Grounded Part

[Anonymous]

Is selection of the grounded part matter?  Because my grounded part is different from given grounded part in the  assignment.

[Binga]

Can you explain better?

[Anonymous]

There was an assignment. For IAM file which specified a particular grounded part. But I did it in my way and finally I found that my grounded part was different from the grounded part given in the assignment. Does it matter?

[JDMather]

Maybe.  Maybe not.

Have you applied any logic to the order of assembly?

[Binga]

Well. I don't know if it matter.
What is your result?
What are the objectives?
(I didn't understand the question yet, sorry)

[Curtis_Waguespack · Accepted solution]

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@Anonymous wrote:

Is selection of the grounded part matter?  Because my grounded part is different from given grounded part in the  assignment.

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Hi fiatnm ,

Sometimes it matters if we are trying to configure that part to move in the assembly using what is called a Positional Representation, or if we are trying to Drive the constraint.

Basically, you don't want to ground a part that might move in that assembly.

Typically there is a "base" part and that will be the grounded part.

However, I used to design products where I had to start with the moving parts and design the housing around those parts, so often I grounded a part that was intended to move at first. Then once the design was done, I would ground the housing part, and unground the other part.

So, if you'd like to do so, you can ground the part that was grounded in the exercise and unground the other part.

Also, you can have as many grounded parts as want to at the same time, but generally we ground just one.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[Anonymous]

My logic is simple. If all the parts were loaded on a one single part that could be the grounded part.

[JDMather]

My logic goes more like this (given experience in the real world).

If I am assembling a house - the Foundation would be a logically grounded part. (I probably wouldn't start with the roof.)

If I am assembling a car engine - the engine block would be a logically grounded part.  (I probably wouldn't start with the oil pan.)

If I am building an alternator sub-assembly for the car - one side of the housing for the alternator would be the logically grounded part. (I probably wouldn't start with the stator.)

Could I start with the roof, oil pan or stator as grounded? Yes. But I probably wouldn't.  Probably wouldn't be the best logic.

But often there might not be any clear-cut logically grounded part.

There might not be any grounded part.

There might be all or some parts grounded.

All depends.

[Anonymous]

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@Anonymous wrote:

Is selection of the grounded part matter?  Because my grounded part is different from given grounded part in the  assignment.

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fiatnm,

If it's part of an academic assignment... you'd probably better get the grounded part right, otherwise you're headed for partial credit.

From a modeling standpoint, I would echo JD. The grounded part should be the most basic part around which your assembly is built. It is usually the first one you think to insert into an assembly. I really appreciate that when a part is inserted into a new Inventor assembly, it is centered at the origin and grounded. This works for the vast majority of assemblies, according to my experience. 

There are instances like a rectangular frame where it doesn't make sense to ground any of them at the origin. Then I would urge you to constrain the parts to the origin planes in a way that makes sense, otherwise things can get a little strange. And if you don't, the next person to check your model will likely be confused. "Why did they do THAT?"

Do a little critical thinking and you'll be alright.

[mdavis22569]

What does your INSTRUCTOR say?      ... if it's for an assignment ... Will you get it marked wrong, or trouble if you turn it in with a different grounded part?

As JDMathers said ... it's how you build things in life ...that make certain things grounded.

What's the assignment?   There was a probably a reason they made a certain part grounded 

[JDMather]

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@Anonymous wrote:
My logic is simple. ....

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Read Post #8 here - House of Cards.

The most important post ever made to this forum.

[Anonymous]

am I right in thinking that you had an assignment which you completed to be dimensionally correct with exception to you ground planes not been the same as what it should be on the assignment.

if the above is true then yes it does matter because although you have completed the assignment and in the real world this could be made without a flaw, the assignment is/should be teaching you the proper constraints and if it isn't exact then it isn't correct.  Pain in the arse I know and sort of doesn't make sense but its a good learning process when you think about it as the simplest little thing not been right can screw a major thing up down the line.

even if you don't agree with them and argue the toss it will still make you think about it in future so good lesson learned (right or wrong)

[Anonymous]

This is a future assignment. If it is incorrect I will redo the work before that I want to make it sure.

