Facing problem in assembly..

Dear All,
I am very new to solidworks and was facing a problem.... While creating an assembly the first part which we bring becomes contraints but as i said i am very new to cad also i realised that i want to change the first part with the third part... Do neone know how to do this...without much hassle.
Thanx in advance Vivek

If I understand you correctly, the first part inserted into an assembly locks or "fixes" automatically. If you want to move it or fix another part instead as you say, right click the component in the tree and choose "float" instead of "fixed".
Personally, (and I don't know why other than personal preference) I find myself a lot of time (depending on the assy) floating the first component after insertion, then lock its planes into the corresponding assembly planes instead. I'm not sure others here would agree or not with the logic in doing this though...
IYM
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IYM wrote:
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I do exactly the same thing. I hate having anything fixed in the assembly as it usually causes red flags somewhere down the road. And by mating to the planes rather than fixing the first piece it assures that you have it in the correct position as well.
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My experience has been the opposite. I have never had a fixed component cause a mate failure that it should not have.

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While I've never had a failure due to having the first (or any) component fixed, I usually float all components and mate them using planes. This is A) - so that I know that they are where they belong, and B) - if the first component isn't in a 'normal' orientation, how would I know where it was fixed? Just doesn't seem like a good practice.

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I see where you're coming from. I rarely have the first component unaligned to the assembly planes, so that's not an issue for me. As for making sure that a component really is aligned to the planes, well that's never been a problem. I have never seen a fixed component move from where it is supposed to be. I once had to do some wokr in AutoCAD after a few years in SW. I found I was a bit uneasy about laying down all that geometry without constraints to keep it where it belonged. Then I remembered that there is nothing in ACAD but me to make it move. Shortly after that I started fixing components instead of mating them to the assembly planes. In SW we have the mate solver that could conceivably move a fixed component, but I decided to trust it. I figure it's more secure than trusting mates to solve correctly. I've been doing this a few years now with no trouble from SW.
Sometimes I have to use mates to align the part after insertion, but I usually fix the part and delete the mates in order to help with rebuild time and stability. I don't have any data to back up the practice though, so we'll just have to keep working the way that seems best.

I struggled with finding an error in someone else's assy one time only to find that the first part was *close * to the origin, not *exactly* there. I don't trust most other people's work if I see fixed parts. If it's mated to the system planes, it's done on purpose and exactly there.
WT
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Interesting. As in the rest of life, our habits are sometimes formed in response to past traumas. I'm not saying that those who disagree with me are necessarily irrational, but differrent environments require different techniques.

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What you will often find in my assemblies is three supressed mates (in a folder, of course) named 'align' or something like that, that are used to orient the first component in an assembly to the assembly planes. I choose my first componet VERY carefully - I want it to be the one component in a changining design that is the LEAST likely to change, and is the closest to the root or base of the assembly. Most assemblies have some sort of root/base that interacts with the existing world and all other components interact with that base - that 'base' is what I choose as my first component. It might interact with the floor, or a wall, or a table - whatever, there is gravity in the real world and a need to keep stuff from sliding around hither and yon and that informs my choice of a critical root component. The reason those mates exist is to orient the root compoenent, and the reason they are suppressed is that I want to replace them with a 'fix' when I get it properly in place.
Afterwards, every other component is mated functionally to the root component or to other compenents based on what they do. Other than mates to the RIGHT plane in assemblies with a functional axes (like a catipult/trebuchet) I do not use the assembly planes for anything else.
The reason I first tried this (and through time embraced it thouroughly) is an old Mike Wilson trick - if you 'fix' the first component and make all mates to the 'fixed' root/base, you have an easy way to test your assembly mates. You can't always count on seeing plus signs next to all components because it is common practice to not fully constrain all cylindrical fasteners. With this technique, you can un-fix the root, drag it, and 'shake' the assembly to see if anything isn't properly contrained - as you move that root component, all improperly constrianed fasteners lag out in space.
BTW - another advantage is that fix is a great way to reduce the number of top level mates. I have adopted the practice of having as few top-level mates as possible - after 100-200 mates SWx, in my experience, gets dodgy. If I bust things into sub-assebmlies (functionally, of course - it is a rare mechanism in my field that has 50+ components come together without having been pre-assembled before insertion, so anything that is pre-assembled gets its own subassembly) mates are much, much, much more robust. And eliminating those first three is just gravy - I reduce the number of top level mates, and I get the Mike Wilson 'shake' advantage. Win-win. Ed

Ed,
Thanks for reminding us of Mike's tip. As a side note, I finally noticed that 07 will suppress a component's mates for you when you fix the component. Another of those nice little changes that make things a bit easier.

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I usually start by assembling the customer part in the assembly file. Our customers usually put their parts in 'car position'. This seems to never be in the orientation that we need to design our parts. This makes mating the part a better solution for me, but I can see where if you were starting green field, fixing the part should work just as well.

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You are very much correct, it may raise some red flags while reordering the parts.My suggestion for vivek is that while bringing the first part think well, that it should be the base or main part for that assembly.added to this, constraint the base part in the empty assembly with origin or CYS.Don' t hesitate to ask any question eventhough it is simple.Clarify it in the learing stage itself.there are lot of guru's to train you.Good luck for your future.
Ajith

I would agree that this would be a good option. It could also be done with a macro IIUC.
TOP

If you re trying to the replace the first component with another component, pick the said component in the assy, and then try File>Replace.