Inverted Extrude?

[Anonymous]

I have a simple sketch and when I try to extrude it, the preview looks great but it always extrudes (or cuts) in the opposite direction.

Selecting to extrude:

Results:

If I select "Do not capture Design History" then it starts working perfectly.  Is there some hidden attribute that could cause this?

[wmhazzard]

It should not work that way, the extrude should follow the blue arrow. Please attach an f3d file of your model so it can be looked at. 

[Anonymous]

I have attached the box.  Use the screenshot as a guide, I try to extrude the small box on the side.

Interestingly enough, the two smaller rectangles on the side of the part I am trying to extrude, work correctly.

[artemSIV]

Super! Great puzzle. I think that the problem is in the prehistory of the first sketch. I'll also try to think.

[g-andresen]

Hi,

the reason:

you´ve created all your  extrusions in one sketch on the xy-plane. But the faces you want to be extruded is perpendicular to xy on yz.

Create a new sketch (yz) and project that profile.

günther 

[artemSIV]

Could you explain why the central rectangle behaves differently from the way extreme rectangles behave? I think the question is the behavior of this geometry.

[wmhazzard]

Fusion does not like the fact that basically you have two separate sketches in one sketch. It is much better to have more simple sketches than one complicated sketch. You also have too many extrudes, you should plan out the model in your head before just putting extrude on top of extrude and hoping to get what you want. I cleaned up the file and you can go from there. 

 If that helps please mark the post as solved. 

[Anonymous]

I am not following you. If I extrude perpendicular plane, then it's going to invert the extrusion?  But only if there is a recorded history?  And only on very specific objects?  Other portions of the sketch on the same plane extrude just fine, and when I remove the history, the original part extrudes just fine.

[Anonymous]

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@wmhazzard wrote:

You also have too many extrudes, you should plan out the model in your head 

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Who does this?  Who knows exactly what they want, down to the last detail, before they start designing it?  Part of the design process is playing with many concepts to see what works and what doesn't.

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@wmhazzard wrote:

I cleaned up the file and you can go from there. 

 If that helps please mark the post as solved. 

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Cleaning up the original sketch isn't the problem, so you cleaning it up for me, while appreciated, isn't a solution.

While I appreciate all of the advice to use multiple sketches, that doesn't answer the question as to why this specific object has this behavior (but only when history is turned on) and other objects do not have this behavior.

[artemSIV]

But is it possible to see the sketch prehistory? It seems to me that this may be the solution. Or was this sketch the first?

[Anonymous]

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@artemSIV wrote:

But is it possible to see the sketch prehistory? It seems to me that this may be the solution. Or was this sketch the first?

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I am not entirely sure what you mean.  Keep in mind that I am relatively new to Fusion 360, and thus far have only created flat 2D/2.5D works.  I started this as a diagram on a different sketch, deleted that sketch and started this one.  There hasn't been much work on this, just a few rectangles and deciding how I am going to extrude it, and if the small rectangle should be on the bottom (same plane) or on the side.

I have extruded quite a few times as someone mentioned, for various reasons (over half of them trying to figure-out this bug) but also because I make changes that require re-extruding (moving the box to a different plane, for example).  Often I will just delete the generated 3d body in this case, and start extruding from a blank slate, or what I assume is a blank slate.

[g-andresen]

Hi,

I deleted the vertical part of this sketch on the yz-plane and created a new one from scratch with no problems at all.

günther

[Anonymous]

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@g-andresen wrote:

Hi,

I deleted the vertical part of this sketch on the yz-plane and created a new one from scratch with no problems at all.

günther

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I am sorry, I don't think I was clear enough.  I don't need a fix.  I can "fix" it in various ways, what I am looking for is an explanation on why it happens.

I can recreate the box on the same plane and it works.  I can even modify the bottom part and get it to work.  (And let's not forget that deleting the history, fixes it without any changes to the sketches)  So clearly its not as simple as not being able to extrude on a different plane in the same sketch.

Not knowing why something is happening and "fixing" it, is just asking for it to happen again, in another situation thats not as easily fixable.  I want to understand what the actual problem is so I can avoid it, or if its a bug in Fusion like it seems, so it can be fixed.

[artemSIV]

It seems that I found the source of the problem 🙂 Turning the profile in the 3D sketch changes the direction of the extrude operation normal

[Anonymous]

This is just what I was looking for!

The only remaining question: Is this a bug, or is this the desired behavior?  If it's the former, what needs to be done to report it?  If it's the latter, can we get a indicator that shows the direction of the normal it uses for extruding?

[artemSIV]

This is for the developers 🙂

[Anonymous]

I am leaning heavily towards this being a bug not only because it shows one direction and extrudes another, but because it's not possible to correctly "cut" with this inversion.  The visualization will only allow you to "visually extrude" in the direction that has something to cut into, but then cuts the other direction.

Knowing _why_ it happens though, will make it easier to fix on-the-fly.

[laughingcreek]

I would agree this is a bug.  there are still a handful of bugs associated with the new 3d sketching workspace.  AD probably knows about this, but it's always good to bring it to somebodies attention  just in case.

@jeff_strater -can you comment on the behavior shown in post 14?

[Anonymous]

I think this bug goes beyond just the 3D sketch workspace because I am having the same problem extruding a sketch with 3D sketch disabled.