Mass_Production_Plan

1. Production analysis Designing such kind of a sleeve involves complicated techniques. The diversity of shapes defined by its cylindrical and plane surfaces determines the complexity and the different types of machines to be used. Also special clamping devices, jigs or fixtures have to be utilized in this kind of production. These facts give us the opportunity to use a lathe with big production rate in a moderate and mass production as well as milling machine and grinding machine with similar capabilities. Other basic requirements concern the necessary technologies to produce the element. They are directed toward the type of production, methods of controlling the accuracy, choosing a billet, feed and speed of cutting, determination of the duration of the different operations. Determination of the qualification of the workers, their number, number of machines involved into the production process are also basic factors in a production of a detail. 2. Determining the type of production The production type can be determined by the production coefficient k. If 250 working days per year are considered each of which with 2* 8 hours’ shifts per day the following expression for N can be derived: [pic] Where: c = working days per year = 250 d = working hours per day = t = average operating time rate = q = amount of unit per year = 45000 [pic] Having in mind that the coefficient N is in the range: - 1 ( 2 for mass production - 2 ( 10 for large production - 10 ( 20 for medium production - above 20 for small production In this case N = 1.67 so the production type can be defined as mass production. In order to calculate the time limit for production of the whole lot of 45 000 sleeves, the following formula is to be used: [pic] Where: q = amount of unit per year = 45000 d = working hours per day = 16 c = working days per year = 250 Using the same data as in calculating the production type coefficient N the given answer is obtained: [pic] sleeves per hour have to be produced So to find out what is the time limit for a single sleeve for the considered requirements: [pic] hours per sleeve Transformed into minutes, this result raises the requirement that the longest operation for machining a sleeve has to be no more than 5.4 minutes. 3. Determining the type of processes Considering the analysis made in point 1 - Production analysis and the shape and geometry of the detail, the quantity and type of production, technological accuracy and the surface roughness the following table for the sequence of the operations is identified: Order of Operations 1. Selecting the billet 2. Cutting off the billet 3. Milling 4. Turning 5. Drilling 6. Grinding 4. Selecting the billet Material, configuration, dimensions, and the quality of the surface must be taken into consideration in selecting the type and the form of the billet. Type of production is also an important factor. The price of the material as well as the expenses for machining it have to be considered in order the right choice to be made thus satisfying the necessary technical and economical requirements. I choose to use steel rods with square cross-section. The steel used is Steel 45 ( BNS: 5785 – 75) according to the Bulgarian National Standard ), because it is with relative good hardness, very good corrosion resistance, widely used and so always easy to find at a good price. Determination the size of the billet: The size of the square cross-section of the sleeve 60x60.However we can’t pick a billet with the same size (60x60) because it will not be possible to obtain the desired roughness of the surface 10. That’s why we pick the next standard size which is 70x70. The length of the sleeve is 50 mm. The length L of a standard rod is 6 m so using the following formula the number of rods cut into billets can be calculated: [pic] where: L – standard length of the rod u – the length of the remaining of each rod needed for clamping it; k=20 mm l – length of the part produced (mm) q – length of the remaining of the material due to the fact that the length of the rod is not a multiple of the used part of the rod (for l 320x1370 mm Nominal revolutions of the spindle -> 31.5-1600 min-1 Angle of inclination -> 45o Power -> 7.5 kW Suitable for this machine are the following tool holder and milling disk inserts which are taken from the Sandvik Coromant catalogue: Tool holder: N331.32.