fully constrained sketch

[office6PUWT]

I've been trying to improve the quality of my sketches having had a few issues with ones that were not fully constrained once I start modelling. I need to create a single octave from an organ keyboard and after a long time trying to work out which dimensions were missing (over 100 at one point) I used the automatic dim and constraint tool which made my sketch into a fully constrained total mess. see attached pic. is this really better going forward? I could use a good online tutorial on constraining sketches as I find the choices baffling. 

Do I need to add a dim to every single line?

what are the little pink squares telling me?

How do I select single lines within constrained geometry to offset?

many thanks

Luke

[JDMather · Accepted solution]

Attach file.

[b.mccarthy · Accepted solution]

I have found the the auto-dimension tool is handy for locating missed constraints/dimensions, but then I undo it, and add everything manually. This allows me to really "know" the sketch instead of hoping Inventor will guess what I want. This usually does not end well. If you fully control the sketch, you control everything downstream. There are a few cases where the auto tool is a good option though.

For your sketch, I would look into using patterns. This would simplify the sketch, and give you the control and result you need.

[JDPL · Accepted solution]

You don't need to add dims to every line. You can uses other constrains (like equal, parallel, etc.). Also you can use patterns.

[johnsonshiue · Accepted solution]

Hi! I believe you may want to look into Sketch Block workflows. I see quite a few repeated sketch geometry. You can make it a sketch block and the sketch block is rigid. You will have a lot less dimensions to deal with. Also, if you edit one block definition, all instances will be updated accordingly.

Many thanks!

[office6PUWT]

Thanks JD, will check it out.

all best

Luke

[office6PUWT]

This sounds like good advice, is their a more direct way to identify unconstrained geometry and missing dimensions? It's not obvious to me where they might be in most cases.

[office6PUWT]

Does this mean finishing a sketch without it being fully constrained and proceeding to the stage is ok in some instances?

[office6PUWT]

Good advice thankyou,

[JDMather]

I hesitate to offer any comments/advice since you have not Attached your file and since you already marked this as solved, but - 

1. Do I need to add a dim to every single line?

Why do you have many lines?  How many?  I have designed some very complex stuff with simple sketches.  My guess is that you are doing too much work - get lazy! (Will, of course, need the actual file to explain how to get lazy (more efficient)).

2. what are the little pink squares telling me?

Sick geometry - you have done something wrong.

3. How do I select single lines within constrained geometry to offset?

Turn off Loop Select (don't forget to turn it back on later).

4. Don't use autodimension/constrain

5. Can't recommend Sketch Blocks without seeing your actual file and understanding your actual Design Intent.

Might or might not be appropriate.

6. a more direct way to identify unconstrained geometry and missing dimensions?

Toggle Show/Hide All Degrees of Freedom.

But normally as a beginner you should probably fully define each geometric entity immediately upon creation.

7. Does this mean finishing a sketch without it being fully constrained and proceeding to the stage is ok in some instances?

Not if you want to pass my class.  You better be very very good and have a good, logical reasoning and explanation.  Maybe if it is a spline, but only maybe...  Can't make any decision without see actual file and understanding the Design Intent.

8. Good advice thankyou,

I think all of the advice given in this thread (including that given by me) is poor advice as no access to the actual file.

[JDMather]

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@office6PUWT wrote:

Thanks JD, will check it out.

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Where did you go?

[office6PUWT]

Hi JD,

I've done it again I'm afraid. Simply not understanding how to constrain geometry which at my level is quite complicated has resulted in my being unable to extrude parts of it when required. I've attached the .pt file you in the hope that you can repair it for me and I can then have a closer look at it's constraints and hopefully learn from it.

ps. This model represents about 6 hours work so I'd like to avoide starting from scratch of possible.

all best

Luke

[JDMather]

How did you arrive at this angle (and how will it me measured in the real world - what measuring instrument)?

What is the purpose of the sketch pattern?

[JDMather]

Examine Sketch1 in the Attached.

What do you observe about the sketch?

[JDMather]

Edit Sketch2.  What do you observe?

Delete Extrusion2 and Extrusion1 (uncheck option to delete the sketches).

Note that the sketches were created without dependency on the extrusions - deleting the extrusions does not cause the sketches to "go sick" (turn pink and indicate an issue in the browser).

[JDMather]

So, as I move along and try to decipher your Design Intent - I decide to move Sketch1 Origin location and add two angled lines.  (To move I simply deleted the Coincident and redid it to new location, nothing fell apart because I fully defined my sketch such that any edits I do would be robust and predictable.)

Note that I seldom create any Workplanes.  I did your Splits with a sketch.

[JDMather]

...I start to really struggle with trying to figure out how you arrived at certain dimensions...

Sweep is normally done from profiles perpendicular to path.

I question that this is really really your Design Intent when I see a Sweep profile that is not normal to the path.

[JDMather]

Fillet does not look aesthetically pleasing to me, but hey, I'm just following along...

[JDMather]

I realize that an earlier Split should have been done to remove material for location of later Mirror.

I could edit that Split1 and fix it, then I would have to fix a couple of cascading errors.

In this case not too difficult, but let's assume really difficult to fix the cascading dependent errors.

No problem - let's leave that feature as is but then Delete the Lump (be careful - this is almost always done incorrectly by beginners, use with caution.

[JDMather · Accepted solution]

See Attached...