授课教师杨宏智教授市公开课一等奖百校联赛特等奖课件.pptx

授課教師：楊宏智教授1【本本著著作作除除另另有有註註明明外外，採採取取創創用用CC姓姓名名標標示示非非商商業業性性相相同同方方式式分分享享台台灣灣3.0版版授授權權釋釋出出】【本本著著作作除除另另有有註註明明外外，採採取取創創用用CC姓姓名名標標示示非非商商業業性性相相同同方方式式分分享享台台灣灣3.0版版授授權權釋釋出出】【本本著著作作除除另另有有註註明明外外，採採取取創創用用CC姓姓名名標標示示非非商商業業性性相相同同方方式式分分享享台台灣灣3.0版版授授權權釋釋出出】第1页楊宏智（台大機械系教授）2第2页Chapter Outline1.Introduction2.Design Considerations in Casting3.Economics of Casting第3页IntroductionSuccessful casting practice requires proper control of a large number of variablesFlow of the molten metal in the mold cavities,the gating systems,the rate of cooling,and the gases evolved would influence the quality of a casting第4页Design Considerations in CastingAll casting operations share the characteristics of phase change and thermal shrinkage during the casting cycleBut each process will have its own design considerationsSand casting will require mold erosion and sand inclusions in the castingDie casting will not have this concernDefects frequently are random and difficult to reproduce第5页Design Considerations in Casting:General Design Considerations for Castings2 types of design issues in casting:1.Geometric features and tolerances incorporated into the part2.Mold features that are needed to produce the desired casting第6页Design Considerations in Casting:General Design Considerations for CastingsDesign of Cast PartsCorners,angles,and section thicknessFlat areasShrinkageDraftDimensional tolerancesLettering and markingsFinishing operations第7页Design Considerations in Casting:General Design Considerations for CastingsLocating the Parting LineParting line is the line or plane separating the upper(cope)and lower(drag)halves of moldsParting line should be along a flat plane rather than be contouredLocation is important as it influences mold design,ease of molding,number and shape of cores required,method of support and the gating systemParting line should be low for less dense metals and located at mid-height for denser metals第8页Design Considerations in Casting:General Design Considerations for CastingsLocating and Designing GatesMultiple gates are preferableGates should feed into thick sections of castingsA fillet should be usedGate closest to the sprue should be placed sufficiently far away from the sprueMinimum gate length should be 3 to 5 times the gate diameterCurved gates should be avoided第9页Runner DesignRunner is a horizontal distribution channel that accepts molten metal from the sprue and delivers it to the gatesIt is used to trap dross and keep it from entering the gates and mold cavityDesigning Other Mold FeaturesGoal in designing a sprue is to achieve the required metal flow rates while preventing excessive dross formationDesign Considerations in Casting:General Design Considerations for Castings第10页Designing Other Mold FeaturesGoal in designing a sprue is to achieve the required metal flow rates while preventing excessive dross formationTurbulent flow rates should be avoidedA pouring basin is used to ensure uninterrupted metal flow into the sprueFilters are used to trap large contaminants and more laminar flowChills used to speed up solidification of the metalDesign Considerations in Casting:General Design Considerations for Castings第11页Establishing Good PracticesHigh-quality molten metal is essential for producing superior castingsPouring of metal should not be interruptedStress relieving necessary to avoid distortions of castings in critical applicationsDesign Considerations in Casting:General Design Considerations for Castings第12页Expendable-mold process cool much slower than die castingImportant design considerations are:1.Mold Layout-must be placed logically and compactly with gates2.Riser Design-consideration in size and placement of risers3.Machining Allowance-require for additional finishing operationsDesign Considerations in Casting:General Design Considerations for Castings第13页Design Considerations in Casting:Design for Permanent-mold CastingDesigns may be modified to eliminate the draft for better dimensional accuracyDie-cast parts are net shaped to remove gates and minor trimming to remove flashing and defectsThey do not require a machining allowance第14页Design Considerations in Casting:Computer Modeling of Casting ProcessesCasting involves complex interactions among material and process variablesA quantitative study of these interactions is essential to the proper design and production of high-quality castingsStudies consist of heat flow,temperature gradients,nucleation and growth of crystals,formation of dendritic and equiaxed structures,impingement of grains and movement of the liquidsolid interface during solidificationCommercial software programs are Magmasoft,ProCast,Solidia and AFSsolid第15页Economics of CastingCost of each cast part(unit cost)depends on several factors,including materials,equipment,and laborEach of individual factors affects the overall cost of a casting operation第16页Economics of CastingCosts are involved in melting and pouring the molten metal into molds and in heat treating,cleaning,and inspecting the castingsLabor and skills required is also a considerationEquipment cost per casting will decrease as the number of parts cast increasesHigh production rate can justify the high cost of dies and machinery第17页