How can I make this spiral? It starts in the center and then spirals out.

[FusionFan3000]

Hi everyone, I'm having trouble figuring out how to make a spiral shape in this particular manner. I'll try my best to explain with pictures. I have watched so many tutorials on using coils or 3D sketches, but I'm still quite stumped.

Hopefully someone can help me please!

This is the closest I've been able to come to my desired shape. It's like a slide that is coiled, but at the top, I want it to start in the center of what would be considered the diameter of the coil. (And once I figure out how to do that properly, I'll probably want to use the same technique to make the bottom of the slide finish in the center as well).

Top view: 

Here's a side angle, showing how it is supposed to start out flat/horizontal at the top, and then transitions into the sloping slide that spirals down:

But as you can see with the red circled area, I can't get the slide to be a continuous, consistent slope.

The way I did this was that I first made a coil, then in a 3D sketch I used "project 3D geometry" for that coil (in purple), and then tried creating an arc (in blue) that would be tangent on both sides. Ultimately I used a sweep command to sweep my target pattern along this path:

But it resulted in the issue I showed inside the red circle. Firstly, the blue arc doesn't honor my attempt to be tangent in all of 3D space. 

Additionally, I would love for the slide to have the same steepness/slope the whole way down, but in this case there's a clear discrepancy between the blue and purple. I wish I had an easy way of figuring out how to make it consistent, or maybe I just have to do some math.

I'm open to radically different and possibly tedious ways of achieving the design, although it would be great to use a method that is easy to modify or do parametrically so I can quickly change the dimensions.

Any thoughts? Other things I was trying to toy around with included ditching the coil feature altogether and instead trying to use 3D sketch to make a custom coil, but even that I couldn't figure out how to do to achieve the specific shape I wanted.

[etfrench]

Use two square section coils.  Make one a spiral of at least 180 degrees.  Make the second as the default helix type.  Move the flat spiral such that the center is at the origin and the arm is tangent to the helix (just by eye).  Split the flat spiral at the tangent point and remove the excess. Mirror the spiral to the top.  Use a rigid joint or the Align tool between the flat spiral arm and the beginning of each the helix. Combine all of them Fillet the top face at each joint.  You may have to increment the fillet in small steps to get the maximum size.   Use one of the top edges as the path to sweep your profile.

The image shows the first spiral:

[FusionFan3000]

Thank you so much for your reply!! Okay, I tried my best to follow your instructions, but I think I may have misunderstood your instructions. Sorry for the trouble...

My interpretation was that I should first make a coil using the "Type->Spiral" setting, and then make a coil using the "Type->Revolution and Height" (or any other setting that makes it look like a Helix).

But I think the alignment part got me confused...and am I supposed to move them in relation to each other to connect them? And then chop off the remaining portion of the spiral that I don't need?

[laughingcreek]

this arc can't tangent at both ends because of the geometry.  you'll need to use a spline instead and approximate an arc. attach your model and I'll demonstrate. 

[FusionFan3000]

Thank you! I have attached a file and I tried cleaning it up to just the bare bones of what I'm trying to do:

[FusionFan3000]

Wow!! Thank you, that's amazing! I will play around with it more and report back soon. I noticed in your video, you did something after creating the straight line using the control point spline, which suddenly opened up the "Spline degrees" menu. What did you do to make that happen?

[laughingcreek]

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@FusionFan3000 wrote:

...you did something after creating the straight line using the control point spline, which suddenly opened up the "Spline degrees" menu. What did you do to make that happen?

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I just selected it.

[etfrench]

Here's a little video showing how to create the path:

Use one of the top edges as the path to sweep your profile.  Varying the size  and settings of the coils may give you a smooth transition between the flat spiral and the helix.

[FusionFan3000]

Thank you so much both of you!! Really appreciate you both taking the time to share videos, I am relieved and grateful because thanks to you both I finally know how to do this now. It was killing me!

@laughingcreek 's method is helpful because it allows me to force the path to be tangent and therefore becomes a continuous path that can be performed in a single sweep. (P.S. I guess I wasn't selecting the spline properly, which is why I missed the "spline degrees" feature). This method is plug-and-play directly in my existing model, so I will mark it as the solution.

@etfrench 's technique is helpful for building it all out visually using coils, particularly when one of the coils needs to very quickly fillet into a flattened spiral. I'm glad I have this method in my repertoire as well because it may come in handy when I'm working on the bottom part of my coil.

I actually learned about several other tools and settings thanks to both your videos, so thank you so much for your time!!