Using Abrasive Flow Machining ( AFM ) to complete high public presentation engine cylinder caputs enhances engine efficiency, public presentation and lastingness. For this cylinder caput application, Al 319 was selected as the stuff of pick. Two AFM attacks can be utilized on the production line, one-way or bipartisan. Factors that affect quality are scratchy grain size, medium viscousness, temperature control, force per unit area and flow rates. Quality control is indispensable to vouching a capable procedure, proper estimating and review frequences are important. Geometric and thermic factors besides play a function in surface finish end product. Cost and environmental consequence properties were besides considered.
Abrasive Flow Machining ( AFM ) Abrasive Medium Economic Engine Performance Environment Quality Control
Table of Contentss
Introduction: Project range, premises and thesis
Abrasive Flow Machining: A brief Definition 1
Thesis: Using AFM to complete High Performance Cylinder Heads: How and Why? 1
Body: AFM – A Deep Honkytonk
Why utilize AFM to complete High Performance Cylinder Heads 2 – 4
Material choice for the cylinder caput 4 – 6
AFM factors that affect the finished merchandises ‘ quality 6
Quality control step for a capable procedure ) 7
AFM: Frictional, geometrical and thermic facets 8 – 9
The Abrasive medium 10
Process Foot print options: Considerations for cost and the environment 10 – 12
Decision: AFM and improved engine public presentation 12
Abrasive Flow Machining ( AFM ) is a finishing method of smoothing, deburring and smoothing complex geometries like internal transitions, decompression sicknesss, pits borders and bring forthing controlled radii. Areas that are impossible to make by other machining operations can be machined by AFM procedure, ensuing is a surface finish quality that can non be matched utilizing conventional machining processes [ 1 ] .
Having won concern for a low supplanting high public presentation four cylinder engine for a major Original Equipment Manufacturer ( OEM ) , my fabrication procedure squad has been tasked with developing programs to implement AFM on the 16 valve, in-line cylinder caput. For this undertaking, the grounds behind the choice of AFM for completing high public presentation cylinder caputs will be discussed. To be discussed besides are the factors that affect the finished merchandises ‘ quality and quality control measures that will vouch dimensionally accurate, consistent and cost effectual rhythms. Material choice for the cylinder caput will be visited. Frictional, Geometric and thermic facets of the AFM procedure will be explained. In this undertaking, we will besides present procedure footmark options that would let for an economic and environmentally friendly production program.
AFM and Engine Performance
On the intake side:
An of import factor that governs the power of an internal burning engine is maximising the sum of air traveling consumption. More air consequences in more fuel initiation, more fuel is burned and more energy is converted to work. The power end product and the average effectual force per unit area are determined by the measure of charge ( mixture of air and fuel ) inducted. Engine initiation effectivity is measured as volumetric efficiency. — — — — — — — — — — — — — ( 1 ) where is the air mass flow rate per shot, N is revolutions per second, Vsw is the swept volume and I?a, I is the recess air denseness. [ k2 ]
At rated velocity ( Max RPM ) , Air denseness, Swept volume and Engine velocity are changeless so the air mass flow rate from equation ( 1 ) is the lone variable which can be increased in order to better the engine ‘s volumetric efficiency. Smoother consumption ports can increase the mass flow rate.
On the exhaust side:
The consumption force per unit area is below atmospheric force per unit area but the exhaust force per unit area is about or above atmospheric. This causes a negative work cringle in the full rhythm and hence reduces the net work. However, the fumes manifold is positive during the stroke.. The exhaust port force per unit area influences the flow rate of the exhaust gases. Smooth exhaust ports really increase the flow rate of the fumes gases and decreases the port force per unit area. This improves volumetric efficiency [ 3 ] .
Volumetric efficiency can be increased in several ways. Using larger valves or increasing the figure of valves per cylinder. Larger valves addition flow but increase the weight, multiple valves per cylinder besides increases the figure of mechanical constituents in the engine, increasing the weight and production cost. Porting is a common attack to increase the volumetric efficiency but is inaccurate and clip consuming.
