Can someone give me a general idea on how to model the twisted ribbon as shown in the image below?

Hello Arun, your ribbon is very special, what is it in the real life ?

Hello Philippe Joseph, thanks for your reply. Yes this ribbon is metal piece inserted into a pipe to change melting and solidifying properties of a Phase Changing Material that I'm studying. I have other types of inserts which were easy enough but I'm struggling a bit with modelling this one. This was already modelled by someone whose information I can't access, So I'm just curious on how they would have modelled this. I can think of a few long complicated ways of doing this,but I want to see if there's any elegant way of modelling this without going into too much trouble which will lead to many confusions and complications.

Hello again, for the ribbon in itself I would use the LOFT command between 2 rectangles correctly located in 3D and then do some material removal with the command SUBTRACT for the notches.With the command LOFT the ribbon will be with facets I think and I'm wondering if the command SWEEP along an helix can be applyable here for a smoothed result ( or only for surfaces and not solids ) because I don't have AutoCAD here at home; I would only try it monday morning. 

You can get a SURFACE shaped like that with LOFT between two concentric HELIXes:  The red edges are the Helixes; the grey Surface in between is the result of LOFTing between them.  That has no thickness, though -- I'm not sure how to turn it into a SOLID with some actual thickness, from which you could SUBTRACT something for the notches.

Hello Kent, in fact I have not finished it but I'm building a ribbon with an extruded rectangle along an helix path or more precisely the union of 2 rectangles along 2 helixes. I have to verify by "playing" with the parameters of the result in the properties palette ( Ctrl+1 ).

[QUOTE=philippe JOSEPH]... I would use the LOFT command between 2 rectangles correctly located in 3D ....[/QUOTE]
 Not between just 2 of them, but an approach that worked for me was to draw a long skinny rectangle, copy it upward multiple times, rotate each copy successively more to create the twist, and then LOFT through the stack of them.  I did them at a distance apart about the same as the length of the rectangle, and at 30-degree successive rotations -- I don't know how large the angle can be and still work right, but 90-degree rotation gave a very different kind of result. That gives a real Solid, rather than a Surface as in my previous reply.  What I haven't found a good way to do yet is to position little Solids appropriately for Subtracting to make the notches -- ARRAYPATH seems likely, but I haven't found the right combination of options and initial orientation to get them to align in the right way.

Or maybe we are going to loose our mind because Arunvigneshram is just teasing us with his Solidworks ans we are working with AutoCAD and not Inventor or an other product.
philippe JOSEPH2018-10-12 20:02:30

A sequence of commands:HelixLoftSweepSubtractThickenResults.

Seant you are number "ONE", tell us more !!!!!!!!!!!!Eventually a "step by step" drawing ?I suppose that LOFT is like Kent's method : LOFT between 2 concentric helixes, and then ...I suppose that THICKEN is what Kent what waiting for or his next step. 

philippe JOSEPH2018-10-13 11:07:38

[QUOTE=philippe JOSEPH]Seant you are number "ONE", tell us more !!!!!!!!!!!!Eventually a "step by step" drawing ?I suppose that LOFT is like Kent's method : LOFT between 2 concentric helixes, and then ...I suppose that THICKEN is what Kent what waiting for or his next step. 

[/QUOTE] That's correct.  I think the "Step by Step" would best be done by each individual.  I can tell you it's possible, you tell me what your specific steps were.  Experimenting is where we find the capabilities, and limitations, of AutoCAD.

Very nicely done and explained SEANT.

HOC ERAT IN VOTIS, but different.
philippe JOSEPH2018-10-15 08:02:33

Nicely done.

Thanks Sean but I have to work the model to make it look much more like the very first image and also I have simplified the SUBTRACTed notches with a "simple" EXTRUDE of a region along a path like a thread that we can see for example on your image.

[QUOTE=philippe JOSEPH]...I suppose that THICKEN is what Kent what waiting for or his next step. 

