Investigation of Effect of Cutting Parameters on Geometric Tolerances in CNC Turning – A Review

PMTadvi1,PMGeorge2,RGJivani3

Mechanical Engineering DepartmentBVM Engineering College, V.V.Nagar

1prakashtadvi@yahoo.co.in2pmgeorge02@yahoo.com3rgjivani@yahoo.com

Abstract - Turning attributes to a major channel of components of manufactured goods. The machines selected are of different capabilities, in order to meet the specifications. The machine component used to achieve both the geometrical and dimensional tolerances requirements. It is one of the most commonly usedmetal removal operations in industry because of its ability to remove material faster giving reasonably good surface qualityapart from geometrical requirements. Conformity of geometry is one of the most significant requirement of turned components to perform its intended functions. The geometrical requiremtents, apart from dimensional requirements are: Circularity, Cylindricity, Perpendicularity etc. Since they have direct influence on the functioning of the components, the effect of the cutting parameters on them has greater significance. This paper brings out the current status of the research in this area. It has been found that not much work has been carried out in this area.Keywords— Turning, Geometric tolerance, Circularity, Cylindricity and Perpendicularity

I. INTRODUCTION

Turning is one of the most commonly used metal removal operations in industry because of its ability to remove material faster giving reasonably good surface quality. It isused in a variety of manufacturing industries including aerospace and automotive sectors, where quality is an important factor inthe production of slots, pockets, precision moulds and dies.Greater attention is given to dimensional accuracy and surfaceroughness of products by the industry these days.[1]

Geometric characteristics are categoriesed as Form, Profile, Orientation, Run out, and Location. Form controls Flatness, Straightness, Circularity and Cylindricity. The form characteristics are always individual. Profile contains of a line and a profile of a surface. Orientation Controls Perpendicularity, Parallelism and Angularity. Run out controls Circular Runout and Total Runout. Location controls Position, Symmetry and Concentricity. Circularity is a form control. A perfectly flat surface is defined as having all its elements in thesame plane. Cylindricity is a Form control that may be used a surface, derived median line or median plane control.

II. LITERATURE REVIEW

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]

Several studies have been done in order to examine the efficiency of different cutting tool materials, such as cemented carbide, coated carbide, and diamond in turning, milling, drilling, reaming, and threading of MMC materials. The experimental analysis highlights that the machining criteria like VB, Ra in composite machining are greatly influenced by the various predominant machining parameters considered in the present study. [3]

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 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. [4]

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. [5]

III. SELECTION OF PARAMETERS IN TURNING

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.

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

National Conference on Recent Trends in Engineering & Technology

B. Feed

The feed of a cutting tool in a lathe work is the distance the tool advances for each revolution of the work. Feed is expressed in millimeter per revolution.

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. Depth of Cut is expressed in millimeters.

IV. GEOMETRIC FORM AND ORIENTATION CONTROL

A. Form Controls

There are four form characteristics. They are Flatness, Straightness, Circularity and Cylindricity. All feature 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. Circularity

Circularity is a two dimensional surface form control. (fig:1) The surface is assessed to determine that all circles that makes up the surface being controlled are within the given circularity tolerance. The circularity tolerance zone consists of two concentric circles the distance apart radially the amount that appears in the feature control frame. The centers of the measured polar profile may be used to determine the out of roundness. The centers which are used unless otherwise specified are determined by the minimum radial separationcenter. Minimum radial separation (MRS) is the center for which the radial difference between two concentric circles which just contain the measured polar profile is a minimum (also known as the center for minimum full indicator movement [FIM].

Fig:1 Measurement of Circularity

C. CYLINDRICITY

Cylindricity is a surface form control (fig.2). It simultaneously limits the allowed out of roundness, straightness and taper a surface may experience. The tolerance given in the feature control frame is considered radial (or per side), therefore a Cylindricity tolerance of 0.003 is able to protect against any pits or bumps larger than 0.003 but may allows bumps of 0.003 to oppose one another at 180° points on a cylinder surface. Cylindricity is a geometric control similar in many ways to circularity. Both circularity and Cylindricity are radial controls to be considered always regardless of feature size.

Fig.:2 Measurement of Cylindricity.

For circularity checks, a probe will contact the workpiece at different cross sections during separate 360° rotations. For Cylindricity, the probe will move up and down the controlled feature during 360° rotations.

D. Orientation Control

There are three orientation or attitude characteristics. They are angularity, perpendicularity, and parallelism. All contro-lled features are related to datum planes or to datum axes or to a combination of datum planes and datum axes.

E. Perpendicularity Perpendicularity is a member of the orientation family (fig 3). It can be used to control the orientation of surface, axes and centerplanes. If used on features of size, it is often used as a refinement of, or to augment a positional control. It is also often used to orient secondary datum features of size to primary plane datums. Perpendicularity is a characteristics of orientation (altitude) applied to a feature or feature of size wherein that considered feature surface, line element, median plane or axis is being controlled (to within a specified tolerance) 90° to a datum plane or datum axis. [6]

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

National Conference on Recent Trends in Engineering & Technology

Fig.3 Measurement of Perpendicularity.

The example given in (fig:4) depicts a typical application of perpendicularity. For the component to function well as part of the assembly, it is required that perpendicularity of the bore Ø 16 with reference to datum A is required as specified at MMCSuch, explicit depictions would produce functional assembly and products.

Fig 4. Use of Perpendicularity.

V. CONCLUSION

Turned 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 turned components to meet their functional requirements as part of an assembly is extremely important. The current status and demands is that the specific requirement of geometrical and dimensional relation need to be achieved for economic and efficient manufacturing apart from creating product which satisfies the customers more.

REFERENCES

[1] Production Technology By R K Jain [2] Tugrul ¨Ozel · Tsu-Kong Hsu · Erol Zeren “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

[3] M. Seeman & G. Ganesan & R. Karthikeyan & A. Velayudham “Study on tool wear and surface roughness in machining of particulate aluminum metal matrix composite-response surface methodology approach’’ Int J Adv Manuf Technol (2010) 48:613 – 624 DOI

[4] Dilbag Singh. P. Venkateswara Rao “A surface roughness prediction model for hard turning process” Int J Adv Manuf Technol DOI 10.1007/00170-006-0429-232: (2007) 1115 –1124

[5] A. Del Prete, A. A. De Vitis, A. Spagnolo “Experimental Development of RSM Techniques for Surface Quality Prediction in Metal cutting Application” Int J Mater Form (2010) Vol. 3 Suppl 1:471 474

[6] James D meadows “Geometric Dimensioning and Tolerancing” marcel dekker, inc.

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

National Conference on Recent Trends in Engineering & Technology