Consequence of AFM on Engine public presentation
Using AFM allows for the addition of the volumetric efficiency utilizing an scratchy media to smooth, debur and edge-radius the consumption and exhaust ports. The ports are impossible to make by traditional machining operations. AFM consequences in a surface finish quality that is superior to that achieved by conventional machining procedures
AFM procedure has ability to increase airflow on all types of internal burning engines. Reducing the opposition in consumption and fumes transitions will increase engine efficiency and public presentation. Blending the Fuel and air is more effectual with smoother consumption transitions. This consequences in higher volumetric efficiency. A 10 % addition in power and torsion can be seen for an engine with a cylinder caput machined by AFM.
Abrasive flow machining procedure creates a transition with less limitation to flux, that allows charge and exhaust gases to flux more rapidly through the ports, maximising the flow speed. These consequences in a decreased pumping work ( negative work ) during exhaust shot and increases volumetric efficiency during Suction stroke. The procedure increases the flow rate in an aluminium cylinder caput by 30 % [ 4 ] .
Engine constituents are subjected to complex thermal and mechanical burden conditions. AFM induces compressive residuary emphasiss in the cylinder caput ; residuary emphasiss relax during thermic enlargement and prevent thermic checking therefore increasing the lastingness and the service life of the cylinder caput [ 5 ] .
Part stuff choice
Material choice for a parts is cardinal to plan and fabricating procedure success. “ Availability of stuffs and their costs are of import considerations, but it is the public presentation which is the most of import standard for choice of any technology stuff for a specific application ” [ 6 ] . In our instance, high hardness media is required. A broad scope of stuffs can suit this demand. Due to the complicated internal form of cool transition and recess and exhausted port, stuffs with good castability should be chosen. The high strength -especially under high temperature conditions – is besides necessary to guarantee that caput withstands of burning force ensuing from thermic enlargement and contraction when fixed stiffly to the cylinder block. The cylinder caput is exposed to low rhythm weariness ( LCF ) due to the thermic distortion during start/shut-off engine rhythms. LCF can do clefts in thin-walled countries. Higher ductileness stuffs are advantageous in avoiding low rhythm weariness and bettering the engine ‘s life [ 7 ] .
Table 1: Comparison of common usage dramatis personae metal for castability and machinability [ 8 ]
From table 1, the first-class castability and machinability features of Aluminum make it a great campaigner for our cylinder caput. Its high thermic conduction, good corrosion opposition and light weight denseness ( at least 50 % less than the dramatis personae Fe ) cylinder caputs make it favourable to other dramatis personae metals [ 9 ] .
Cast aluminium ‘s major chemical composing is aluminum along with different other metal elements. Major elements include Si, Cu and Mg. Silicon is really difficult stage therefore contributes to the metal ‘s wear opposition and to its lower thermic enlargement coefficient due to the specific gravitation. Copper allows for an increased strength and hardness at both room and elevated temperatures ; nevertheless, one of Cu ‘s disadvantages is its low corrosion opposition. Magnesium combines with Si to organize a hardening stage that strengthens and hardens the metal [ 10 ] .
Table 2: Cast aluminium metal series [ 11 ]
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For our application, we have chosen Al 3xx metal household ( debasing elements presented in table 2 above ) . It takes advantage of multi-elements to acquire better balance respects to castability, machinability, and surface hardenability, corrosion and wear opposition and cost of fabrication. For our application, the best combinations of strength and ductileness are offered by cast metal with low Fe such as A319 ( AlSi8Cu3 ) can be selected. This Cu and Ni-containing metals can supply better high strength at elevated temperatures while maintain ductileness and fatigue public presentation. Mg in this metal is kept in low degree to diminish the oxides formation but still can unite with Si to better hardness and machining features. The concentration by mass per centum for AL 319 is shown in table 3 below:
Table 3: The composing of Al 319 [ 12 ]
AFM factors that affect the finished merchandises ‘ quality:
The quality of the finished surface is based on a figure of Abrasive Flow Machining parametric quantities like the work stuff, design of tooling, the figure of rhythms, the scratchy grain size, the concentration and the flow velocity of the scratchy medium. The figure of rhythms at any given period of clip depends on the speed of the scratchy medium. More stuff is removed as the thickness of the scratchy medium additions, nevertheless, the surface raggedness value of under this status would be higher in comparing to that during the Sue of finer grains. The surface raggedness and material remotion rate are affected by the bulge force per unit area and medium ‘s viscousness. The viscousness is affected by the temperature. With a little addition in temperature the viscousness of the medium reduces drastically therefore doing a decrease in stuff remotion effectivity. As the concentration of the abradants additions, the viscousness increases. As the size of the scratchy medium additions, the viscousness decreases. The stuff remotion and surface raggedness decrease additions with the per centum concentration of scratchy in the medium.