[/QUOTE]
 Yes, it is [a newer command than the version of AutoCAD I used for years, so I wasn't aware of it].  BUT if the small difference matters, THICKEN goes only one way from a Surface, with no center-the-thickness option -- it's not like giving a Polyline width [which is centered].  So if the thickness of the ribbon needs to be centered across the zero-thickness twisting Surface, I think it's necessary to LOFT from one Helix to the other, and also LOFT in the other order [from the other to the one], and THICKEN both of the Surfaces by half the desired total thickness, then UNION the two Solid results together [and Erase the Surfaces if you like, if DELOBJ wasn't set to do that in the process of Thickening].

I have placed my AutoCAD file : Modeling a Twisted Ribbon-01.dwg here in the CAD/BIM Blocks library.

Very nice model, and excellent tutorial.  I see now that your earlier request to me was an opportunity/offer to create the tutorial.  This may be a little late but, Thank you.  I'll see if some time presents itself - perhaps I can put something together that has something new to offer. 

[QUOTE=Kent Cooper][QUOTE=philippe JOSEPH]...I suppose that THICKEN is what Kent what waiting for or his next step. 

[/QUOTE]
 Yes, it is [a newer command than the version of AutoCAD I used for years, so I wasn't aware of it].  BUT if the small difference matters, THICKEN goes only one way from a Surface, with no center-the-thickness option -- it's not like giving a Polyline width [which is centered].  So if the thickness of the ribbon needs to be centered across the zero-thickness twisting Surface, I think it's necessary to LOFT from one Helix to the other, and also LOFT in the other order [from the other to the one], and THICKEN both of the Surfaces by half the desired total thickness, then UNION the two Solid results together [and Erase the Surfaces if you like, if DELOBJ wasn't set to do that in the process of Thickening].[/QUOTE] Good point.  If I do find the time to create a version of a tutorial, I'll keep accuracy in mind.  

I suppose keeping a mind towards accuracy requires hard parameters.  The OP (Arunvigneshram) had a picture, and a description of a strip of metal inserted into a pipe.  A new tutorial should make use of philippe's dimensions - a 20 mm inside diameter pipe @ 180 mm long with a .2 mm thick strip with one twist.I'll see what I can do.


SEANT2018-10-18 10:17:56

I’m not sure what level of precision the OP implied; conceivably the intention was for a demonstrational level or, maybe, to prep Rapid Prototyping.  Be that as it may, I tried to prep a model to as high a degree of accuracy as I could manage.  An initial quandary was the notion of constant thickness.  Sweeping a Rectangle keeps a constant Cross Section thickness, but the thickness perpendicular to the face varies through the radius.  See illustration in TwistRibbnConstThick_1.  Now, Elastic/Plastic deformation of a twisted ribbon may thin a material to some extent.  For my presentation, though, I’m going to stick with a constant thickness.Another area that needed addressing was the final diameter.  I could keep that very constant by using some of the early construction geometry to slice an explicitly sized cylinder. And a final area of concern was the notching.  Conceivably, the notch should have walls perpendicular to the spiral face.  That face changes Ramp angle through it’s radius, then so too should the notch.  See model in TwistRibbnConstThick_2.I have to assume I've made the process way more complicated than necessary.  The process is interesting, though.  High tolerance fabrication brings additional sets of concern to an AutoCAD modeler. 

Hi, great post and challenge , i almost had it but i receive an error on the last substract action............Any ideas ? Error Code Number is 84028.......

I don't know what that error code means.  Try something, though; move the blue coil up just a bit then subtract.  

thanks for your reply but unfortunately that does not help.

Hello Seant and all the others, if we see Arunvigneshram again and if he could give us the dimensions of the ribbon section, the total length of a rotation of 180 degrees + the dimensions of the nothes we could verify our various solids.If it's just an image our solids are very good mainly because I wouldn't have thougt it could be possible to modelize this twisted ribbon without facets, thanks again Arunvigneshram !!! philippe JOSEPH2018-10-19 13:38:12

After a load of errors ....... if i use a bigger diameter on the helix, errors keep popping up. But for now i am glad with the result.