Sweep - Deformation of profile

[Lars]

Dear Fellow FreeCAD users,
We are preparing the design of a tube coil applying the sweep feature of FreeCAD but face a challenge, maintaining the profile shape when sweeping along the center line of the part, and we would be so grateful for your contribution for overcoming this problem.

1. Original design (attached image Tube Coil 01)
We prepared this part applying the helix functionality for generating a center line followed by the sweep feature of the part design workbench. Works great. Unfortunately, the processing equipment for manufacturing this part can handle only bends with constant radius.

2. Modified design (attached image Tube Coil 02)
In order to accommodate limitations of the processing equipment, the center line of the part was discretized applying the curves workbench, and disctances between points were modified to bends with constant radius or straight lines.
Upon sweeping the tube profile along the new center line, the shape of the tube can not be maintained but slowly becomes deformated along the sweep edge.


Q: Obliged to design the coil with a center line consisting of 1) straight lines or 2) arcs with constant radius, how could we successfully avoid the deformation when sweeping?




SIncerely
Lars

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.4 (GitTag)
Build type: Release
Branch: releases/FreeCAD-0-18
Hash: 980bf9060e28555fecd9e3462f68ca74007b70f8
Python version: 3.6.6
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedKingdom (en_GB)

[hammax]

... bending the pipe with controllable rollers instead of a die.

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[Vincent B]

Right Corner option for the sweep seems get some troubles. Because a very close coplanearity issue with paths?
Some thoughts?

[hammax]

Hey Lars,
I tried to model your pipe helix in a regular manner => constant bend radius and straight run after each other.
Done by intersection of a loft and helix sweep - only to understand the principle of bending sequence.
Making up the pipe sweep my PC and/or FC.18.4 are really gasping.
Some minutes of calculation and 18MB file size.

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[mario52]

hi

converted in unique bspline

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(only the wire the file with sweep 2.63 mega and 10 minutes for create)

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mario

[hammax]

... the helix body has without in- and outlet a total length of about 7,55m.
Making a cylindrical helix with minimum diameter gives some 24 rounds.
This helix can be subdivided to 4 "symmetrical" parts and get defined markers.
Bending to greater radii afterwards could easily be done and gives this hour glass form?
Question: what's the use of this apparatus?
Heat exchanger fluid-fluid or fluid-gas?

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[papyblaise]

Hi
simply part whith conical helix > miror > clone
and do addpipe whith

[papyblaise]

Hi
simply part whith conical helix > miror > clone
and do addpipe whith

[hammax]

... another answer/solution to the starting question.
Sometimes the shape has a high angular resolution value and gets splintered/incomplete.
Insert smaller resolution values.

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[hammax]

... a really interesting task, to build a helical pipe with a controlled contour - more than cylindrical or conical.
The icon of the Section tool in PartWB only promises a cut with a plane - but it can apparently do more.
Here a helix done as a sweep with an edge, is cut with a rotation profile and produces a space curve.
Using this space curve as a sweep path delivers long calculation times => maybe a too complex dataset.
But using Discretized_Edge to reduce the dataset (36 points per round) from CurvesWB
and making an Approximation_Curve out of them, reduces the data volume apparently about 1/10.
Now the modelling is an easy going.

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A25 Sep_LTHW_6.FCStd

FC.18.4

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..oh and I found the trick to reduce the data overflow in the Section feature
check Approximation to true!

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