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 Seite 1 Content Introduction Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting Seite 2
Introduction Sheet Forming Process Manufacturing Processes according to DIN 8580ff Casting Forming Cutting Joining Coating Changing of Material Properties Compressive Forming Open Die Forging Closed Die Forging Cold Extrusion Rod Extrusion Rolling Upsetting Hobbing Thread Rolling Tenso- Compressive Forming Deep Drawing Ironing Spinning Hydroforming Wire Drawing Pipe Drawing Collar Forming Tensile Forming Stretch Forming Extending Expanding Embossing Bend Forming With linear Tool Movement With rotating Tool Movement Shear Forming Translate Twist Intersperse Severing Shearing Fine Blanking Cutting with a single Blade Cutting with two approaching Blades Splitting Tearing 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. Seite 4
Content Introduction Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting Seite 5 Demands on blanking parts Required quality of blanking parts surface evenness angular deviation draw-in achievable roughness cutting burr smooth sheared zone rupture zone Seite 6
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 Seite 7 Shearing - Introduction Shearing Introduction application IT-classification costs output fine (IT 7) high low sheared surface Shearing rough (IT 11) low high Seite 8
Shearing - Characterisation of the process Open and closed cut in shearing open cut closed cut tool flank open flank Seite 9 Shearing - Characterisation of the process Differentiation of blanking and perforating blanking piercing waste waste Seite 10
Shearing - Characterisation of the process Tool design of shearing u die clearence app. 0,05 x sheet thickness with: u = ½ (a a 1 ) a dimension of cutting die U punch blank holder a 1 punch dimension sheet metal α relief angle of cutting die blanking die 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 Seite 12
Shearing - Characterisation of the process Stresses in shearing punch F σ τ τ σ F cutting die shearing and tensile stresses cause cracking Seite 13 Shearing Achievable accuracy Errors on sheared workpieces draw-in draw-in height h E h E shearing zone rupture zone h G burr height h G t R crack depth t R Seite 14
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. Seite 15 Shearing Achievable accuracy Quality of sheared surface depending on specific die clearance specific die clearance: die clearance u S / sheet thickness s Seite 16
Shearing Achievable accuracy Influence of specific die clearance on crack depth blanking Crack depth t R sheet thickness s specific die clearance u s / % Seite 17 Shearing Achievable accuracy Relation between burr height and number of cuts ductile sheet brittle sheet burr height Seite 18
Shearing - Forces in shearing Reduction of cutting force by modification of tools plane cut sloped cut F max h = 0 (plane cut) 0,9 F max h = 1/3 s (sloped cut) s h force F 0,6 F max work s(h=0) = h = s (sloped cut) = work s(h=2s) h = 2s (sloped cut) 0,3 F max Contact between punch and sheet 0 s 2s 3s total punch stroke Due to workpiece-bending, sloped cut is only suited for piercing. Seite 19 Shearing - Forces in shearing Reduction of cutting force by modification of tools plane cut sloped cut grooved punch conical punch conical die grooved die punch offset Seite 20
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 (F s ) referring to the cutting surface (A s = l s *s) 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 Seite 22
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 open cut closed cut Source: reiner, Müller Weingarten, Feintool Seite 23 Shearing Tool design Multi-stage blanking tool 4 stage Multi-stage blanking tool for shearing of rotor- and stator-sheets stator rotor Seite 24
Shearing - Examples of sheared parts Multi-stage cut including assembly of an electronic connector Gesamtlaufzeit 1:49 min 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 Seite 26
Fine blanking - Introduction Fine blanking - Introduction application IT-classification costs output fine (IT 7) high low sheared surface fine blanking shearing rough (IT 11) low high Seite 27 Fine blanking Characterisation of the process Animation of fine blanking clamping plastic deformation cutting Seite 28
Fine blanking Characterisation of the process Stresses in fine blanking punch blankholder with vee F ring σ σ σ σ σ F τ σ τ σ F σ σ σ σ σ F counter punch cutting die superposed compression prevents cracking Seite 29 Fine blanking Characterisation of the process Differences between shearing and fine blanking shearing fine blanking F S punch force F S punch force F R vee ring and blank holder force F G 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% die clearance 0,5% Seite 30
Fine blanking Details Geometry of vee rings thin sheets vee ring cutting line sheet thickness s 3 5 mm outward notch toothed inward notch cutting die blank holder with vee ring thick sheets sheet thickness s 5 15 mm vee ring cutting line intention: create compression stresses prevent horizontal movement of the sheet / material flow 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 die clearance sheet thickness blank holder force counter punch force Seite 32
Fine blanking obtainable precision Definition of degree of difficulty in fine blanking degree of difficulty edge angle a S1 easy S2 medium S3 difficult slot a, stick b / mm edge radius r i, r a / mm sheet thickness s / mm sheet thickness s / mm 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% Seite 34
