Extrude-Remove-Offset from Surface to retain wall thickness?

christopher_owens

Maybe this will come in handy and maybe there are various ways to achieve this. I want to Extrude-Remove a feature that stays a value (eg wall thickness) away from a surface. That way if the height of the part changes I don't have to modify the "cuts". Plus the surface matches the "curve"/"angle" of the offset from surface. Similar to Shell but not removing all the face. I tired Move Face, creating an offset surface from the bottom surface to use "Up To Next" (Offset Surface?)

See that the Up to Surface goes all the way through the part. I would like a "wall thickness" at the bottom that stays even if the height of the part (where the sketch plane is located) changes or the angle of the Moved surface is modified.

jakeramsley

I would do it as a blind then change the terminating face using a replace face with an offset.

1. Start with a small blind remove extrude to get the start of the faces you want to remove.

2. Start a replace face command.  We are going to replace the terminating face of the remove with the surface we want to offset from.


3. Select the terminating face as the face to replace.  Select the surface we want to offset from to be the surface to replace with.  Since the normals of the faces are pointing opposite, we need to choose 'Flip alignment'.  From here, enter the offset that you wish.


4. Go back to your driving sketch, edit it and if done correctly should update with the offset correctly.

andrew_troup

I agree: the "Offset" option is pretty well concealed, and at minimum I think there should be a tooltip ("Offset Distance") which hovers BEFORE you click to enter a figure.

At present, it only tells you what you need to know once you have decided to use it.
It was attention to nuances of this nature which the early Apple Mac team realised was crucial to what became known as an "intuitive" interface.

nav

Hi @christopher_owens below a Video of a possible solution to this using offset planes, I drew the planes after I created the draft feature, hope it helps somehow.

http://recordit.co/NW264lS5EO

jakeramsley

I would do it as a blind then change the terminating face using a replace face with an offset.

1. Start with a small blind remove extrude to get the start of the faces you want to remove.

2. Start a replace face command.  We are going to replace the terminating face of the remove with the surface we want to offset from.


3. Select the terminating face as the face to replace.  Select the surface we want to offset from to be the surface to replace with.  Since the normals of the faces are pointing opposite, we need to choose 'Flip alignment'.  From here, enter the offset that you wish.


4. Go back to your driving sketch, edit it and if done correctly should update with the offset correctly.

andrew_troup

That's elegant, @jakeramsley ; I'm sure I'm not the only one who'd lost sight of the fact that 'replace face' has an offset capability built-in.

"Onshape; doing more with less"

For those unfamiliar with "face normals": they are vectors, perpendicular to the  face in question, whose "sign" is arranged to they always point towards open space, away from the solid. 

nav

Great solution @jakeramsley, thanks for sharing.

christopher_owens

@jakeramsley  Thanks!! I would of been clicking a long time to figure that out! Even if I would of gotten to Replace Face I might not of known what the value was for...doesn't say "Offset". And the offset does remain after I modified the driving features. I know these were "simple" part for demonstration, I did try it with a curved surface at first. I foresee using this on some 3D Printed parts!

 

andrew_troup

I agree: the "Offset" option is pretty well concealed, and at minimum I think there should be a tooltip ("Offset Distance") which hovers BEFORE you click to enter a figure.

At present, it only tells you what you need to know once you have decided to use it.
It was attention to nuances of this nature which the early Apple Mac team realised was crucial to what became known as an "intuitive" interface.

christopher_owens

In the training video which Replace Face is at the end of, and now that I know where Offset is, it is mentioned but... "I'll leave it at it's default value". The End.

christopher_owens

@andrew_troup  & @jakeramsleyI did use all this to create an "Xacto Knife" groove in a model to represent where a door/window would be. (For 3D Printing the replica) From a "Right Plane" sketch I created a Surface using two directions (great update!), then a Thicken to make a part, then the Replace Face-Offset to give the part the shape of the elliptical surface and be half way into the wall thickness. From that I did a Boolean-Subtract to get my Xacto Knife cut in the plastic part!