The 4 Pipe Intersection shape is the flat pattern (development) of one branch of a junction where four thin walled pipes of the same diameter meet at one point. The four pipe axes lie in one plane and radiate from a common centre; each pipe is cut where it meets the walls of the other pipes. You enter the pipe diameter, the length of each branch and the angles between the branches, then choose which of the four pipes to develop. The shape cuts the flat blank for that pipe and can mark its fold lines. To make the whole junction, develop each pipe in turn (one part per pipe). The 3D view shows all four pipes, with the pipe being developed drawn in green and the others in grey.
It appears in the shapes library under Thin Walled Developments.
4 Pipe Intersection in PrimeShape: the property page (left) and the shape as a wireframe with its dimensions (right).
How the shape is built
In 3D the centre of the junction (the point where the four pipe axes cross) is at the origin, and all four axes lie in the YZ plane. Pipe #1 runs along the Z axis from Z = –Pipe Length up to the centre. Pipe #2 is Pipe #1 turned about the X axis by 1-2 Angle, Pipe #3 is turned a further 2-3 Angle, and Pipe #4 a further 3-4 Angle. The angle between Pipe #4 and Pipe #1 is not entered: it is whatever is left of 360° (90° with the defaults).
Each round wall is approximated by Dev. Segs flat facets whose corners lie on a circle of diameter Pipe D. Every pipe is then trimmed by the facets of the other three pipes, so its inner end takes the shape of the joints with its neighbours. The outer (free) end of each pipe is square to its axis, Pipe Length from the centre.
The facets of the pipe chosen in Dev. Pipe are unrolled side by side into one closed outline. The insert point is on the first seam edge of the blank, at its inner (joint) end; that edge runs along +X towards the square free end, and the circumference is laid out along –Y, so before any Transform the blank lies below the insert point. The joint end of the blank is the shaped (curved) edge; the free end is the straight edge. The fold lines between the facets (Dev. Segs – 1 of them) are added as marking lines when Show Bends is on.
Properties
Property |
Description |
Default |
Pipe D |
Diameter of all four pipes (mm or inch). The facet corners and fold lines lie on this diameter. The shape has no material thickness setting, so enter the diameter at which the blank should be developed – normally the mean (neutral axis) diameter of the wall. The property page sets no minimum for this value; see Notes. |
50 mm (2 in) |
Pipe Length |
Length of each pipe, measured along its axis from the centre of the junction to the square free end (mm or inch). The same length is used for all four pipes. The blank itself is shorter than this, because the part of the pipe inside the other pipes is trimmed away. The property page sets no minimum for this value; see Notes. |
100 mm (4 in) |
1-2 Angle |
Angle between the axes of Pipe #1 and Pipe #2, measured about the X axis (degrees). |
120° |
2-3 Angle |
Angle between the axes of Pipe #2 and Pipe #3, in the same direction (degrees). |
90° |
3-4 Angle |
Angle between the axes of Pipe #3 and Pipe #4, in the same direction (degrees). The angle from Pipe #4 back to Pipe #1 is 360° minus the sum of the three angles. |
60° |
Dev. Pipe |
Which pipe is developed into the flat blank: Pipe #1, Pipe #2, Pipe #3 or Pipe #4. The selected pipe is drawn in green in the 3D view. All four pipes are still built and trimmed; only the selected one is unrolled. |
Pipe #1 |
Dev. Angle |
Turns the facets of every pipe about its own axis by this angle (degrees), which moves the seam (the joint where the blank closes) round the pipe. At 0° the seam lies in the plane of the four pipe axes. Use it to put the seam where it is wanted on the finished part, for example away from a joint. |
0° |
Dev. Segs |
Number of flat facets each pipe wall is divided into. Each facet is one strip of the blank, and there is one fold line between each pair of facets. More segments give a rounder pipe and a smoother joint edge; the number of fold lines between facets is Dev. Segs – 1. 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. 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 (0.5 in) |
The dimensions shown on the shape are Pipe Length, Pipe D, 1-2 Angle, 2-3 Angle and 3-4 Angle.
Notes
•The angles are not checked. Nothing stops the three angles adding up to 360° or more, or an angle of 0 or less, and either can make the pipes overlap or the geometry fail. Check in the 3D view that the four pipes meet as intended before cutting.
•The property page sets no minimum for Pipe D or Pipe Length, and the code does not reject 0 or negative values, so enter values greater than 0. Dev. Segs cannot be set below 3.
•If the 3D geometry 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 Pipe D and Pipe Length are 50 mm and 100 mm in metric, and 2 in and 4 in in imperial. The Bend Length default is 12.5 mm in metric and 0.5 in in imperial.
•Dev. Angle, Dev. Segs and Pipe D apply to all four pipes, so blanks developed one pipe at a time from the same values fit together.
•The shape has no aliases (no former names).
The 4 Pipe Intersection 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; those apply to 2D shapes only.