docForming - Blanking
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Forming - Blanking
Forming - Blanking Manufacturing Technology II Lecture 6 Laboratory for Machine Tools and Production Engineering Chair of Manufacturing Technology Prof. Dr.-Ing. Dr.-Ing. E.h. F. Klocke © WZL / IPT Seite 1 Content Introduction Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting © WZL / IPT Seite 2 1 Introduction Sheet Forming Process Manufacturing Processes according to DIN 8580ff Casting Forming TensoCompressive Forming Compressive Forming Open Die Forging Closed Die Forging Cold Extrusion Rod Extrusion Rolling Upsetting Hobbing Thread Rolling Cutting Deep Drawing Ironing Spinning Hydroforming Wire Drawing Pipe Drawing Collar Forming Tensile Forming Stretch Forming Extending Expanding Embossing Joining Bend Forming With linear Tool Movement With rotating Tool Movement Coating Changing of Material Properties Shear Forming Severing Translate Twist Intersperse Shearing Fine Blanking Cutting with a single Blade Cutting with two approaching Blades Splitting Tearing © WZL / IPT Seite 3 Introduction What is blanking? Definition: Mechanical separation of workpieces without appearance of shapeless material, therefore without chips … if necessary, including additional forming-operations. © WZL / IPT Seite 4 2 Content Introduction Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting © WZL / IPT Seite 5 Demands on blanking parts Required quality of blanking parts surface evenness angular deviation draw-in achievable roughness rupture zone smooth sheared zone cutting burr © WZL / IPT Seite 6 3 Content Introduction Demands on blanking parts Shearing – – – – – – – Introduction Characterisation of the process Achievable accuracy Forces in shearing Wear Tool design Examples of sheared parts Fine blanking Laser cutting Water-jet cutting © WZL / IPT Seite 7 Shearing - Introduction Shearing – Introduction application IT-classification costs output fine (IT 7) high low rough (IT 11) low high sheared surface Shearing © WZL / IPT Seite 8 4 Shearing - Characterisation of the process Open and closed cut in shearing open cut closed cut tool flank open flank © WZL / IPT Seite 9 Shearing - Characterisation of the process Differentiation of blanking and perforating blanking piercing waste waste © WZL / IPT Seite 10 5 Shearing - Characterisation of the process Tool design of shearing punch u – die clearence app. 0,05 x sheet thickness with: u = ½ · (a – a1) blank holder a – dimension of cutting die U sheet metal a1 – punch dimension α – relief angle of cutting die blanking die © WZL / IPT Seite 11 Shearing - Characterisation of the process Process sequences of shearing charging of the punch 1 2 elastic & plastic deformation shearing & cracking 3 4 break through © WZL / IPT Seite 12 6 Shearing - Characterisation of the process Stresses in shearing punch F σ τ τ σ F cutting die shearing and tensile stresses cause cracking © WZL / IPT Seite 13 Shearing – Achievable accuracy Errors on sheared workpieces draw-in draw-in height hE hE shearing zone rupture zone hG burr height hG tR crack depth tR © WZL / IPT Seite 14 7 Shearing – Achievable accuracy Influence of die clearance on the sheared surfaces formation of distortion wedge small clearance no formation of distortion wedge big clearance By a small die clearance, distortion wedges are generated by squeezing of a the material between two cracks. © WZL / IPT Seite 15 Shearing – Achievable accuracy specific die clearance: die clearance uS / sheet thickness s Quality of sheared surface depending on specific die clearance © WZL / IPT Seite 16 8 Shearing – Achievable accuracy Influence of specific die clearance on crack depth Crack depth tR sheet thickness s blanking specific die clearance us / % © WZL / IPT Seite 17 Shearing – Achievable accuracy Relation between burr height and number of cuts ductile sheet brittle sheet burr height © WZL / IPT Seite 18 9 Shearing - Forces in shearing Reduction of cutting force by modification of tools sloped cut plane cut h = 0 (plane cut) Fmax 0,9 Fmax force F h = 1/3 s (sloped cut) s h work s(h=0) = work s(h=2s) = 0,6 Fmax h = s (sloped cut) h = 2s (sloped cut) 0,3 Fmax Contact between punch and sheet 0 s 2s 3s total punch stroke Due to workpiece-bending, sloped cut is only suited for piercing. © WZL / IPT Seite 19 Shearing - Forces in shearing Reduction of cutting force by modification of tools plane cut conical die © WZL / IPT sloped cut grooved die grooved punch conical punch punch offset Seite 20 10 Shearing - Forces in shearing Dependence of quality on shearing strength of carbon steel carbon concentration tensile strenght breaking elongation sheet thickness die clearance part diameter aspect ratio draw-in Cutting resistance is defined as the cutting force (Fs) referring to the cutting surface (As= ls*s) © WZL / IPT Seite 21 Shearing – Wear Wear on the punch fatigue wear and