Tutorial, Step Stool, Step 8, extrude/remove or pocket leaves a thin wall

ali_e280

Hi,

I'm trying to complete the the step stool exercise.  The instructions are to create on offset on the face and use extrude/remove to create a 5 mm indent.  When I apply the remove extrude, I get an unexpected thin wall.  This thin wall prevents the shell step following this step.

https://learn.onshape.com/learn/course/fundamentals-part-design-using-part-studios/creating-draft-shell-and-rib-features/exercise-step?page=2

SKETCH

EXTRUDE OPTIONS

PART WITH THIN WALL

What step am I missing here?

Thanks,

Ali

_anton

Because the sides of the part are drafted (at a nonzero angle with respect to the vertical), and you're extruding straight down, you'll get a really thin wall with a triangular cross-section.

robert_scott_jr_

Hello. It looks like you've selected the wrong sketch area for the extrude. I read the intent in the design is to create a depression on the step surface in order to have a corrugated surface for traction. The sketch area you selected is the 5mm perimeter. I believe you need to select the large inside area of that perimeter. - Scotty

ali_e280

Thank you.  Looks like you were right about the intent of the exercise, but the question still remains, why is there a thin wall if I remove the 5mm area around the part?

_anton

Because the sides of the part are drafted (at a nonzero angle with respect to the vertical), and you're extruding straight down, you'll get a really thin wall with a triangular cross-section.

ali_e280

Thank you.  Looks like you were right about the intent of the exercise, but the question still remains, why is there a thin wall if I remove the 5mm area around the part?

_anton said:

Because the sides of the part are drafted (at a nonzero angle with respect to the vertical), and you're extruding straight down, you'll get a really thin wall with a triangular cross-section.

Thank you for the explanation.