Reference Section > Shape Library > Pipe Development Shapes

Pipe with compound miters is a thick walled 3D pipe development: a straight round pipe with each end cut by two flat planes instead of one. The shape draws the 3D pipe and its flat pattern, the plate you cut and then roll into the pipe. Use it for a pipe section whose ends must fit against two flat faces at once, for example two plates meeting at an angle. Earlier versions of this manual called it Compound Mitered Pipe. The shape has no aliases (no former names) in the software. For one miter at one end use Mitered Pipe; for one miter at each end use Pipe Mitered both ends.

It appears in the shapes library under Thick Walled Developments and Pipe Development Shapes. The pipe-cutter version, for cutting the ends of an existing pipe, is Pipe Cutter - Pipe with compound miters under Pipe Cutter Shapes. The pipe cutter version has the same miter properties. Its pipe properties are Pipe OD, Pipe ID (read only), Pipe Wall Thickness and Pipe Length. It has no Neutral Axis Frac(K Factor), Development Start Angle, Dev. Segs, Show Bends or Bend Length properties, and no Transform group. Its neutral axis is the outside diameter, its circumference is divided into 360 segments, and it draws no bend lines and no "OD is Up, Fold Down" note.

Pipe with compound miters in PrimeShape: the property page (left) and the shape as a wireframe with its dimensions (right).

Insert point and how the shape is built

In the 3D model the pipe axis runs along Z. The first bottom plane crosses the axis at the origin, and the first top plane crosses it at Pipe Length. Each end is cut by two flat planes:

•Each plane is tilted from square by its Miter Angle and then turned about the pipe axis by its Spin angle, which sets which side of the pipe the miter faces.

•The second plane at each end crosses the axis at the same point as the first, moved along the axis by its Angle2 Offset.

•Every line along the pipe wall is trimmed by the planes at its end, so the end of the pipe follows one plane on part of the circumference and the other plane on the rest. Where the two planes cross, the end profile has a corner.

With the default values the two planes at each end are both at 45° and face opposite sides of the pipe (Spin 90° and 270° at the top, 0° and 180° at the bottom), and the miters at the top end are turned a quarter turn from those at the bottom end.

The flat pattern is laid out in the plane with its origin at the top end of the seam. The first strip edge, at the Development Start Angle, lies on the X axis with its top-end point on the origin and its bottom-end point at +X. The pipe length runs along X and the circumference runs in –Y. The pattern is drawn with the outside of the pipe facing up, and is folded down to roll it. The shape shows the note OD is Up, Fold Down.

The pipe wall is divided into Dev. Segs flat strips around its circumference. Each strip is unrolled at the neutral diameter (see Neutral Axis Frac(K Factor) below). The width of the pattern is the circumference at that diameter, measured as Dev. Segs chords of the circle, which is very slightly less than π × neutral diameter. Each end of the pattern is the curve that, once rolled, lies in the two planes at that end.

The two end profiles carry bevel hints. The bevel at each point is set from the height difference between the outside and inside of the wall, so that a bevel head cuts the edge in the miter plane through the full wall thickness.

Properties

The shape's own properties are listed first, in the order the property page shows them: the miter planes, then the pipe, then the development settings.

Property	Description	Default
Top Miter Angle 1	Angle of the first plane at the top end, from square (0° is a square end). A negative value tilts the plane the other way. Angle units.	45°
Spin Top Angle 1	Turns the first top plane about the pipe axis, so the miter faces a different side of the pipe. Angle units.	90°
Top Miter Angle 2	Angle of the second plane at the top end, from square. Angle units.	45°
Top Angle2 Offset	Moves the second top plane along the pipe axis. It crosses the axis at Pipe Length + Top Angle2 Offset from the origin, so a positive value moves it away from the bottom end and a negative value towards it. Can be negative. Length units.	0
Spin Top Angle 2	Turns the second top plane about the pipe axis. Angle units.	270°
Bottom Miter Angle 1	Angle of the first plane at the bottom end, from square. Angle units.	45°
Spin Bottom Angle 1	Turns the first bottom plane about the pipe axis. Angle units.	0°
Bottom Miter Angle 2	Angle of the second plane at the bottom end, from square. Angle units.	45°
Bottom Angle2 Offset	Moves the second bottom plane along the pipe axis. It crosses the axis at –Bottom Angle2 Offset, so a positive value moves it away from the top end and a negative value towards it. Can be negative. Length units.	0
Spin Bottom Angle 2	Turns the second bottom plane about the pipe axis. Angle units.	180°
Pipe OD	Outside diameter of the pipe. Minimum 1. Length units.	900 mm (36 in)
Pipe Wall Thickness	Wall thickness. The inside diameter is Pipe OD – 2 × Pipe Wall Thickness. Minimum 1. Length units.	50 mm (2 in)
Neutral Axis Frac(K Factor)	Where in the wall the pattern is unrolled, as a fraction of the wall thickness measured from the inside: neutral diameter = inside diameter + Neutral Axis Frac × 2 × Pipe Wall Thickness. 0 unrolls at the inside diameter, 1 at the outside diameter. Use 0.5 (mid-wall) for plate that is rolled into pipe, or the K factor for your rolling process. Range 0 to 1, no units.	0.5
Pipe Length	Length of the pipe along its centre line, between the points where the first bottom plane and the first top plane cross the pipe axis. Length units.	1500 mm (60 in)
Development Start Angle	Position around the pipe axis where the pattern starts and finishes, which is where the seam will be once the plate is rolled. Angle units.	90°
Dev. Segs	Number of flat strips the circumference is divided into for the development. More segments give smoother end profiles and more bend lines. Minimum 3.	240
Show Bends	When ticked, the pattern includes a bend line between each pair of strips, as marking (not cutting). The line on the seam is not drawn.	True
Bend Length (0 for Full)	Used when Show Bends is ticked. Each bend line is shortened to two marks of this length, one at each end of the pattern. A bend line not longer than 2.1 × Bend Length is left full length. 0 marks every bend line full length. Minimum 0. Length units.	12.5 mm (0.5 in)

The dimensions drawn on the 3D model are the pipe length (Height), the outside diameter (OD) and Top Miter Angle 1 (Angle). The angle dimension is drawn in a fixed position; it does not turn with Spin Top Angle 1.

Limits and errors

If the shape cannot be built from the values entered, the property page shows the red bar Warning: Cannot build shape from these parameters, and the 3D model is cleared.

The shape does not check that the values make a sensible pipe. Check these yourself:

•Pipe Wall Thickness at or above half of Pipe OD gives an inside diameter of zero or less, which is not a pipe.

•A Miter Angle of 90° makes that plane parallel to the pipe axis, so it does not cut the end of the wall. Keep every Miter Angle below 90°.

•Steep miters, large Angle2 Offsets or a short Pipe Length can make a plane at one end cross a plane at the other inside the pipe. The 3D model and the pattern then cannot be trusted.

Check the 3D view and the pattern before cutting whenever the miters are steep, the offsets are large or the pipe is short.

This shape also has the Transform properties (Base X, Base Y, Rotation, Scale, Mirroring X), listed after the pipe and development properties. Polar Array applies to 2D shapes only, so this 3D development has no Polar Array group.