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Tool and Die Design PTB 31304 Raja Aziz Raja Ma’arof Institute of Product Design and Manufacturing UniKL IPROM

References § Suchy Suchy,, I., Handbook of die design; design; McGraw Hill 2nd Ed., § § § § §

2006. Boljanovic,, V., Sheet Metal Forming Processes and Die Boljanovic Design,, Alkem Design Alkem,, 2004. Alvarez, W., Roll Form Tool Design: Fundamentals, Fundamentals, Alkem,, 2006. Alkem Szumera,, J., The Metal Stamping Process, Szumera Process, Alkem Alkem,, 2003. Spitler,, David (tech. reviewer), Spitler reviewer), Fundamentals of tool design,, Society of Mechanical Engineers, 2003. design Paquin,, J. R., Die design fundamentals, Paquin fundamentals, Industrial Press, 1986

Credit hours § Four (4) credit hours (2K, 2P) § Lecture (room nr 2038) § Two credit hours § Two hours per week § Every Tuesday, 0830 – 1030 hrs

§ Practical (room nr 0016) § Two credit hours § Four hours per week § Wednesday, 0830 – 1230 hrs

§ § § § § § § § §

Main topics Sheet metal die design principles Press machine specifications Die plates and insert materials Detail single die design Detail design for progressive dies, incorporating piercing, blanking, bending, forming, embossing, etc. Deep Drawing Dies Casting Dies Basic operation and design knowledge of specialized dies Large and Super Large Stamping Dies

Sheetmetal Die Making flow Sheet metal product & Product design Ordered volume Volume per batch

Forming machine Forming machine selection Sheet metal die design…

Assessment § Coursework, 60% § At least two assignments: total 40% § At least one on sketching (at 10%) § At least one on Die design using CAD system (SolidWorks / Catia / Inventor) (at 30%)

§ At least one test (mid semester): 20% § Approx 30% on theory § Approx 70% on practical using CAD system

§ Final exam, 40% § Approx 30% on theory § Approx 70% on practical using CAD system

Product design Flat Blank design

Sheetmetal Die Design…

Strip layout design Die design

Machining Assembly Trial and debugging (trouble shooting)

Die commissioning

Sheet metal product design § Dimensioning tolerances § Positioning tolerances § Burr direction § Tensile strength (δ (δ or Rm) (supplier) § Material content (supplier) § Thickness § Surface pressure... Burr:

Flat blank / blank sheet design § Def: Unfolded representation of sheetmetal product design. § It incorporated the forming processes, eg eg.. Bending, deep drawing, embossing, lancing, etc.

§ Cutting clearance § Normally 2 to 5% of strip thickness per side § Die clearance: total clearance (both sides) § Less than 1% per side: to use fine blanking technology 26 July 2011

§ Bending factor / processes § Drawing factor / processes

Blank design with bending § Bending factor (v) parameters § Bending radius (r) § Sheetmetal thickness (t or s)

§ L = a + b + c + ……- n.v § § § §

L = flat blank length a, b, c = flange length (outer side) n = number of bendings v = bending factor

Bending operation: minimum allowable internal radius (r)

Bending operation: determining Bending Factor (v) value

Bending angle: other shapes §

ß = 0º to 90º

§

ß = >90º to 165º

Verhaeltnis r:s = Ratio of radius:thickness

L=a+b–v v = Equivalent Value k = Correction Factor S = Material Thickness

Springback by bending § r1 = kR . (r2 + 0.5.s) – 0.5.s § § § §

r1 = bending radius on tooling r2 = bending radius on product kR = springback factor s = sheet thickness

§ α1 = α2 / kR § α1 = bending angle on tooling § α2 = bending angle on product / workpiece

Springback by bending

Deep drawing (Tiefziehen (Tiefziehen)) § Deep drawing process and components: § § § §

Flat blank sheetmetal Drawing punch Drawing insert Drawing thrust plate

§ Flat blank calculation § Refer to die catalogue #2 § To be discussed in later

Piercing punch stroke § Punch stroke = x + t + y §x= §t= §y= x t y

Punch & Die dimensions

Dpunch

§ Piercing / punching § Dpunch = hole dimension on product

§ Blanking § Ddie = blank dimension on product

Ddie

Cutting & Die clearances § Cutting clearance (Shneidspalt (Shneidspalt), ), U § Per side § U = Ddie - Dpunch 2

