Dumb(?) Origin Question

Hi,

First, I make all of my parts, paying close attention to front, back, right
side, origin, etc. like we all should.

Question:

When creating a new assembly, starting with the base (fixed) part, how do I
get the origins aligned?

I have been doing this via mates to the three planes (or use the origin)
between the new part and the new assembly I am starting to create. It would
seem to me that the first part should automatically be aligned to the origin
(and orientation to the front, side planes, etc.) of the new assembly when
you are creating the new assembly from the first part???.

Hope I have made sense

Aron

 

upon inserting a base part in new assy,

select the check mark in fm
or
pick assy origin from graphics screen or fm.

 

The part "front" plane does not necessarily have to line up to the assy
"front" plane - you can rename the planes to anything you want. I think you
are trying to simplify something that isn't necessarily easily done - let me
explain what I mean and how I try to train others.

Sw gives you the opportunity to drop a part into the FT of an assy and then
it will align it with the assy planes and fix it in place. Quick & easy, no
doubt, and at times, that's an acceptable method.

But I try to impress on others that there might be a reason to not have it
there. If you look ahead a bit at how you will be using the assy, and that
part in particular in relation to the other parts in the assy, you might
realize that some feature of it might come in handy later if it were
positioned a particular way. For example, you might model a part with the
system plane at the bottom of it based on the geometry of the part.
However, 2/3 of the way up there is a hole in it that will have bearings and
a shaft associated with it. So, to facilitate the assy model's relations to
the shaft, you may want one or two of the assy system planes to go through
the center of the hole, and this can be accomplished by using the temp axis
in the hole.

Another reason to avoid the "fixed part" approach is especially important if
you are not the only one doing the modeling. If you drop the part into the
graphics area of the assy, rather than the FT area, it will nail it down
right where you drop it. Maybe close to the system planes, and then again,
maybe not. Or even worse, a co-worker does it and drops it pretty close,
but not right on, and then you get it and use the assy system planes to
locate the assy. Then later you scratch your head trying to figure out why
bolt holes don't quite line up. Can you really trust everyone to do it
correctly? If the part is just "fixed" rather than mated to planes, you
don't know for sure which way they did it.

By aligning the part to the planes manually, it makes you take the time to
consider how this part really needs to go. You may not know for sure, and
its orientation is changeable, but at least you put a bit of thought into
it.

Another general rule of thumb that I preach is to always use midplane
extrusions & symmetry for parts, unless you have a specific reason not to.
I don't know how many times I have seen models created where the person has
the system planes coincident to flat faces, and then has created extra, new
planes coincident to midpoints on edges. If you have a reason to put them
on the sides, etc, do it, but make it a conscious decision, rather than the
default because it's the easiest. So many times you will come back and line
up parts by their centers, etc. If you need the outer edges or faces, use
them - you don't always need to use planes.

Long reading, but I hope it has opened your eyes a bit.

WT