topic Re: What's making this geometry overconstraind? in Fusion Design, Validate & Document Forum

What's making this geometry overconstraind?

karl — Mon, 16 Nov 2020 04:06:00 GMT

In the attached file (and this screencast), I'd like to move the four holes and two cutouts (for a fan) .3" left to prevent the crash near the upper-right hole. When I try to add a dimension between the left edge of the sketch and the center of the hole/cutout geometry, Fusion tells me the geometry is overconstrained. I've tried fixing/unfixing the center point, but to no avail. I can't see what else would be preventing this dimension. Thanks for any tips.

Re: What's making this geometry overconstraind?

billbedford — Fri, 20 Nov 2020 15:55:23 GMT

There is a locked sketch point at the centre of that square.

Re: What's making this geometry overconstraind?

TheCADWhisperer — Fri, 20 Nov 2020 16:01:20 GMT

I would significantly simplify this design, starting by breaking this up into at least 2 sketches, probably 3, maybe 4 sketches.

Use sketch points for hole locations and then place Hole Features.

Re: What's making this geometry overconstraind?

karl — Fri, 20 Nov 2020 17:30:39 GMT

> There is a locked sketch point at the centre of that square.

I gather that the way to unlock a point is to delete the coincident constraint. When I do this, though, I'm still unable to add a dimension to the left edge of the sketch, even if I delete the constrains five times. In any event, I want those points to be coincident so all the geometry moves together. Is there another way to unlock the point?

Re: What's making this geometry overconstraind?

karl — Fri, 20 Nov 2020 17:37:42 GMT

> I would significantly simplify this design, starting by breaking this up into at least 2 sketches, probably 3, maybe 4 sketches.

I'm happy to do that, but what's the advantage? I'm still a newb, but when I was first starting out with Fusion I was criticized for breaking my designs into too many sketches. What's the rule (or rule of thumb) for deciding when to "Finish Sketch?"

Also, how do I break up an existing sketch into multiple sketches?

> Use sketch points for hole locations and then place Hole Features.

I won't be extruding this sketch (except to get a sketch free of construction lines from which to make a DXF). What's the advantage of using Hole Features over circles?

Re: What's making this geometry overconstraind?

TheCADWhisperer — Fri, 20 Nov 2020 18:01:53 GMT

@karl wrote:
...when I was first starting out with Fusion I was criticized for breaking my designs into too many sketches.

I won't be extruding this sketch (except to get a sketch free of construction lines from which to make a DXF). What's the advantage of using Hole Features over circles?

Do you have a link to that reference?

OK, in that case I would probably create the solid body (any thickness).

Project the face into a new sketch and Save as dxf the projected sketch...

Re: What's making this geometry overconstraind?

TheCADWhisperer — Fri, 20 Nov 2020 18:03:19 GMT

BTW - I saw several other "errors" in you sketch.

Re: What's making this geometry overconstraind?

karl — Fri, 20 Nov 2020 18:20:11 GMT

> Do you have a link to that reference?

If you mean the criticism I mentioned, unfortunately it's buried in my post history. It made sense at the time as my timeline was very long, so I thought a shorter timeline would be cleaner. Maybe I'm overdoing it. I've noticed that some operations (e.g. dimensioning) take several seconds to complete. Would these speed up if I used more sketches? I can imagine the calculations only being performed from the previous sketch instead of from the start of the timeline, which would make things faster, but, of course, that's just a guess as I have no idea what's going on under the hood.

> OK, in that case I would probably create the solid body (any thickness). Project the face into a new sketch and Save as dxf the projected sketch...

Which is what I'm doing, so I guess I can skip Hole Features?

Re: What's making this geometry overconstraind?

karl — Fri, 20 Nov 2020 18:21:08 GMT

> BTW - I saw several other "errors" in you sketch.

Please share. You won't hurt my feelings. 😉 I'm here to learn.

Re: What's making this geometry overconstraind?

TheCADWhisperer — Fri, 20 Nov 2020 20:26:36 GMT

Examine the Attached example.

I keep each sketch relatively simple and easy to edit.

Another difference that I might make is to use a single datum (generally the Origin) for most if not all positioning dimensions.

Re: What's making this geometry overconstraind?

TheCADWhisperer — Fri, 20 Nov 2020 20:28:19 GMT

@karl wrote:
> BTW - I saw several other "errors" in you sketch.

Please share. You won't hurt my feelings. 😉 I'm here to learn.

Missing Tangents on your slotted arcs. In fact, if you use the sketch Slot command to create these - Fusion will do this for you.

Re: What's making this geometry overconstraind?

karl — Fri, 20 Nov 2020 23:12:11 GMT

Aah, thanks for pointing out that tool. That'll save a ton of time in the future.

Re: What's making this geometry overconstraind?

karl — Fri, 20 Nov 2020 23:16:35 GMT

> Examine the Attached example...

Got it. How'd you convert my single sketch into multiple sketches?

Re: What's making this geometry overconstraind?

TheCADWhisperer — Sat, 21 Nov 2020 00:22:55 GMT

I never trust someone else’s work- I started over from scratch.

Re: What's making this geometry overconstraind?

karl — Sat, 21 Nov 2020 01:21:14 GMT

Oh, jeez. I'm embarrassed you invested the time, however short it might have been. Thanks so much. Still, is there a way to split up an existing sketch into multiple sketches, just in case someone didn't want to recreate everything (asking for a friend)?

Re: What's making this geometry overconstraind?

etfrench — Sat, 21 Nov 2020 07:06:04 GMT

There is no need to use a point there. All of the circles or arcs have center points which can be used in the same manner as a single point.

I can't see any reason to make this into multiple sketches. It just has a lot of holes and a couple of cutouts. Turning off the visibility of constraints and dimensions will make it less cluttered and show that it really isn't that complex. There are quite a few extraneous construction lines which could be removed. Note: Construction line end points will need to be dimensioned in order to fully dimension the sketch.

@jeff_strater: I can find no horizontal dimension or constraint for that geometry, so I would suspect file corruption or bug.

Re: What's making this geometry overconstraind?

karl — Sat, 21 Nov 2020 14:45:43 GMT

> Turning off the visibility of constraints and dimensions

How do you do that?

Re: What's making this geometry overconstraind?

karl — Sat, 21 Nov 2020 14:47:48 GMT

> There is no need to use a point there.

Where? I don’t know what you’re referring to, I’m afraid.

Re: What's making this geometry overconstraind?

TheCADWhisperer — Sat, 21 Nov 2020 14:50:37 GMT

Re: What's making this geometry overconstraind?

etfrench — Sat, 21 Nov 2020 18:13:59 GMT

I missed the locked point 😣 I'll change my assertion of a bug on a horizontal constraint to a UI bug on only exposing properties of geometry with color, especially on points. One should be able to see the properties like X,Y, Z position, Fixed/Unfixed, constraints, etc. in a dialog.