Title: numerous cross-sections etc. to close tolerances for

 

 

 

 

 

 

 

 

Title: Review of conventional and advance Milling machines

 

Student
Name: Patel Ravikumar

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Student
Number: 8030710

Course
Name: College reading & Writing skill

Course
Instructor: Lubna sheikh

Assignment
Due Date: January 4th ,2018

 

 

 

 

 

Milling machine is one of the most significant machine
tools in any machine shop, all the operations can be executed on it with high precision.
The indexing head makes the machine appropriate for various purposes as exact
rotation of job is possible by its use. Milling machine enhances the work of
lathe and can produce the ordinary and bent surfaces and also helical indentations
etc. The milling machine may be so arranged that the several cutters are
mounted on the arbor at the same time, thus increasing the metal removal rate
and allowing several surfaces to be machined at the same time and also ensures accuracy.
It is a process in which metal elimination takes place when the work is fed
past a rotating cutter. Its significance lies in its size to perform a great
number of operations which no other single machine tool can achieve. At the
same time, it delivers a high production rate with very precise tolerance. Evaluation
of technology, Milling has mainly substituted other machine tools like shapers,
and planers for several kinds of operation. Milling machines can be used for
machining plane surfaces, contoured surfaces, intricate and asymmetrical areas,
surfaces of revolution, slotting, external and internal thread, gear cutting, helical
surfaces of numerous cross-sections etc. to close tolerances for both limited
and mass production. This review study would describe different aspects of
milling machine and machining and its costs.

Firstly, milling machine history goes the distance
back to the mid 1800’s, with the primary machines advancing from the procedure
of revolving filling, which basically included running a round saw on a machine.
Filling had been around for a long time preceding the milling procedure being
presented. These early machines were not enthusiastic about exactness, and were
utilized to make a harsh cut. The completing touches were finished by hand.
The machines of that period kept on budding, however
it was not generally until the 1840’s that enormous changes truly began to
happen. It was through this phase that the Lincoln miller was carried into existence.
This machine is considered by many to be of major reputation in milling machine
antiquity, as it was somewhat of a hybrid mechanism set together using many of
the best parts from a number of establishments. While this was absolutely a
sign of advancement in the industry, there was still one chief aspect missing. Recent
milling machines drill on 3 and 5 axes, but these primary machines still only worked
on two, with the vertical axis. It was the 1860’s numerous improvements in
milling were made, and it was a machine perceived by Joseph R. Brown that pretty much opened the doors for new transformations.
His was the first machine to accurately integrate 3-axis drilling. It was then
that the axes were names XYZ, which is how they still remain to this day. Further
discrepancies came later World War 1, and by the time the 1940’s rolled around,
gigantic instabilities were trendy in the milling industry. This led to the
first wave of mechanization, and by 1952 numerical control had been familiarized
into a machine. From the 1970’s onwards, computers started to lead the
industry, with the NC machines of the past now being advanced to CNC machines.
As the technology nurtured and the software established, the tasks that the
machines could take on raised with them. There are now machines that operate on
5-axes, churning out incredibly intricate pieces rapidly and with the least excess.
The necessity for any kind of operation by hand, other than that of the systems
analyst, is now pretty much gone. The amount of time and money that an engineering
company can save by using CNC machines is off the charts, which is why the
history of milling is still to come for the subsequen1t chapter to be written. Milling
machines are classified in four different types. Column and knee type milling
machine, Bed type, Planer type, Special type. Column and knee type milling
machines consists of base having different control mechanisms housed in there.
The base consists of vertical column at one of its end. The other work table is
identified as “Knee”. Bed type milling machines are also known as manufacturing
milling machine. The table movement is restricted to reciprocation only.
Special type milling machines are designed for special purpose, which is
entirely different in design and construction form conventional milling
machines.

 

Secondly, cutting tools and material to be machined
both are most significant factor in the production. Trend of tipped tool in
mass production is increased drastically, and this tipped tools/indexable tools
are known as “Inserts”. Its cutting edges consist of separated piece of metal,
either brazed, welded or clamped on separate body.  There are two major type of cutting tools:
Linear and rotary. Linear cutting tools consists single point cutting tool and
broaches. However, drill bit, countersink, counterbore, taps and die, reamers
and cold saw blades are considered as rotary cutting tools. Apart form this,
band saw blades, hacksaw blade and fly cutters haver both rotary and linear
motion. Cemented carbide polycrystalline diamond and cubic boron nitride are
the common material used as tips. Fly cutters, endmills, tool bits and saw
blade are known examples of inserts. Earlier, there were major problems arise
in tool and job set up. Spyridi and Requicha (1990) use visibility as tool for
the setup of workpiece on a coordinate measuring machine. To eliminated
problems three basic method are used: Visibility of workpiece, visibility of
milling machine and resolution of problem. Although, by adjusting cutting
speed, feed, depth of cut, table feed and spindle speed can eliminate errors
very precisely.

Thirdly, technology involved in milling machines, the
most critical of which was touched on in our recent assessment of precision
tools post, has been developing continually. Milling machines and cutters come
in numerous designs, special purpose and many sizes and shapes,
respectively.  The challenge modern
industries are mainly concerns on accomplishment of superior quality, in terms
of dimensional consistency of job, better surface finish, high production rate,
less wear on the cutting tools, cheap machining in terms of cost effective and
efficient performance with minimum environment effect. High speed steel cutters
are widely use for machining, which are least expensive.  When cobalt is added in HSS can be run 10%
faster than regular high-speed steel. There are many factors which improved
swiftly i.e. number of flutes, diameter, coating, tipped tool, helix angle.
However, the cost for the same is increased. Such factors may very according
properties of material. Moreover, speed of spindle, feed and depth of cut are
also major concerns of surface finish and productivity. In addition, coolant is
most substantial aspect of machining. Conventional lubricating methods are used
to machine material having less hardness. In such techniques air, water, oil,
mixture of oil and water, etc. are used as coolant. Hybrid lubrication is used
to machined hard metal, which are very difficult to machine. Cryogenic cooling
is most developing cooling technique is used to machine hard and precise
machining. Liquid nitrogen is used to cool component.

To conclude, milling machines are most efficient
machines in present time. It eliminated number of other machines by its hybrid
development in all aspects. Highest production rate with minimum labor cost
will be obtained by more modification in milling machines like CNC milling
machines.

 

References

References

Spyridi, A. (1990). Accessibility
Analysis for the Automatic Inspection of Mechanical Pans by Coordinate
Measuring Machines. In A. Requicha, Accessibility Analysis for the
Automatic Inspection of Mechanical Pans by Coordinate Measuring Machines.

Stephenson. (1997). Metal cutting theory
and practice. In D. A., Metal cutting theory and practice.
Walker, J. R. (2018). Modern
Metalworking. In K. W. Stier, Modern Metalworking.