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...
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.
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
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.
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
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
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.
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
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
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.
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.