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Extrusion

bart_harrisbart_harris Member Posts: 29
I have two questions:

1/ Why isn't Sketch 1 fully constrained? It's a rectangle!!!

2/ How can I extrude only Sketch 1, leaving 2 and 3 where they are? I actually managed to do this before and I think I did it the same way but clearly not.

https://cad.onshape.com/documents/6851b01973b14124bcd6224a/w/44ab6ee4efae4df08c015b92/e/113a983fdf6246b8a7d3c679

Many thanks,

Bart

Best Answers

Answers

  • _Ðave__Ðave_ Member, Developers Posts: 712 ✭✭✭✭
    Sketch 1 isn't fully constrained because it isn't defined to the origin and there is free to move.

    Extrude 2 is set to add instead of remove or if you wanted to actually add material the you'll need to reverse the direction.

    I can't find an extrusion in the document for sketch 3.
  • 3dcad3dcad Member, OS Professional, Mentor Posts: 2,470 PRO
    edited May 2015
    Is this what you need?
    https://cad.onshape.com/documents/302e1bb2a2294fbc93e5c52c/w/59c6a70b676748108e9b835e/e/ceb194d5f95347bb896fa7a9

    Edit: Added another tab for cleaner design if I got your intended model right.. 
    //rami
  • bart_harrisbart_harris Member Posts: 29
    3dcad said:
    1. Fully constrained means that you can't change size or move. This one moves freely since there is no constrains to any references.
    2. I'm not exactly sure what you mean? All your sketches are there and you seem to have two extrusions overlaping.. Do you wan't a cut out for sketch 2 and 3?

    If you wan't you can add me to share so I can help you directly. My email is info@[my forum name].fi
    1. I actually meant to write defined, not constrained. I thought all the lines turn black when you define them, which I surely have. But they are still blue. Maybe this is not important but I like to know why things are happening.

    2. I want to extrude sketch 1 leaving sketches 2 & 3 as cutouts. I managed to do it once before but this time sketch 2 is not selectable/unselectable. Even when I managed to do it before there were still shaded areas where the cutouts were. I hate to invoke SketchUp, because I hear it is an inferior product, but with that you can delete faces very easily and in Onshape that does not seem possible.

    I will try adding you to share...

    Many thanks.
  • bart_harrisbart_harris Member Posts: 29

    3dcad said:
    Is this what you need?
    https://cad.onshape.com/documents/302e1bb2a2294fbc93e5c52c/w/59c6a70b676748108e9b835e/e/ceb194d5f95347bb896fa7a9

    Edit: Added another tab for cleaner design if I got your intended model right.. 
    Yes! That is what I'm aiming for. I see that you extruded the outline, and then did you extrude the other two sketches "through all" as one extrusion? I also see that to remove the shaded areas one can just hide the sketches. Is this correct?
  • andrew_troupandrew_troup Member, Mentor Posts: 1,584 ✭✭✭✭✭
      I thought all the lines turn black when you define them, which I surely have. But they are still blue. Maybe this is not important but I like to know why things are happening.

    We need to know what you mean when you say "I surely have", otherwise we cannot tell you "why things are happening".

    In other words,  what had you done, exactly, to define either: 

    - endpoint locations

    - or dimensions (entity lengths and entity angles)

    - or some combination of locations and dimensions in your sketch?

  • andrew_troupandrew_troup Member, Mentor Posts: 1,584 ✭✭✭✭✭
    edited May 2015
    @bart_harris: You might find this video clip answers at least some of your questions:

    https://cad.onshape.com/help/#constraints.htm?TocPath=Modeling%20in%20Onshape|Part%20Studio|Sketch%20Tools|_____37 

    One thing which might not be self-evident even after digesting this clip: a line can be fully defined (black) yet either or both endpoints may still be undefined (blue): these are separate questions.

    This is because defining a line in a parametric modeller essentially means defining the underlying 
    location of the infinite line.

