Buffer (Production
Planning) (New) (Better): Buffer(s) are segments of time
that are placed at the end of a sequence of tasks for the purpose of protecting
the schedule of those tasks. Buffer(s) can also be used to protect cost, much
like a contingency for unexpected expenses in a budget. The size of time
buffers is based on the total duration of the task sequence to which they are
attached. Basically, the size of the buffer is determined by calculating the
total of the contingencies in the task that make up the sequence.
(Effective Project
Management: Traditional, Agile, Extreme, 5th Edition Robert K. Wysocki, Chapter 10, p. 4)
Buffer (Previous): The
purpose of the buffer is the smooth handling of works for unmanned
manufacturing, and TAKT balance is very important for automated lines. If not
balanced, the production line may suffer considerable line disturbance. The
control of connecting a few assembly processes cen introduce the ‘PULL MODE’
operation, which is optimum WIP. The whole process is dynamically controlled
using the shop-floor control system and a so-called ‘IC’ cardwhich is a small
memory unit for the information controlling the operation. All production
information will be retained and used to control the next process. If required,
the information will be transferred to a host system and distributed to people
required to take quick actions. The assembly production line is fully automated
by the computers: this is computer-integrated assembly. Normally th buffer
sizes are optimized by computer simulation of the production process. Recently,
cell-type production has been applied to specific processes in mixed production
in Japanese enterprises.
(Asai K.,
Takashima S., Edwards P. R., Manufacturing, Automation Systems, and CIM
Factories, 1994, pg.125
***
Turning Center
(Manufacturing) (New) (Better): When a CNC lathe is equipped with an automatic tool
changer it is called a turning
center.
The
basic framework of a CNC lathe is very similar to that of a manual lathe.
Recall that turning centers are CNC lathes with the addition of an ATC. Turning
centers are also specially designed for production work and aggressive material
removal rates, and do not have provisions to be used manually. Most turning
centers also have an angled bed on which the X-axis rides, and are called “slant-bed”
machines for that reason.
Production turning centers also feature low-friction linear guideways
for sliding machine surfaces. The use of these greatly minimizes wear, reduces
friction (enabling the ultra-high rapid traverse feeds), and allows for very high
accuracies due to a zero- clearance preloaded ball bearing design. Today,
turning centers are available that are able to perform milling and other
machining operations besides just turning. Special live
tooling attachments make this possible. Live tools are small motorized spindles
that enable a turning machine to perform light-duty milling and
to perform hole-work such as drilling, tapping, and reaming
off-center and cross-ways. Live tooling attachments are
available for end-working (for machining on
the face of a part), cross-working (for drilling cross holes, milling keyways, etc.), and in adjustable
anglehead variations
(Precision
Machining Technology, Peter J. Hoffman, Eric S. Hopewell, Brian Janes,Kent
M. Sharp, Jr, p. 564, 579-580)
Turning center (Previous): A modern CNC turning center is capable of performing
various turning and related operations contour turning and automatic tool
indexing all under computer control.In add,t,on most sophisticated turning
centers can accomplish workpart gaging,tool monitoring, automatic tool changing
when tools become worn and even automatic workpart changing at the completion
of the work cycle.
(Fundamentals of Modern
Manufacturing:Materials,Processes and systems,Mikell P. Groover )
***
Hoist (Material Handling) (New) (Better): A
hoist is a device for lifting or lowering objects suspended from a hook on the
end of retractable chains or cables. It is usually supported from overhead by a
hook or it travels on a track.
Applications:
Services a machine or work area.
Types
of Hoists: Hand hoist (chain
and ratchet)
Power hoist (electric wire rope,
electric chain, air wire rope and air chain)
(Raymond A. Kulwiec, Material Handling Handbook, Second edition, p.111)
Hoist (Previous): Load-suspensions
parts of a manually operated hand chain hoist are the parts that are subject to
direct load forces from the load attached to the load hook. Load- suspensions
parts are the means of suspension, including the trolley, suspension hook,
clevis or lug. The hoist frame which supports the load wheel, the load wheel,
load chain, and the load block. Load suspension parts are normally designed so
that the static stress calculated for the rated capacity load does not exceed
25% of the average ultimate strength of the material used for the parts. The
resultant design factor is 4.
Standart models of manually operated
hand-chain hoists are intended for general industrial use in ambient
temperatures from O Fahrenait degree to 130 Fah. Enviramental conditions such
as hazardous locations, excessively low or high ambient temperatures, corrosive
fume atmospheres, dust-laden atmospheres, moisture-laden atmospheres, and
exposure to outdoor-weather conditions that could be detrimental to a manually
operated hand-chain hoist are considered abnormal operating conditions.
(Raymond A. Kulwiec, Material handling
Handbook, Second edition, page 480-481)
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