Help constraining a sketch

[ad_johnson6E7LY]

I have a sketch which looks like the following:

Essentially, I have two vertical lines connected via a diagonal line with a fillet to round them off - ultimately these will be offset and joined at the edges, as shown by the vertical rectangle on the right, then cut out of a body.  This is part of a Sheet Metal design, as an unfolded cylinder and when 3D printed, the grooves thus created will be stuffed with thin wires - what I'm doing is creating paths across a cylinder face.

I can't work out how to constrain these lines such that if the fillet radius, (parameter driven), the width of the vertical construction lines, or the height of the horizontal construction lines change.  

I can "fix" elements but any change can't be computed, obviously, but in fact I can't find any way to constrain these lines/fillets such that changes to parameters can still be computed.  Can anyone help?  Perhaps the answer is "in this case, don't constrain".

Note there will be 26 instances of these lines to be created.  I've also attached the sketch.

Thanks for your help.

[g-andresen]

Hi,

Dimension the short line or creating a restriction for whatever purpose

günther

[ad_johnson6E7LY]

Thanks for getting involved.  

I had tried that but the problem with that approach is if I change the height of the horizontal construction line, my "groove" line (for want of a better name) doesn't adjust.  As I progress with adding in more and more of these connections, the spacing may become constrained and I will need to adjust the positioning of things including the lengths of the vertical "stubs".  The biggest issue being that the size changes when a fillet is introduced between the vertical and diagonal lines.

However you did prompt me to think about that approach a little bit more closely.  I originally wanted the fillet to bend around the junction point between the vertical/horizontal construction lines.  If instead I drop that thought and have it start at the junction, I can fix the height of the stub and then it fully constrains as you show AND it can also follow the height of the horizontal construction line.  Further, I think I could then create these stubs with a pattern and reduce the amount of potential future editing.

I'll play with that approach and report back.

Thanks again.

[g-andresen]

Hi,

From your sketch and explanations, I do not understand what exactly you want to achieve.
Please create a screenshot with a supplementary hand sketch that makes the desired result clearer.

günther

[ad_johnson6E7LY]

Perhaps the following would help.  The first image shows something like what I'm aiming for: each coloured line would actually be a groove in a cylinder surface that I could stuff with a coloured wire.  You can envisage it as a connection between an input at the top and an output at the bottom.  I have the approach worked out but I'm struggling with getting a fully constrained sketch.

The second image gives a more sketchy view: here you can see I am attempting a little bit more order.

I can constrain the vertical "stubs" and when the diagonals are added, the sketch stays fully constrained.  Let's say the stubs are 5mm long and dimensioned as such.  I need to provide a radius where the diagonal joins the verticals: adding that radius automatically adjusts the length of the stubs, even if previously dimensioned, and the diagonal can then be dragged around - i.e. the sketch is no longer fully constrained. 

I've achieved something similar but with horizontal and vertical lines (not diagonal and vertical) with bends and it is possible to keep it fully constrained.  That won't work with this case because there's too many connections to be made - you can see with the red lines I initially attempted to do it!

Incidentally, I tried the approach where I added a dimension to the "stub" lines before joining with a diagonal.  As I said, adding the fillet then resizes the stubs and removes the dimension constraint.  If I then add back a dimension it works and the sketch becomes fully constrained again.   

Hopefully this makes it a little clearer?  I've also added a separate model that shows how I did it by only working with horizontals and verticals.

[TrippyLighting]

I've attached a model where I keep the sketch simple, fully constrained and dimensioned but without fillets.

Would that satisfy your design requirements?

[ad_johnson6E7LY]

That might work.  I had thought of adding fillets after the extrude (cut) but it seemed more work - I hadn't thought of extruding a line and then thickening it.  I'll try that with the model I have with more connections and see how it goes.

[etfrench]

Making the radius relative to the length of the stubs allows the sketch to be fully constrained and adjustable.

[ad_johnson6E7LY]

You mean something like setting the stub length to a parameter, say StubLength = 5mm, and making the radius StubLength * 0.25?  

I need to be careful with the radius because if it's too small, the wire won't bend through it; if it's too large it takes up too much space.  I found through experimentation that 1.75mm was a good dimension for the wire size I have.

Thanks for the response though - it's a neat idea for the future where I might need it.

[etfrench]

You can use 'ceil' and 'floor' in formulas as well as 'if' to control size and count in parameters.

[ad_johnson6E7LY]

Peter,

I've followed through what you've done and applied it to my model.  I can "Thicken" a number of surfaces but if I do more than has been currently thickened, Fusion crashes - beach ball of death.  In my model there seems to be a limit and the attached model shows this - edit the thicken feature, select one more additional surface and Fusion just hangs when I press OK.

Is there a chance you could look and see if I've done anything wrong?  

Thanks.

[etfrench · Accepted solution]

Why would you use a surface extrude when a thin extrude can be done at the desired width?

[TrippyLighting]

The sketch does not include fillets. If you thin-extrude the sketch, you'll need to apply fillets to the grooves afterward.

That would be another alternative workflow, which might work better for this.

When all surfaces are thickened at the same time, Fusion literally eats all available memory (64GB on my machine) trying to calculate all the intersections between the thickened surfaces. 

[ad_johnson6E7LY]

I don't know - I was trying to follow what Peter was suggesting.  There are other problems occurring with that approach which I've just come across as well.

I assume with thin extrude I'd have to fillet the bends afterwards?

[TrippyLighting]

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@ad_johnson6E7LY wrote:

I assume with thin extrude I'd have to fillet the bends afterwards?

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Correct, but ...

You'll have to select something somewhere. I just tried thin extrude, and it is so quick and uncomplicated that filleting after the thin extrude is probably the most robust way forward.

You can calculate the size of the concave and convex fillets from the wire bend radius and the wire thickness and make them user parameters.

[ad_johnson6E7LY]

I found that if I did the thicken 4 times, with different surfaces in each thicken I could get through it.  However, in some of them it was leaving the surface within the cut channel, and on others it wasn't fully extruding the cut leaving bits that would need manually tidying up to cut them out.

It's an interesting approach but I think it might be better to look at the thin extrude and filleting the bends afterwards.

[ad_johnson6E7LY]

I think this is the way to go.  The sketch is fully defined and I already have the parameters set up. 

[ad_johnson6E7LY]

Just to finish.  Thanks for all the advice from everyone who contributed, I learnt a lot from this - I'm quite new to Fusion so I don't know all the feature and capabilities yet.  Here's a picture of the finished, printed model - at least as a prototype.  It needs some finagling but I got there with your help.

[TrippyLighting]

Please mark one or more of the posts as the solution. I'd start with @etfrench thin extrude post.