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.
Resultado
—
Força de puncionamento (corte de chapa)
A força de puncionamento para cortar um furo redondo numa chapa é F = π·D·t·τ, a partir do diâmetro do furo D, da espessura t e da resistência ao cisalhamento do material τ. O produto π·D é o perímetro de corte; multiplicado pela espessura, dá a área a ser cisalhada; e multiplicado pela resistência ao cisalhamento, dá a força. O puncionamento (e o corte de chapas em geral, como o recorte de blanks) é uma das operações mais comuns da estamparia: um punção desce contra uma matriz, com uma pequena folga entre eles, e cisalha o material, separando a peça ou o refugo. Calcular a força é essencial para selecionar a prensa (cuja capacidade, em toneladas, precisa superar a força com folga) e para dimensionar o ferramental. A força pode ser reduzida com artifícios como dar um ângulo de corte (cisalhamento) ao punção ou à matriz, fazendo o corte progressivo em vez de simultâneo em todo o perímetro — o que reduz o pico de força (mas aumenta o curso da prensa). Conhecer a força também permite estimar o trabalho e a energia da operação, e verificar se o ferramental e a prensa resistem aos esforços de cada golpe. Informe o diâmetro do furo, a espessura e a resistência ao cisalhamento.
Related Tools
Punching Work
Calculate the work (energy) consumed in punching or sheet cutting, W = (k·F·t) ÷ 1000, from the penetration factor k (~0.3-0.6, the fraction of thickness the punch travels shearing before fracture), the cutting force F (N) and the sheet thickness t (mm); the result is in joules. While the cutting FORCE sets the press tonnage, the WORK sets the ENERGY the press must deliver in the stroke — a distinct and equally important parameter, especially in eccentric and friction presses that store energy in a flywheel. The factor k appears because the cut does not consume maximum force over the full thickness: the punch penetrates shearing, force rises to a peak, then drops as the material FRACTURES abruptly (the fracture propagates and separates the material before the punch crosses the whole thickness). So the work is only a fraction (k) of the maximum-force × thickness product. Knowing the work is essential to size the press flywheel and motor (which must replenish the energy between strokes) and to avoid heavy cuts 'stalling' the press from lack of stored energy. Enter the penetration factor, cutting force and thickness.
Cutting Clearance (Punch-Die)
Calculate the per-side cutting clearance between punch and die in sheet cutting, c = (a ÷ 100)·t, from the recommended percentage clearance a (% of thickness) and the sheet thickness t (mm). Cutting clearance is the small gap between punch and die, and one of the MOST important parameters in sheet-cut quality. As the punch descends, it shears the material, but the cut is not a clean slice: the material first deforms (roll-over), then shears giving a smooth zone (burnish), and finally FRACTURES, giving a rough zone and a burr. The correct clearance makes the cracks starting from punch and die MEET, giving a clean cut with minimal burr. The ideal clearance depends on material and thickness: typically 5-10% of thickness per side for steels (less for soft materials, more for hard). Too SMALL a clearance gives a secondary cut (double burr) and tool wear and needs more force; too LARGE gives heavy burr, distortion and poor edge quality. Getting clearance right is essential for tool life, required force and cut-part quality. Enter the recommended percentage clearance and the sheet thickness.
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.
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.