Surface raggedness mensurating machine are devices that measures the random, irregular closely infinite divergence from ideally smooth surfaces on a little graduated table ( Kalpakjian.s, ) . Initially, the merely 2 dimensional measuring of the surface raggedness was taken. The tabular array below shows the different parametric quantities that can be measured utilizing 2 dimensional surface mensurating devices:
Table 1.1: two-dimensional raggedness parametric quantities
Arithmetical mean value
Root mean square value of the tallness
Maximum vale deepness
Maximum extremum tallness
Maximal tallness profile
Among all these parametric quantities, the arithmetic mean value is normally used to specify the surface raggedness of the stuff being measured.
However, presents, with the research worked carried out and the technological promotion, new surface raggedness mensurating technique has emerged leting the user to obtain a three-dimensional topology of the surface being measured. Therefore, the parametric quantities ( pseudonym, ) usage to specify the surface raggedness involve:
The amplitude parametric quantities which characterize the belongings of the surface.
The spacial parametric quantities which define the denseness of acme on a unit trying country and the uniformity of the texture facet.
The loanblend parametric quantity which is a combination of both amplitude and spacing.
Although clash is closely related to come up raggedness, there is no definite relationship between the surface raggedness and clash. Therefore, to enter the frictional belongings of a stuff, surface raggedness consequence can non be used and a different machine shall be used. A common parametric quantity to specify frictional belongings of different stuff is the coefficient of clash Aµ . There are many machines used to mensurate the frictional belongings of different stuff but some makers decide to include both clash and surface raggedness mensurating devices together.
Therefore, there is a big assortment of machine that can be used to enter the surface raggedness and frictional belongings of different stuff but depending on the different demand of the stuff to be measured and the fiscal resource of the client, different machine can be used.
Background job description.
Surface Roughness occurs in any mechanical processing and the grade of surface divergence is dependent on both the procedure and the manner it is carried out. Figure 1.1 shows the surface divergence with different mechanical processing.
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Figure 1.1: a barchart of surface divergence against mechanical processing
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Surface raggedness is a common happening in metal, plastic and wood where it affects different belongings the lastingness and the public presentation of the stuff. Indeed, in bearing fabrication industries where the average divergence from ideally smooth surface is of the order 10-8-10-6m surface raggedness and clash dramas an of import function in finding the tolerance evaluation and the public presentation of the bearing. Furthermore, one of import facet that defines the flow feature of fluid in a pipe is the surface raggedness. In fact, harmonizing to the Karman-Nikuradze equation, as the surface raggedness additions, the speed of the fluid fluxing in the pipe decreases ( ) . The lessening in speed will ensue in a turbulent flow which may do the happening of cavitation ( formation of air bubbles ) . Furthermore, in paper fabrication industries, the surface raggedness and the clashs of the wood mush affect the absorbency of ink on the paper and therefore the quality of the paper. Finally, the haptic comfort of cloth is straight related to the frictional belongings of the stuff and the surface raggedness which is of the order of 10-5 to 10-4m. Many machines, holding the ability to mensurate surface raggedness and the frictional feature of the stuff, are available on the market. However, these machines, being extremely accurate, are rather expensive and in some instances like in cloth and wood industries, where big truth is non required it may non be cost effectual to put in such a dearly-won machine. Therefore, it may be interesting to plan a cheaper but less accurate machine for these intents.
Existing theoretical accounts of surface raggedness and clash measuring machines.
Many machines step surface raggedness but do non mensurate clash of the surface being measured. Similarly, on the market, there is a twosome of machine that step surface clash merely. However, since the undertaking is covering with both surface raggedness and clash measurement device, both classs shall be considered.
1.3.1 Surface raggedness mensurating devices
There are different methods used to mensurate surface raggedness. Indeed, the methods used to mensurate surface raggedness can be classified as:
Non reaching method.
The mechanical profilometer ( reaching method ) .