§ Die clearance, 2U

U

U

§ Both sides

§ Punch (Schneidstempel (Schneidstempel)) § Die (Schneidplatten (Schneidplatten)) § Hole (Lochen (Lochen)) § Blanking (Ausscheiden (Ausscheiden))

Draft (Free) angle (Freiwinkel)

Cutting angle on Die § Cutting Clearance § § § §

(Schneidspalt Schneidspalt)) Material (Werkstoff (Werkstoff)) Sheet thickness (Blechdicke Blechdicke)) Mit Freiwinkel (with Flat cutting surface cutting angle) Ohne Freiwinkel (Flate cutting surface)

U

Cutting Clearance (U) Based on: 1. Strip thickness 2. Cutting angle on Die 3. Strip Tensile Strength

14 Feb 12

Strip layout design § Production volume (yearly, monthly) § Type § § § §

Single Compound Transfer Progressive (normally Production Vol > 10k / month)

§ Burr direction

Strip layout design (2) § Strip flow § Scrap flow § Product flow § Force calculation § § § § § §

Cutting Stripping Spring Bending Drawing Force centre point

Cutting force (F (Fcut) § Tensile strength (δ (δ or Rm) [N/mm2] § Shear Stress (t (t) = 0.7 to 0.9 δ § Fcut = t [N/mm2] x Acut [mm2] § Fcut = t [N/mm2] x Lcut [mm] x tcut [mm] § Where: § Acut = Cutting cross sectional area § Lcut = Cutting length § tcut = Material thickness

Stripping force § Function: § To strip punches from strip layout

§ The smaller the cutting clearance, the higher the stripping force required § Also it depends on strip material and thickness § Fstrip = 0.2 to 0.5 (Stripping Factor, SFac) of cutting force § SOP for piercing or blanking process § Thrust plate touches and holds strip layout § Then piercing or blanking punch cuts through the strip layout

§ Thus, at opening position, punch must be securely positioned inside the thrust plate

Spring § Types § Elastomer / urethane (normally for stripper spring) § Coil (round & rectangular cross sectional type) § Leaf 21 feb 2012

Strip layout design (3) § Pitch puncher / Notching punch § Function: To ensure strip layout moves forward at a fixed distance § No autoauto-feeder machine § ‘U’ profile; material overcut to avoid obstruction of strip flow § Based on material thickness

§ Pitch / strip stopper § Function: to ensure strip layout stops at the desired position § Fixed on guide fence or die plate (more precise) § Web width

Web design § Minimum web width is required: § To have a stable strip layout § During forward motion § Avoid sagging § To have sufficient thrust force to hold the strip § Insufficient thrust, the strip will be pulled by the punch, hence damaging the strip

Bridge / Web width (W (Wweb)

§ Based on material thickness § Minimum width

§ To reduce scrap. Optimise material utilization, ηMatlUtil (flat blank area / pitch area)

§ Optimum width

§ To have sufficient thrust force to hold the strip. Insufficient thrust, the strip will be pulled by the punch, hence damaging the strip § To avoid incomplete blank / punch operation § To avoid deformation on web, hence strip pitch distance will be distorted § To minimise strip overhang

Streifenbreite = Strip width

§ a = Web width at external profile § b = Web width between profiles

Web design

Strip layout design (4) § Bullet Casing, Mini Stapler § One One--side carrier (bridge / web) § Consider also: § Burr direction § Strip flow (on die or with springspring-activated guide lifter) § Strip over hang condition

Strip layout design (5) § Hinge, Door Bracket § Centre carrier § Take note on three (3) idle stations

Strip layout design (6) § Cap § Two Two--side carrier

Mon 31 Jan 2011

Strip layout design (7) § Opening and closed conditions § Punches and dies § Displacement (closed to open positions)

§ Punch and blank processes § From top preferred § Scrap downwards

§ Strip level position during forward direction § On die plate preferred. No over hang. No guide lifter. Bend down on product parallel to flow (slot on die plate) § At a distance above die plate (with strip lifters) § For product with bends. § For drawing process

Strip layout design (8) § Force calculation § Cutting (pierce, blank, etc.), bending, drawing § Spring § Stripping § Drawing § Return (bending, levelling) § Strip carrier

Stripper spring design

Gap

Stripper spring calculation § FTotalCut=? § FStrip =? § Punch travel distance (x + t + y) § Spring load, Fmax and Maximum deflection fmax per spring? § Nr of spring? § Fstrip strip/spring /spring