I made CENTRAL KEY as a grounded part, book made PISTON as a grounded part.  

[CCarreiras]

Why dont you just change the grounded part to be compliance with the task???!
problem solved!!!

[Anonymous]

Not just for a solution. Solution with a valid reason.

I am struggling to find out the reason. You are just saying copy the book. I am unhappy with your answer.

[Mark.Lancaster]

@Anonymous

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@Anonymous wrote:

Not just for a solution. Solution with a valid reason.

I am struggling to find out the reason. You are just saying copy the book. I am unhappy with your answer.

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WOW I guess you can't read either...  What does your assignment say in step 5?  That's why they grounded the PISTON first, it was the first part placed in your assembly per the steps in the assignment.

If that's what your supposed to do why are going on about it?  I don't get it... 

Update:  You state "I am struggling to find out the reason. You are just saying copy the book. I am unhappy with your answer."  And why is that?  You are doing an assignment, follow ot or don't follow the steps.  Simple as that...   Its not a real world thing..  Its just a method teaching you things about grounding or constraining or whatever.   All I can say is WOW at this point..

[CCarreiras]

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@Anonymous wrote:

Not just for a solution. Solution with a valid reason.

I am struggling to find out the reason. You are just saying copy the book. I am unhappy with your answer.

The grounded part is commonly the first part to place in the model... the anchor, the most central, most representative part in the model, the one which all other parts will connect (or not all) (look at JD post above). There's not a closed rule, it's your appreciation that counts here, so, think about it, and choose that part without too much "struggling"... because...

...Of course in some models can be more than one part that can be the grounded part, or we can have also several grounded parts in the same model, or in some stage of the project we can decide to change that part status, so,again,there's no rules to follow, only your opinion, your experience, your feelings, your inteligence... whatever it makes it work!!!...

You thought that would be better other part to be  the grounded one? Ok!!! Maybe your choice it's also right!!! but...

IN THIS CASE, YOU HAVE TO FOLLOW A SIMPLE TASK!!!! SO DO IT!!!!!!

Now you have the reason, and the solution...

You're struggling??!!!! Open your eyes, use your head, and avoid to ask dumb questions...is embarassing to you..

[Anonymous]

Thanks

[Curtis_Waguespack]

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fiatnm wrote:

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Hi fiatnm,

I don't know what this assembly is used in, but I think you're correct to think that a piston would typically be the moving part in the assembly, and therefore I don't think it's unreasonable  to question that the exercise asks you to ground it.

As I'm sure you've seen by now, there are many exercises and youtube videos that aim to teach the software tools, but some of them do not always show the real world application of those tools, or in the case, might not show the real world design intent of the mechanism used in the exercise.

Many exercises are written by technical writers and curriculum subject matter experts who are not designers or engineers, and they sometimes overlook some real world details. Sometimes this is on purpose, as it makes the exercise work more predictably, and allows the student to focus on the subject (in this case assembly constraints). Other times the author might simply have not considered the design intent of the mechanism in the exercise, thinking that it does not matter, after all it's just an exercise.

I would expect that your instructor would welcome you to question the design intent of the mechanism, once you've completed the exercise as written.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[JDMather]

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Curtis_Waguespack wrote: 

I would expect that your instructor would welcome you to question the design intent of the mechanism, once you've completed the exercise as written.

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Ditto on Curtis' (or is it Curtis's?) observation.  Ditto on @Curtis_Waguespack (there we go) observation.

I like to see my students question the mistakes I've made as it shows they have learned something.

And when I was a student - I never did things the way the book said - if, I knew the book was wrong.  Even if it hurt my grade.

In the other thread you have running on this same assembly - you found two errors that I made.

How are you going to fix them?