Antiparallel path segment OR how to create custom shaped helix

[etfrench]

I get this error no matter how the sketch is orientated

The start direction of a path segment is antiparallel to the end direction of the previous path segment.

Repro steps:

1. Create a coil
2. Create a sketch parallel to the axis of the coil
3. 3d Project the coil to the sketch
4. Create a new sketch by selecting one end face of the coil
5. Create a custom shape in the sketch
6. Sweep the custom shape using the coil path

[innovatenate]

Creating a plane along path construction plane will insure that your profile is perpendicular to the sweep path. Check out the below screencast recording for further suggestions.

http://autode.sk/1R9maJ3

Thanks,

[etfrench]

Thanks for the screencast. 

It fails with the same error when using a circular coil and creating a plane on the path.  I was able to get it to work using a triangular coil.  Unfortunately, it will take far too long to figure out how to make an acceptable helix gear with this workflow.

Given the number of requests for a way to make custom threads, I would think this should be high on the implementation map.

[innovatenate]

Is this something you're looking to manufacture or just to show in a design?

If it's just for show, it's pretty easy "hollywood" some helical/herringbone gears. You can loft between two rotated spur gear profiles, to make a feaux helical gear. If the intent is to manufacturer, then you will need to model everything with very high precision. It may be easier to use something like the Design Accelerators in Autodesk Inventor (if you have access) via the Product Design Suite.

I hope that helps. Please let me know if you have any quesitons.

Thanks,

[etfrench]

For future reference, it's actually a bit more difficult to create a workable herringbone (or helix) gear.  Lofting between two spur gears won't create a usable gear because the loft follows a straight path not a path around the inner cylinder.  A spline path also needs to be generated.  I did this be creating multiple .5mm thick spur gears, then stacking and rotating them to the correct position for the helix angle. The spline path was created by selecting the same point on each of the spur gears.

And the completed gear

[TrippyLighting]

Kudos for the beatiful and creative workaround!

I am wondering wheter this is something that could actually be added as functiojnality through a python script.

[etfrench]

I don't think it would be too hard to create the script.  I did it graphically, but the math should be pretty straightforward.

• Calculate the height needed to rotate the gear: Cosine(Helix_angle) * (Pitch_diameter/2)
• Decide how many layers are needed for the desired resolution: 10
• Decide how many teeth: 12
• Divide the angle between two teeth by the number of layers -1 to get the amount to rotate each layer: 360/Teeth/(Layers-1)

As long as the layer count and height remain the same, any tooth count gears will mate (as long as one is left hand and the other right hand). 

[OceanHydroAU]

To answer the original (old!) question properly now: the solution is to create a triangular inner spiral.  This creates 3 spirals (the triangle corners).  You can then use one for the guide, and the other for the rail, which keeps the orientation the way you want it.

Was that possible in 2015?  Probably not.  It is now however, and this post is top in google on the topic...

[HughesTooling]

Today you don't need a helix at all, just use Sweep and Twist Angle.

Mark