How do I position one oblong inside another oblong?

bart_harris

I have a small oblong that I would like to position in a big oblong, centred horizontally and offset to a fixed distance vertically. Can anyone help please?

I'm new to professional CAD and should probably take a course.

andrew_troup

I would add points near the two top horizontal lines, then use 'midpoint' constraints to place those points half way along those lines, then a 'vertical' constraint between the two points. I would dimension the width of each rectangle.

For the heightwise constraint I would dimension the height of each rectangle, and include either the 9mm or 27mm dimension to relate their heightwise position

brucebartlett

Chris_Kaspian said:

I'm trying to figure out what you're saying, Andrew_Troup, and will take a look as soon as I can. Thank you.

Coleman, the interior feature is a recess. I actually tried extruding it into my already extruded outer oblong but this resulted in the strangest error message I have ever encountered (see image). I was going to move onto this but clearly my intermediate knowledge of SketchUp is no match for professional software like Onshape...

@Chris_Kaspian  the Error message your seeing is because the extrude is going back into the existing solid and merging result in no change to the existing solid.

Try change to New and you will see 2 parts in your list, Change to Remove and you see the hole cut-out. Maybe try playing with the different optios on the extrude dialogue, you will soon get the idea.

All so try changing the Blind to Though all, that will blow the hole right through everything. 

jakeramsley

1. Start with a well defined first sketch.  I did a center point rectangle about the origin and made it 236mm x 174mm,


2. Start a second sketch and sketch the rectangle about where you want it to be.  Start a construction line at the mid-point of the top line.  Drag it so that it is perpendicular to the top line.



3. Select the end point of the line that isn't constrained and the top line of the other sketch.  Make the point a midpoint of that line.  The rectangles will now be centered about that line.  Note: If you have filleted the line so that the midpoint isn't the part you want centered, you can create points that are coincident with the vertical and horizontal edges.  From here if you select the two points and the end of the line, you can apply a midpoint between all three and constrain the line that way.


4. Add your dimensions to the rectangle as well as the construction line to get the offset.

3dcad

@Chris_Kaspian
Is this what you need?
https://cad.onshape.com/documents/f3902dfa90e641629cddc21d/w/17311692521a42d5afeeeb06/e/1fee2feb39f9479f9d79d5c3

3dcad

Just make your own copy and click edit for sketch and same to extrude.

What I did was a sketch with both rectangles in it and extrude for that whole sketch.

coleman

Can you please post a pencil drawing and basic dimensions and I'll model it and show you how I did it.  

bart_harris

I greatly appreciate your help. Thank you! Here is a sketch.

andrew_troup

I would add points near the two top horizontal lines, then use 'midpoint' constraints to place those points half way along those lines, then a 'vertical' constraint between the two points. I would dimension the width of each rectangle.

For the heightwise constraint I would dimension the height of each rectangle, and include either the 9mm or 27mm dimension to relate their heightwise position

coleman

Ok simple enough.  Do you want to interior feature to be a hole or a separate part?

If a separate part...how much clearance between the two?

bart_harris

I'm trying to figure out what you're saying, Andrew_Troup, and will take a look as soon as I can. Thank you.

Coleman, the interior feature is a recess. I actually tried extruding it into my already extruded outer oblong but this resulted in the strangest error message I have ever encountered (see image). I was going to move onto this but clearly my intermediate knowledge of SketchUp is no match for professional software like Onshape...

3dcad

If I understood correctly, you are trying to create some kind of screen. 

1. Create outer shape sketch and extrude to body thickness.
2. Create inner sketch on the top face of outer and extrude with option 'Remove' (flip direction if needed).

The best way to get help is to make a public copy and share link so others can actually see your model.

brucebartlett

Chris_Kaspian said:

I'm trying to figure out what you're saying, Andrew_Troup, and will take a look as soon as I can. Thank you.

Coleman, the interior feature is a recess. I actually tried extruding it into my already extruded outer oblong but this resulted in the strangest error message I have ever encountered (see image). I was going to move onto this but clearly my intermediate knowledge of SketchUp is no match for professional software like Onshape...

