Forming - Bulk Forming

Transcription

1 Forming - Bulk Forming Manufacturing Technology II Lecture 4 Laboratory for Machine Tools and Production Engineering Chair of Manufacturing Technologies Prof. Dr.-Ing. Dr.-Ing. E. h. F. Klocke Outline Introduction Cold forming Warm forming Seite 1

2 Introduction Methods of Forming Classification DIN 8580 ff Manufacturing Processes Casting Forming Cutting Joining Coating Changing of Material properties Compressive Forming Tension Compressive Forming Tensil Forming Bending Shear Forming Severing Open die forging Closed die forging Cold extrusion Rod extrusion Rolling Upsetting Hobbing Thread rolling Deep drawing Ironing Spinning Hydroforming Wire drawing Pipe drawing Collar forming Stretch forming Extending Expending Embossing With linear tool movement With rotational tool movement Translate Twist Intersperse Shearing Fine Blanking Cutting with a single blade Cutting with two approaching blades Splitting Tearing Seite 2 Introduction Process of Forming Technology: Bulk Forming Sheet Metal Forming Bulk forming: Sheet metal forming large changing of cross section and dimension large form modification large material strain hardening high forces high tool stresses no or low unwanted changing of the original wall thickness smaller deformations smaller material strain hardening lower forces than by bulk forming procedures Seite 3

3 Introduction What is Bulk Forming? Bulk forming massive semi-finished material component Seite 4 Introduction Advantages of Bulk Forming Cutting Forming 1,3 kg 0,4 kg semi-finished part component basic workpiece component Seite 5

4 Introduction Advantages of Bulk Forming Joining of singel-piece Function integration by bulk forming flange can fitting joined by welding formed by extrusion bulk forming allows function integration e.g. stability and leak tightness Seite 6 Outline Introduction Cold forming Introduction Upsetting Extrusion Warm forming Seite 7

5 Cold forming Iron-Carbon Diagramm fcc recrystallizing bcc Carbon content in weight percent Cermentite content in weight percent Seite 8 Cold forming Material Properties Layer of scale / µm Strain j Flow stress k f / MPa workpiece temperatur / C high flow stresses and low achievable strain by classic steel materials Seite 9

6 Cold forming Advantages and Disadvantages of Cold Forming Advantages: Cold Forming low tool material costs low influence of forming velocity no energy costs for heating no dimension faults caused by dwindling high surface quality increasing strength of the component Disadvantages: high forces limited plastic strain Seite 10 Cold forming Efficiency forming cold warm hot workpiece weight 0, kg 0, kg 0, plasticity φ < 1,6 (for classicr<4 forming steels) r<6 finishing effort less low high semi-finished part Cold forming with cold forming processes a good workpiece quality can be reached by low strain Seite 11

7 Cold forming Efficiency Forming process Cold extrusion IT-statement like DIN ISO quality centerline average Ra / µm 0, Warm extrusion Hot extrusion achievable with special proceedings achievable without special proceedings small shape, dimension and position tolerances as well as good surface qualities are possible Seite 12 Cold forming Forming Processes extrusion full extrusion hollow extrusion cup extrusion before after forward extrusion backward extrusion radial extrusion a: punch, b: die, c: workpiece, d: ejector, e: counter punch, f: spike Seite 13

8 Cold forming Full Forward Extrusion workpiece insertion compression extrusion ejection punch workpiece cavity ejector die production of a pin Seite 14 Cold forming Cup Backward Extrusion workpiece insertion compression extrusion ejection punch workpiece die ejector production of a cup Seite 15

9 Cold forming Radial Extrusion of a Cardan Joint workpiece insertion closing of the die extrusion ejection upper punch upper die workpiece lower die lower punch production of a cardan joint Seite 16 Cold forming Typical Cold Formed Components gear shafts Hirschvogel tubes denticulations Hirschvogel screws Fuchs Schraubenwerk Seite 17

10 Cold forming Process Chain of a Screw Production Prozesskette ejector upper die die finished part almost all screw geometries are produced by extrusion processes. Seite 18 Cold forming Process Chain of a Gear Shaft Production blank full forward extrusion full backward extrusion radial extrusion the production of components is usually charactarized by a combination of different extrusion processes Seite 19

11 Cold forming Film: Cold Extrusion of a Gear Shaft Seite 20 Cold forming Cracks by Radial Extrusion Processes during upsetting or radial extrusion processes surface cracks can appear on the collar surface Seite 21

12 Cold forming Crack Reduction by Superposition of Compressive Stresses punch gasket die workpiece pressure medium relief pressure valve tearing could effectively be shift to higher strains by superposition of compressive stresses Seite 22 Cold forming Crack Prevention by Superposition of Compressive Stresses without axial pressure superposition with axial pressure superposition fixed fixed max. available deformation superposition of compressive stresses can be realized by modifying the tool concept Seite 23

13 Cold forming Chevron Cracks by Full Forward Extrusion Seite 24 Cold forming Chevron Cracks by Full Forward Extrusion Chevrons DEFORM FEM-Simulation 3. forming step real workpiece a unfavourable dispersion of the interior material generates cracks Seite 25

14 Cold forming Phases of Production of a Bevel Gear bucking upsetting indirect cup extrusion cutting radial extrusion burr cutting calibration recrystallization recrystallization recrystallization achievable deformation can be increased by recrystallization Seite 26 Outline Introduction Cold forming Warm forming Seite 27

