My SimulatorEngland / Printing Heritage

English Letterpress
Simulator

Set the type. Ink the plate. Make an impression.

Interactive 3D • Letterpress

Virtual demonstration only — real presses can crush fingers. Model values, not a workshop manual.

Lab & science

Drag to orbit, wheel / pinch to zoom, tap a gold dot or part to inspect it. Space = print, R = reset, M = mechanism.

Setup

Paper (soft cotton compresses more and takes less pressure than smooth card)

Ink on the rollers (film thickness)

Roller passes over the forme

Press speed

Camera

Graphics (High on every device; Low = 1x pixel ratio, smaller shadow map)

Live readout (model values)

Gold: force on the forme. White: torque the flywheel must supply. Dashed line: crank angle now.

Experiments

Each button recomputes the whole print for a range of values and marks the best grade.

Missions

Mission 6: at the current pressure setting and text, what total force (kN) does the platen apply at dead centre?

Independent numerical checks

The science

What you see

A small platen press: a cast-iron frame, a hinged platen, a tilted ink disc with two rollers, and a flywheel whose crank pin drives the platen through a short coupler. You set type in a forme (your text plus a woodcut-style sprig), ink it with the rollers, lay a card on the platen and turn the wheel once. The ink film splits at every roller nip, then half of it is pressed onto the paper.

Equations

crank-rocker (four-bar) loop:  |P(θ) − A(φ)| = L
   P = C + r(cos θ, sin θ),  A = H + ρ(cos(φ+ψ), sin(φ+ψ))
dead centre (coupler folded on the crank):  dφ/dθ = 0
   ⇒ torque τ = F · ℓ · |dφ/dθ| / η → small, force large

paper:  p(δ) = −p_k ln(1 − δ/δ_m)         (MPa, mm)
frame:  δ_paper + F/k_f = ε,  F = A_ink · p
work:   W = A p_k δ_m[(1−x)ln(1−x)+x] + F²/(2k_f),  x = δ/δ_m

ink film splitting (50/50 at each nip):
   h_n = s(h_r + h_{n−1})  ⇒  h_n = h_r · s/(1−s) · (1 − sⁿ)
   paper film  h_p = ½(1 − e^{−p/0.8 MPa}) · h_n
   optical density  D = D_s (1 − e^{−h_p/h_c}),  D_s = 1.55,  h_c = 0.9 µm
squash (ink pushed past the face edge):  Δ ≈ 0.05 mm · (h_n/4.4 µm) · √(p/2 MPa)

What the grade measures

Grade = 40 % density (best 1.35 to 1.65), 30 % edge squash (best below 0.03 mm) and 30 % deboss depth (best 0.06 to 0.17 mm). The ink area is counted pixel by pixel from the very picture that is printed, so more or bigger letters really raise the force at the same pressure setting.

Honest simplifications

The paper and frame constants are typical values, not a measured press. The density and squash laws are simple saturating forms chosen to behave like real inks (more ink gives more density but more squash). Type is shown reading the right way round; real type is cut as a mirror image. The sheet gap, the card size and the type are scaled up for visibility. This is educational: a real platen press can crush fingers.

Made with Blender · Three.js. Educational only.

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English LetterpressSimulator

English Letterpress
Simulator