Constant Groove Width with Twist

[Anonymous]

I'm trying to model what is best described as a ball screw with a custom profile and lead. I have attached a screenshot of what I'm trying along with the model in .f3d and .stp formats. The problem I am having is keeping the groove a constant thickness.

I've tried a couple of approaches, one of which is based on lofting two or more sketches:

1. Sketch the screw end in the x-y plane.
2. Copy and paste the sketch and offset it in the z-direction. Rotate the sketch 45deg around the z-axis.
3. Create a loft between the two sketches.

The above results in a shape that looks correct, but if you measure the width of the groove as you move up the z-axis, you find that it increases.

The second approach is based on a lofted cut through a cylinder in an attempt to control the twist of the cut:

1. Extrude a cylinder
2. Extrude a coil with a triangular profile.
3. Project the curve formed by the tip of the triangle into a new sketch to get a coiled line.
4. Create a Plane Along Path at the top and bottom of the coiled line.
5. Sketch the groove profile on each of those planes.
6. Loft the two profile.

The above does not result in a correctly oriented profile. Even when I try to move the "control points" on the sketch profiles, the twist of the cut is not correct and the cut does not work.

I've also tried to model it as a surface and then thicken the surface, but I can't get that approach to work either because of the nature of the profile. Surface modeling is not my strong suit. 

Any new insights are appreciated as I've been trying to model this for at least a week now.

Thanks,

Geoff

[TrippyLighting]

I am wondering whether you are somewhat being fooled by your own design. you've done several things that are a no-no in the design and Engineering world.

1. The profile is so symmetric that you only have only sketch 1/8 of it.
2. The sketch is mostly undefined and I m wondering ho you have been able to do tis without creating all the necessary constraints.Unless of course you've deleted them. That would be another no-no 😉
3. Then to copy the profile you moved the copy elements away from the sketch plane creating even more unconstrained sketch elements.

I'll see if I can come up with a good way to create this shape. the we can discuss 

[Anonymous]

I definitely did not intend for the attached model to be the end product, as I would ensure that all final sketches were fully defined. It was more of a quick and dirty experiment on how to achieve a constant width groove. An explanation on how I arrived at the current state:

The "X" was derived from two concentric circles and two arcs that were then circular patterned to form the final "X". Since I knew lofting all seven "X" profiles would mean selecting many profiles within each "X", I chose to trim the parts so that only one selection was necessary for each "X". In order to trim the sketch, I needed to break the pattern link. Also, copy and pasting away from the sketch plane was again the fastest way for my experiments. Could you recommend a better way? Always looking to improve.

If we can figure out a good way to achieve the desired model, I'll be sure to post my fully constrained sketches and model to the end of this forum, for everyone's peace of mind, including mine 😉

[TrippyLighting]

To be honest, these helical structures can be done in  Fusion 360 but are difficult to do correctly.

The sweep tool suffers from outright faulty implementation and the coil tool is severely lacking in basic functionality.

Both are core tools that need urgent fixing.