Silicone gum elastic is a good scratchy medium to smooth the surface and give it a smooth surface coating since it has low flow rate and high viscousness. The material remotion rate and surface raggedness can be improved upon “ by using a magnetic field around the workpiece ” [ 13 ] ; [ 14 ] .
Manufacturing squads can plan the best procedure out at that place, if agencies to commanding this procedure are non taken in consideration amid the design stage, the procedure will non be capable. Procedure failure manner effects analysis ( PFMEA ) is a footing for finding what parametric quantities and what operations need to be tightly controlled and monitored. PFMEA is a structured method that allows for the designation of possible failures that may ensue in a fabrication procedure. Quality control is a procedure in which all the factors that are identified by the PFMEA monitored and checked. The frequence of review is established harmonizing the dimensional or structural importance.
For the AFM procedure, Pressure qauges sould be installed and attached to alarm systems where a bead below certain values or an addition above a certain value would close off the system. Hysteresis should be taken into consideration where the force per unit area has some room to fluctuate ( to avoid frequent break of the production line ) while still non impacting the surface finish quality. Thermocouples need to be installed in order to supervise the work pice ‘s temperature every bit good as the medium ‘s temperature. As mentioned earlier, a little rise in the abradant ‘s temperature would change the surface finish drastically. Fluid viscousness is to be checked on a frequent mode every bit good. Cycle times are to be monitored and figure of rhythms are to be counted and reviewed.
The scratchy medium demands to be inspected. The grain sizes should be measured and recorded in order to maintain path of the medium ‘s production life. If the medium is have oning out excessively shortly and enduring for excessively long, the quality squad needs to look into. Production parts needs to be pulled on a regular footing for dimensional review and stuff belongingss. This information needs to be recorded and charted in a mode that presents the lower bound allowed for the operation, the upper bound allowed for the operation and the mean targeted. Six Sigma analysis determine whether the procedure is under control or if any alterations are required.
Proper processs need to be established in respects to cleansing and recycling the scratchy media. These processs would include inspector signatures that verify that recycle periods are being adhered to and that logs are being updated. A corrupt medium would hold terrible impact on finished merchandise quality. All of these parametric quantities and their associated values ( with tolerances ) are to be organized in a quality control chart that is posted on the production line and in range of the operators. This allows operators to look into for any suspected mistakes such as verifying the Piston force per unit area for illustration. All of the gages used on this production lines need to graduate from clip to clip. Go-No-Go gages can besides be utilized.
AFM in Frictional, Thermal, and Geometric Aspects:
AFM is similar to lapidate crunching where the scratchy medium is a “ self-deforming ” rock. Figure 1 below is a conventional that shows the interaction forces of a individual grain on the work piece ‘s surface.
Figure: Free Body Diagram of a simple grain actin on the Work Piece Surface [ 16 ]
The sheer force “ F ” shown supra will move on the work piece by the grain ( assumed to be a sphere for simplification ) and let the remotion of stuff via a individual base on balls ( assumed to be additive for simplification intents besides ) . The thickness of the removed stuff will be “ 500 – wear in grain ” . Two constituents constitute the force “ F ” , plowing and frictional forces. The frictional force is the transmutation of normal forces due to friction coefficient values that are about 0.2 for AFM.
