Why does this happen?

Hello. I have been working on a model. I noticed something that seems weird to me. I have recreated the behavior in the attached assembly. The only real difference in the assembly presented here and the assembly where I first noticed the behavior is that Floating Torch Plate in the attached assembly is constrained to the XY plane just to give some basis for orientation. In the actual assembly, another part is aligned to the XY plane and keeps everything else straight through constraints.

While dragging parts around to see the mechanism move and check movement limits, if I drag the Duramax 85 Machine Torch part up and down it moves up and down, just like I'd expect, constrained to the Torch Clamp 3 part on axis. It just moves up and down and nothing else moves. When I move the Torch Clamp 3 part up and down it, and the Floating Torch Plate (which is constrained to it) both move up and down, which I would also expect. When I drag the Floating Torch Plate up and down it, and the Torch Clamp 3 it's mated/constrained to, both move, as expected. What's weird to me is that the Duramax 85 Machine Torch also moves.

The only constraint on the Duramax 85 Machine Torch is the axis constraint to the Torch Clamp 3. I would expect that the other two parts would move and just slide up and down the Duramax 85 Machine Torch part, similarly to how the Duramax 85 Machine Torch part just moves inside the Torch Clamp 3. But no, it all three parts move together. I even deleted the Mate:1 constraint on the Floating Torch Plate to break the mate to the XY plane (just in case), but the same thing happens.

It's not a huge deal but I don't understand it and I'd like to try to find out why so if it happens again and it is a huge deal I know why and what to do about it.

Thank you.

--HC

SampleTorchHolder.zip

It is because there is no direct constraint between the plate and the torch. When you grab the plate it is only solving constraints attached to the plate. The plate is fixed to the clamp. when you select and move the plate, the clamp moves with it, and the torch goes along for the ride. When you grab the clamp, the program will now solve for the constraints between it and the torch. A solution would be to replace the constraints between the plate and clamp and re-constrain the plate to both the clamp and the torch. Another would be to demote the plate and clamp to a subassembly then add constraints. Also since your parts are symetrical about the YZ plane, I would have modeled them centered about that plane. Then your could also constrain to the work planes and axis and have fewer issues keeping things aligned and symetrical.

It is because there is no direct constraint between the plate and the torch. When you grab the plate it is only solving constraints attached to the plate. The plate is fixed to the clamp. when you select and move the plate, the clamp moves with it, and the torch goes along for the ride. When you grab the clamp, the program will now solve for the constraints between it and the torch. A solution would be to replace the constraints between the plate and clamp and re-constrain the plate to both the clamp and the torch. Another would be to demote the plate and clamp to a subassembly then add constraints. Also since your parts are symetrical about the YZ plane, I would have modeled them centered about that plane. Then your could also constrain to the work planes and axis and have fewer issues keeping things aligned and symetrical.

Thank you for the reply. It still seems odd that moving the clamp moves the plate (that part I get) so the plate moving in this case doesn't move the torch, but moving the plate moves the clamp (I get that) and the torch. In one way, the plate moving moves the torch, in one way the plate moving does not move the torch. It seems inconsistent.

I will play with the subassembly, as you mention (I'm not particularly adept at using Inventor and certainly not a professional). I will also go back and work on the part drawings to see about changing their orientation to the YZ plane. Sounds like good practice and might, as you say, help me put my assemblies together if the parts are already pointing/oriented like they'll be used in the assembly.

Thanks again.

--HC

As a follow up, hopefully to help others: I went back and re-drew my parts. For the first time, based on the suggestion of eschclark, above, I paid attention to the orientation of the sketches in regard to how I would then use the parts in a subsequent assembly. In doing so, my assembly was much easier because the parts were already oriented correctly. I should have been doing this all along. Thanks, ecshclark.

--HC