@Chris_Kaspian  the Error message your seeing is because the extrude is going back into the existing solid and merging result in no change to the existing solid.

Try change to New and you will see 2 parts in your list, Change to Remove and you see the hole cut-out. Maybe try playing with the different optios on the extrude dialogue, you will soon get the idea.

All so try changing the Blind to Though all, that will blow the hole right through everything. 

bart_harris

Andrew_Troup said:

I would add points near the two top horizontal lines, then use 'midpoint' constraints to place those points half way along those lines, then a 'vertical' constraint between the two points. I would dimension the width of each rectangle.

For the heightwise constraint I would dimension the height of each rectangle, and include either the 9mm or 27mm dimension to relate their heightwise position

Thank you for this!

I couldn't make it work initially because I made the oblongs separate sketches but now i've figured it out using just on sketch.  

bart_harris

3dcad said:

If I understood correctly, you are trying to create some kind of screen. 

1. Create outer shape sketch and extrude to body thickness.
2. Create inner sketch on the top face of outer and extrude with option 'Remove' (flip direction if needed).

The best way to get help is to make a public copy and share link so others can actually see your model.

Thank you for this but as I explained in my reply above, I could not see how to align the inner rectangle if it was a separate sketch. Any ideas?

jakeramsley

1. Start with a well defined first sketch.  I did a center point rectangle about the origin and made it 236mm x 174mm,


2. Start a second sketch and sketch the rectangle about where you want it to be.  Start a construction line at the mid-point of the top line.  Drag it so that it is perpendicular to the top line.



3. Select the end point of the line that isn't constrained and the top line of the other sketch.  Make the point a midpoint of that line.  The rectangles will now be centered about that line.  Note: If you have filleted the line so that the midpoint isn't the part you want centered, you can create points that are coincident with the vertical and horizontal edges.  From here if you select the two points and the end of the line, you can apply a midpoint between all three and constrain the line that way.


4. Add your dimensions to the rectangle as well as the construction line to get the offset.

bart_harris

@JakeRamsley 
That's amazing. Thank you! Now I'm wondering:

1/ How do I hide the construction line without un-constraining the sketch?
2/ How do I make the centre rectangle a hole (ie. delete the internal face)?

Very many thanks.

andrew_troup

@Chris_Kaspian
You need to edit the extrude distance of the inner rectangle to "Through"
No need to hide construction lines; they do not confuse Onshape (it ignores them when using the sketch) 
If they confuse you, simply hide the entire sketch by clicking to the right of the sketch entry in the feature tree. An icon of an eye with a diagonal slash denotes a hidden sketch.

bart_harris

Andrew_Troup said:

@Chris_Kaspian
You need to edit the extrude distance of the inner rectangle to "Through"
No need to hide construction lines; they do not confuse Onshape (it ignores them when using the sketch) 
If they confuse you, simply hide the entire sketch by clicking to the right of the sketch entry in the feature tree. An icon of an eye with a diagonal slash denotes a hidden sketch.

I have tried extruding "through all" and it deletes the entire sketch. I have tried it where the internal rectangle is a separate sketch and where it is part of the same sketch. The former simply hides the internal rectangle leaving a solid surface. The latter deletes everything and I am left with nothing.

Also, why would I delete an entire sketch if it's the only thing I have on the page?

3dcad

@Chris_Kaspian
Is this what you need?
https://cad.onshape.com/documents/f3902dfa90e641629cddc21d/w/17311692521a42d5afeeeb06/e/1fee2feb39f9479f9d79d5c3

bart_harris

3dcad said:

@Chris_Kaspian
Is this what you need?
https://cad.onshape.com/documents/f3902dfa90e641629cddc21d/w/17311692521a42d5afeeeb06/e/1fee2feb39f9479f9d79d5c3

More or less, yes! Yes, please. How did you achieve that? Where am I going wrong? Thank you.

3dcad

Just make your own copy and click edit for sketch and same to extrude.

What I did was a sketch with both rectangles in it and extrude for that whole sketch.