Cantilever clamp vid turorial, stuck!

daniel_chow

Hello everyone, 

I'm stuck on the cantilever clamp tutorial at 1:23.
Here is the link to my document (public viewing)

I can't seem to extrude the smaller cantilever arm. You can see where the red arrow is, it won't let me form a solid shape. What am I doing wrong that it won't let me extrude it? 

THank you in advance! 

andrew_troup

If you hover over the red "Extrude 1" title of the edit dialog, it should tell you why it is failing. Maybe there is a tiny gap in your sketch? There are a number of possibilities...

3dcad

Just wanted to mention that Onshape fills different color for closed sketches for easy identification in sketch mode:

Closed shapes at left

andrew_troup

Good point, @3dcad

It's not specifically helpful in the OP case, though,  because there the problem was not a gap, but a tiny overlap of entities, creating two enclosed sliver areas which remained unselected. 
As a consequence, a pair of sliver cavities would have been created in the extruded body which butted together at a single point, created a "zero thickness geometry" situation.

If the OP had zoomed right in and selected the two enclosed sliver areas, the extrude operation would not have failed, if I'm right about zero thickness geometry.

ON EDIT
it just popped into my head when thinking of something else entirely:  selecting just one of the two sliver areas should be enough for the extrude to succeed.

andrew_troup

If you hover over the red "Extrude 1" title of the edit dialog, it should tell you why it is failing. Maybe there is a tiny gap in your sketch? There are a number of possibilities...

andrew_troup

I've had a look at your model, and the problem is flagged by a tiny sliver of daylight where my added arrow is pointing. (Zoom in to see it clearly)
If you carefully inspect the geometry of the first sketch, you will see there is a mismatch between two straight lines and two arcs.
This can be fixed by recreating the straight lines so their endpoints are coincident with the arcs, and tangent to them.

It also falls short of best practice (in that first sketch) that it is not fully constrained: 
For robustness, sketches should all go black before you use them as the basis for further modelling


.

daniel_chow

andrew_troup said:

I've had a look at your model, and the problem is flagged by a tiny sliver of daylight where my added arrow is pointing. (Zoom in to see it clearly)
If you carefully inspect the geometry of the first sketch, you will see there is a mismatch between two straight lines and two arcs.
This can be fixed by recreating the straight lines so their endpoints are coincident with the arcs, and tangent to them.

It also falls short of best practice (in that first sketch) that it is not fully constrained: 
For robustness, sketches should all go black before you use them as the basis for further modelling


.

Thank you Andrew for your prompt and detailed response! On your advice, I took a closer look and extruded the areas excluding the areas marked with the dash, this is what I got: 


ANd zooming in on the area, I found a conflict... 

daniel_chow

Fixed it, thank you! 

3dcad

Just wanted to mention that Onshape fills different color for closed sketches for easy identification in sketch mode:

Closed shapes at left

andrew_troup

Good point, @3dcad

It's not specifically helpful in the OP case, though,  because there the problem was not a gap, but a tiny overlap of entities, creating two enclosed sliver areas which remained unselected. 
As a consequence, a pair of sliver cavities would have been created in the extruded body which butted together at a single point, created a "zero thickness geometry" situation.

If the OP had zoomed right in and selected the two enclosed sliver areas, the extrude operation would not have failed, if I'm right about zero thickness geometry.

ON EDIT
it just popped into my head when thinking of something else entirely:  selecting just one of the two sliver areas should be enough for the extrude to succeed.