Piercing punch stroke § § § §

Punch stroke = x + t + y x = Distance inside trust plate t = Strip thickness y = Punch penetration distance from strip bottom

x t y

Citation & References

§ In text: Based on 90º bending formula, L = a + b + c +… -nv (Heinzler et al., 1997), the flat length is thus xx mm…. (p. 260). § In text: Heinzler et al. (1997) proposes the 90º bending formula, L = a + b + c +… -nv (p. 260). § In references: Heiznler Heiznler,, M., Kilgus Kilgus,, R., Näher,, F., Paetzold Näher Paetzold,, H., Röher Röher,, W., Schilling, K. (1997). Tabellenbuch Metall Metall.. Leinfelden--Echterdingen Leinfelden Echterdingen,, Germany: Europa--Lehrmittel Europa Lehrmittel..

Die design § Standard plates § Top, pressure, punch holder, stripper, thrust § Bottom, die, guide fence

German design

Die design

Japanese design

Die design (Japanese typical design) § Paper stapler, spring puncher § Note: stoppers on top & bottom dies are crucial to avoid over travel of bending and drawing punches

Die design (German typical design)

§ Paper Puncher: Base

Die design § Datum (normally die top position) § Closed position § § § §

Piercing / blanking punches Bending punches Drawing punches Spring maximum load condition

0 Die plate

Die design § Opening position § Spring prepre-load condition. Better life span § Spring selection § Elastomer / urethane spring § Higher force (approx. 20 times higher than coil spring: 150kN) § Lower compressible length (approx. 20%)

§ Coil spring § Higher compressible length (up to 50%) § Max. load approx. 7kN

§ Gas spring § Linear load increase (300N to 180kN) § Drawing and deep drawing process

§ Disc spring

Die design – Spring selection § Lpre pre--Comp, PrePre-load length: 2mm or 5% – 10% of spring length. Higher length for higher compression § Lstroke, Punch stroke = X + T + Y § LDeflTotal compressed length (Deflection) § Consider punches (pierce, bend, draw, etc.) movement

§ Load to strip the strip layout § Spring load at prepre-load length + piercing punch travel up to thrust plate bottom level = F strip

Die design – Spring selection § Assume material: St 7070-2, 3mm thick, total § § § § §

cutting length at 300mm Tensile strength, δ or Rm for St 7070-2 = 690 - 830 N/mm2. assume average, δave = (690 + 830)/ 2 = 760 N/mm2 Shear stress, t = 0.7 to 0.9 δ. Assume average, tave = 0.8 x 760 N/mm2 = 600 N/mm2 F shear or cut = ? N F strip = ? N

Die design – Spring selection § F shear or cut = t x Area cut = t x Lcut x thick = 600 N/mm2 x 300mm x 3mm = 540,000N = 54,000kgf =54T § F strip = 20% - 50% of F cut . Assume Fstrip = 35% of 54T = 19T § E.g. PrePre-load distance = 2mm (Lpt (Lpt), ), pierce punch distance to thrust bottom level distance is 3 (x) and working stroke is 9mm (t + y) § Total spring compressed length = Lpt+x+t+y

Die design – Coil spring selection (Stripper Spring) § Compressed length, f = LPre Pre--Comp + LStroke § LPre Pre--Comp = PrePre-compressed length § fmax (Spring Tech Spec) > f

§ Compressed length, fmax = 2+3+3+6 = 14mm § Consider to use 20 springs § Thus, F strip/spring 19T/20= 0.95T = 9,500N § Select coil spring SB x dia50x70L § 9,807N at 14mm compressed

Die design – Elastomer spring selection § Or 4 springs § Thus, F strip/spring 19T/4= 4.75T = 47,500N § Find spring fmax at 14mm, nearest Fmax at 30,100N for elastomer spring 246.5.090.040 § Nr of springs is 190,000N / 30,100N = 6 springs

Die design – Strip lifter spring § Strip weight = ρ x Volume § Number of springs § Weight per spring to hold strip § Spring selection § Compressed Length f = Lpc + Lstroke § Lpc = PrePre-compressed length § Lc = Ldefl = Lpc + Lstroke

§ fmax (Spring Tech spec) > f

Die design § Punches safety level § Opening and closed positions § Piercing / blanking punches § Bending punches § Drawing punches § Punch stroke § Die total stroke

Die type determination

§ Die life § § § §

Small life volume (