wear on front face espacially appear for lower sheet thickness (s < 2 mm) fatigue wear on front face wear on front face wear on shaft area is caused by friction between punch and sheet in direction of punch movement. Appears during cutting of thicker sheets (s ≥ 2 mm) wear on shaft area © WZL / IPT Seite 22 11 Shearing – wear Influences on wear Tool Machine material hardness surface guidance die clearance stiffness kinematics tool wear Workpiece Type of process alloy stiffness hardness dimension shape open cut closed cut closed cut open cut Source: reiner, Müller Weingarten, Feintool © WZL / IPT Seite 23 Shearing – Tool design Multi-stage blanking tool 4 stage Multi-stage blanking tool for shearing of rotor- and stator-sheets stator © WZL / IPT rotor Seite 24 12 Shearing - Examples of sheared parts Multi-stage cut including assembly of an electronic connector Gesamtlaufzeit 1:49 min © WZL / IPT Seite 25 Content Introduction Demands on blanking parts Shearing Fine blanking – – – – – – – Introduction Characterisation of the process Process details and degree of difficulty Achievable accuracy Field of application Tool design Production examples Laser cutting Water-jet cutting © WZL / IPT Seite 26 13 Fine blanking - Introduction Fine blanking - Introduction application IT-classification costs output fine (IT 7) high low rough (IT 11) low high sheared surface fine blanking shearing © WZL / IPT Seite 27 Fine blanking – Characterisation of the process Animation of fine blanking clamping plastic deformation cutting © WZL / IPT Seite 28 14 Fine blanking – Characterisation of the process Stresses in fine blanking blankholder with vee F ring punch F σ σ σ σ τ τ σ σ σ σ σ σ σ σ F F counter punch cutting die superposed compression prevents cracking © WZL / IPT Seite 29 Fine blanking – Characterisation of the process Differences between shearing and fine blanking shearing fine blanking FS – punch force FS – punch force FR – vee ring and blank holder force FG – counter punch force 1 – cutting die (2 – guiding plate) 3 – punch 1 – cutting die 2 – vee ring and blank holder 3 – punch 4 – counter punch 5% © WZL / IPT die clearance 0,5% Seite 30 15 Fine blanking – Details Geometry of vee rings vee ring thin sheets sheet thickness s 3 – 5 mm cutting line outward notch toothed inward notch cutting die thick sheets blank holder with vee ring sheet thickness s 5 – 15 mm vee ring intention: cutting line • create compression stresses • prevent horizontal movement of the sheet / material flow © WZL / IPT Seite 31 Fine blanking - Details Dependence of workpiece quality on influencing quantities Process parameters affect workpiece quality: example: counter punch force draw-in width draw-in height smooth shearing zone deflexion Workpiece quality can be influenced by process parameters: example: draw-in height © WZL / IPT die clearance sheet thickness blank holder force counter punch force Seite 32 16 Fine blanking – obtainable precision Definition of degree of difficulty in fine blanking degree of difficulty S1 – easy S2 – medium S3 – difficult slot a, stick b / mm edge radius ri , ra / mm edge angle a sheet thickness s / mm sheet thickness s / mm © WZL / IPT Seite 33 Fine blanking – comparison of techniques Comparison of sheared surface in shearing and fine blanking shearing fine blanking In fine blanking, the smooth sheared zone can take a share of 100% © WZL / IPT Seite 34 17 Fine blanking –application Application examples fine blanking shearing In fine blanking, the sheared surface can be used as a functional surface © WZL / IPT Seite 35 Fine blanking – Field of application Application examples in automotive industry gear shifting gate door lock window lift synchronising disc valve plate belt pretensioner gear ABSpulse generator brakes seat adjustment © WZL / IPT seat belt components cooling system Seite 36 18 Fine blanking – Tool design Example for a compound press tool In fine blanking, several cuts can be done at the same time. © WZL / IPT Seite 37 Fine blanking – Tool design Compound press tool – disc brake © WZL / IPT Seite 38 19 Fine blanking – Tool design Example for a multi-stage tools fine blanking of a disc using multi-stage tool fine blanking of a clutch disc Feed direction stage 1 stage 2 stage 1: fine blanking stage 2: burr stamping © WZL / IPT Seite 39 Fine blanking – Tool design follow-on composite tool 3 stages in a Follow-on composite tool forming – thread forming – fine blanking connecting strap of a car door © WZL / IPT Seite 40 20 Fine blanking – Production examples Production of a clutch disc Gesamtlaufzeit 2:13 min © WZL / IPT Seite 41 Fine blanking – Production examples Planet carrier: Starting point combined fine blanking / forming A combination of fine blanking and forming realises the production of complex parts © WZL / IPT Seite 42 21 Fine blanking – Production examples Example planet carrier: Approach alternative A - inappropriate