Moving components parametrically

[Anonymous]

I'm trying to build a large assembly where the overall dimensions are based on editable parameters.  The overall design consists of a cube(rectangular prism) frame made from extrusions, and I need to position various other components (mostly linked) to points around the cube frame. 

I still have a problem understanding why moves are treated completely differently between bodies and components.  If you move a body, this creates a move in the design history, and I can translate by specific distances based on my overall frame dimension parameters.  If I later edit these parameters it seems to work that bodies follow the changes appropriately. 

However if I move a component then there is no Move command in the history and I can only capture position?  Then any later change to parameters does not get picked up by capture position.  It seems to just record absolute position of everything and throw away specific parameter based movements?

Is my understanding correct that components can't be placed in a parametric fashion that allows editing of parameters(which should affect the placement) after the fact?

[whittakerdw]

Components do not show that they were moved in the timeline unless the position was captured. If the position was captured then that will show in the timeline. Components have movement from joints and are free to move depending on the joint applied. The movement can be limited through the joints. Bodies are not meant to have joints or movement and this is why every move is shown in the timeline. Every new move for a component is shown if the position is captured. After the components are placed, limitations can be used to affect and limit the freedom of movement.

[TrippyLighting]

I'd add to @whittakerdw reply that in an assembly he position capture feature should be used very sparingly and is mostly not necessary.

[whittakerdw]

@TrippyLightingI agree with that

[Anonymous]

@whittakerdw

My issue is specifically with updating parametric variables for placement of components.

Here is a screencast that hopefully demonstrates the issue more clearly:

Screencast will be displayed here after you click Post.

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[HughesTooling]

If you build an assembly using components and position them using joints then the components will keep their position after editing the part they're joined to. So no need to have lots of references to update in your moves. Have you looked at any lessons on building assemblies and also have you seen Rule#1?

This blog might help, haven't had time to read it all but looks quite good.

Also some hands on exercises in the help might be worth going through.

Mark

[Anonymous]

Having difficulty posting this screencast, trying again

[kb9ydn]

Normally when you put together an assembly you want to define the positions of components relative to other components, one of which will be grounded so that it doesn't move.  So for example; you would ground one of the components of your extrusion frame and then use joints to define the locations of each of the frame pieces relative to the grounded component.  Then you would use joints to position the rest of the components with respect to the frame, so that if the frame dimensions change, the components' positions will update as things move.  You can also use parameters in joints to have them change in more complex ways.

C|

[Anonymous]

OK, it appears that Joint Origins can be positioned and offset using parameters that actually update when variables change so I guess I have to just define them in all cases that can possibly change.

So here is my updated understanding of how components are positioned with regards to parametric designs:

-Capture position will break your design when any parameter is adjusted.

-As-built joints are never viable in parametric design because there is no way to moved/position components parametrically.

-You must define joint origins for anything that uses parameter-based offsets from edges/corners of your components.

[TrippyLighting]

Before coming to more incorrect, or at least incomplete conclusions you should really go through some of the educational materials Hughes Tooling has posted.

As built joints are perfectly fine in a parametric design, but it still matters how you designed that parametric design.

If you follow a top-down design methodology and design parts in their final location (in-place) then as buildt joints are fine.

However, if you use a bottom up approach for example  it would not make sense to move a component into place using the point-to-point move or the align function and then use a as-built joint.

[chrisplyler · Accepted solution]

Components are meant to be Jointed into position. You can Joint a Component's Origin (or any snapping point of the Component) right to the main Origin (or any Origin or snapping point of another Component), and use offsets with parameters.

Any Move used on a Component isn't necessary. It might be useful to Move and Capture Position just so that you can easily see the snapping point you want to select, but after the Joint is completed you go to your timeline and delete the Capture event anyway.

Don't use the Move tool on a Body to position the whole component. Moving a Body should be reserved for locating one body relative to another WITHIN a Component. For example, you've Combined two cube bodies that are intersecting each other. You realize you want to change their relative positioning. You roll back the timeline to before you Combined them, Move one of them, and then roll the timeline forward again. And really, you should be controlling this with a sketch more often than not.