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# 3D Equation Curve

## 3D Equation Curve

(OP)
Hello, (Inventor 2013 suite) I am trying to create a variable pitch worm screw,so went about trying the 3D Equation Curve with a view to sweep a cut down the length of a shaft, the 3D curve looks ok, pretty much what i wanted, but when i created a sketch to sweep/cut the end result went haywire, nothing like what i wanted.
Is 3D Equation Curve the right way to achive a variable pitch screw?
Replies continue below

### RE: 3D Equation Curve

Trying to envision what you are trying to do...Is the cutter shape for the screw always the same, just the pitch varies? So, you created a 3d curve of the variable-pitch helix? Via importing points and fitting a spline? Or...?

Did you try specifying the cut profile sketch to stay perpendicular to the shaft axis?

I don't know much about the 3D equation curve tool...I would have tried to make the part with a sequence of linked helices (helix-es?).

(OP)

### RE: 3D Equation Curve

Do you have the formula for the pitch.
Attach the file here.

### RE: 3D Equation Curve

(OP)
Hi folks, think i have cracked it, check attachment, only thing is coil 1 the sketch shows a rectangle which is fine, but what i wanted to do was to radius the internal corner starting with R1=30 and at the end R2=15, a 'variable rad', but Inventor would not let me do this, so coil 28 shows a Rad of 30R which is constant down the length.
Its the best I can do at the moment!

Thanks anyway for the input

### RE: 3D Equation Curve

I do not use Inventor but I do use ACAD.None theless reading your OP, it dawn on me that may be you could UNION two or three separate segments to form the whole wood auger, if the UNION command exist in Inventor.

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