The Billet Material Cost Engineering Essay

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The manufacturing cost of the finished cylinder block is the most important factor in determining the selection of the manufacturing process and the material. The cost to manufacture a cylinder block is made up of the cost of material ( C1 ), the salary of the technician/operator ( C2 ) who made this block, the cost of tooling ( C3 ) ,the capitalized cost of the equipment ( C4 ) (milling machine), cost of overhead ( C5 ) and the cost of purchased component(Cylinder liners)(C6)

Total Unit cost Cu = C1 + C2 + C3 + C4+ C5 +C6

Material cost ( C1 ):-

The material cost is determined by the quantity of material that is required and the unit price of that material. The amount of material is determined by the cylinder block size and the production quantity.

The main cylinder block is made from the aluminium alloys. For that need to buy the aluminium billet block from outside company. Also need to buy the fixture material. As mentioned earlier the cast iron is the best material for the fixture, need the buy the cast iron as well from outside company. For design-2, need to buy a cast iron for the main bearing cap. Material cost, independent of the number of parts, but strongly dependent on its mass.

Billet material cost (Cylinder block):-

Volume of the Aluminium block (Billet material) v = L x B x H

= 115 mm x 145 mm x 165 mm

= 2751375 mm3

= 0.002751375 m3

(Note: - The order billeted material block size is 5 mm more in thickness than the required block dimension from each side)

The specific weight or the density ( ρ ) of the Aluminium is 2710 kg- m3. (CES Edu Pack)

So the mass of the Aluminium block (Billet material) is M = ρ x v

= 2710 x 0.002751375

= 7.4562 kg

Total material cost per unit (Account for scrap) = (M x Cm)

Where Cm is the material cost (1.35 - 1.50 GBP/Kg) ( CES Edu Pack )

= (7.4562 x 1.50)

= 11.1843 GBP

Fixture Material Cost:-

The 2 number of the same fixture required here. One for head stock side and one for foot stock side.

Fixture - :

Volume of the Cast iron block (Billet material) v = L x B x H

= 85 mm x 25 mm x 145 mm

= 257600 mm3

= 0.000308 m3

The specific weight or the density ( ρ ) of the Cast iron is 7870 kg- m3. (CES Edu Pack )

So the mass of the Cast iron block (Billet material) is M = ρ x v

= 7870 x 0.000258

= 2.4239 kg

Material cost per unit = (M x Cm)

Where Cm is the material cost ( 0.438 - 0.482 GBP/Kg) ( CES Edu Pack )

= (2.4239 x 0.470)

= 1.13926 GBP

For two fixture the cost will be 1.13926 X 2 = 2.2785 GBP

Total material Cost (C1) (Aluminium Block + Cast iron (Fixture 1 ))

= 11.1843 + 2.2785

= 13.50 GBP

(Note: - The delivery and other formalities to bring the material in the workshop is not considering in cost analysis.)

(Note:-Assuming the Pipe welded on the fixture to dividing head is already available in workshop (store). And also the size of the pipe is very small as finding difficulties to buy that size. So considering cost of the pipe is negligible and not counting in the cost analysis. )

Main bearing cap material: (For option 2 design)

Volume of the Cast iron block for main bearing cap (Billet material)

V = L x B x H

= 60 mm x 25 mm x 150 mm

= 225000 mm3

= 0.000225 m3

The specific weight or the density (ρ) of the Cast iron is 7870 kg- m3. (CES Software)

So the mass of the Cast Iron block (Billet material) is M = ρ x v

= 7870 x 0.000225

= 1.770 kg

Material cost per unit = (M x Cm)

Where Cm is the material cost (0.438 - 0.482 GBP/Kg) (CES Edu Pack)

= (1.77 x 0.470)

= 0.8319 GBP

( Note :- The cost of the Main bearing cap material is not going to be included in total material cost because the manufacturing of Main Bearing cap is part of the second option design(Short block).