    In the case of an endpoint which is shared by two entities (eg the corner of a rectangle), this distinction no longer applies: when the two lines are defined, the location of the shared endpoint is inevitably defined.

    If the location of the shared endpoint is defined, however, the lines may still be undefined (in terms of their angles) ... and even once the angles are defined, their lengths, and hence locations of the far endpoints of the lines, may also remain undefined.

    An intensely methodical mindset is a big help when working out how to define a complex sketch in a way which is both robust + resilient, while remaining flexible to future changes.
  • bart_harrisbart_harris Member Posts: 29
    @bart_harris: You might find this video clip answers at least some of your questions:

    https://cad.onshape.com/help/#constraints.htm?TocPath=Modeling%20in%20Onshape|Part%20Studio|Sketch%20Tools|_____37 

    One thing which might not be self-evident even after digesting this clip: a line can be fully defined (black) yet either or both endpoints may still be undefined (blue): these are separate questions.

    This is because defining a line in a parametric modeller essentially means defining the underlying location of the infinite line.

    In the case of an endpoint which is shared by two entities (eg the corner of a rectangle), this distinction no longer applies: when the two lines are defined, the location of the shared endpoint is inevitably defined.

    If the location of the shared endpoint is defined, however, the lines may still be undefined (in terms of their angles) ... and even once the angles are defined, their lengths, and hence locations of the far endpoints of the lines, may also remain undefined.

    An intensely methodical mindset is a big help when working out how to define a complex sketch in a way which is both robust + resilient, while remaining flexible to future changes.
    Thanks Andrew,

    I have watched that video a few times and still can't work out how you're meant to tell from the dimensions in the last shot that the sketch has mirror symmetry. But maybe that's not important...

    In my original question, I mean that I drew a rectangle then dimensioned the length and width. The lines remain blue. What more can/should I do for Onshape to be happy that I have fully defined it?

    Thanks again,
    Bart
  • 3dcad3dcad Member, OS Professional, Mentor Posts: 2,470 PRO
    @bart_harris You shouldn't concern yourself with the blue lines, it is not the goal to have everything black. It's just to inform you about the existing constraints. After you get things going with cad, you will bump into design intent and then you will benefit the colouring information.
    //rami
  • andrew_troupandrew_troup Member, Mentor Posts: 1,584 ✭✭✭✭✭
    edited May 2015
    Hmm ... I have a slightly different view of the blue-line question.

    I reckon leaving geometry under-defined is a risky habit to develop.

    I say this because such entities can get 'knocked' out of position at some future date when anybody edits that sketch, probably without realising, which could cause a serious failure of the model due to relations with other entities, perhaps in other sketches or even other parts.
  • brucebartlettbrucebartlett Member, OS Professional, Mentor, User Group Leader Posts: 2,137 PRO
    I never would lever a sketch with blue lines, always has to be locked down.

    When it comes to rectangles Onshape can create rectangles with a centre points to constrain to. Heres some short gif example to make it clearer.

    1. In this I have locked down to the origin using a centre point rectangle.

    2. Alternatively you could place a ref line from corner to corner and pickup the mid and constrain when not using the centre point rectangle.

    Hope this helps. Sure you get the hang of it with practice.


    imageimage
    Engineer ı Product Designer ı Onshape Consulting Partner
    Twitter: @onshapetricks  & @babart1977   
  • 3dcad3dcad Member, OS Professional, Mentor Posts: 2,470 PRO
    @Andrew_Troup I agree. But there is plenty of time to learn about design intent after you know how to create some basic sketch and create extrusions, cutouts, revolves, mirror, pattern, assembly etc..

