3 (Courtesy of Trek Bicycle, 2002) Make a Mountain BikeSelect Processes to Manufacture a BikeHandle BarTopTubeSeatPostSaddleForkRear BrakeFront BrakeDownTubeRearDerailleurPedal(Courtesy of Trek Bicycle, 2002)
4 Manufacturing Process Decisions How to choose the specific manufacturing processes?How do the selected materials influence the choice of manufacturing processes?Would product function or performance issues influence the choice of processes?What criteria should be used to select processes?What are the Priority of the Criteria?Who makes the final decisions?
5 Design for Manuf (DFM) Guidelines Keep Functional & Physical Characteristics as SIMPLE as PossibleSimple & Sturdy parts are Easier to Make, and have Higher ReliabilityDesign for the LOWEST COST Production MethodCritical for HI-VOLUME Parts
6 Design for Manuf (DFM) Guidelines Design for the Minimum Number for Processing Steps (what’s a “step”?)Try to ELIMINATE Steps thru Thoughtful Product DesignSpecify Tolerances NO TIGHTER than Actually NeededOverToleranced Design leads to Increased Cost thruUnNeeded Processing Efforts“False Positive” ScrapSometimes hard to define a “step” => Think making a photo copy. Usually defined as the movement of material between processing stations
7 Part-Processing Sequence Primary Process alter the (“raw”) material’s basic shape or form. e.g.,CastingRollingForgingDrawingMoldingExtrudingThat is, take a “bolb” of material and give it a basic shape; e.g.Angle IronTube/PipeSheet/PlateSp12: Recall the Pacific Steel Casting Company
8 Part-Processing Sequence Secondary Process add or remove geometric features from the basic forms alter the (“raw”) material’s basic shape or form. e.g.,Machining of a brake drum casting (flat surfaces)Drilling/punching of refrigerator housings (sheet metal)Trimming of injection molded part “flash”
9 Part-Processing Sequence Tertiary Process surface treatments. e.g.,PolishingPaintingHeat-TreatingJoiningPlatingAnodizingThin Film CoatingTOP = ElectroPolish • BOT = Color Anodizing
10 Process Selection Criteria Compatibility with Selected MaterialsDimensional Accuracy and ToleranceSize & Weight CapacityLead TimeMin/Max Production QuantitiesSurface FinishNeed for Post-Process Operationse.g., Heat Treating
11 Cost Factors Influence of Special Desired Features e.g., Threaded Inserts, DoveTail GroovesMaterials AvailabilityNeed for Special ToolingPostProcess Finish OperationsSpecial Handling EquipmentSpecial Inspection EquipmentYieldi.e., Scrap Rate
12 Manuf Process Classifications ECM = ElectroChemical Machining
13 Deformation Processes RollingExtrusionDrawingForgingRollingRollers in compressionthick slabthin sheetPlastic deformation
14 Roll To Different Final Shape bloomstructuralingotsheet orcoilslabbilletbar orrod
15 Extrusion & Drawing Extrusion Drawing Extrusion Die Drawing Die OutPut CrossSectionsOutPut CrossSectionsRamPulling forceBilletBillet
16 Forging (Closed Die Version) BlockedpreformGutterRam pressureFlash
19 Die Casting Parting line Plunger Sprue Moving die Stationary die Ejector pinsMoltenmetal
20 Molten metal solidifies in cast Ceramic mold is removed Investment CastingCeramic mold(hardened slurry)4-part pattern treeWax patternis castWax removedby meltingMolten metal solidifies in castCeramic mold is removed
30 Machining Material Removal Sawing ≡ using a toothed blade.Milling ≡ form a flat surface by a rotating cutter tool.Planing ≡ using a translating cutter as workpiece feeds.Shaping ≡ form a translating workpiece using a stationary cutter.Boring ≡ increasing diameter of existing hole by rotating the workpiece.Drilling ≡ using a rotating bit forming a cylindrical hole.Reaming ≡ to refine the diameter of an existing hole.Turning ≡ form a rotating workpiece.Facing ≡ form turning workpiece using a radially fed tool.Grinding ≡ form a surface using an abrasive spinning wheel.Electric Discharge Machining ≡ by means of a spark.