Labour Cost (C2):-

The worker or technicians working time behind the cylinder block cost is considering in the labour cost. It depends on the total time of the individual machining operations, set-up time of machine and load/unload time of the cylinder block and tools/cutters.

Tooling Cost (C3):-

The tooling cost for machining is determined by the total number of cutting tools required and the unit price for each tool. Tooling cost is normally varies inversely with the number of parts. The cost of whole sets of the tools and cutters (end mill (Rough and Finish), Face mill, drills, taps, slot mill, marking punch and Honing tool) are consider in the tooling cost. Also the cost of Dividing head and the milling vice are considered in the tooling cost.

Capital Equipment cost (C4):-

The 3-axis milling machine cost is considering the cost of the machine also the Hydraulic press and induction machine cost is going to consider in the machine cost. The university already brought the milling machine. So milling machine cost is not considering here in this cost analysis.

Overhead Cost (C5):-

The electricity, Workshop building and other like cutting fluid cost are considering in the overhead cost.

Cylinder Liners ( C6 ):-

The cost of the cylinder liners is very difficult to find as no manufacturer found to make such small diameter liners. So for the total cost calculation cylinder liners prices is estimated of £ 70 per set of 8 liners.

The tooling cost ,Labour cost ,capital equipment cost and over head cost perform major role in total cost analysis .Each one of them can make the major difference in costing values.

The individual costing of the tools, milling machine, workshop building charge, and labour charge for only one pieces of product is bit hard to find due to unavaiblities of proper costing value information.

It is not advisable to buy a new tools and cutter set just for the one pieces of the cylinder block machining, not even the dividing head and chucks. To pay the rent of this would be economical.

Workshop of the Coventry University normally charges £ 450 per day. This is estimate value. It includes a Workshop building cost (C5), Electricity, Labour cost (C2), Tools and cutters cost (C3), machines and insurance cost (C4) but not the material cost. Considering this all cost is equal to total cost (Ct).So to use the University workshop would be cheaper for cylinder block machining.

With taking into consideration the normal working time 9:30 am to 5 pm, lunch time, (small breaks), tool, work piece and machine setting time and other unexpected time, the complete machining of the cylinder block from beginning to end will take approximately 7 to 8 days. This is estimated time. So the total cost will be 7 - 8 x £ 450 = £ 3150 to 3600.

So with this estimation the total unit cost will be

Total Unit cost = C1+ (C2 + C3 + C4 + C5) +C6

= C1 + Ct +C6

= 13.50 + (3150 to 3600) +70

= 3233.5 to 3683.5

So to manufacture a cylinder block by machining in Coventry university workshop will cost approximately £ 3233 to 3683. This seems cheaper compare to the casting techniques.

Approximately operation time of main design analysis:-

The design geometry of the cylinder block is very complex and also need very accuracy with good surface finish quality. To satisfy these requirements it pushes the technician to do work carefully and accurately without having any mistake. And this sense will take a bit long time to do all machining operations. Also the some design of the block will take a very long time (i.e. slotting of water jacket, side material removal etc.) for machining. Here some of the major times consuming machining operation are described below with the estimated time.

Front face (T):- For extra material remove Operation.

Fig shows above the extra amount of material removed for light weight concept from the front face, which are 7mm thick and 90 m wide. This rough end milling operation takes approximately 50 to 60 minutes to complete.

Rear face (U):- For extra material remove operation.

Fig shows above the extra amount of material removed for light weight concept from the rear face, which is 6 mm thick, 60 m wide and 65 mm long. This rough end milling operation used here to remove this amount of material and it takes approximately 50 to 60 minutes to complete.

Top Face ( P ) :-

Fig shows above the extra amount of material removed from the top surface of the cylinder block, which is 10 mm thick, 70 m wide and 125 mm long. This rough end milling operation used here to remove this amount of material and it will takes approximately 60 to 80 minutes to complete.

Bottom face ( R ):-Metal removing for the crankshaft (Bulkhead).

