National Conference on Recent Trends in Engineering & Technology
Effect of Machining Parameters on Geometric Form
Control and Orientation Control – A Review
NAVora1, PMGeorge2,SPJoshi3
Mechanical Engineering Department
BVM Engineering College, V.V.Nagar
1
[email protected]
2
[email protected]
3
[email protected]
AbstractA major channel of machined components are
produced by CNC milling. The milling machine has got specific
capability to produce components meeting both the dimensional
and geometric requirements. These requirements are to be met
with in order to meet the functional requirements by each
components as a part of an assembly. This paper exposes the
various research work carried out in this direction especially in
the content of form and orientation control. The controls
considered in this review papers are : Flatness, Straightness and
Parallelism. The effect of various cutting parameters on these
geometrical parameters are of paramount significance for
effective part functioning. Literature surveys indicates that not
much work has been carried out in this area.
Keywords
– Milling ,GD&T, Flatness, Straightness, Parallelism.
I. MILLING
Milling is process of generating machined surfaces by
progressively removing a predetermined amount of material or
stock from the workpiece, which is advanced at a relatively
slow rate of movement or feed of a milling cutter rotating at
comparatively high speed. The characteristics feature of the
milling process is that each milling cutter tooth takes its share
of the stock in the form of small individual chips. Greater
attention is given to the geometry in addition to the dimensional
accuracy and surface characteristics of products by industries
these days. Milling operations are performed with milling
cutters of different types and sizes. Owing to the fact that they
give better components leading to faster and economical
assembly.[1]
II. LITERATURE SURVEY
In this study, the effects of cutting edge geometry,
work-piece hardness, feed rate and cutting speed on
surface roughness and resultant forces in the finish hard
turning of AISI H13 steel were experimentally investigated.
This study shows that the effects of work-piece hardness,
cutting edge geometry, feed rate and cutting speed on surface
roughness are statistically significant.[2]
In this Paper experimental investigation was conducted to
determine the effects of cutting conditions and tool geometry on the
surface roughness in the finish hard turning of the bearing steel
(AISI 52100). The effect of the effective rake angle on the surface
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finish is less, the interaction effects of nose radius and effective rake
angle are considerably significant. Mathematical models for the
surface roughness were developed by using the response
surface methodology. The investigations of this study indicate that
the parameters cutting velocity, feed, effective rake angle and nose
radius are the primary influencing factors, which affect the surface
finish. The results also indicate that feed is the dominant factor
affecting the surface roughness, followed by the nose radius, cutting
velocity and effective rake angle.[3]
The aim of this work is to analyze the influence of cutting
conditions on surface roughness with slot end milling on
AL7075-T6.The considered parameters are: cutting speed,
feed, depth of cutting and mill radial engage. Surface
roughness is influenced by: tool geometry, feed, cutting
conditions and other factors such as: tool wear, chatter,
tool deflections, cutting fluid, and work-piece properties.[4]
Influence of tool geometry on the quality of surface
produced is well known and hence any attempt to assess the
performance of end milling should include the tool
geometry. In the present work, experimental studies have been
conducted to see the effect of tool geometry (radial rake angle
and nose radius) and cutting conditions (cutting speed and feed
rate) on the machining performance during end milling of
medium carbon steel. The first and second order mathematical
models, in terms of machining parameters, were developed for
surface roughness prediction using response surface
methodology (RSM) on the basis of experimental results. The
significance of these parameters on surface roughness has been
established with analysis of variance. An attempt has also been
made to optimize the surface roughness prediction model using
genetic algorithms (GA). The GA program gives minimum
values of surface roughness and their respective optimal
conditions.[5]
III. GEOMETRIC FORM CONTROLS AND ORIENTATION
CONTROLS
A. Form Controls
There are four form characteristics. They are Flatness,
straightness, Circularity and Cylindricity. All feature
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National Conference on Recent Trends in Engineering & Technology
controlled are individual and are not related to datum. They are
assessed by comparison to a perfect geometric counterpart of
themselves a feature formed perfectly flat, straight, circular or
cylindrical.
B. Flatness
Flatness is a surface form control. A perfectly flat surface is
defined as having all its elements in the same plane. Flatness
feature control frames create a tolerance zone not related to
any datums. The tolerance zone consist of the distance
between two parallel planes. All elements of the produced
feature under control must lie within the tolerance zone. This
control is commonly used on planer surface capable of resting
on matting planar surfaces without significant rocking. The
control is usually limited to a flatness symbol and a geometric
tolerance, although if used on a rate basis the control may
contain two level of control. The upper level of control contain
the usual overall surface control while the lower level of
control contain a tighter tolerance to be held over limited
portion of the surface. For example if one is concerned about
abrupt surface variation within a relatively small area. It may
be specified that the out of flatness allowed per 25 x 25 mm2 is
smaller than the overall surface flatness tolerance ( fig 1(a) ).
registered must be smaller than or equal to the tolerance in the
feature control frame.
Another alternative for registering flatness deviation is to set
the controlled surface in contact with a surface plate that is
equipped with a plunger type indicator protruding from its
surface and move the part over the indicator point, noting the
full indicator movement. Since this type of set up is rare an
option is put parallels on the surface plate and put the
controlled surface on the parallels. Then with the height gage
and the indicator, indicate the controlled surface for deviations
in flatness.