A mechanical profilometer is a extremely sensitive machine which is used to mensurate surface raggedness typically on difficult stuff surfaces. It consists of a diamond tipped stylus, a transducer to change over the additive supplanting into electromotive force ( normally a additive variable differential transformer or a capacitive detector ) , a signal conditioning component and a show. The stylus arm is loaded against the sample and the stylus is driven across the velocity at changeless velocity. As the stylus moves, the diamond tip rides over the sample surface observing the divergence as illustrated in figure 1.2.
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Figure 1.2: a typical agreement of a mechanical profilometer.
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The linear signal from the transducer is amplified, conditioned, digitized and recorded.
The atomic force microscopy ( reaching method ) .
The atomic force microscope is an instrument that allows three-dimensional measuring and has a preciseness of 10-9m. It uses a little tip to scan the morphology of the surface of the sample being measured. In fact, it consists of a stylus ( mechanical tip ) , a cantilever and a mean to mensurate the warp of the cantilever tip ( typically, the warp is measured by contemplation as shown in the figure1.3 )
Beam Deflection diagram
Figure 1.3: warp measuring technique used in atomic force microscopy.
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The tip of the stylus is attracted to the stuff surface by mean of atomic force when it is close to the sample. This causes a warp in the cantilever which is measured and conditioned and processed consequently through package to obtain the morphology of the surface being measured.
Scaning negatron microscope ( non contact type ) .
In this method a extremely focussed negatron beam impinges on a solid surface and gives rise to a back scattered negatron beam which is collected and amplified. By scanning the entrance negatron beam and at the same time analysing the low energy portion of the backscattered beam, topological information on the solid surface can be obtained with high sidelong declaration of the order 10-9m. Figure 1.4 shows the working agreement of a scanning negatron microscope.
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Figure 1.4: agreement of a scanning negatron microscope.
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1.3.2 Friction mensurating devices.
The pin on phonograph record machine
This machine fundamentally consist a pin and a rotating phonograph record. The phonograph record is rotated at changeless velocity and the pin is pressed against the phonograph record at changeless force. The force required to maintain the pin heterosexual is measured. An agreement of the pin on phonograph record machine is shown in figure 1.5.
MICROPROCESSOR CONTROLLED PIN ON DISC MACHINE
Figure 1.5: Pin on phonograph record machine
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Twin phonograph record tribometer
Basically the machine consists of 2 phonograph record revolving at different velocity that are brought in contact to each other. The frictional force can so be determined by entering the force required to maintain the phonograph record moving, through the burden cell. A typical agreement of the system is shown in figure 1.6.
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Figure 1.6: Conventional agreement of twin phonograph record tribometer.
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1.3.3 Friction and surface raggedness mensurating machine.
The Kawabata surface examiner.
This machine is used to mensurate the surface raggedness and the frictional belongings of cloth. The machine, as shown in figure 1.7, fundamentally consists of a horizontal platform upon which the cloth is placed without any fold. The cloth is driven on the horizontal platform at a changeless velocity.The clash on the surface of the cloth is measured through the burden cell which is connected to the standard burden 50 g/force while the surface raggedness is measured by a investigation connected to a additive displacement differential transformer ( LVDT ) .
KES-FB4 Surface Tester
Figure 1.7: The Kawabata surface examiner
( beginning: hypertext transfer protocol: //www.tx.ncsu.edu/tpacc/comfort-performance/kawabata-evaluation-system.cfm )
The Kawabata surface examiner measures 2 different parametric quantities:
The standard average divergence of the surface raggedness, SMD.
The coefficient of clash, Aµ .
Note: As the SMD additions, the surface raggedness of the cloth besides increases ( pseudonym, 1/12/12 ) .
1.4 Purposes and aim of the undertaking.
The aim of the undertaking is to plan a machine that measures and displays the arithmetic mean value Ra, the root mean square value Rq and the maximal tallness of the profile Rt. It must besides step and expose the frictional force ( dynamic clash ) Aµ as a map of supplanting.
