Assemblies Shifting relative to assembly coordinate system

[perry_a_gray]

I am using Inventor 2019 but I don't think it is a release specific problem. When I am starting an assembly, I will insert the first component usually one that I want to be grounded. However, during the process of adding components that component should snap to the grounded component, the grounded component shifts and not the new component. So you get to doing your 2D projections, now the whole model is shifted relative to the coordinate system. Why does this happen and how do I fix it without having to rebuild the assembly. Sometimes the added component is now grounded and the original component is not grounded anymore. This seems really backwards to me. 

Perry

[CGBenner]

@perry_a_gray 

Hi, can you describe the exact steps you take when placing yout first component, and the same with subsequent components?  Something in how you are placing the first is probably the key.

[JDMather]

Can you Attach an assembly here that exhibits this behavior?

Or at least show a screenshot?

There is an easy fix, but it might be useful to Root out the original cause to the Ground.

[perry_a_gray]

Added a zip to main post. I am in the design process. These are by no means finished drawings. You can see in the idw that things are skewed. The draw bar mount is the grounded component. 

[CGBenner]

@perry_a_gray 

The first component is missing from the assembly.  Was it not in the zip?  Back plate.

[perry_a_gray]

Added back to original post. 

[CGBenner]

@perry_a_gray 

Can you share a screenshot of what you are seeing?  I'm not sure what is skewed in the .idw.  I did notice in your assembly that Side arm_MIR is not constrained.

[perry_a_gray]

[SharkDesign]

Is it actually grounded?

There's an option in application options under assembly to ground the first item placed.

If this is unticked then it will float as you mention.

[perry_a_gray]

The side arm mirror was one of the problems. My floor reference is off by 1 deg. Trying to figure that out now. I created that by offsetting the origin plane by 12 inches on the draw bar mount part. 

[SharkDesign]

Your first component is not grounded and your grounded component has an error on it. 

So as you say, your first part is out by less than a degree:

You need this option ticked to get the functionality you were talking about in the original post.

[SharkDesign]

Your first component, back panel only has one mate so it can rotate like this:

There's also no constraints to the origin, so it's not tied to that. 

These three mates are all tied to a suppressed part which is also not tied to the origin:

So your only actual reference to the draw bar mount is an insert, which of course can rotate.

I would guess that it's moved at some point, rotating on this mate and then you have grounded it, hence why the angle is out. 

You should probably start by finding the part you want to be exactly square are grounding at the origin:

Assuming that you have drawn it symmetrical around the origin of the part file. 

Hope this helps!

[perry_a_gray]

Ok see if this is better. I turned back on the backhoe frame and got things aligned again to the origin. The 3 pts arms and the backhoe frame will not be on the tractor at the same time. The 3pt arms need to come off with the side rails on the tractor. I am trying to recreate a mounting frame for a backhoe. The frame being the side arms. These connect to an existing front end loader frame at the skinny end of the side arms. At the back, they will connect to the back plate and the drawbar mount. I am trying to locate the side arms in space before designing the mounts to them. I think I am within an inch or two to the correct position. This is for a Mahindra (3016) tractor that I bought a backhoe (3720) for but don't have the parts that mount it to the tractor. I have access to a water jet cutter and will probably make some test pieces out of thin stock to do a final fit check. If I had an inside at the factory they could send me a drawing of the part. They are not making parts for the new tractors at this point much less a 10 yr old one.