Spiral Extrusion?

jeff hammond

use your 2nd method except make the helix your profile and melding curves... the 1/2 circles are the rails..

[not tested but i think it should work out ?]

jeff hammond

yeah, it works..

Jim57

You must lead a charmed life, Jeff, it doesn't work for me. In this model, I tried it with rails at 1080° and also at 900° (essentially, in the same or opposite direction).. The second way worked better but it still flattens out.

Helix 2.skp

jeff hammond

oh, you still have to do what you described in method 2
draw the semicircle every half turn of the helix.
a little more work than doing it all in one shot but definitely a timesaver when compared to doing it all manually.
i did the one earlier from scratch in 5-6 minutes so it's not too bad.

Box

Curviloft works for this quite well, using the middle one, follow given path.
It does tilt the spiral slightly so if you want a perfectly vertical spiral it's best to make it with two full faces so that you create a tube, then you can just pop a cylinder up the middle and remove the inner half of the tube.

Spiral Curviloft.skp

fredo6

In a next version of Curviloft, there should be a 'sweep' method for this kind of cases.

Curvi Sweep 1.gif
Fredo

shura

Good Idea, that boolean with the cylinder. Anyone mentioned already that the Draw Taper tool in Draw Metal has a similar function?
http://forums.sketchucation.com/viewtopic.php?f=323&t=33406

majid

@unknownuser said:

In a next version of Curviloft, there should be a 'sweep' method for this kind of cases.

[attachment=0:htg8prus]Curvi Sweep 1.gif[/attachment:htg8prus]
Fredo

taht'd be great Fredo ...seeing forward to see it... and thanx...

jeff hammond

@unknownuser said:

In a next version of Curviloft, there should be a 'sweep' method for this kind of cases.

Fredo

that'd be sweet!

Aqualung

@jim57 said:

I'm trying to extrude a curve around a helix. I'd like it to be convex the whole way around. I tried TIG's EEby Rails and this is my result— the profile flattens and reverses as it wraps. I'd like it to remain normal to the rails.

Here is a test run with a 360° helix, diverging as it rises. In Method 1, I used the semicircle as both Profile and Melding Profile, then the two helii (sp?) as Rails. At 90° and 270° the profile flattens and at 180° it reverses.

In Method 2, I break the helix in half with a rightward semicircle at 180° and use this as my Melding Profile. It still flattens at 90°, which suggests that even if I break it further the profile will flatten somewhat.

Is there a trick I'm missing, or is there another tool that will give me what I want directly?

What I'm shooting for is a helix that wraps between 4 and 5 times, which is to say 1440-1800°. That's a lot of hand drawing— I could use a tool big time.

Thanks in advance,

Jim

Attached is a sample spiral using SpirixCode - 5 revolutions of a semi-circle with a scale factor of 2.0 using linear interpolation along the z-axis - Maybe this plugin will help create the shape(s) you're looking for?

http://sites.google.com/site/spirixcode

Sample Spiral created with SpirixCode

Jim

@aqualung said:

Attached is a sample spiral using SpirixCode - 5 revolutions of a semi-circle with a scale factor of 2.0 using linear interpolation along the z-axis - Maybe this plugin will help create the shape(s) you're looking for?

Hi Aqualung - is that your plugin? How about a tutorial?

Aqualung

@jim said:

Hi Aqualung - is that your plugin? How about a tutorial?

Hi Jim - Yes, it's mine - The only tricky thing to using it is getting the entities in the right order - The plugin uses any un-grouped geometry as input - Additionally, any subsequent operation on the geometry (such as moving, scaling, etc.) potentially alters the order it is returned in a list - My workaround for this is to first create the reference geometry I need, put it in a group, and then trace any new geometry to be used as input.

To reproduce the spiral in question, create a circle (I used 12" for the diameter), position it where desired, and then put it into a group:

Next, create a semi-circle using the three-point circle tool:

For five turns of 48 segments each, 240 segments total are needed - In order to spread out the turns, a height of 120" was used along with a scaling factor of 2.0:

The result should be as shown below:

If you try to edit the original circle into a semi-circle and subsequently use it as input, you will prpbably end up with something like:

This is a result of modifying the geometry after it's created.

Aqualung