Surface Roughness Turning of Carbon Steel Assignment Sample

Materials and Manufacturing

Executive Summary of Surface Roughness Turning of Carbon Steel

“Manufacturing is one of the bright spots of a generally disappointing recovery, and there are signs — preliminary, but hopeful, nonetheless — that a sustained comeback may be underway.” (Krugman, 2011) Now more than ever sustainable manufacturing processes are the backbone of society. As our industry and technology grow so too much the processes of the secondary industries.

Accordingly, it logically follows that analytical techniques must be astutely applied to both the processes and safety of our manufacturing processes.

The process of particular interest to this in this report will be surface roughness turning. Turning is the process by which a material is rotated in an automatic lathe while a cutting tool is fed perpendicular to the axis the material rotates about. The material is held in place by a “collet” and rotated by the “spindle”. (Palmer, 2003)

Different parameters were adjusted one at a time to observe the effect they had on the overall perceivable and measured “surface roughness”. Surface roughness is described as the measure of vertical displacement from the ideal surface. (Sulaiman, 2012). A carbon steel rod was used for all four applications of turning, the effects of ductility/ young’s modulus and vacancy/density were ignored due to the constant of material across all experiments. The parameters adjusted for each experiment were the substitution between two different sharp single edge carbide cutting tools and variation of spindle speed. Whilst feed rate is also a factor it is dependent on the selected Rpm for the machine. The feed rate was selected at 0.22 mm/rev. The ambient temperature of the workroom was observed to be 22^oC but was treated as a constant and ignored for its effect on the malleability of the subject material.

It was concluded from the experiment that an increase in cutting speed (v) (m/min) produced little difference roughness (µm). Changes in the carbide cutting tool produced greater variance than changes in cutting speed.

Table of Contents

Statement of Contribution of Members.

Executive Summary..

Introduction.

Procedure..

Results.

Inference from Data..

Industrial Applications.

Work Cited..

Introduction to Surface Roughness Turning of Carbon Steel

The process of turning has been in use for over two millennia. The earliest surviving account of a lathe dates back to the third century BC (The Wood turner’s workshop, 2008) Advances made in the industrial age as well as those discovering new and stronger alloys allowed for turning to be applied to metals.

The applications of turning are as widespread as manufacturing and secondary industries themselves. Turning is a method of “Material removal” By which a fixed dimension, presumed cylindrical, metal has one end fixed within the “Collet” of the lathe.

Once the workpiece is secured, the cutting tool is manually zeroed into the endpoint of the piece in the x and y planes. After this zero point is applied, accurate information can be programmed about the cut length and cut depth.

Surface roughness can be controlled by changes of variables in the machine including feed rate and the cutting piece. Specifications on CAD blueprints of machined goods are provided in many cases for how smooth a part needs to be. In some cases smoothness is desirable, whilst in others, it is not.

Procedure

A piece of carbon steel measuring Ø 50mm x 200mm is used. The piece was affixed to the turning machine via the collet, allowing 100mm to be exposed.

Low cutting speed of 73.827 m/min was selected. The relative Rpm for the turning machine is given by the following equation

A feed rate of 0.2 mm/rev was selected at the advice of the lab instructor. The length of the affixed piece of carbon steel was divided into 4 pieces of approximately 50mm. of which 100mm was visible from the end of the machine. These two pieces were denoted “1” and “2” respectively.

For pieces 1 and 2 a cutting piece with a sharp nose radius of 0.2mm was used.

The y and x-axis were zeroed on the turning machine against the edge of the carbon steel cylinder. A designated cut depth of 2mm was then programmed.

Section 1 was turned at 470 Rpm (73.827 m/min) with a feed of 0.22mm/rev. During the process, the cutting piece was lubricated with oil, and the swarf was observed to be long and helical. The piece was observed to have a high surface roughness that was anisotropic.

The turning was disengaged once the y value read 50mm. it was zeroed at the new location. Cut depth remained 2mm.

Section 2 was turned at 1500Rpm (235.619 m/min) with a feed of 0.22 mm/rev. during the process, the cutting piece was again lubricated and the swarf was observed to short and chip like. The piece was observed to have a high surface roughness that was anisotropic.

The carbon steel rod was then reversed so the uncut side protruded from the collet. Because the device measures Rpm from its central point no adjustment in cutting speed occurs due to the piece in the collet measuring Ø 46mm. The exposed piece is still Ø 50mm.

The cutting piece measuring 0.2mm was swapped out for a piece measuring 1.2mm.

Section 3 was turned at 470 Rpm (73.827 m/min) with a feed of 0.22mm/rev. During the process, the cutting piece was again lubricated with oil, and the swarf was observed to be long and helical. The piece was observed to have a low surface roughness that was anisotropic.

The turning was disengaged once the y value read 50mm. it was zeroed at the new location. Cut depth remained 2mm.

Section 4 was turned at 1500Rpm (235.619 m/min) with a feed of 0.5 mm/rev. during the process, the cutting piece was again lubricated and the swarf was observed to short and chip like. The piece was observed to have a low surface roughness that was anisotropic

The 4 sections were felt by hand for an idea of their roughness. They were compared to a chart of specific roughness to ascertain their approximate values.

The sections were then measured using a Surface Roughness Measurement Instrument.

Results of Surface Roughness Turning of Carbon Steel

There was a distinctly observable difference between using the smaller cutting tool and the larger. The larger cutting tool produced significantly better results with the carbon steel used. Visually it seemed that an increase in Rpm produced a better result, however the chipped swarf suggested to us that perhaps there was more damage than could be observed by the naked eye.

