What determines available terminations?

A simple sketch on a plane extruded to a radius surface and also touching a
drafted surface. 'Up to next' is the ideal selection when picking extrusion
termination but it is not available. An identical sketch (as far as I can
tell and I've looked really good) has the 'up to next' available. What are
the rules used in determining what termination is available? I've been
training a newbie and he has ran across this. He is presently using a VAR
installed eval copy and is considering a purchase but inconsistencies like
this are hindering a purchase decision. I feel that there is something that
I'm not seeing but for the life of me I can't find it. Can anyone offer a
suggestion?

Thanks in advance,

Jeff

 

Can you clarify your terminology so we can home in on the problem:

When you say "Surface", do you really mean surface? In SolidWorks, a surface
is a zero-thickness entity, such as would live in the "Surface Bodies"
folder.

Perhaps by "surface" you meant "face", ie the face of a solid body.
"Up to next" requires a solid face, and it must be a contiguous face on a
single body, with no undercuts.
What is perhaps confusing the issue (and many users do not realise this):
the options on display will be restricted according to the direction
SolidWorks picks to try and extrude your sketch. Because of this, "Up to
Next" will NOT be listed until you reverse the direction of extrusion (by
clicking on the "Reverse direction" icon).
The reason this limitation is not widely recognised is that, in ordinary
modelling, SolidWorks' default direction usually doesn't expose the
limitation.

If you really did mean "Surface", you will have to use "up to Body"; "up to
next" is not available. The region in question must be a single surface with
no undercuts, and it must overlap the projection of the extrusion -- at
least, it is sometimes problematic if the edge of the projected sketch
coincides anywhere with an edge of the surface.

This different behaviour is a function of whether the surfaces are
analytical or algorithmic. The former are simple geometric primitives, the
latter, essentially spline based, freeform shapes, cannot be extrapolated by
the software beyond the user-defined boundaries. Hence an "extrude up to
surface" will happily infer where to terminate in the first category, even
though the analytic surface in question is not big enough or is out of
position. Features extruded up to a freeform surface must however fall
within the boundaries of the terminating surface, or they will fail.

HTH

 

Andrew,

I think you must be pretty smart, or at-least, extremely tenacious and
observant. Great tip!

Sincerely,
Jerry Forcier

 

To be more specific... I said 'surface" because that is one of the
terminations available. No there are no 'surfaces' on the part. Imagine a
rectangular base sketch (with the corners filleted .5 inches) extruded to a
depth of 4 inches with .5 degree of outward draft. This is then shelled to
a thickness of .175 . A plane id created .75 inches from the inside base
(parallel to original sketch plane). On this plane are sketched the simple
keyway shape in the top corner and the bottom corner. Theses are two
different sketches BTW. The sketches are dimensioned identically from their
corresponding corners. Looking planer to the sketches you will see that
when extruded they will contact first the side of the shell cavity that is
drafted .5 degrees. As the extrusion gets closer to the termination
'surface' or 'face' the extrusion comes in contact with the fillet on the
inside of the solid. On the top sketch the 'up to next' is available while
on the lower sketch it is not. Up to surface works but there is a
difference between the two visually and the 'up to next' is preferred.

I hope this is more descriptive and will lead to a more specific answer to
this question. I will attempt to duplicate the issue if I am able to get
away from the 'real' work today. Thanks for looking into this for me

Jeff

----- Original Message -----
From: "Andrew Troup" <>
Newsgroups: comp.cad.solidworks
Sent: Thursday, February 19, 2004 9:10 PM
Subject: Re: What determines available terminations?

 

Yeah, I've tried to do that. But that is not the case here...

 

Direction of the extrusion is a common reason for "up to next" not showing
up when you think it should. If you just switch the direction, does it
show up?

It also might not show up if any of the sketch hangs off the part and would
extrude into empty space, or if there is a hole in the part where you're
trying to extrude.

matt

 

Thanks for the info but neither of your suggestions are the case. I've
found that I can use the modify sketch command to move the problem sketch
just far enough so that it overlaps another face, update, and then when I
edit the feature "up to next" is available. From this point I edit the
sketch again and place it back where it was, update and "up to next" is
still available. Maybe a bug? Anyway, I now have a work-around.

thanks,--
Jeff