Numerical technology. The part may be designed and

      Numerical
control (NC) machine is an automated machine-tool that is operated by accurately
programmed commands fixed on a standard. Most of NC machines are today computer
numerical controlled (CNC), in which computers play an integral part of the
control (Lan, 2010). The first NC
machines were built in 1940s and 1950s, based on existing tools that were
modified with motors that moved the controls to follow points served into the
system on pressed tape. These early servomechanisms were rapidly enlarged with
analog and digital computers, creating the modern CNC machine tools that have reformed
the machining processes (Mukherjee, et al., 2014).

     CNC lathes
are swiftly replacing the older production lathes due to their ease of setting,
operation, repeatability and accuracy. These are designed to use modern carbide
tooling and are more compatible with modern technology. The part may be
designed and the tool paths are programmed by the CAD/CAM process or manually
by the programmer and the resulting file is uploaded to the machine. After
setting and taking trials, the machine will continue to turn out parts under
the irregular control of an operator (Moriwaki, et al., 2006).

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     With speedy
growth in this industry, different CNC lathe manufacturers use different user
interfaces which sometimes make it difficult for operators as they should be informed
with them. With the beginning of cheap computers, free operating systems such
as: Linux and open source CNC software, the entire price of CNC machines has
been dropped (Suresh, et al., 2012). In modern CNC
systems, end-to-end component design is highly automated using computer aided
design (CAD) and computer-aided manufacturing (CAM) programs (Hao &
Liu, 2017).
The programs produce a computer file that is interpreted to obtain the commands
needed to operate a machine via a post processor and then biased into the CNC
machines for production. Since any module might require the use of several
different tools – drills, saws, etc., modern machines often combine multiple
tools into a single “cell”. In other installations, several different
machines are used with an external controller and human or robotic operators
that move the unit from machine to machine. In either case, the series of steps
needed to produce any part is highly automated and produces a part that closely
matches the original CAD design (Pawar, et al., 2016).

      With the
recent development of high speed machining technology, two-dimensional contour
end milling has achieved an increasing demand in the manufacturing of die and
mold products. This is partially since an unexpectedly larger number of
mechanical parts are made of two-dimensional contour and even more complex
objects are generally created from a billet by using two-dimensional roughing,
semi-finishing and finishing processes. In two-dimensional contour end milling,
conventional offset contour CNC tool paths generated by commercial CAM software
are extensively used to machine these mechanical parts (Xu, et al.,
2013).

         In
recent times, as the incredible demands for mechanical parts with high
geometric and dimensional accuracy increase, a requirement to produce those
parts with such accuracy is greatly understood by today’s manufacturing
industries. To this end, CNC machine tools are the most important means of production
for the manufacturing industries (Zhu, et al., 2012). CNC machine tools have been widely useful
to a range of applications, for example, in the aerospace industries. With the
recent advancement of the machine tools manufacturing technologies including
high speed feed drives and highspeed spindles, high speed end milling on the
CNC machine tools has become constantly popular, and is being performed to manufacture
the sections with the required contour geometry and dimensional accuracy (Sawula, et
al., 2012).
however, the geometric accuracy of the machined surface is greatly influenced
by the numerous errors sources ranging from errors existing in the machine tool
system itself to the errors due to the cutting process.

      Motivated with the background and issues on
errors of structure and application or program in the machine tool system and
the cutting process which cause machining geometric errors as discussed above,
and compare with the current research work about tool path modification methods
for the improvement of the machining geometric accuracy in 3-axis CNC machine.

     With this
aim, this review paper proposes comparing or to evaluate different from offset
structure (such as tool path, geometric positioned) generation by forward and
backward tool path modification methods to regulate the cutting engagement
angle and therefore the cutting force at a desirable constant level, which will
consequently response how improve the machining geometric accuracy in 2D end
milling on a 3-axis machining center, and how is choose suitable method in any
section of 3-axis CNC machine.