By using the roughness chart the team members made the following predictions about the surface roughness of the sections:

	Section 1	Section 2	Section 3	Section 4
Jordan	≈12.5 µm	≈6.3 µm	≈6.3 µm	≈3.2 µm
Wei	≈12.5 µm	≈6.3 µm	≈3.2 µm	≈3.2 µm
Mukund	≈12.5 µm	≈6.3 µm	≈3.2 µm	≈3.2 µm
Manpreet	≈12.5 µm	≈6.3 µm	≈6.3 µm	≈3.2 µm

 

	No.1	A	B	C	Average
Sample 1 (0.2mm)	3.2	5.55 µm	6.027 µm	5.419 µm	5.665 µm
Sample 2 (0.2mm)	1.6	4.194 µm	3.89 µm	4.164 µm	4.084 µm
Sample 3 (1.2mm)	0.8	2.845 µm	3.240 µm	3.023 µm	3.036 µm
Sample 4 (1.2mm)	0.4	1.569 µm	1.571 µm	1.558 µm	1.564 µm

Figure 9.Measurement of roughness using cutting tools of 0.2mm and 1.2 mm

 A graph can be constructed using the data above comparing cutting speed, surface roughness, and nose size of the cutting tool:

Inference from Data

The data suggest that a larger nose creates a smoother surface. How far this relationship between nose size and surface smoothness can be applied is unknown and cannot be concluded from the sample size of this data. It seems like a counter-intuitive conclusion given that the rate of precision has been reduced by a rate of three however it is possible that because of the feed rate remaining constant for both the larger nose covers a greater surface area per revolution and therefore “smooths” the material more effectively. Contrary to our observed results, Sulaiman argues that a carbide nose must be run at high speeds to achieve a higher smoothness surface finish (Sulaiman, 2012). These conclusions are much more logical as the increase in speed generates more heat on the surface, making the material easier to deform and lathe due to creep and other factors.

The trade of increasing the speed to increase the wear is that the effect translates both ways, onto the nose as well as the worked piece. Accordingly, the life of the carbide nose is reduced. (Sulaiman, 2012). Sulaiman also argues that the single biggest factor in surface roughness is feed rate, a factor we did not change.

The difference in the reflectivity of the finishes affected the perceived smoothness to the eye, however it can be argued that the reflectivity is due to the exposure to greater heat and not an argument of smoothness. The increase of heat due to friction against the carbide bit could have caused a change to its reflective index using a change to its molecular latticework at the surface (L. A. Mal’tseva, 2010).

By looking at the equation for the shear modulus we can derive that an increase in the force applied to the steel results in an increase in the shear. The equation is given by:

Because the instantaneous force at the point of contact is increased with N, so to is the shear.

Industrial Applications

Surface 1:

Surface 1 had an average surface roughness of 10.83 µm RMS anisotropically with a deviation of ± 0.17 µm. This degree of smoothness and uniformity has industrial applications in fields such as adhesion of metals to other surfaces (Persson, 2005). At the 10-20 µm, range adhesion to tacks like scotch tape (Ra ≈20 µm RMS) (Persson, 2005) is at its best. Accordingly, metals whose primary function will be to interact in friction generating environments are best within the aforementioned range. A surface roughness this coarse may be specified with corrosion-resistant (CR) and have applications as such (Sandvik Materials Technology, 2014).

Surface 2:

Surface 2 had an average surface roughness of 10.93 µm RMS anisotropically with a deviation of ± 0.07 µm. Similar to Surface 1 this surface roughness is optimal for use with polymer adhesives. Similarly, this surface roughness falls within the allocated guidelines of the CAD for the machined part shown in figure 2. Again, this level of surface roughness has applications in CR sections of a machine, such as engine exteriors (Sandvik Materials Technology, 2014).

Surface 3:

Surface 3 had an average surface roughness of 6.9µm RMS anisotropically with a deviation of ± 0.15 µm. The application of a surface roughness Ra ≈7 µm RMS is for annealed and heat resistant properties required by the machined part (Sandvik Materials Technology, 2014).

Surface 4:

Surface 4 had an average surface roughness of 6.86µm RMS anisotropically with a deviation of ± 0.14 µm. similar to surface 3, the application of a surface such as this is best suited for annealed and heat resistant properties required by the machined part (Sandvik Materials Technology, 2014).

Work Cited for Surface Roughness Turning of Carbon Steel

CNC cookbook. (2012). CNC COOK BOOK. Retrieved from CNC COOK BOOK: http://www.cnccookbook.com/img/LatheStuff/ColletChuck/P1010405.JPG

Krugman, P. (2011, May 19). The New York Times - The Opinion Pages. Retrieved from The New York Times: http://www.nytimes.com/2011/05/20/opinion/20krugman.html?_r=0

A. Mal’tseva, V. A. (2010). PROPERTIES OF METASTABLE STEEL 03Kh14N11K5M2YuT. Metal Science and Heat Treatment, 557-562.

Palmer, S. (2003, 1 15). Lathe Machining. Retrieved from Modern Machine Shop: http://www.mmsonline.com/articles/threading-on-a-lathe

Persson, B. N. (2005). On the nature of surface roughness with application. J. Phys.: Condens. Matter, 1-62.

Sandvik Materials Technology. (2014). applications of surface roughness. Retrieved from SMT: http://www.smt.sandvik.com/en-au/products/plate-sheet-and-coil/surface- finishes/

Sulaiman, M. C. (2012). Optimization of Turning Parameters for Titanium Alloy Ti-6Al-4V ELI Using the. Journal of Advanced Manufacturing Technology.

The Woodturner's workshop. (2008). Turning, An Introduction. Retrieved from The woodturn's workshop: http://www.turningtools.co.uk/history2/history-turning2.html

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