Fig 2. Flatness verification Techniques.
( a)
(b)
Fig.1 Example of flatness
The regular flatness control looks like Fig 1 (b) Which means
the entire surface of the control feature must lie within a total
wide tolerance zone which is the 0.001 distance between two
parallel planes.Flatness is a geometric control in which a part
surface is compared to a perfectly flat geometric counterpart of
itself. A part surface is real; therefore it has flaws—ridges,
grooves, pits, bumps etc.
Fig 3. Alternate Flatness verification Techniques
B1. Flatness Verification Techniques
B2. Tolerance zone
Use three jackscrews set on top of a surface plate and at the
same time underneath the part. The jack could be adjusted
until the top surface (Controlled surface) is parallel to the
surface plate top Fig 2 & Fig 3. Once the controlled surface is
as level ( parallel ) is possible, an indicator on a height gage or
surface gage ( Which sits on and runs across the top of the
surface plate ) is put in contact with the controlled surface and
pulled along registering surface deviation. The deviations
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The tolerance zone is to be considered the distance
between two parallel planes. Consequently, all elements of the
controlled surface must be between two parallel planes which
are the distance apart reflected by the tolerance in the feature
control frame.
Flatness may be applied on a rate or unit basis. This is
done to prevent abrupt variations in the surface within a
relatively small area. When using this method a total control
B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology
should be used in conjunction with the unit control. The size
and shape of the area being controlled should be made clear.
D. Orientation controls
There are three orientation or attitude characteristics. They are
angularity, Perpendicularity and Parallelism. All Control
feature related to datum planes or to datum axes or to a
combination of datum planes and datum axes.
Fig 4. Correct method of Tolerance zone
D1. Parallelism
C. Straightness
Straightness is a form control that may be used as a
surface, derived median line or derived median plane control.
Fig 5. shows the each of the infinite number of line
elements that comprises this surface in the direction shown in
controlled by its own tolerance zone. Each tolerance zone
consist of two parallel lines 0.003 apart and begins at the
optimal location and angle that will allow it to contain the line
element that it controls.
Parallelism is a member of orientation family. It can be used to
control the orientation of the line elements, surface , axes, and
center planes. Parallelism symbol is //.
When applies this characteristics, it must also be stated what
the controlled feature is parallel to. In other words, a datum
feature is necessary and must be included in the feature
control frame. If the tolerance zone were defined by two
parallel planes within which all elements of the controlled
surface must lie and datum was a plane.
Fig 7. Surface to a datum plane
In Fig 7. tolerance zone is the distance between two parallel
planes separated by 0.005 and both parallel to the datum plane
A Datum plane is formed by the 3 highest points ( minimum )
of the datum feature.[6]
Fig 5.Straightness of a surface
This Control does not apply to the line elements running 900 to
the view in which the straightness of the surface control is
shown. At no time may the surface of the part exceed its size
limit requirements.
A. Speed
The speed of a tool is the speed at which the metal is removed
by the tool from the work piece. In a lathe it is the peripheral
speed of the work past the cutting tool expressed in RPM.
B. Feed
Fig 6. Correct method of straightness
Straightness is an individual control. Therefore, no datums are
allowable in the feature control frame.
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IV SELECTION OF PARAMETERS IN MILLING
The feed of a cutting tool in a Milling work is the distance the
tool advances for each revolution of the work. Feed is
expressed in millimeters per min.
B.V.M. Engineering College, V.V.Nagar,Gujarat,India
National Conference on Recent Trends in Engineering & Technology
C. Depth of Cut
The depth of cut is the perpendicular distance measured from
the machined surface to the uncut surface of the work piece.
V.CONCLUSION.
Milled component represents a wast majority of parts
produced in industries. The adherence of the geometrical
parameters for attaining the form and orientation controls on
the Milled components to meet their functional requirements
as part of an assembly is extremely important and the same is
planned in this investigation. The influence of cutting
parameters on the geometrical features is planned to gradually
by developing empirical models which could be used by
process planners for creating components which can function
better, can be assembled without any problem as well as can be
produced most economically.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
A Treatise on milling and milling machine 3rd edition The Cincinnati
milling machine co.
Tugrul ¨Ozel • Tsu-Kong Hsu • Erol Zeren (2005) “Effects of
cutting edge geometry, workpiece hardness, feed rate and cutting speed
on surface roughness and forces in finish turning of hardened AISI H13
steel” Int J Adv Manuf Technol (2005) Vol 25: 262–269
Dilbag Singh. P. Venkateswara Rao (2007)“A surface roughness
prediction model for hard turning process” Int J Adv Manuf Technol
DOI 10.1007/00170-006-0429-232: (2007) 1115 –1124
A. Del Prete, A. A. De Vitis, A. Spagnolo (2010) “Experimental
Development of RSM Techniques for Surface Quality Prediction in
Metal cutting Application” Int J Mater Form (2010) Vol. 3 Suppl 1:471
474
N.SureshKumar Reddy. P. Venkateswara Rao(2005), “Selection of
optimum tool geometry and cutting conditions using a surface
roughness prediction model for end milling” Adv. Manuf. Technol
Vol.26: 1202– 1210
James D meadows “Geometric Dimensioning and Tolerancing” marcel
dekker, inc.
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B.V.M. Engineering College, V.V.Nagar,Gujarat,India