Mould design of twisted shape

[davemorl]

Hi,

What would be the best way to create a mould for a twisted body, for say something like a fan blade or prop blade. I would imagine design the body you want then create a body over it then subtract it.

My problem is then splitting the mould body along the contours of the twisted curved shape along the edge of the blade to the mould parts. I'm obviously missing something that I've never used yet.

Thanks.

[TheCADWhisperer]

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

[davemorl]

Hi

I've attached the file as requested. My aim is to mill a mould from aluminum to make this lead fishing spinning weight.

[davemorl]

Sorry I've tweaked it a little. This is more accurate

[TheCADWhisperer]

These two areas would be of particular concern to me.

[davemorl]

Yeah I see the problem. I'll try and resolve theses.

Any idea how I'd go about making a mould for this sort of shape.

Would it be best making a body over it and trying to split with a curved split along the widest part?

The only other way I can think would be to make separate bodies and then joining them?

[Beyondforce]

Hi @davemorl,

I have created several videos on how to create Propellers and Twisted bodies. Maybe they can help you: https://www.youtube.com/channel/UCv0LDps_1xX8NqkfiBK1LaQ

Cheers / Ben
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[davemorl]

Thank you for your comment. I've watched a few on how to make twisted bodies and also how to subtract bodies from another to create a mould.

The problem I have is that I won't have a linear parting line with a twisted body. Any links on how to do this or something similar please?

[HughesTooling]

Unfortunately Fusion doesn't have a 3d silhouette feature. I put a request on the idea station Here. If you look at the 4th reply there is a work around using shell. You'll need to improve your surfaces to get that to work on your part.

The other option is to build the model using lofts and make sure the seam is at the point where you need the split line.

Mark.

[HughesTooling]

Here's a screencast I made a while ago for someone wanting to mould a wing. The idea is to use 2 splines and make sure the handles at the ends are perpendicular with the split line.

Mark

[davemorl]

Ah I see now. I'll give this a go. Once you project the spline line do you just then click on the projection on the split body options?

I'll give it a go tonight after work.

[HughesTooling]

Split and Combine Cut fail quite often with surfaces that form split lines on parts like this. I've found the patch workspace and the Offset face command set to a zero offset will let you extract faces you can use to build the mould. In the screencast below I run through how. One thing I'd do differently in the previous screen cast is I'd project the edge to a plane before extruding the split face rather than use the 3d curve, using a 2d curve will give a simpler surface. In the screencast below the first thing I do is make a copy of the part and cut in half, the reason I did that is because projecting a curve the doubles back on itself will create a bad curve.

Mark

[davemorl]

Jesus! Thank God you have just told me this! My head feels like it's gonna explode. The doing back thing won't allow the split. I've been trying all sorts for hours.

I'll try cutting the screen cast in half but still not 100% sure it's going to work as when I project the curve it's doubles back and because of the geometry of the cast it is still trying to split it into many parts.

I've even tried splitting into 4 bodies and the joining them back into 2! I'm close to giving up to be honest ha!

[davemorl]

I've also tried cutting the projection with the body the remove the excess doubled back projection. This got rid of the excess projection and I can split the body on one side but not on the other.

Any other suggestions. I've even move one projection around a little to make sure it's all in contact with the body. Still no joy. Ah!!!

[HughesTooling]

Are you still trying to work with the form? If you are I don't think you'll have a lot of luck, even with a loft split can fail if it's running along a seam in the model. Really you need a seam in the model you can use as the split line then you can extract the face like I did in the second screencast.

Mark

[davemorl]

Yeah I've given up. I think I'm going to try and start all over concentrating on getting that seam the whole way down the body on either side so it's a definite parting line.

I'll have another bash tomorrow and let you know how I get on!

Thanks for your help! 😉

[TheCADWhisperer]

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@davemorl wrote:
.... I'm going to try and start all over ...

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Concentrate on symmetry.  And I doubt I would use the Form tools for this design.

[davemorl]

Thanks for pointing that out. I suppose that's the limitations of the form tool. Would you recommend using the loft function. With having maybe around 5 or 6 geometric shapes along the length and have the rails be the parting line and the other 2 creases along the narrow width?

I'll have another go at trying to loft it tonight. I've thrown myself in the deep end here it's by far the most complex body I've tried to design but no better way to learn I suppose.

[TheCADWhisperer]

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@davemorl wrote:
... I suppose that's the limitations of the form tool. .....

---

I wouldn't say that's a limitation of the form tool, but rather a limitation of experience using the tools.  I'm sure Phil could get the job done quite nicely.

But that is more of an art.

With the parametric tools it is easier to drill down to problem causing issues and to communicate possible changes to the design.

One mistake (IMO) I see many users make it trying to create too many sketches to control geometry.

I try to use as few as possible with most basic geometry possible (don't create a spline with dozens of points).

Here is a tutorial for a core/cavity mold that I wrote years ago (Fusion has changed since then, so techniques might need tweaking).

https://forums.autodesk.com/t5/post-your-tips-and-tutorials/toy-car-core-cavity-mold-tutorial/m-p/51...

[davemorl]

I'm just about to give this ago again. How many sketches do you think I'll need? I've been pondering all day on this haha!

I'm thinking one either end, 2 for the curved twisted parts and one for the centre line? With this be enough?

Wish me luck!