Is there still no way to group curves in a sketch?

joshtargo

We have many situations where we are trying to work out the geometry of the moving parts of a robot.  This needs to be done in 2D, with rough approximations of parts and other elements. In Sketchup, I can group curves together so they can be transformed as a single object. Is there still no way to do anything like this in Onshape? It gets very messy and very complicated very quickly if I need to dimension or constrain every single line and curve in a sketch. I can't do this with flat or 3D objects in an assembly because the dimensions of the objects themselves need to be able to change as their positions change. Please any solutions?

eric_pesty

One strategy that could help would be to split up the sketches a bit more and use the "final" button when editing an "earlier" sketch to see the final result You could potentially also "derive" stuff in there attached to your sketch geometry, and use multiple windows to edit the "components" in parallel.

matthew_stacy

@josh_targo, have you explored the "Composite Curve" tool? Seems like a possible match for what you're trying to do.  Here is a screenshot of two splines, subsequently defined (see feature tree) as a composite curve:

joshtargo

that wouldn't work, composite curve is not a sketch function.  I need the curves to be grouped within a sketch, so they all move as one.

nick_papageorge073

You can make a window selection around a group of curves and then use the sketch transform tool to move them. But that is not parametric, and probably not what you are after.

It sounds like you are in the brainstorming stage of a design? Why not make a first guess of the curves, then make simple extrudes from them. Then make a test assembly to check the motion. Adjust and repeat until you have a good direction. Then redraw the design from scratch with the full engineering details.

Motion is designed to be done within an assembly, not a part studio.

joshtargo

yeah, none of that will do what I need.  at the brainstorming level, we are still trying to figure out the basic configuration of elements that can fit in a certain space and reach certain points, essentially asking "what combination of dimensions will be able to do all the things we want", but the number of dimensions that are variable is large, and so the solution space is huge. it is not feasible to guess one out of thousands and go through the process of making it 3D just to "test it out" in an assembly.  I need to be able to fix certain dimensions, apply certain constraints, and then translate, rotate, scale elements to see what all of the other variable elements do in response. a literal group constraint in sketches, as exists in assemblies, would work perfectly.

martin_kopplow

What about making a sketch of each 'group' and then arrange these sketches in an assembly? You could use mate connectors and even create (groups of) interconnecting curves in context.

joshtargo

Won't work. I need various lines, shapes and circles to move, rotate, and scale as I drag other elements. I may need the diameter of a swing radius of an arm to stay tangent to a limit box but shrink and grow in size as the center of the circle moves.

_anton

Can you share an example? Assemblies really are the correct way to do this, AFAICT. You may be able to add mate connectors to supporting geometry and use those to emulate what you're trying to do in a sketch.

S1mon

I would also be very interested to see an example. You can do quite a bit within the sketcher depending on how much detail you need and how much you're willing to add dimensions.

joshtargo

S1mon said:

I would also be very interested to see an example. You can do quite a bit within the sketcher depending on how much detail you need and how much you're willing to add dimensions.

I can do it if I add a bunch of dimensions, but it gets really messy fast. That's why I want to just group the curves so they move as one.

Ste_Wilson

Could you provide a few sketch up screen shots, or sketches, and talk through the process to give a bit better context?

joshtargo

here's a simple example from early on in the process. many of the orange shapes must be allowed to change size, angle, and position (within constraints) as I drag other things around.  the triangle is a simplified version of the manipulator, which got more complicated (in profile) as the design was developed.

there are also now new parts stuck to some of the moving parts that need to move as we continue development. (second image). even if i reduce the new parts to profiles, that's still a lot of dimensioning I would need to use to keep the shape intact as it's dragged around with other parts.

I understand from the responses that onshape still can't do what I want, and i haven't heard any practical solution other than fully dimensioning and constraining the shapes. moving things in assemblies will not work, as parts, lines, and circles will not scale as they are moved.  and it is the position and dimensions of elements that we are trying to determine by playing around with the degrees of freedom available in the design space.

_anton

(So, separately, what you're doing is very cool.)

A couple of workarounds come to mind. You could configure the Part Studio, and twiddle the configurations from the Assembly. Or dimension the entities via a Variable Studio and do the same from the variable table. Admittedly, that's not as interactive.

joshtargo

maybe a better example: this is the kind of part that will be moving around on the screen relative to the movement and paths of other parts.  even if i just use the outer profile, it's a very complicated shape to hold with constraints and dimensions, which easily start to clog up the view of whatever we're trying to look at.  

on top of that, everything behind and above the hook is not set in stone and needs to be allowed to change size, shape, position, and orientation as we try to narrow down our design options.

eric_pesty

One strategy that could help would be to split up the sketches a bit more and use the "final" button when editing an "earlier" sketch to see the final result You could potentially also "derive" stuff in there attached to your sketch geometry, and use multiple windows to edit the "components" in parallel.

joshtargo

eric_pesty said:

One strategy that could help would be to split up the sketches a bit more and use the "final" button when editing an "earlier" sketch to see the final result You could potentially also "derive" stuff in there attached to your sketch geometry, and use multiple windows to edit the "components" in parallel.

not sure if Derive will help as it won't move as I move the sketch in real time (until i commit), but maybe Final will help.  I will experiment...

joshtargo

eric_pesty said:

One strategy that could help would be to split up the sketches a bit more and use the "final" button when editing an "earlier" sketch to see the final result You could potentially also "derive" stuff in there attached to your sketch geometry, and use multiple windows to edit the "components" in parallel.

I believe this is as close a solution as I can get in Onshape.  Thanks! 

joshtargo

I'm making progress, but it's still slow and clunky to make it work.  Grouping curves (same as with the Group assembly Mate) would solve everything.

To get dimensions out of the way, I make a Skeleton sketch with all the geometry simplified into straight lines, triangles, and circles, then I make a copy of that sketch set each line and circle = to the same element in the skeleton.  But this still restricts me to triangularizing the shapes.

For complex shapes that need to be dragged around, I hve to make a sketch in another studio, set the object at the origin, (which is out of correct robot position), and derive that sketch directly into position in my geometry part studio.  I can't even transform the sketch after it's derived.

people can see what i'm doing here:

https://cad.onshape.com/documents/bf8d9231688bc4be9a456aeb/w/0bb4b33a996783fbc392f6a6/e/6178e797647d23fe178adbf8?renderMode=0&uiState=66758245afe5aa080c1d3a8c

S1mon

If you’re ok with deriving sketches, why not use sketches in an assembly? You can create all the revolute mates you need and the sketches don’t need any dimensions.

joshtargo

S1mon said:

If you’re ok with deriving sketches, why not use sketches in an assembly? You can create all the revolute mates you need and the sketches don’t need any dimensions.

1. elements in the sketches are not all static, and need to change as other parts move.
2. we need to be able to edit the sketches in order to design things, and it's slow to have to jump back and forth between sketch and assembly
3. we also need to be able to set multiple constraints on different elements within sketches to multiple elements of other sketches
4. setting/removing constraints in a sketch is a lot faster than setting mates in an assembly 

if you go to the assembly in the link you can see what I set up, but some of the elements are not free to move as I want, and I'm not sure how to mate some things that would be easy in a sketch.