contur for forming - requires machining alternative B - No mashining required example „planet carrier“ properly for manufacturing through Redesign © WZL / IPT Seite 43 Fine blanking – Production examples Planet carrier: Implementation in an 8-stage follow-on composite tool 1 pre-blanking, pin stop hole 3 5 7 bending tabs 45° chamfering of hole fine blanking of slots and holes step coining piercing Ø39 H9 shape coining of tabs 2 bend tab 90° 4 burr stamping at slots 6 final cut 8 Development of forming and blanking sequence © WZL / IPT Seite 44 22 Fine blanking – Production examples Planet carrier: Follow-on composite tool in modular design bottom tool upper tool © WZL / IPT Seite 45 Fine blanking – Production examples Planet carrier: Follow-on composite tool in modular design stages / module 1 © WZL / IPT 2 3 4 5 6 7 8 Seite 46 23 Content Introdution Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting © WZL / IPT Seite 47 Laser cutting – Characterisation of the process Principle of laser cutting power distribution across laserlaser-profile Cutting by local melting and exhausting of material © WZL / IPT Seite 48 24 Laser cutting – process variables Cutting speed for several materials structural steel (O2 0,5 – 4 bar) CrNi - steel (O2 0,5 – 4 bar) Al. - alloy (O2 10 – 18 bar) CO2-laser, PL max = 2,6 kW m min 12 feed speed vf / 8 4 0 4 8 12 sheet thickness s / mm 16 20 Top feed speed depends on material and sheet thickness © WZL / IPT Seite 49 Laser cutting – process variables Comparison of cutting speeds 20 feed speed vf / m min shearing laser cutting (1500 W) water-jet cutting 15 10 5 0 4 8 12 16 20 24 sheet thickness structural steel s / mm Top feed speed depends on material and sheet thickness © WZL / IPT Quelle: Trumpf Seite 50 25 Laser cutting – Process comparison Comparision shearing - nibbling - laser beam cutting special process: rotational cutting nibbling laser cut 30 sec 40 sec 17 sec B 4 sec - 16 sec C 3 sec 15 sec 12 sec shearing (rotational) contour A speed St37 465mm x 5400mm x 2mm flexibility © WZL / IPT Seite 51 Laser cutting – process variables Comparison of machinable sheet thicknesses structural steel high-grade steel aluminium shearing laser-jet cutting (1500 W) laser-jet cutting (2600 W) water-jet cutting 0 20 40 60 sheet thickness / mm 80 Quelle: Trumpf © WZL / IPT Seite 52 26 Laser cutting – Field of application Examples of series production electronic connector (low lot sizes) synchronising disc climbing clamp stator sheet for special engines Quelle: tecnologix © WZL / IPT Seite 53 Content Introdution Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting © WZL / IPT Seite 54 27 Water-jet cutting – Characterisation of the process System design principle water supply abrasive medium guard mixing pipe © WZL / IPT Seite 55 Water-jet cutting Properties of the jet groove Verrundung rounding offder at the jet entry St rahleint rit t skant e Konizit ät der beveled hole Schnit t f uge Abplat zungen chipping at theamexit St rahlaust rit t scoring, erosion and cracks on the Rief en, Ausw aschungen, surface Risse auf Schnit t f lächen Quellenangabe: XYZ © WZL / IPT Seite 56 28 Water-jet cutting cutted surfaces and gaps feed speed 1 2 vf = 20 mm/min Rz,1 = 25 µm Rz,2 = 30 µm vf = 200 mm/min Rz,1 = 25 µm Rz,2 = 140 µm gap surface 1 2 material sheet thickness : AlMgSiO.5 : 25 mm abrasive medium mass flow pressure : Granat 80 Mesh : 400 g/min : 300 MPa The surface quality is heavily dependent on the feed speed © WZL / IPT Seite 57 Water-jet cutting – process parameters Characteristic of the surface α bG b0 bSO bSu : angle of shoulder : burr width : width of „jet influenced zone“ : notch width on workpiece top : notch width on workpiece bottom © WZL / IPT hG R0 u M s : burr height : edge radius : rectangular and inclination tolerance : measuring range of u : sheet thickness Seite 58 29 Water-jet cutting – influencing parameters Influences on notch width 2,5 3 notch width bSU / mm notch width bSO / mm 3,5 2,5 2 1,5 1 0,5 0 2 1,5 1 0,5 4 8 10 12 2 6 treatment distance aD / mm pressure nozzle diameter lenght of focussing pipe feed speed abrasive medium mass flow material sheet thickness : 300 MPa : 0,3 mm : 50 mm : 50 mm / min : Granat 80 Mesh : 250 g / min : AlMgSi0.5 : 5 mm © WZL / IPT 0 4 8 10 12 2 6 treatment distance aD / mm focussing pipe diameter d = 1,8 mm d = 1,5 mm d = 1,2 mm d = 0,8 mm Seite 59 Water-jet cutting – Dependences Dependence of surface quality on particle size © WZL / IPT Seite 60 30 Water-jet cutting – Performance characteristic Performance characteristics of different materials 80 depth of notch hK / mm depth of notch hK / mm 80 60 40 20 40 20 0 0 0 150 250 200 pressure / MPa nozzle diameter lenght of focussing pipe abrasive medium mass flow © WZL / IPT 60 300 : 0,3 mm : 50 mm : Granat 80 Mesh : 250 g / min 0 150 250 200 feed speed / mm/min 300 material : AlMgSi0.5 : TiAl6V4 : 1.4375 Seite 61 31
