Extruding from projected geometry leads to a profile falling outside the boundary of the selected (projected) body

[jeremy.meeson]

Hi, I'd be very grateful for any help on this challenge. I've been at it for a while with much frustration...

The objective is to create a mold for a thin panel (aircraft rudder) but I can't seem to cut out the material from the tool above the part using the part outline. I have tried 3 approaches (amongst others):

Approach 1.

a) Boolean subtract from the tooling block of the part - works ok

b) Project outline of part onto surface of tool - seems to work ok

c) Extrude from the projected surface down to the part using cut - Fails with "Cannot extend extrusion to object. The extrusion profile falls outside the boundary of the selected body..."

But if the outline was projected, surely its just effectively doing the same on reverse? I can't understand why it doesn't work.

Approach 2.  

a) Project outline of part onto surface of tool - seems to work ok

b) Boolean subtract from the tooling block of the part - works ok

c) Split body using the projected outline - Error - Compute Failed

Approach 3.

a) Project outline of part onto surface of tool - seems to work ok

b) Split body using the projected outline - works ok to leave part in a 'sandwich'

c) try to split the sandwich with boolean cut of the part from middle - Fails with "problem combining the geometery together...ensure the bodies have a clear overlap..."

I'm a relative amateur with Fusion and would really appreciate some guidance on whether

1. any of these approaches are correct to create the open mold.

2. why I've been getting these failures

3. what to do to resolve / move forward.

4. Is there a better way? Is it possible to extrude the part upwards to break through the surface of the mold? I just cant seem to find how...

I have attached the model using approach 1, at a state just before extruding from the projected profile from the tool surface back down to the part.

Many thanks in advance

[davebYYPCU]

Not sure exactly what you want.  Will check the file later in the day.

You successfully subtract the part from the block.

Now you want the block trimmed to the outline of the part?

Option 3 says you can do that.

Can I presume the part edges are normal to the faces?  I suspect the errors are due to edges of your part, causing the top view of the part projection taking some of the top, and some of the bottom edges, even duplicate or overlapping lines in the sketch.

I would try trimming the block first, then cutting the block for part thickness, with Combine Cut - Keep Tool, and if you have one piece block, it will be the edge angles causing the trouble.

Might help....

[jeremy.meeson]

Some additional thoughts...

Edge angles are different across the part and indeed their angle with the tool surface will vary according to how the part is placed. I was 'expecting' that by taking the outline it would cope with the different edge angles as the CAD model wouldn't know the difference between an inside edge or an outer one. In general as the part is concave, it will be the lower edge that is outside the upper edge. Indeed if I offset the outline inwards by 1 mm the extrude 'hits' within the boundary of the part, but as you will expect, this is useless for creating a mold where the part can be extracted. What I don't understand is why the extruded projection wouldn't just hit within the boundary of the part from where it was originally projected?

I guess must be missing something.

Or is it possible to extrude the other way around - from the part up to the surface?

Alternatively should I break it up into individual surfaces and extrude each? (seems like a right pfaff)

[davebYYPCU]

Well, extruding to or from anywhere with a hole in it isn't going to work.

Same with Split Body.

Check with Section view, the lips are doing as I expected.

Yes Fusion does work down to this sort of accuracy.

Might help....

[jhackney1972]

The creation of a "closed" mold for you part is easy but hard part is finding a parting line on your part that can be use to split the mold.  This is obviously the requirement of a mold, to get the part out once it is cast.  Your part has a variety of none planar edges and offsets making the creation of the parting surface rather difficult.  I would like to know how you plan to use your mold once completed?

[jeremy.meeson]

Thanks. I'll block the hole and give it another try

[jeremy.meeson]

The mold is an open mold for laying up glass fiber. As such there are no parting lines, but of course the part will need to be lifted out once cured

[jeremy.meeson]

Covered over the hole but still having the same issues.

Split Mold around perimeter (after being hollowed out) shows "compute failed". If the hollowing-out (cut) is supressed then this split is performed but the cut then fails.

Extruding down to object cannot complete the extrusion as the profile falls outside teh boundary of teh selected body...

New file attached

[jeremy.meeson]

I guess that somehow the projected profile is not mapping exactly back to the part/body.

I'm grateful for any help.