Blank Holder Force
Calculate the blank holder force in deep drawing, F_s = p·(π/4)·(D² − d²), from the blank holder specific pressure p (N/mm²), the blank diameter D (mm) and the punch diameter d (mm). In drawing, besides the punch forming the cup, there is a BLANK HOLDER pressing the disc rim (the annular area between blank and punch) against the die, with a controlled force. Its role is CRITICAL: to prevent WRINKLE formation on the rim. As it draws, the rim material flows inward and, reducing its perimeter, tends to wrinkle (like crumpled fabric), because it is under circumferential compression. The blank holder grips the rim with enough pressure to prevent wrinkles, but NOT so much as to stop the material from flowing (which would tear the bottom). It is a delicate balance: too little pressure → wrinkles; too much → rupture. The specific pressure p is typically a small fraction of the material strength (0.5-3 N/mm² for steels), and the total force is that pressure times the annular area where the holder acts. Computing this force is essential in drawing-tool design and press setup (which applies the holder via springs, pneumatic or hydraulic cushions). Enter the specific pressure and the blank and punch diameters.
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Força do sujeitador (prensa-chapas)
A força do sujeitador (prensa-chapas, ou blank holder) no embutimento é F_s = p·(π/4)·(D² − d²), a partir da pressão específica do prensa-chapas p, do diâmetro do blank D e do diâmetro do punção d. No embutimento, além do punção que forma o copo, há um sujeitador que pressiona a borda do disco (a coroa circular entre o blank e o punção) contra a matriz, com uma força controlada. Sua função é crítica: evitar a formação de rugas (enrugamento) na borda. Ao embutir, o material da borda escoa para dentro e, ao reduzir seu perímetro, tende a enrugar (como um tecido sendo amassado), porque está sob compressão circunferencial. O prensa-chapas segura a borda com pressão suficiente para impedir as rugas, mas não tanta que impeça o material de escoar — o que rasgaria o fundo. É um equilíbrio delicado: pressão de menos → rugas; pressão demais → ruptura. A pressão específica p é tipicamente uma pequena fração da resistência do material (0,5 a 3 N/mm² para aços), e a força total é essa pressão vezes a área da coroa onde o sujeitador atua. Calcular essa força é essencial no projeto de ferramentas de embutimento e no ajuste da prensa, que aplica o sujeitador por molas, almofadas pneumáticas ou cilindros hidráulicos (que permitem variar a pressão durante o curso — útil em peças complexas). Informe a pressão específica e os diâmetros do blank e do punção.
Related Tools
Punching Force (Sheet Cutting)
Calculate the force to punch (cut) a round hole in sheet metal, F = π·D·t·τ, from the hole diameter D (mm), sheet thickness t (mm) and the material shear strength τ (N/mm²). The product π·D is the cut perimeter; times thickness gives the area to be sheared; times shear strength gives the force. Punching (and sheet cutting in general, like blanking) is one of the most common stamping operations: a punch descends against a die, with a small clearance, and shears the material, separating the part or scrap. Computing the force is essential to select the press (whose tonnage capacity must exceed the force with margin) and to size the tooling. Force can be reduced with tricks like adding a shear angle to the punch or die, making the cut progressive instead of simultaneous over the whole perimeter — reducing the peak force (but increasing stroke). Knowing the force also lets you estimate the operation's work and energy. Enter the hole diameter, thickness and shear strength.
Cup Deep-Drawing Force
Calculate the deep-drawing force to form a cylindrical cup, F = π·d·t·σ_r·(D/d − 0.7), from the punch (cup) diameter d (mm), the sheet thickness t (mm), the material tensile strength σ_r (N/mm²) and the blank (disc) diameter D (mm). Deep drawing turns a flat disc into a hollow body (cup, can, pot, fuel tank, body panel): a punch pushes the disc center through a die, and the rim material flows radially inward, forming the cup wall. Force grows with the drawing ratio D/d (the larger the disc relative to the cup, the more material must flow and the higher the force), with material strength and thickness. The (D/d − 0.7) term is a classic empirical approximation (Siebel's formula) including friction and deformation work. Computing the force is essential to select the press and avoid RUPTURE of the cup bottom (if the force exceeds the already-formed wall's strength, the bottom tears). It is a central calculation in metal packaging, appliances and auto parts. Enter the punch diameter, thickness, tensile strength and blank diameter.
Blank Diameter for Cup
Calculate the blank (initial flat disc) diameter needed to draw a cylindrical cup, D = √(d² + 4·d·h), from the cup diameter d (mm) and the cup height h (mm), by area conservation. The calculation rests on a fundamental drawing principle: the operation does NOT significantly change the sheet thickness (ideally drawing conserves volume and, with constant thickness, conserves surface AREA). So the flat disc area must equal the cup surface area (bottom + side wall). Equating π·D²/4 = π·d²/4 + π·d·h and solving for D gives the formula. This is the starting point of any drawn-part design: it sets the disc size to cut from the coil or sheet, which determines material consumption (and thus cost and yield, optimized by blank arrangement — nesting). For cups with flange, rounded bottom or non-straight walls, add the corresponding areas. Correct blank calculation avoids waste (disc too big) and incomplete parts (disc too small). Enter the cup diameter and height.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.