Figure 1 could be characterized as a kinetic energy transportation between the traveling grain and the inactive work piece. After all, the scratchy compound is mobilized under a specified force per unit area with a specific volumetric flow. This could be interpreted utilizing Bernoulli ‘s Equation for Fluid Kinetic Energy where presuming laminar flow ( where V is unstable speed and can be deduced from the volumetric flow rate ) . The frictional constituent of the force “ F ” ( due to rubbing ) will ensue in a temperature addition of the work piece every bit good as the scratchy fluid.
As in any balanced energy equation, the input energy will ensue in end product in add-on to heat coevals due to efficiency losingss [ 17 ] . The followers is a theoretical account for the heat exchanged between the work piece and scratchy medium:
Figure: Thermal Model for Heat Exchange between Work Piece and Abrasive [ 18 ]
A elaborate derivation of the thermic exchange during AFM has been studied by Rajendra K. Jain and V.K. Jain in their paper titled “ Specific Energy and Temperature Determination in Abrasive Flow Machining Process ” . The paper concluded that rise in work piece temperature is straight relative to the abradant ‘s force per unit area and figure of rhythms. The writers noted that empirical analysis showed that the scratchy medium ‘s viscousness drops significantly with minimum additions in temperature. This minimum alteration could be every bit low as 2A°C [ 19 ] . This viscousness bead would change the coating features of the medium and therefore make fluctuation in the finished merchandises.
To avoid this issue, the quality control program should let for scratchy alteration overs where multiple scratchy containers ( all having the same features – denseness, grain size, viscousness, etcaˆ¦ ) are rotated to let for chilling clip in order to avoid viscousness decrease effects on the finished merchandise due to increase in temperature. A proper use of the down clip for the scratchy container is to clean out the medium from stuff yak and recycle it. In Larry Rhoades ‘ “ Abrasive Flow Machining: a Case Study ” , he states that larger transitions require really high viscousness ( about solid ) media while smaller transitions requires lower viscousness media.
The Geometry of the work piece is a major parametric quantity in the AFM procedure capablenesss and surface finish end product. The AFM fixture serves as a clinch for the work piece and as a usher for the scratchy. Improper fixturing could take to non-uniform Material Removal Rates ( MMRs ) with roughness mistakes [ 20 ] . The geometry of the merchandise dictates the parametric quantities of the procedure ( force per unit area, grain size, viscousness, fixturing, etcaˆ¦ ) . Geometry besides dictates the figure and order of operations in the machining procedure. Our work piece is a 16 valve, SOHC Aluminum cylinder caput. We will be completing the consumption and exhaust ports.
The Abrasive Medium:
Figure: an illustration of The Abrasive Media in AFM
A semisolid polymer Acts of the Apostless as a bearer to the scratchy grains. This composing is referred to as the scratchy media ( see figure 4 above for an image ) [ 21 ] . An arc furnace is used to bring forth Silicon carbide ( SiC ) . It is composed of “ 60 % silicon oxide sand and 40 per centum finely land crude oil coke. The Si carbide crystals are farther processed into scratchy grains. ” The grain size and media viscousness are direct subscribers to the surface coating. Ports with big diameter to length ratio necessitate a medium with a different grain size and viscousness ( big grains, higher viscousness ) than those with smaller diameter to length ratios ports ; these require smaller grains and lower viscousness media [ 22 ] .
Process Foot-Print Options:
The undermentioned image is a transverse subdivision of a 16 valve cylinder caput obtained from the website billzilla.org.
Figure: Cross subdivision of a 16 Valve Cylinder Head
For this undertaking, two different machining attacks can be utilized. Approach A would use a Double Piston tooling ( see figure 4 below for illustration ) where the scratchy medium is pumped through ports one and three on the intake side and ports two and four on the exhaust side. Valve root bushing ports five and six would be plugged during this operation in order to direct the scratchy flow in a mode that would let for the unvarying machining of corners seven and eight.