15 Warm forming Iron-Carbon Diagram fcc recrystallization bcc Carbon content in weight percent Cermentite content in weight percent Seite 28 Warm forming Material properties Layer of scale / µm Strain j Flow stress k f / MPa workpiece temperatur / C reduction of flow stress and increase of the avchievable strain Seite 29

16 Warm forming Advantages and Disadvantages of Warm Forming Advantages: Warm forming strengthening of the workpiece small range of tolerance caused by dwindling good surface quality Disadvantages: energy input for heating high flow stresses Hirschvogel Seite 30 Warm forming Efficiency forming cold warm hot workpiece weight 0, kg 0, kg 0, kg plasticity φ<1,6 j<4 j<6 finishing effort less low high semi-finished part cold forming warm forming Seite 31

17 Warm forming Efficiency Forming process Cold extrusion IT-statement like DIN ISO quality centerline average Ra / µm 0, Warm extrusion Hot extrusion achievable with special proceedings achievable without special proceedings mean shape, dimension and position tolerances as well as mean surface quality are possible Seite 32 Warm forming Typical Warm Formed Components Audi Hirschvogel Hirschvogel hinge flange cylinder injector Seite 33

18 Outline Introduction Cold forming Warm forming Introduction Open die forging Closed die forging Ring rolling Seite 34 Iron-Carbon Diagram fcc recrystallization bcc Carbon content in weight percent Cermentite content in weight percent Seite 35

19 Material Properties Layer of scale / µm Strain j Flow stress k f / MPa Workpiece temperatur / C low flow stress and high achievable strain Seite 36 Advantages and Disadvantages of Advantages: less effort high plasticity Disadvantages: high energy input for heating high material costs for tools dimension faults by shrinkage material loss and finishing caused by tinder Seite 37

20 Efficiency forming cold warm hot workpiece weight 0, kg 0, kg 0, kg plasticity φ<1,6 j<4 j<6 finishing effort less low high initial state cold forming warm forming forging Seite 38 Efficiency Forming process Cold extrusion IT-statement like DIN ISO quality centerline average Ra / µm 0, Warm extrusion Hot extrusion achievable witht special proceedings achievable without special proceedings low shape, dimension and position tolerances as well as low surface quality possible Seite 39

21 Heating Methods Furnace Heating in furnaces: furnaces are heated by gas, oil or electricity heat transmisson to the workpiece by radiation and convection Heating by induction: heat in the workpiece rim is generated by electromagnetic induction by eddy current formation Inductive heating facility Conductive heating: heating by high-frecuency current with direct workpiece contact inductive and conductive heating reduces the production of primary tinder as a result of the heating rate Seite 40 Tinder if Ironmaterials are heated above 600 C under the influence of oxygen, ironoxid will be generated on the surface, which is called tinder tinder peels away of the workpiece during the forming process the results are loss of material, surface marking and tool wear Saarstahl Seite 41

22 Generation of Tinder During Operations Seite 42 Processes Saarstahl Free forming Streching Rotary swaging Latidudinal forming Upsetting Driving Free curving by streching Thinning Smoothing Bulging Corrective streching a step by streching Surfacing Upending streching and upsetting are the main processes of open die forging Seite 43

23 Processes Open Die upsetting Saarstahl streching Saarstahl flat back gage acuminate back gage round back gage simple tool geometries are used for open die forging processes Seite 44 Process cycle Freiformschmieden round forging blank upsetting wastage forging and shearing streching forging a step upsetting forging streching forging a step simple tool geometries can produce complex workpiece geometries Seite 45

24 Open Die Saarstahl Seite 46 Material Properties Override a: tensile strength b: strain at fracture Z c: ductile yield A d: yield strength R p e: notch impact strength a k Saarstahl parallel vertical direction of deformation across the direction of deformation transition direction across along decrease by material impurity Streching degree l R by increasing the streching degree the material poperties can be improved Seite 47

25 Film: Open Die Seite 48 Closed Die Upper die Lower die Upper die Lower die part Burr cavity part without burr: low forming forces complete material utilization max. permitted volume fluctuation 0,5% exact workpiece positioning required with burr: less standards on workpiece volume fluctuation no exact workpiece positioning required the removal of the burr needs an extra process step Seite 49

26 Stages of Closed Die forging crankshaft connection rod hinge bearing an effective preform production is the key for short production chains Seite 50 Closed Die Seite 51 26

27 Die Wear wear / adbrasion 1/3/4 2 - thermal fatigue / crack formation 1/4 3 - mechanical fatigue / crack formation 4 - plastic deformation /4 the main reason for tool change is the abrasion on edges and cracks in cavitations Seite 52 Wear in the Burr Channel Area abrasion massive burr formation as reason for abrasion in the burr channel area Seite 53

28 Wear in the Burr Channel Area Massive flash formation as reason for abrasion in the burr channel area Seite 54 Wear in the Burr Channel Area Massive flash formation as reason for abrasion in the burr channel area Seite 55

29 Film: Closed Die with Hammer Seite 56 Film: Closed Die of a Crankshaft Seite 57

30 Processprinciple: Radial Axial Rolling Mill axial rolls ring centering roll pin roll main roll by ring rolling small output rings can be formed to big, thin-walled, and profiled rings Seite 58 Ring Rolling Seite 59

31 Possible Ring Geometries Possible profiles by profiling the pin- and/or main roll many different ring geometries can be produced Seite 60 Dimensions Kleine Ringe Schmiedjournal big and small rings can be produced by ring rolling Seite 61

32 Typical Components Walzen Ringwalzen SMS Eumuco Seite 62 Film: Axial Radial Ring Rolling Seite 63