The different purposes of the undertaking are:
To plan a construction that accommodates both surface raggedness and clash measurement devices.
To plan an electrical system that allows the user to run each maps of machines individually.
To do usage of vision system to obtain the surface profile of the stuff being measured.
To guarantee the precise mechanical building for concentrating the camera.
To utilize package to change over the image into utile consequence.
To utilize appropriate package to expose consequence on the Personal computer.
To enter torsion of dc motor at different clip interval.
To expose the consequence of coefficient of clash in graphical signifier utilizing MATLAB.
1.5 Proposed methodological analysis.
The machine is designed such that it either steps surface raggedness or frictional belongings of the stuff depending on the user scene. Therefore, the machine shall suit a system that allows the user to toggle between the 2 different manners.
In order to find the surface raggedness, multiple images ( utilizing a camera and suited lens ) of the stuff will be taken and utilizing appropriate package ( Roborealm and ocular BASIC ) , an norm of the different parametric quantities shall be taken. The machine will dwell of a horizontal platform upon which the stuff will be placed. The camera can be driven on a rail by a motor and utilizing a suited control circuit, the camera will be made to take exposures at regular clip spacing. All the images will be transferred on a Pc upon farther processing will take topographic point in order to obtain the consequence. One of import facet when utilizing a vision system is the lighting. Therefore, the whole set up will be enclosed in a box and therefore an appropriate lighting system shall be provided to hold good images.
For finding the surface raggedness, a standard weight will be driven on the surface of the stuff through a belt and block system. The weight will be driven at changeless velocity by a dc motor. The velocity of the District of Columbia motor is monitored by an encoder which sends a signal to a microcontroller which controls an H-bridge connected to the DC motor. The torsion required to keep the changeless velocity ( i.e. the current Federal to the motor ) will be digitized through an ADC convertor and sent on a computing machine. Using the appropriate package ( MATLAB ) , a graph of frictional force versus supplanting will be plotted.
Driver of motor
Camera drive motor
Image Processing Software
Personal computer control plan
Data logging system
Interface plan plan
Load driving motor
Function control switch
Start push button
Figure 1.8: Overview of proposed methodological analysis
Figure 1.8 shows an overview of the proposed methodological analysis. The map of the different chief constituents is:
Function control switch – The machine consists on a individual start push button. However, since the machine can either step surface raggedness or the frictional force, a toggle switch shall be used for taking either surface measurement manner or clash measurement manner.
The microcontrollers- The system consists of 2 different microcontrollers to command the operation of the 2 different maps. In the surface raggedness mensurating manner, the microcontroller shall command the supplanting of the camera. In clash measurement manner, apart from commanding the velocity of the motor, it shall besides direct the consequence on the Personal computer for farther processing.
The vision system- this consists of the camera that will be use to obtain the surface profile, the necessary lighting system and the image processing package.
Interface Programs – the interface plans are responsible for exposing the consequence that is recorded by either the camera ( surface raggedness mensurating manner ) or the microcontroller ( clash mensurating manner ) . The interface plan is besides responsible for composing the control for the camera.
1.6 Scope of undertaking
The undertaking range will be as follows:
Choice of appropriate constituents for the system.
Design and mechanical building of the system.
Identifying vision system demands.
Interpreting the image organize the camera.
Communicating between the microcontroller and Personal computer.
Exposing consequence on the Personal computer.
1.8 Outline of thesis
Chapter 2 goes in item on the conceptual design of the surface raggedness and clash measurement machine and describes the different method of execution of the machine.
Chapter 3 describes the mechanical design & A ; building of surface raggedness and clash mensurating machine in full item.
Chapter 4 consists of the electrical and electronics design for the system. It includes connexion circuit between microcontrollers an different constituents of the system.
Chapter 5 is based on the package development. This includes package for image processing and the package for exposing the consequences.
Chapter 6 considers the consequences obtained after the machine has been implemented and tested.
Chapter 7 amounts up the study. It consists of reasoning comments and elaborates farther betterment.