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Is it possible to unfix a instance

baumarbaumar OS Professional Posts: 53 PRO
I tried to move an instance to the origin, but it didn't work properly.
Now I read in https://cad.onshape.com/help/index.htm#triad.htm
"If an instance is fixed, you cannot drag it." apparently that's true. Is there a way to unfix?
Is there any description about ways to fix a 3d object that is hollow? Maybe starting with an easier case like a cylinder where the origin should be in the center of the circle and somewhere on its extension line...
imho it would be worth to have a video only about that triad, maybe even an exercise, since positioning is such a crucial feature

thx for help


  • michael_mcclainmichael_mcclain Member Posts: 178 PRO
    Select the instance in the Assembly tree or model space, right click and select "Unfix". You can use the same method for fixing

    You can also put a mate connector in the part studio to assist with assembly placement. A common workflow is to create a sketch to position this connector. The only caveat is that you need a solid part to tie the connector to.

    Also, if you hover the mouse over the origin in the model space during a mate command, there will be three lines that appear and you can mate directly to the origin. the highlighted line indicates the primary axis (Z-axis) of the origin

    I cant find a video to explain the triad connector, but it is not an overly complex tool. Use the circle in the center to re-orient it where you want on the model and move it from there.

    Assembly Mating Video: https://www.onshape.com/videos/assembly-mates
  • baumarbaumar OS Professional Posts: 53 PRO
    Hi Michael, thanks for the hint with the unfix. I didn't see that in the menu. Maybe my assembly is kind of stocked, but I cannot move it with the triad.

    However the major issue is that the center of my construction is hollow and I didn't find a solution rsp trick how to overcome this issue.

    Thanks for helping


  • bruce_williamsbruce_williams Member, Developers Posts: 335 PRO
    edited January 2018

    Hi Markus,  I think @michael_mcclain ; gave you a solution for your 'hollow' part.  Place a Mate connector using a sketch in Part Studio. 

    For an example see this video. At about 2:25 Cody explains adding a mate connector to the center of a spring.

  • michael_mcclainmichael_mcclain Member Posts: 178 PRO
    The reason why you are not able to move your assembly using the triad may be because you have a "fix" constraint applied in a sub assembly.

    I recently found that I shouldn't use fix as much because it can mess with my top level assemblies. I was always a stickler for locking my assemblies to the assembly origin but for many cases it doesn't matter. I've found that grouping parts and leaving them to float around the assembly achieves the same outcome I want.

    You may have a different example, but look through any sub assemblies for unnecessary fix constraints.
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