Fine blanking application Application examples fine blanking shearing In fine blanking, the sheared surface can be used as a functional surface Seite 35 Fine blanking Field of application Application examples in automotive industry gear shifting gate door lock window lift valve plate synchronising disc gear belt pretensioner brakes ABSpulse generator seat adjustment seat belt components cooling system Seite 36
Fine blanking Tool design Example for a compound press tool In fine blanking, several cuts can be done at the same time. Seite 37 Fine blanking Tool design Compound press tool disc brake Seite 38
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 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 Seite 40
Fine blanking Production examples Production of a clutch disc Gesamtlaufzeit 2:13 min 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 Seite 42
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 Seite 43 Fine blanking Production examples Planet carrier: Implementation in an 8-stage follow-on composite tool 1 3 5 7 pre-blanking, pinstophole bending tabs 45 chamfering of hole fine blanking of slots and holes step coining piercing Ø39 H9 shape coining of tabs bend tab 90 burr stamping at slots 2 4 6 final cut 8 Development of forming and blanking sequence Seite 44
Fine blanking Production examples Planet carrier: Follow-on composite tool in modular design bottom tool upper tool Seite 45 Fine blanking Production examples Planet carrier: Follow-on composite tool in modular design stages / module 1 2 3 4 5 6 7 8 Seite 46
Content Introdution Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting Seite 47 Laser cutting Characterisation of the process Principle of laser cutting power distribution across laser-profile Cutting by local melting and exhausting of material Seite 48
Laser cutting process variables Cutting speed for several materials CO 2 -laser, P L max = 2,6 kw structural steel CrNi - steel Al. - alloy (O 2 0,5 4 bar) (O 2 0,5 4 bar) (O 2 10 18 bar) 12 m min feed speed v f / 8 4 0 4 8 12 16 20 sheet thickness s / mm Top feed speed depends on material and sheet thickness Seite 49 Laser cutting process variables Comparison of cutting speeds m min feed speed v f / 20 15 10 shearing laser cutting (1500 W) water-jet cutting 5 0 4 8 12 16 20 sheet thickness structural steel s / mm 24 Top feed speed depends on material and sheet thickness Quelle: Trumpf Seite 50
Laser cutting Process comparison Comparision shearing - nibbling - laser beam cutting special process: rotational cutting shearing (rotational) nibbling laser cut contour A 30 sec 40 sec 17 sec B 4 sec - 16 sec C 3 sec 15 sec 12 sec speed St37 465mm x 5400mm x 2mm flexibility 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 80 sheet thickness / mm Quelle: Trumpf Seite 52
Laser cutting Field of application Examples of series production electronic connector (low lot sizes) synchronising disc climbing clamp Quelle: tecnologix stator sheet for special engines Seite 53 Content Introdution Demands on blanking parts Shearing Fine blanking Laser cutting Water-jet cutting Seite 54
Water-jet cutting Characterisation of the process System design principle water supply abrasive medium guard mixing pipe Seite 55 Water-jet cutting Properties of the jet groove Verrundung rounding off der at the jet entry Strahleintrittskante Konizität der Sch beveled n i t t f u ghole e Abplatzungen chipping theamexit Strahlaustritt Riefen, scoring, Auswaschungen, erosion and cracks on the Risse surface auf Schnittflächen Quellenangabe: XYZ Seite 56
Water-jet cutting cutted surfaces and gaps feed speed 2 1 v f = 20 mm/min R z,1 = 25 µm R z,2 = 30 µm surface gap v f = 200 mm/min 2 1 R z,1 = 25 µm R z,2 = 140 µm material : AlMgSiO.5 abrasive medium : Granat 80 Mesh sheet thickness : 25 mm mass flow : 400 g/min pressure : 300 MPa The surface quality is heavily dependent on the feed speed Seite 57 Water-jet cutting process parameters Characteristic of the surface α : angle of shoulder b G : burr width b 0 : width of jet influenced zone b SO : notch width on workpiece top : notch width on workpiece bottom b Su h G R 0 u M s : burr height : edge radius : rectangular and inclination tolerance : measuring range of u : sheet thickness Seite 58
Water-jet cutting influencing parameters Influences on notch width 3,5 2,5 notch width b SO / mm 3 2,5 2 1,5 1 0,5 notch width b SU / mm 2 1,5 1 0,5 0 2 4 6 8 10 12 0 2 4 6 8 10 12 treatment distance a D / mm treatment distance a D / mm pressure : 300 MPa focussing pipe diameter nozzle diameter : 0,3 mm d = 1,8 mm lenght of focussing pipe : 50 mm feed speed : 50 mm / min d = 1,5 mm abrasive medium : Granat 80 Mesh mass flow : 250 g / min d = 1,2 mm material : AlMgSi0.5 sheet thickness : 5 mm d = 0,8 mm Seite 59 Water-jet cutting Dependences Dependence of surface quality on particle size Seite 60
Water-jet cutting Performance characteristic Performance characteristics of different materials 80 80 depth of notch h K / mm 60 40 20 depth of notch h K / mm 60 40 20 0 0 150 200 250 300 pressure / MPa 0 0 150 200 250 300 feed speed / mm/min nozzle diameter : 0,3 mm material lenght of focussing pipe : 50 mm : AlMgSi0.5 abrasive medium : Granat 80 Mesh : TiAl6V4 mass flow : 250 g / min : 1.4375 Seite 61