Post by mattaside from that, you might try lofting as a surface and see if the error
still exists. you might also try lofting individual sketch segments using
contour selection.
First, each loft is its own animal. If anything I write below sounds mealy
mouthed - it is. There are so many little issues that could be behind this
that I cannot be definitive without having the part myself.
I like matts suggestion of lofting the individual 'sheets', though I have to
admit I am novice to the contour selection part of it (I gave up on contour
selection after my first few ugly problems with it). I usually do what
needs to be done by converting entities into new sketches.
About the knitting sheets together error - Solid lofts are a little program
(like a macro) that automatically creates a bunch of surface lofts. What a
solid loft does is it lofts each face one at a time from your profile -
these individual surfaces are for some reason called sheets (why they are
not called faces or surfaces in the error message is beyond me). Then the
sheets are connected (knit) to enclose a volume, which then gets defined as
a solid.
When SWx cannot 'knit the sheets together' that means the sheets overlap,
intersect, or pull away from one another - basically, some condition exists
that will not allow the indidual surface to be stitched into a single closed
volume. What will cause this? Frankly, sometimes SWx just sucks, the loft
is not behaving as it should and there is nothing you can do about it.
Sometimes its because your loft section placement adds too much 'pressure'
to the loft (which seems to me to be the case with your loft), but we would
have to go into a lot more stuff to talk through that bit of business.
If you were to loft the sheets individually or in smaller groups yourself as
individual surface lofts instead of having SWx loft all the sheets at once
as a solid, you would probably get to see where the problem is. You then
might be able to add some guide curves to help eliminate the overlap,
intersection, or gaps that are causing the knitting problems. Sure, guide
curves add pressure and problems of their own, but they look like they may
be appropriate in this case (but don't think you will get off lightly - my
guess is you will need one for each of the four corners)
Post by mattare you using any end conditions like tangency or direction vector on the
loft?
The preview of your loft in the last image sure takes an ugly turn where it
starts on the left side. According to the group boxes in the PM it is not
due to a start or end direction or tangency condition, though matts
suggestion is what I would have guessed had the PM not been shown.
It would be useful to see how the angles of the profiles work - profile
angle can add 'pressure' that kill a loft. To learn about pressure, get in
the habit of looking at the 'face curves' (see the hlep) of lofts you make
to get a sense of what happens to the UV lines of a face based on these
things that influence their pressure. You will see strange jogs, kinks,
convergences in the face curves, and you can then amalize your model to
figure out what causes the imperfections.
Based on that shaded preview, you really ought to try to add two guide
curves on the 'hub' end of the loft. The guide curves are easy - use 2
curves through reference point or sketch splines in two 3D sketches (the
same thing, when you strip away the 'macro' junk) that connects the
appropriate 3 points of the 3 profiles. This will clamp out any tendency
for those faces to cross.
Post by mattit looks like part of the problem might be that the profiles are at such
steep angles to the shape you're trying to create. Ed E would be able to
articulate this better.
I wish! I hate talking about lofts because it is such a subtle, situational
art.
Just because you downloaded something from the
Post by mattSolidWorks website doesn't mean that it shows good techniques. This is
definitely a goofy loft. I downloaded the part you're following, and I
wouldn't approach it that way, (not that what I'd do matters). I would
probably loft the other direction, which would be a more complex set up,
but is more likely to produce better results, especially on the leading and
trailing edges of the blade.
matt
Post by JohnI wish to re-trace the steps of creating a computer fan (file download
from 3Dcontentcenter site). I create 3 sketches (#5, #9, #10) on the
hub. Then use a loft feature, selecting Sketch #5, 9, 10
respectively. After hitting the green check mark, I receive this
Loft: Cannot knit sheets together.
Note: I did try to select the sketch in different order and still get
the same message.
Does anyone have an idea what I am missing here?
http://home.comcast.net/~wangphk/SolidWorks/Parts/Loft-Feature-Failed.jpg