-08S27DM Mounting: bore with key way Machining tools: all types Material: all types Inclination angle: 5o Effective number of teeth: zc=z/2 z=6 Kg=0.3; Dc=80; E=16; Bkw=7; Ci=29.8 l1=min(12) l1=max(13) Max ar=19.5 ap=7.9-10 asp=5.6 dm=27 Insert: N331.1A-05 45 08H-PL Insert size: 0.5 ap=12.6-2r( Ia=5.7 Iw=9.5 dI=2.9 L=6.5 s=4.5 bs=1.2 r(=0.8 Vco=285 Cvc=-0.2707 kc=1500 N/mm2 HB=125 Milling from square 70mm to square 60mm with roughness 10 According to Sandvik Coromant’s Cutting data module for milling for the following parameters of our detail: Cutting diameter (Dc) = 80mm Cutting edge angle (Kr) = 5 degrees Number of eff. Edges (Zc)=z/2=3 Depth of cut (ap) = 10mm Working engagement (ae) = 70mm The following recommended cutting data is obtained : |Cutting speed (vc): |[pic] m/min | | Spindle speed (n): |[pic] rpm | | Feed speed (vf): |[pic] mm/min | | Cutting power for removal of chips (Pc): |[pic] kW | | Metal removal rate (Q): |[pic] cm³/min | | Cutting torque (Mc): |[pic] Nm | 6. Choosing the machine and the tools for turning Choosing a lathe Automatic CT251 lathe with CPU is chosen with the following characteristics: Max. diameter in the chunk – 200 mm Max. length of a detail – 400 mm Max. axial path – 460 mm Max radial path – 215 mm Rounds per minute – (20 – 3000) Fast axial travel of the headstock – 10 m/min Fast radial travel of the headstock – 9m/min Power: 15kW Tool holder of lever design PCLNR/L (fig.1) from the Sandvik Coromant catalogue is chosen with the following characteristics: h = 25mm h1 = 25mm b = 25mm l1 = 150mm l3 = 27mm f1 = 32mm r( = 0,8mm Afterwards the insert type CCMT 09T308-UM is selected again from the Sandvik Coromant catalogue with parameters given on fig2: Turning operations: In the turning operations the following formulae have been used which were taken from the Sandvik Coromant catalogue: [pic] [pic] [pic] [pic] [pic] [pic] where: Dm – machined diameter (mm) Vc – cutting speed (m/min) n – spindle speed (r/min) Tc – period of engagement (min) Q – metal removal rate (cm3/min) Im – machined length (mm) Kr – entering angle degree (degree) ap –depth of cut (mm) Pc – net power requirement (kW) Kc(0.4) – specific cutting force for chip thickness 0.4 mm (N/mm2) fn – feed per revolution (mm/r) Rmax – profile depth ((m) r( - insert nose radius (mm) Facing of the sleeve The data bellow is determined by the geometry of the sleeve and by the Sandvik Coromat catalogue: The machined length Im is 30 (mm) The depth of cut ap is 0.75 (mm) The feed per revolution fn is 0.3 (mm/r) The spindle speed n is 700 (r/min) The cutting speed Vc is 300 (m/min) but adjusted for tool life of 120 min: Vc=300x0.4=120 (m/min) Kr – entering angle degree– 95o(degree) Kc(0.4) – specific cutting force for chip thickness 0.4 mm - 2100(N/mm2) [pic]min [pic]m3/min [pic] W Relatively small feed rate fn for better quality of the surface is chosen and the check of the capabilities of the machine are performed thus assuring the feasibility of the operation. Both surfaces are faced which increases the operational time. Internal turning of stage with diameter d=29mm In order to obtain a diameter d=29 we need to use at least 2 drills for good accuracy. Firstly, we insert a drill with diameter d=10mm According to Sanvik Coromant’s catalogue for diameter of the drill d=10mm and hole depth = 46mm we should use the following data: |vcMin - vcMax | | |Cutting speed (vc): | | |Spindle speed (n): | | | | | |80 - 140 | | |[pic] m/min | | |[pic] rpm | | | | | |fnMin - fnMax | | |Feed (fn): | | |Feed (vf): | | | | | |0.15 - 0.34 | | |[pic] mm/r | | |[pic] mm/min | | | | | | |[pic] kW | |Net power (Pc): | | | |[pic] N | |Feed force (Ff): | | | |[pic] Nm | |Torque (Mc): | | | | | | |[pic] cm^3/min | |Metal Removal Rate (Q): | | | |[pic] sec | |Cutting time per hole (t): | | | |[pic]xDC | |Hole Depth: | | | |[pic]l/min | |Cutting flow(q): | | After that we insert a drill with diameter d=29 and make the final hole. According to Sanvik Coromant’s catalogue for diameter of the drill d=29 mm and hole depth = 46mm we should use the following data: Net power (Pc): 40kW Feed force (Ff):4460 N Torque (Mc): 69 Nm Metal Removal Rate (Q): 908 cm^3/min Cutting time per hole (t): 2 sec Hole Depth: 1.59 xDc Cutting flow(q): 55 l/min Rough turning of the stage with diameter d=47mm from square 70mm to d=51mm