topic Re: Errors with coil in Inventor Forum

Errors with coil

WillL84 — Mon, 18 Mar 2024 18:05:16 GMT

I'm trying to make two circles follow a coil, it's a model of a twisted pair wiring. However I keep getting errors no matter what I do. I made a sketch with the two circles then another with the rotation axis (center line). I keep getting the error shown in my screenshot.

I saw another post about making a 3D sketch with a helical curve and doing a sweep instead but that didn't work either, it won't let me select the helical curve as the sweep path.

Re: Errors with coil

kacper.suchomski — Mon, 18 Mar 2024 18:26:18 GMT

Make sure all sketches are correctly defined and positioned relative to each other.
You can also check out Sweep with the twist option.

(view in My Videos)

Re: Errors with coil

johnsonshiue — Mon, 18 Mar 2024 20:14:55 GMT

Hi Will,

Based on the screenshot, it looks that the coil is probably located very far away from the origin. Or the number of revolutions is too many.

Please share the file here. It should work fine if neither is the case.

Many thanks!

Re: Errors with coil

WillL84 — Tue, 19 Mar 2024 11:09:04 GMT

That makes a deformed spiral though which is strange.

Re: Errors with coil

WillL84 — Tue, 19 Mar 2024 11:20:36 GMT

The origin is apoint at the center of where the two circles meet and it's where the center line starts from. I did eventually get it to work, I had to space the circle out from the origin to get it to work.

I only did this to calculate the length of wire needed in the twisted pair for a given foot of final product. In this case the model says it's 17.443" of wire for one foot of twisted pair.

However I found an online calculator that says it's 14.893" per foot of twisted pair which is strange.

I've attached the file as well.

Re: Errors with coil

JDMather — Tue, 19 Mar 2024 12:20:38 GMT

@WillL84

Is your circle profile perpendicular to the start of the path. (Hint - like the real world.)

...and with unwound end...

Re: Errors with coil

WillL84 — Tue, 19 Mar 2024 13:21:00 GMT

That might be the issue. How did you get the work plane for the sketch for the wire at an angle like that? I tried double-clicking on the plane but I don't see any constraints or anything for it. I've never messed with surface modeling so I'm just trying to reverse-engineer how you got that to work.

Also if I measure the centerline for the coil (adjusted with my dimensions) I get 12.404", which is a fair bit less than the 14.893" I'm getting from the calculator. I know they'll never be exact, but a couple inches is quite a bit, especially when we need thousands or hundreds of thousands of final product.

I did get it to work though, I replied with screenshots and pictures but I can't see my reply for some reason. My measurement is far over what the calculator suggests, but I think that's because I was measuring along the outside. Come to think of it I don't really even need to model the whole thing - I can probably just make the coil sketch and measure that.

Re: Errors with coil

kacper.suchomski — Tue, 19 Mar 2024 17:22:07 GMT

That makes a deformed spiral though which is strange.

This is normal and logical.

I think you mixed up a few aspects:

The wire length should be measured along the neutral axis, not the outer edge. Hence the difference between your result and the calculator's.
All you need is a 3D sketch and a helical curve with given parameters. And then measure its length.
In the case of a spring, the circle is the cross-section of the coil, not the cross-section of the center axis of the spring as you tried to model (and made me do :)).
You can obtain a plane perpendicular to a path by clicking the path and then clicking its endpoint.

Re: Errors with coil

JDMather — Wed, 20 Mar 2024 13:02:39 GMT

@WillL84

I like to use Surface Coil rather than 3D Sketch Helical Curve as I find it easier to edit the parameters.

I made a mistake in my example in that I selected the outside helical edge rather than the inside helical edge when creating the perpendicular to path workplane for the circle sketch.