The Cylinder shape is the flat pattern (development) of a thin walled straight cylinder with both ends cut square to its axis. You enter the diameter and height of the finished cylinder; the shape cuts the flat blank that is rolled or brake-formed into that cylinder, and can mark the fold lines on it. The 3D view shows the formed cylinder.
It appears in the shapes library under Thin Walled Developments. For a cylinder with one or both ends cut at an angle use Truncated Cylinder or Arbitrary Cylinder.
Cylinder in PrimeShape: the property page (left) and the shape as a wireframe with its dimensions (right).
How the shape is built
In 3D the cylinder stands on the XY plane: the bottom edge is at Z = 0 and the top edge at Z = Height, centred on the Z axis. The round wall is approximated by Dev. Segs flat facets whose corners lie on a circle of diameter D. The seam (the joint where the blank closes) is on the +X side.
The facets are unrolled side by side into one closed outline: a rectangle Height wide and one circumference long. The fold lines (Dev. Segs – 1 of them, one between each pair of adjacent facets) run across the width, so each is Height long, and the circumference runs along the length. The blank is laid out with its first fold line on the X axis and one end at the origin (0, 0), so the insert point is a corner of the blank. When Show Bends is on, the fold lines are added as marking lines.
Because the facets are chords of the circle, the developed length is Dev. Segs × D × sin(180° / Dev. Segs), slightly shorter than π × D. With the default 24 segments it is about 0.3 % short (313.3 instead of 314.2 for D = 100). Increase Dev. Segs to bring the length closer to π × D.
Properties
Property |
Description |
Default |
D |
Diameter of the cylinder (mm or inch). The facet corners lie on a circle of this diameter, and the blank is developed to it. The shape has no wall thickness setting. Cannot be set below 1. |
100 mm (4 in) |
Height |
Height of the cylinder along its axis (mm or inch). This is the width of the blank and the length of each fold line. |
50 mm (2 in) |
Dev. Segs |
Number of flat facets the round wall is divided into. There is one fold line between each pair of adjacent facets, and the seam closes the ring, so the blank has Dev. Segs – 1 fold lines plus the seam. More segments give a rounder cylinder and a developed length closer to π × D. The least allowed is 3. |
24 |
Show Bends |
True adds the fold lines to the blank as marking lines, so they are processed with the marking tool. Alternate lines are reversed so the marking runs back and forth across the blank. False cuts the outline only. |
True |
Bend Length (0 for Full) |
Length of the fold-line marks (mm or inch). A value above 0 replaces each fold line with two short marks of this length, one at each edge of the blank, which is quicker to mark and leaves the middle of the part clean. A fold line shorter than 2.1 × Bend Length is marked full length. 0 marks every fold line full length. Only used when Show Bends is True. Cannot be negative. |
12.5 mm |
The dimensions shown on the shape are Height and D.
Notes
•D cannot be set below 1 and Dev. Segs cannot be set below 3. Height has no minimum on the property page, and the shape code does not check its value.
•If the blank cannot be built from the values entered, the property page shows Warning: Cannot build shape from these parameters and the 3D view is cleared. Correct the values to rebuild it.
•The defaults for D and Height are in millimetres in metric and in inches (4 in, 2 in) in imperial. The Bend Length default is 12.5 mm (about 1/2") in both.
•When Show Bends is on and Bend Length is above 0, each fold line longer than 2.1 × Bend Length is split into two marks, one at each edge of the blank. The marks are then reordered into a back-and-forth path along the edges of the blank. That reorder is skipped if any fold line is left at full length.
•The shape has no aliases (no former names).
The Cylinder also has the Transform properties (Base X, Base Y, Rotation, Scale, Mirroring X), listed after the shape's own properties. They place the flat blank. As a 3D development shape it has no Polar Array properties; the polar array applies to 2D shapes only.