Newbie Question: How do I create a sketch plan at 90 degrees to a face?

john_smith077

Hello

Please excuse this newbie question, but if I select a plane (e.g. "A.") and want to create a sketch plane at 90 degrees to it, how do I achieve this?

Obviously one solution would be to draw a square, extrude it a bit, then select one of the faces of the new square to draw then next Sketch face on. But this seems cumbersome and I would then end up with unwanted geometry in my model...


e.g. Should I move the Origin for the entire model to the center of my hollow cylinder (above), and then click on one of the planes (in pale blue)? Or would that screw up all my parametric dimensions?

I told you it was a basic question!

Many thanks

J

øyvind_kaurstad

And to the OP, if the plane you are after is parallell to one of the default planes (which it looks like it is), you can use "Plane point", with the chosen default plane and the center point of your circle (might have to unhide the sketch to see the point). Like so:

dennis_20

1. Good modeling practice would have you utilizing the origin ALWAYS, usually at the center of the first feature or a corner.
2. If your new plane is parallel to an existing plane then you should be doing an offset from that existing plane.  Otherwise you'd need a line or a set of points in addition to a plane in order to define the new plane.  In common practice it is infrequent that one would have to define new planes, especially if the new planes are parallel to existing ones.
3. As you learn more about parametric modeling you'll develop better techniques.  Using the origin to constrain the center of a circle is just one of the more obvious ones that you haven't yet picked up on.  It appears that the plane you are trying to add would already be there if you had started your sketch centered on the origin.

øyvind_kaurstad

Regarding your point 2, you say that it is infrequent that one has to define new planes. I don't get that. I often have to define new planes to be able to sketch where I want to. It may often be pure offset planes to some existing plane, but still needed.

If it is possible to sketch on a part surface I will of course not create a new plane for that, but that's not always possible.

øyvind_kaurstad

And to the OP, if the plane you are after is parallell to one of the default planes (which it looks like it is), you can use "Plane point", with the chosen default plane and the center point of your circle (might have to unhide the sketch to see the point). Like so:

john_smith077

@dennis_20
I am confused - are you saying that I should move the XYZ origin to wherever the new sketch plane is? And if so how is that done?

øyvind_kaurstad
Yes! Plane Point is exactly what I was looking for.  
So to get clear: I right click on a default plane ==> "Offset plane" ==> Change "Offset" to "Plane Point" ==> Select the point I want.

Many thanks

jakeramsley

If you select the plane and the point before starting you construction plane it should default to Plane Point.

_Ðave_

henry_feldman

I would add that plane points don't have to be simple planes either. For instance if you want the "make a screw" or "make a nut" videos, then you will note he makes a point plane to the sweep of a helix so you can draw the thread profile...

dennis_20

@john_smith077 I was suggesting you start the sketched circle with its center point on the origin.  Most sketchers will let you start your sketch anywhere in space, but then it (the sketch) is floating in space unless you add some dimensions or other constraints.  This is a common newbie practice and I remember doing it myslef.  If you were to go back and edit the sketch of the first feature, a circle I assume, then you should be able to drag the center point to the origin and get it to snap there, thereby constraining it there.  This is so much easier than adding other constraints or dimensions just to lock it down.

john_smith077

OK I think I got all that.

But as I build my parts of gradually increasing complexity how should I use the XYZ 'origin'?
For best practice, should I be moving the Origin around the part, or should I just start designing part using the origin for one's first Sketch and thereafter leave the Origin in place at say one corner (or the notional centre) of the part?

dennis_20

@john_smith077 "Design intent" is a good phrase to embrace.  A lot of times you are well advised to model a part in a manner similar to how it will be made.  For instance, if the part is mostly a turned part (on a lathe) then it would be good to start out with a cylinder or a revolved shape with the axis located on the origin and normal to a principal plane.  After that your features build as necessary.  You aren't moving the origin around the part since the origin is set with the first feature.

My suggestions above were made based on what looks like a cylindrical part that is not centered on the origin.  It appears that if your part had been started with the center of the sketched circle on the origin you could have used one of the existing primary planes for the other feature you are trying to make, rather than trying to make a secondary plane.

henry_feldman

dennis_20 said:

@john_smith077 "Design intent" is a good phrase to embrace.  A lot of times you are well advised to model a part in a manner similar to how it will be made.  For instance, if the part is mostly a turned part (on a lathe) then it would be good to start out with a cylinder or a revolved shape with the axis located on the origin and normal to a principal plane.  After that your features build as necessary.  You aren't moving the origin around the part since the origin is set with the first feature.

My suggestions above were made based on what looks like a cylindrical part that is not centered on the origin.  It appears that if your part had been started with the center of the sketched circle on the origin you could have used one of the existing primary planes for the other feature you are trying to make, rather than trying to make a secondary plane.

And in the spirit of embracing "Design Intent" I would suggest you watch this short webinar from OnShape regarding the meaning of Design Intent. It was well done, and makes you think about what you are doing and the ramifications of it.