Fig shows above is the material need to remove from the bottom face of block for the crankshaft passage. This is one of the longest (time consuming) operation during the machining of the whole cylinder block. The size 65mmx28mmx68mm of removed piece of material with the rough end mill and slotting will take approximately 50 to 60 minutes. And they are 4 in number, so the total time will be 200 to 240 minutes.

Cylinder Bore (faces P-Q and P-S ):-

Fig shows above is to remove material from the cylinder bore, which is 30mm in diameter and 46 mm long. Assume this operation will take two go and leave the 5mm more material with rough surface for honing operation. (Honing operation is included).This will take approximately 50 to 60 minutes per bore. So total time will be 400 to 480 minutes to complete all 8 bore.

Side faces (Q and S ):

Fig shows above is the material removed from the both sides of the cylinder block. This is also very long time consuming operation, which will take approximately 60 to 80 minutes top triangles and 1.30 to 2 hour for the bottom triangle section. Total of one side will be 2.30 to 3 hours. And the total time of both sides will be 5 to 6 hour to complete the operation.

Cooling water Jacket:-

Fig shows above is the material removed from the cooling water jacket with the slotting operation. The removed material size is 15 mm deep, 132 mm long (straight) and 42 wide. The drilling operation time in between the bore and jacket is not counting here. The total time to complete straight water jacket channel is approximately 60 to 80 minutes.

(Note:-The operation times described above are based on standard recommended feed, speed and depth of cut of milling machine and availability of the tools and cutters. And also consider that no break during the operation. The machine and cylinder block set-up time, cleaning, washing, inspecting, and measuring time is not considering here due to its totally depends on the working technician on it and other minor operations (filing, chamfering, de-burring etc) time as well. Again all operation time described here are estimated value.)

The operation time for main design described above will take/need more operation and time to complete final design features. For example the boring operation for the cylinder bore take 56 to 60 minutes (estimate value) for one cylinder bore, which time is just only for the rough metal removing time in circular manner. But after that the cylinder bore needs a more operation like inspection, measurement with dial gauge of bore size, levelling and cleaning of cylinder block for honing, Setting of honing tool (honing stones) with cylinder bore and machine, actual Honing operation. Also during the honing operation every after some interval, it need to check the size of the bore and also need to give the cool down time so the metal will return to its original size. This all operations are necessary and it will take a lot time to complete the final design feature.

But it will be very hard to say or predict the total time of all this extra operations as this is depends on factors like, technicians, quick availability of required stuff, machine settings, atmosphere (for cooling)etc. This total time might be the greater than the original time of boring (60 minute).

So considering the same situation for all different individual machining operation, add extra time (as per the required operation) in main operation time will increase the total operation time of that particular operation.

The total number of the various size holes in the cylinder block is around 150-180. Compare to the other operation figure this figure is big. Normally for drilling a hole require a simple operation. If we estimate the drilling time for hole needs a 4-5 minutes per hole in aluminium block. Then the total number of the drilling operation time of will be moderate. But here again there is some extra operations like some hole needs a tapping, reaming, counter boring ,machine and cylinder block setting for angular hole and surface hole etc. which add extra time in the main drilling operation. For example for connection bolt of cylinder head to block and crankcase to blocks need half plain and half threaded holes to avoid distortion at the surface which prevent good seating of the mating parts. And to make this (for example tap M8 size hole) needs three different operations:

Drill smaller size hole ( 6.8 ) then required tape size up to full depth.

Drill the clearance hole up to half way ( 8.5 ).

Taping operation ( M8 )

The time estimation for all this operation/activities is very hard as it's depends on same factors which are described earlier.

In summery of this whole operation time analysis, it is been conclude that the overall machining operation time is hard to calculate except some described operation above as most the machining operations times depends on factors which are described earlier. And finally conclude on the basis of the workshop technician estimation/advice and personnel experience that the total machining operation times of the whole cylinder block is in between 7 to 8 working days.

The japans company NTS making a cylinder block from the billet material on the 5 axis MAM72-63V CNC milling machine. This machine completed in ''one hit'' the finished cylinder block took a little under a 120 hours to machine using 58 tools.

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