38 Manufacturing CostsTotal Manufacturing Cost = Material + Tooling + Processingraw mat’ls molds labor fixtures electricityjigs suppliestool bits O/H(deprec.)TMC = M T P (6.1)
39 Material Cost per Part Let M = total materials costs (raw, bulk) q = production quantityThen material costs per part, cM iscM = M/q = (cost/weight x weight) / number of partsLet’s reorganize the variables in the equation abovecM = [cost/weight] [weight/number of parts]= (cost/weight) (weight/part), and thereforecM = cost/part
40 Material Cost per Part (cont.) Letcw = material cost per unit weight, andwp = weight of finished partww= weight of wasted material (the scrap) = Scrap-to-Useful Ratio →[wasted material weight]/[finished weight]= ww / wpThen the material cost per part, cM iscM = cw (wp + ww ) = cw (wp + wp ) (6.2)cM = cw wp (1+ ) (6.3)e.g. sand castingcM = ($1/lb)(1lb/part)(1+.05) = $1.05/partIs the
41 Tooling Cost per Part Let T= total cost of molds, fixtures per production runq = number of parts per runThencT= T/q (6.4)e.g. sand castingcT = ($10,000/run) / (5000 parts/run) = $2.00/partSp12: Pacific Steel Casting had ro RELINE the mold (a tooling cost) after only TWO uses.
42 Processing Cost per Part Letct = cost per hour, (machine rate + labor)t = cycle time (hours per part)then cP = ct t (6.5)e.g. sand castingcP = ($30/hr) (0.3 hrs/part) = $9/part
43 TOTAL Cost per Part Cost per part, c = cM + cT + cP c = cw wp (1+ ) + T/q + ct t (6.6)e.g. sand castingc = $ $ $9.00c = $12.05 / part
44 Example 5000 Part Run$45 of Bronze Part is due to Machining
45 Run Volume Sensitivity A ≡ Sand Casting B ≡ Inj. Molding C ≡ Machining
46 How to Lower Part Cost In Cost Eqn Minimize the SUM of Terms c = cw wp (1+ ) + T/q + ct t (6.6) purchase less expensive materials,keep our finished part weight lowproduce little manufactured waste (scrap, flash, etc.)design simple parts that require less expensive toolingmake many parts per production run (i.e., use large quantities between ReTooling)choose a manufacturing process that has a low-cycle-time & low-cost-per-hour
47 Electro Chemical Machining All Done for TodayElectro Chemical MachiningECM
49 ElectroPolishingBenefits of Electropolishing - Electropolishing produces a number of favorable changes in a metal part which are viewed as benefits to the buyer. All of these attributes translate into selling advantages depending upon the end use of the product. These include: • Brightening • Burr removal • Total passivation • Oxide and tarnish removal • Reduction in surface profile • Removal of surface occlusions • Increased corrosion resistance • Increased ratio of chromium to iron • Improved adhesion in subsequent plating • Reduced buffing and grinding costs • Removal of directional lines • Radiusing of sharp edges • Reduced surface friction • Stress relieved surface • Removal of hydrogen Electropolishing produces the most spectacular results on 300 series stainless steels. The resulting finish often appears bright, shiny, and comparable to the mirror finishes of "bright chrome" automotive parts. On 400 series stainless steels, the cosmetic appearance of the parts is less spectacular, but deburring, cleaning, and passivation are comparable.
50 ECMWhat is the Electrochemical Machining Process ? The process is based on Michael Faraday's Law of electrolysis, which is normally used in the electro plating of metals. Electrochemical machining is the reverse of plating, the work-piece is made the anode, which is placed in close proximity to an electrode (cathode), and a high-amperage direct current is passed between them through an electrolyte, such as salt water, flowing in the anode-cathode gap. Metal is removed by anodic dissolution and is carried away in the form of a hydroxide in the electrolyte for recycling or recovery. A major advantage of electrochemical machining is that it can be used as a de burring or machining process on any metal, no matter how hard or corrosion resistant it is, without creating any residual thermal or mechanical stress in the work-piece. The ECD process produces smooth, burr free edges and ECF can produce smooth, three dimensional forms with a good surface finish in single plunge forming pass. The process is simple to operate and offers fast production rates for difficult to conventionally machine alloys, with low running and tooling costs. ECM does not create any physical or thermal stress during machining and components may be machined either before or after heat treatment. Metal removal rates are approximately 60 cubic mm per minute per 1000 amperes DC current employed. Surface finish may be less than 0.4 microns for some materials. Otherwise difficult to conventionally machine alloys can be easily machined or de-burred by ECM.Examples include the stainless steels, high performance and high temperature alloys such as Inconel, Rene, Hastelloy, Titanium, Waspalloy and the latest generation corrosion resistant nickel alloys such as 617 and Alloy 59.