine shuttle and the external handling system.
(Kumar, A., Suresh, N., Production of Operations Management, Second Edition, pg. 258-259)
5- Viscoelasticity (Previous)
5- Viscoelasticity (Previous)
Although rubber is highly elastic
it is not completely so. The best the chemist can achieve is probably
represented by the high bounce rubber ball from the toy store, which is a
rubber compound with an extremely high proportion of BR ( Polybutadiene Rubber)
and a vulcanization system designed for a high state of cure. The chemist can
also design a compound, so that a ball made from it hardly bounces at all; toy
stores probably have them too. This low bounce ball is said to have a
significant viscous component and a low elastic component. This combination of
viscous and elastic properties results in the definition of viscoelasticity.
(Andrew Ciesielski, An
Introduction to Rubber Technology, pg.127)
Viscoelasticity (New andBetter) (Material Property)
Viscoelasticity is a
generalization of elasticity and viscosity. It is characterized by the
phenomenon of creep which manifests itself as a time dependent deformation
under constant applied force. In addition to instantaneous deformation, creep
deformations develop which generally increase with the duration of the force.
Whereas an elastic model, bydefinition, is one which has the memory only of its
reference shape, the instantaneous deformation of a viscoelastic model is a
function of the entire history of applied force. Conversely, the instantaneous
restoring force is a function of the entire history of deformation. The ideal
linear viscous unit is the dashpot The rate of increase in elongation or
contraction e is proportional to applied force f: Wd = f, where i/is the
viscosity constant (the overstruck dot denotes a time derivative). The elastic
and viscous units are combined to model linear viscoelasticity, so that the
internal forces depend not just on the magnitude of deformation, but also on
the rate of deformation. The
stress-strain relationship for this assembly has the general form ~z2E+a,~+aoe=b~]+b,j
+bof, (1) where the coefficients depend on the spring and viscosity constants..
(Terzopoulos, D., Fleischer, K., Modeling Inelastic Deformation: Viscoelasticity,
Plasticity, Fracture, pp. 271-272)
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