The data bellow is determined by the geometry of the sleeve and by the Sandvik Coromat catalogue: The machined length Im is 45(mm) The depth of cut ap is 9,5 (mm) The feed per revolution fn is 0.3 (mm/r) The cutting speed Vc is 325 (m/min) but adjusted for tool life of 120 min: Vc=325x0.4=130 (m/min) Kr – entering angle degree– 95o(degree) Kc(0.4) – specific cutting force for chip thickness 0.4 mm - 2100(N/mm2) r( - insert nose radius – 0.8 (mm) [pic](r/min) [pic]m3/min [pic] [pic] [pic]((m) The calculation of the revolution of the spindle gives 592 (r/min) but instead of this value a standard one of 600 (r/min) will be used. It is obvious that achieving higher metal removal rate Q leads to greater power consumption. Fortunately the power requirements of the machine are fulfilled. The roughness of the surface nevertheless is not satisfactory which will be fixed by the assigned grinding. As it is seen additional material is left for implementing it Fine turning of the stage with diameter d=47mm from d=51mm to d=48mm + channel 3x0.3 The data bellow is determined by the geometry of the sleeve and by the Sandvik Coromat catalogue: The machined length Im is 45(mm) The depth of cut ap is 1,5 (mm) The feed per revolution fn is 0.3 (mm/r) The cutting speed Vc is 325 (m/min) but adjusted for tool life of 120 min: Vc=325x0.4=130 (m/min) Kr – entering angle degree– 95o(degree) Kc(0.4) – specific cutting force for chip thickness 0.4 mm - 2100(N/mm2) r( - insert nose radius – 0.8 (mm) [pic](r/min) [pic]m3/min [pic] [pic] [pic]((m) The calculation of the revolution of the spindle gives 812 (r/min) but instead of this value a standard one of 800 (r/min) will be used. It is obvious that achieving higher metal removal rate Q leads to greater power consumption. Fortunately the power requirements of the machine are fulfilled. The roughness of the surface nevertheless is not satisfactory which will be fixed by the assigned grinding. As it is seen additional material is left for implementing it. Channel-1 3x0,3 The machined length is 3 (mm). The depth of cut ap is 0.3 (mm). The feed per revolution fn is 0.3 (mm/r). The cutting speed Vc is 325 (m/min) but adjusted for tool life of 120 min: Vc=325x0.4=130 (m/min). [pic](r/min) so 900 will be taken. The time for this operation is [pic] [pic] Rotating the detail to 180 degrees and turning from d=29 to d=35+channel 3x0.3+chamfer 1x450. Machining internal surfaces requires different type of tool holder and different type of insert. From the Sandvik Coromant catalogue the following tools have been selected and their characteristics are listed bellow: Tool holder –> S25T- PTFNR/L 11 Dmin=25mm h = 23mm b = 25mm l1 = 300mm l3 = 34mm f1 = 17mm r( = 0,4mm The data bellow is determined by the geometry of the sleeve and by the Sandvik Coromant catalogue: The machined length Im is 46(mm) The depth of cut ap is 3 (mm) The feed per revolution fn is 0.2 (mm/r) The cutting speed Vc is 325 (m/min) but adjusted for tool life of 120 min: Vc=325x0.4=130 (m/min) Kr – entering angle degree– 91o(degree) Kc(0.4) – specific cutting force for chip thickness 0.4 mm - 2100(N/mm2) r( - insert nose radius – 0.4 (mm) [pic](r/min) [pic]m3/min [pic] [pic] [pic]((m) The calculation of the revolution of the spindle gives 1427 (r/min) but instead of this value a standard one of 1500 (r/min) will be used. The roughness of the surface is satisfactory. As it is seen there is 1 mm additional overtravel of the tool to calculate the real time for machining. Channel-2 3x0,3 The machined length is 3 (mm). The depth of cut ap is 0.3 (mm). The feed per revolution fn is 0.3 (mm/r). The cutting speed Vc is 325 (m/min) but adjusted for tool life of 120 min: Vc=325x0.4=130 (m/min). [pic](r/min) so 1200 will be taken. The time for this operation is [pic] [pic] Chamfering 1x450 For the chamfer we use the same tool for the lathe but rotated at 450. n = 500rpm s = 0,10mm/rev The time required is: [pic] Chamfering 2x150 For these chamfers we use the same tool for the lathe but rotated at 150. n = 500rpm s = 0,10mm/rev The time required for one chamfer is: [pic] Since we have to do 2 chamfers we multiply the time by 2. So T=2x0.04=0,08min. Chamfering 3x450 For these chamfers we use the same tool for the lathe but rotated at 450. n = 500rpm s = 0,10mm/rev The time required for one chamfer is: [pic] Since we have to do 4 