2D Spiral

[zjhetzle]

Hello,

 

I'm very much a novice at Inventor, so I'm sorry if this is a simple task, but I can't seem to get it working.  I'm trying to make a 2d spiral with an inner and outer wall and connecting it to the rest of my 2D sketch. Imagine a long, skinny rectangle twisted into a spiral. To accomplish this, I created a 3d coil/spiral in 3D space, then projected the cut edges onto my 2D drawing. I've validated this method by testing it in a blank .ipt file. However, when I apply the same process to my in-progress 2D drawing in an .ipt file, one of two problems happens:  (i)  If I select my in-progress 2D drawing, the spiral disappears, or (ii) if I start a new 2D drawing on the plane, an error box appears saying "failed to project cut edges".

Can anyone help either suggest an alternative method to create this spiral, or suggest a workaround for the error?  Thanks for taking a look!

[Scott_Parker]

I would suggest using  "Equation Curves" to create the spirals.  In 2D Sketch you can find it under the Line drop down.  Below is an example of a equation that will create a spiral.  In this example you will need to change the from Cartesian to Polar coordinates in the equation curve dialog.

You can either create 2 spirals using 2 different equation curves or you can create a single spiral using the equation curve and offset it for the second spiral.

[zjhetzle]

Thanks Scott!

Follow-up question...I was able to play around with the equation to get a curve that seemed appropriate, then used the offset feature to create the spiral shape with fixed width.  The end goal is to create a spiral that loops around in the middle and spirals back out.  I played around with a few different functions in for r(t) as well as theta(t), but wasn't able to control the curve "sprialing out" of the design to stay within the lines of the curve spiraling in.  I splined the curve out to show the intended design.  Any suggestions for how to create this sort of feature?

Zach

[JDMather]

@zjhetzle 

Can you Attach the *.ipt files of your attempts here?

And do you have a picture of something similar (I suspect that you are doing way too much work if your end goal is what I think it is).

[IgorMir]

Wouldn't a Spiral option do what you need? As it is in the attached IV2020 file.

Cheers,

Igor.

[zjhetzle]

Thanks @JDMather  & @IgorMir !

Thanks to IgorMir's suggestion, I created a spiral using the coil function, then used the 2D slot function to incrementally spiral back out (extruding as I went).  The design seen below is what I'm aiming for, but in 2D.

From here, I tried projecting cut edges onto my 2D sketch, but when I enter sketch mode, the coil vanishes, and projecting isn't an option.  I've attached the .ipt file if that helps with providing a suggestion.  Thanks again for all the help!

[pcrawley · Accepted solution]

Kudos for the effort!  Spiralling back with the slot tool though... it created a shape similar to my straight-line walking ability on new-year.

Attached is my attempt (using Inventor 2022 - hope that's OK).  You can use the 3d Sketch > Helix to create a 2d spiral - the inputs require a vertical axis and the inside diameter, neither of which are in your model but are easy to create.  

For the sake of keeping it simple, I created each spiral in its own 3d Sketch.  I linked all the spiral parameters to each other, so changing the "Spiral1" will update "Spiral2".  One thing to note with spirals (and helix): They (usually) appear unconstrained after creating them.  I projected the axis and the inside diameter circle (using "include geometry" and then added coincident constraints until the spirals were fully constrained. 

After creating the spirals, I made a 2d sketch (Sketch4) and projected the spirals into it.  In this 2d sketch, I added the lead-in and lead-out legs and that bit in the middle - which is more complex than it looks.  Since the spirals are splines, it is not simply two tangent arcs.  The incoming tangencies on the spirals mean you need three arcs to join it all up (OK, six arcs - three for each side, and I don't think my dimensions are quite right). 

I hope my model is clear enough to follow the process.

 

[IgorMir · Accepted solution]

I don't quite follow the design intent here. Would Part2 fit the purpose?

Alternatively, if you require a 3D spiral input - here is Part3, which utilize that approach.
IV2020 format. 

Cheers,

Igor.

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@zjhetzle wrote:

Thanks @JDMather  & @IgorMir !

Thanks to IgorMir's suggestion, I created a spiral using the coil function, then used the 2D slot function to incrementally spiral back out (extruding as I went).  The design seen below is what I'm aiming for, but in 2D.

From here, I tried projecting cut edges onto my 2D sketch, but when I enter sketch mode, the coil vanishes, and projecting isn't an option.  I've attached the .ipt file if that helps with providing a suggestion.  Thanks again for all the help!

---

[JDMather · Accepted solution]

@zjhetzle 

My attempt Attached...

[zjhetzle]

I wasn't quite able to replicate the beauty you had created.  Drawing some inspiration from your approach, I created 4 spiral lines (offset by channel diameter), then projected it onto the 2D drawing.  I was only able to connect the 2D spiral to the rest of my drawing with 3D lines (??), but it seems to be working-ish.

[zjhetzle]

This is a design for a photomask for soft lithography.