Why this with Sweep 1

So I’m sweeping a circle along a crv. Just before clicking OK, everything looks right, corners are symmetrical, etc. However, look what happens after OK. No difference between “Freeform” and “Roadlike”.

depends on your control point structure…

Why don’t you use the Pipe command?

Hello CalypsoArt
It’s always hard to judge these things without the file but to me the upper image is showing the isoparms, where as the lower image is showing edges and linework (isoparms are set to off). I would be more concerned that you seem to be generating closed polysurfaces on the corners rather than single closed surfaces. Maybe your corners are a bit too tight?

I’ve never used the pipe command. I’ll take a look to see if it helps make things easy. I’ve also noticed that after the sweep, the tube is no longer matching the initial circle crv.

I don’t know what isoparms are. Are the lines visible in the preview, and are you’re saying that they are not the same as the surface joint line visible after the process?

Sweep1_Frame.3dm (124.3 KB)

Isoparms is the old term (pre-V3) for Isocurves… It’s short for Isoparametric curves, which is the technical term. They are the NURBS curves that represent the surface in the U or V direction at any given point (parameter) on the surface.

This is what I usually do when working on pipe structures:

  1. I always build the guide curves where the center of the pipe should be.

  2. I use the “Pipe” command" for the straight sections.

  3. For the bent areas I use the “Revolve” command and extrude the end of the straight pipe along the center of the arc that represents the middle of the bent pipe. Why? Because using “Pipe” along arcs creates unnecessary amount of control points and is incapable to keep a constant radius of the bent, despite the perfectly even radius of the input arc. This is where Rhino’s “Pipe” command has a disadvantage.

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What’s the point of that extra work? The minuscule(within-file-absolute-tolerance) difference in dimensions and extra data on disk is irrelevant, especially for pipe structures where that centerline is the only thing that matters for production.

I just experimented with the Pipe command. I could not find a way to pipe without the guide crv being center. For my own edification and future use, is there a way to use pipe with the guide crv on a Quad or some other location?

If it’s inevitable for your application to use a guide rail at the quad instead of the center line, then you could use the “Offset curve” tool with a distance equal to the radius of the pipe, in order to build a curve that represents the center line of the pipe. Sometimes I do that and it works nicely. In areas that are not planar you may want to place a CPlane prior using the “Offset curve” command to specify the direction of the offset.

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The “Revolve” command allows me to have a much cleaner end result of the bent sections of the pipe. Plus, it delivers a perfect equal radius that sometimes I need, because of the following reasons:

a) I use that revolved surface to build an offset surface for the thickness of the pipe. A bad surface with irregular radius leads to a bad offset surface, too.

b) I use it as a guide for matching or building corresponding laser cut plates.

c) I may use the exact radius to take proper measurements at the inner radius of the pipe. I always place the surface seam at the inside of the bend, so that it’s where the smaller radius is located.

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