    When the design process is clear in your mind, you probably know when sketches needs to be fully constrained and when you can be a bit sloppy not affecting to end result. 
    //rami
  • bart_harrisbart_harris Member Posts: 29
    @andrew_troup This seems very useful, and I have implemented it on this sketch. However, still blue lines! What is underdefined here, please? And how can you tell?

    https://cad.onshape.com/documents/89d21b4e63624f45b1d3fc3e/w/10e564195f6449daaef1bffe/e/97f9c4d1a896448998a96dfd
  • bart_harrisbart_harris Member Posts: 29

    3dcad said:
    @Andrew_Troup I agree. But there is plenty of time to learn about design intent after you know how to create some basic sketch and create extrusions, cutouts, revolves, mirror, pattern, assembly etc..

    When the design process is clear in your mind, you probably know when sketches needs to be fully constrained and when you can be a bit sloppy not affecting to end result. 
    Surely we don't want to be a bit sloppy! :smiley: 
  • 3dcad3dcad Member, OS Professional, Mentor Posts: 2,470 PRO
    I like to leave some blue lines in sketch sometimes, if don't know the exact place for say a shelf - I like to add driven dimension drag and test the looks to find the best place..

    You can always select all the blue lines and set 'Fix' constraint if you have all the necessary dimensions and constraints in place.
    //rami
  • bart_harrisbart_harris Member Posts: 29
    3dcad said:
    I like to leave some blue lines in sketch sometimes, if don't know the exact place for say a shelf - I like to add driven dimension drag and test the looks to find the best place..

    You can always select all the blue lines and set 'Fix' constraint if you have all the necessary dimensions and constraints in place.
    I actually tried using 'fix' which was fine for turning all the lines black, but "Sketch 1" in the sidebar remained red, which meant that I could not export it for CNC routing. That is what has become an issue now! Baby steps...
  • jakeramsleyjakeramsley Member, Moderator, Onshape Employees, Developers Posts: 657
    3dcad said:
    I like to leave some blue lines in sketch sometimes, if don't know the exact place for say a shelf - I like to add driven dimension drag and test the looks to find the best place..

    You can always select all the blue lines and set 'Fix' constraint if you have all the necessary dimensions and constraints in place.
    I actually tried using 'fix' which was fine for turning all the lines black, but "Sketch 1" in the sidebar remained red, which meant that I could not export it for CNC routing. That is what has become an issue now! Baby steps...
    While in the sketch, if you click on "Show constraints" in the Sketch dialog all of the constraints in the sketch will show.  Constraints that are conflicting will show in red.  Because sketches are solved simultaneously, this often results in a lot of red constraints when something goes red.  However, if you have some idea what might be conflicting or what was added that you didn't want, you can select them and hit the backspace/delete key to remove them until you result in a happy sketch.

    Can you expand on what is preventing you from doing the CNC routing?  
    Jake Ramsley

    Director of Quality Engineering & Release Manager              onshape.com
  • bart_harrisbart_harris Member Posts: 29
    @andrew_troup You're a genius! Thank you so very much for your patience and clear instructions :smiley: 
  • bart_harrisbart_harris Member Posts: 29
    3dcad said:
    I like to leave some blue lines in sketch sometimes, if don't know the exact place for say a shelf - I like to add driven dimension drag and test the looks to find the best place..

    You can always select all the blue lines and set 'Fix' constraint if you have all the necessary dimensions and constraints in place.
    I actually tried using 'fix' which was fine for turning all the lines black, but "Sketch 1" in the sidebar remained red, which meant that I could not export it for CNC routing. That is what has become an issue now! Baby steps...
    While in the sketch, if you click on "Show constraints" in the Sketch dialog all of the constraints in the sketch will show.  Constraints that are conflicting will show in red.  Because sketches are solved simultaneously, this often results in a lot of red constraints when something goes red.  However, if you have some idea what might be conflicting or what was added that you didn't want, you can select them and hit the backspace/delete key to remove them until you result in a happy sketch.

    Can you expand on what is preventing you from doing the CNC routing?  
    I have managed to fix the redness now, which was a sidebar, not workspace, redness.

    I will post my CNC queries in a new thread. Many thanks.
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