chamfers we multiply the time by 4. So T=4x0,06=0.24min. 8. Drilling: From King Sang Machinery’s catalogue (www.kingsang.com.tw) We select drilling machine KSA-16A with the following characteristics: | | | |Diameter of quill |Ø65 | | |Spindle taper |MT 2# | | |Spindle step |4 | | |Spindle travel |100 | | |Spindle to column |175 | | |Spindle to table |420 | | |Spindle to base |620 | | |Drilling capacity |Ø4-Ø16 | | |Cover sizes |608x214x125 | | |Column diameter |Ø80 | | |Table diameter |Ø320 | | |Base sizes |500x300 | | |Speed 50Hz |450-1700 | | |Speed 60Hz |550-2000 | | |Motor |1/2; 1 ; 2 (HP) | | |Machine sizes |650x410x1090 | | |Machine weight |105kg | We want to drill all the 4 holes at the same time for best performance. For this purpose we need to attach a multi-spindle drill head. The requirements are that the head has 4 spindles with possibility for 45mm distance between them. From the catalogue of Hann Kuen Machinery & Hardware (http://www.machine-tools.tw) we select Hardy 124 multi-spindle Head with the following characteristics: Collet – C-9 Max. Distance between spindles – 126mm Min. Distance between spindles – 26mm Speed rate – 1:1 Max. drilling diameter – 9mm Number of spindles – 2-4 We set the head to have 4 spindles each with diameter d=6.6mm and to be the edges of a square with side=45mm. According to Sandvik Coromant’s Cutting data module for drilling for the following parameters of our detail: Drill diameter (Dc) =6.6 mm Hole depth (L) = 5 mm The following recommended cutting data is obtained : |vcMin - vcMax | | |Cutting speed (vc): | | |Spindle speed (n): | | | | | |80 - 140 | | |[pic] m/min | | |[pic] rpm | | | | | |fnMin - fnMax | | |Feed (fn): | | |Feed (vf): | | | | | |0.15 - 0.34 | | |[pic] mm/r | | |[pic] mm/min | | | | | | |[pic] kW | |Net power (Pc): | | | |[pic] N | |Feed force (Ff): | | | |[pic] Nm | |Torque (Mc): | | | | | | |[pic] cm^3/min | | |Metal Removal Rate (Q): | | | | |[pic] sec | |Cutting time per hole (t): | | | |[pic]xDC | |Hole Depth: | | 9. Grinding: The 1,25 roughness of the detail can be achieved most efficiently by grinding so the ШК322.31 with CPU control grinding machine is chosen. The parameters of the machine are listed bellow: Max. operational diameter : 320 mm - external grinding Max. operational diameter : 200 mm - internal grinding Max. operational length : 1500 mm external grinding Max. operational length : 200 mm - internal grinding Revolutions : 20 – 15880 min-1 Power : 2.2 kW The grinding disk is with straight profile (fig.8) type 23A16-25 C2 CT1 K. It is made of elektrocorundum Al2O3 and has the following dimensions: D=250 mm d=20 mm h=16 mm In order to have roughness of 1,25 the speed of the grinding disk must be in the range of 45 ( 60 m/s [“Grinding manual”-Reference literature ]. So v=60m/s. is chosen because the operating speed of the disk is 45-60 m/s (by manufacturer). 10.Grinding operations: The time necessary for grinding a surface with the given parameters can be calculated using the following relations: [pic] L=lx - (Bk- lx1) where: k=1.2-1.7 is the coefficient for adjustment and wear of the disk Sb - axial feed in divisions of the grinding disk (mm/min-1) n – revolutions (rpm) Bk – width of the grinding disk, the same as h on the drawing lx1 = 0.6 Bk = 0.6x16 = 9.6 mm lx = 45 mm the length to be grinded L= 45– (16 – 9.6) = 38.6 mm Sb=0.2h=0.2x16=3.2 mm For n =1000 rpm [pic] 11. Calculating the servicing times for the whole process Cutting off Total servicing time (including transport to and from the jig-saw) 0.75 min Total time for cutting off=1.60 min Milling - fixing the detail 0,08 min - positioning the detail 0.06 min (Pp=length_of_the_milling_table/2 = 300/2=150mm=0.15m Tp=Pp/fast_move_of_the_table=0.15/2.5=0.06 min) - rotating the detail (3x0.05min=0.15 for each plane) 0.15 min - removing the detail 0.06 min - measuring the detail 0.27 min Total servicing time for the milling 0.62 min Th=Total time for milling 1.10 min Turning - time for transporting from the milling machine 0,20 min 1.Facing - initial measuring of the detail 0.16 min - time for fixing the detail in the chuck 0.17 min - fixing the tool 0.10 min - changing the revolutions 0.04 min - adjusting the feed 0.06 min Total servicing time for facing 0.53 min 2.Turning of the external surface - changing the revolution 2*0.04 min - time for changing the feed 