Flexo Plate Distortion Calculator
Flexo plate distortion and repeat calculator. A plate wrapped on a cylinder stretches around the circumference, so the image on the print comes out longer than on the flat plate. Pick the plate and tape thickness and one cylinder value: the calculator shows how much to compress the image in your layout.
- Flat plate length: 634.8 mm
- Difference between the print and the plate: K = 15.162 mm
- Length on the print (repeat): 650.0 mm
The plate and tape thickness is drawn about 12 times thicker than real, otherwise you could not see it. The difference in length is also drawn larger than it is.
How it is calculated
The neutral line is the plate's base (backing): it does not stretch when bent, while the layer above it does. So the plate is shorter than the print by K = 2π · (plate thickness − base thickness). The base is 0.127 mm (0.1778 mm for the 0.76 and 1.14 mm plates). K comes from the table for the standard thicknesses and from the formula for a custom one.
The repeat P is the largest image length on the print. Distortion factor = (1 − K / P) · 100%: the share of its length that the image keeps. Plate length = P − K. Image length in the layout = image length on the print × factor.
P from what you know: repeat as is; teeth: P = teeth × 3.175; metal circumference C: P = C + 2π · (plate + tape); cylinder diameter D: P = (D + 2 · plate + 2 · tape) · π. The tape is not in K; it only matters for converting between P and the cylinder.
K = 2π·(t_plate − t_base) (table for standard plates) factor = 1 − K / P (shown as a percentage: · 100) plate length = P − K layout image = print image · factor
Where the method comes from
Worked example
Plate 2.54 mm (100 mil), repeat 650 mm.
K = 15.1617 mm (from the table). Multiplier = 1 − 15.1617 / 650 = 0.976674, that is a distortion factor of 97.67%. Plate length = 650 − 15.1617 = 634.838 mm. A full-repeat image in the layout = 650 × 0.976674 = 634.838 mm.
From a diameter: cylinder Ø163 mm, plate 2.54, tape 0.3 → P = (163 + 2 · 2.54 + 2 · 0.3) · π = 529.924 mm.
An estimate for planning, not a production standard: real distortion depends on the plate, tape, pressure and your platemaker's own calculation.
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