Figure: Double Piston Tooling Schematic [ 23 ]
Approach B would be to utilize a individual force per unit area Piston where the abradant would be channeled through ports one and five on the intake side and ports two and six on the exhaust side. The force per unit area from the individual Piston would let for a higher flow speed in ports five and six therefore deviating the scratchy flow towards corners seven and eight leting for a unvarying finished merchandise. The diameter of recesss six and seven demands to be reduced during the casting procedure in order to counterbalance for the stuff remotion during the AFM procedure. Although transitions five and six have a smaller diameter, a common scratchy medium would be used, hence it a individual Piston operation.
Multiple factors are to be considered before choice an attack. These factors include production volumes, rhythm continuances and Numberss, tooling cost ( individual vs. dual Piston tooling and piece cost amortisation ) amongst other factors.
Environmental and Cost Considerations:
During AFM, the scratchy media and the aluminium french friess which removed from the work piece will blend together. As we extend the life of the scratchy medium, we lower operational cost and cut down effects on the environment. In simple words, recycled scratchy medium means fewer landfills. To make so, we have to invent an operation that would let us to divide the aluminium from the scratchy medium station the coating operation. Since Aluminum is non magnetic, bring oning chemical reactions provides us with a path that we can utilize to recycle the scratchy medium. Two attacks can be followed here. Approach A would be to add chemical ingredients that would aim the Aluminum merely ( maintaining the scratchy medium intact ) . These chemicals would fade out the aluminium and let for separation of the 2 constituents.
Approach B would be similar to near A except that we would aim the scratchy medium with chemicals to disintegrate it. Once the aluminium is separated from the medium, the chemical is removed and the scratchy medium is restored. And since Aluminum ore extraction requires high degrees of energy ( higher than Fe ) , recycling aluminium saves 95 % of the energy normally used to pull out aluminium from bauxite. Another ground that aluminium recycling is efficient and economic is the high corrosion resistibility [ 24 ] , so it can be merely melted and molded to new merchandise with minimal to no extra operations. In contrast, pull outing Aluminum from bauxite could be rather expensive, consumes big sum of energy and emits high degrees of pollutants into the environment [ 25 ] . The reused aluminium metal bar for projecting generates lower CO2 emanation than these from a same sum of metal bar from bauxite. Lapp with other related air such as NOx, SO2 and other organic compounds emanations [ 26 ] . Above all, the aluminium recycle proved to be environment friendly and energy-efficient manner.
Harmonizing to the EPA: “ Emissions generated in the production of bonded scratchy merchandises may affect a little sum of dust generated by managing the loose scratchy, but careful control of sizes of scratchy atoms limits the sum of all right particulate that can be entrained in the ambient air. Devicess such as scrubbers and electrostatic precipitators can be used to command atom affair emanations from abradants grain and merchandises fabricating ” [ 27 ] .
The material choice of the scratchy medium is highly of import for environmental grounds. Material with high decomposition rates should be favourable when it comes to scratchy medium stuff choice. Materials should besides be selected based on their H2O solubility degrees every bit good there sourness degrees. Materials that are non water-soluble with PH degrees closer to 7.0 should be utilized during material choice in order to minimise the consequence on the environment. To cut down landfill effects every bit good as operational costs, big grain size size scratchy medium should besides be considered as a get downing medium. Once the grain size is excessively little to execute efficaciously in the intentional procedure, the media can be utilized in completing other parts in the works where smaller size grains are needed to complete lower diameter to length ratio constituents.
Decision: AFM and improved engine public presentation
In this paper, the Abrasive flow machining procedure was discussed in respects to its effects on high public presentation engine cylinder caputs. AFM allows for the addition of engine efficiency doing it really desirable for high public presentation engines where application overthrows cost concerns. Aluminum 319 was chosen for the cylinder caput application. Factors that affect the finished merchandises ‘ quality and quality control steps were presented. These factors will vouch dimensionally accurate, consistent and cost effectual rhythms. Frictional, Geometric and thermic facets of the AFM procedure were besides explained and process footmark options that stress on economic and environmentally friendly production programs were discussed.