2*0,06 min - time for measuring the detail 0,16 min Total servicing time for the external turning 0.26 min 3.Turning of the internal surface - changing and fixing the toll 0.10 min - changing the revolution 2*0.04 min - time for changing the feed 2*0,06 min - time for measuring the detail 0,16 min Total servicing time for the internal turning 0.36 min 5.Turning of the chamfers - changing and fixing the toll 0.10 min - moving the tool 7*0.08 min - changing the revolution 0.04 min - time for changing the feed 0,06 min - removing 0.10 min Total servicing time for the chamfers 0.46 min Th=Total time for turning 3.61 min Drilling - time for transporting from the lathe 0,20 min - fixing the detail 0,08 min - removing the detail 0.06 min Total servicing time for the drilling 0.34 min Th=Total time for drilling 0.39 min Grinding - time for transporting from the drilling machine 0,20 min - fixing the detail 0,08 min - removing the detail 0.06 min Total servicing time for the grinding 0.34 min Th=Total time for grinding 1.24min Considering that all the machines will be working simultaneously the limiting time is determined by the longest operating time Th which is the so called bottleneck. The following estimations are made according it. Some unpredictable service time has to be added which is 2,5% of the bottleneck time to assure the possibility of continuing manufacturing in emergency cases: Ts = 2,5%(Th)= 0,025(3.61)=0,09 min And time for the rest of the workers which is 4%: Trest = 4%(Th)=0,04(3.61)=0,14 min The production time is: T=3,61+0,09+0,14=3,84 min As it is seen this satisfies the precondition that the production time should be less than 5.4 min. Adding the time for cutting off, milling, drilling and grinding Twhole=3.84+1.6+1.1+0.39+1.24= 8.17 min 12. Calculating the price of the production: In order to calculate the price of the detail, the first thing is to determine its mass. It can be calculate from the following formula : m=(steel *V Where: (steel=7.85x103kg/m3 V is the volume of the body , in our case we take the volume of the billet with size 70x70x51,5. The formula for this rectangular prism is V=side1*side2*side3 Thus V =70*70*51 = 252350 mm^3 m=(steel *V=1.981kg m=1.981 kg Price of the steel: 2.5 leva/kg But as the initial material is rod Price of material = 2.5x1.981=4.953 leva This price is referred to the cost of the useful material involved in the sleeves so the real profitability to be calculated as a function of the net economic constraints. It must not be neglected the fact that the sleeves are cut off from standard rods thus additional losses have to be added as some material is left for holding the material when cut, also the length of the mechanical jigsaw is considered, the left material for the applied operations. Average quantity per hour – 11 sleeves Salary per hour – 2.5 leva per worker Each machine is operated by a single worker so there are 5 workers: Cost per piece per hour = 12.5/24 = $0.521 leva per piece The total cost = 4.953+0.521 = 5.474 leva per piece TOTAL COST = 5.474 leva per piece 13.Operation Sheet |Operation |Name of the Operation |Machine |Cutting tools | |No. | | | | |1. |Cutting- off |Mechanical |- | | | |Jig Saw | | |2. |Milling |ВФ 323.01 |Coromant Rigid Clamp | | | | |LF123H13-1616B | |3. |Facing |201 |Type 5 -25x20 | |4. |Internal turning |201 |Type 3–25x16 | | |rough | | | |5. |Internal turning |201 |Type 5 -25x20 | | |fine | | | |6. |Channel |201 |Type 3–25x16 | |7. |Rough turning |201 |Type 3–25x16 | |8. |Fine turning |201 |Type 5 -25x20 | |9. |Channel |201 |Type 3–25x16 | |10. |Chamfering 1x450 |201 |Type 5 -25x20 | |11. |Chamfering 2x150 |201 |Type 5 -25x20 | |12. |Chamfering 3x450 |201 |Type 5 -25x20 | |13. |Drilling |KSA-16A |Coromant Rigid Clamp | | | | |LF123H13-1616B | |14. |Grinding |ШК 321.21 |- | 15. Reference Literature: 1. “Grinding Manual” – M.Naerman – publisher “Tehnika” – Sofia, 1989 2. “Manual for exercises in machine building technology” – G.Getev, A. Georgiev - publisher “Tehnika” – Sofia, 1980 3. “Machine building technology” – S.Pashov - publisher “Tehnika” – Sofia, 1990 4. Sandvik Coromant Catalogue 2010 5. Hann Kuenn Catalogue 2010 – www.machine-tools.tw 6. King Sang Catalogue 2010 – www.kingsang.com.tw Drilling machine [pic] Multi-spindle drilling head [pic] ----------------------- Fig.1 Fig.2 D d h Fig.8 Step 7 Step 3