Better to have multiple simple features, or 1 complex feature?

Better to have multiple simple features, or 1 complex feature?

Post by SW Monke » Tue, 17 May 2005 22:44:45


Ive always wondered if its better to have multiple simple features in
model, or 1 complex feature. Example, cut extrusion. I have some
parts that have 30+ holes, and I have each set of holes as its own
feature (also named for easy viewing). 5 holes may be for sideguards,
and another 10 can be mounting points, etc. Is it better to group some
of these holes in 1 feature, or does it really make a difference?
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by Wayne Tiff » Wed, 18 May 2005 00:13:58

Performance wise, I don't know - I have never tried to test it. I do know
that simple sketches work better than complex ones, but where that point is,
I don't know.

I think what will make a bigger difference is doing it like you do. It is a
bit more organized as you can name the features accordingly, you can
suppress certain ones for different configs, and you can populate hardware
with feature patterns, rather than manually.

WT

 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by Sean-Micha » Wed, 18 May 2005 02:02:29

Hi Monkey -

Heart felt rules for myself-

- 1 sketch for everything if possible: it allows me to adjust the whole
mess from one point. I have even taken this to draw "phantoms" in one
sketch and convert them in a subsequent feature to make the feature
supressable, but to have both features controlled by a single sketch.
This, for me, is a very valuable thing - maybe not for others. I
usually also do all fillets in a sketch - perhaps bad in other
ciscumstances.

- Holes are always made by the hole wizard. My only exception to this
is when I know for sure that I only need one hole and will not ever
need two of a certain size - also on revolved parts - the center is
always part of the base revolve. Having patterns helps me when
patterning hardware in assemblies later.

- Sketch patterns when not too big, but external patterns when they get
big - supressible.

- Supressible features if showing a progression is needed for machining
or forming.

I always try for the tightest feature tree - it's a little bit of an
obsession, but a needful one for me. Most of my parts are prismatic
solids - no splines or surfaces.

For what it's worth. Do what makes the best for you - no two working
styles are the same and sometimes mixing styles is a problem.

Later,

SMA
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by <<>> » Wed, 18 May 2005 04:07:20

Avoid complex sketches. Rule of thumb: if you're struggling to make a
sketch work you should be doing it with more than one feature.

Sketches are dumb. Features are smart. Don't do a revolved cut for a
hole, use the hole feature. You'll also benefit when you go to do the
drawing, you'll get a hole callout if you use a hole feature, etc. etc.
Also, don't sketch fillets unless you have to. Seperate features can
be reordered, supressed, or easily modified, they have properties
specific to their just their feature type.

Overall you should strive to have a short well ordered model tree, but
at the same time you should not try to do everything with one or two
features.

Layout sketches are very helpful too. And if you're smart you can
reuse sketches for several features, especially by selecting contours.

On top that use folders to organize related features. Always name your
features and sketches, with descriptions if possible.

I can't say for sure in SolidWorks but in Pro/E using the approriate
feature for every aspect of your model decreases regeneration time.

As per your holes, I'd use the hole wizard and a sketch pattern for
each set. Then put them in a folder that identifies what they mount
to.

OT: why doesn't SW have derived feature patterns? In Pro/E they are
called reference patterns. I used to define a hole patern(s) in a mold
plate and then do a reference pattern in the mating plate(s). It was
great b/c all my holes were tied together and all I had to (re)design
was the mold plate.
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by modelsin3 » Wed, 18 May 2005 04:48:24


mold


I dont see why you would not be able to do this. At the Assembly level,
you could make a component/feature pattern and base it off the other
part file so that if the one changes they both do.
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by matt » Wed, 18 May 2005 08:03:56

"SW Monkey" < XXXX@XXXXX.COM > wrote in



Others have hit on some good points. I'll just add my votes for a few of
them.

- Simple sketches. Complex sketches fail easily when changed and take a
long time to regenerate.

- Sketch fillets are notorious for busting up the sketch when things
change. Plus, if you want to get rid of them it's a real pain. Use
feature fillets unless you absolutely have to use a sketch fillet.

- Definitely try to use patterns. SW has some nice ways to pattern stuff.
Don't overlook the sketch driven pattern (feature position driven by a
bunch of points). The hole wizard pattern with multiple points works just
like the sketch driven pattern. Remember that for the Hole Wiz, by default
the pattern sketch is a 3D sketch and you can pattern holes to faces other
than the first face, and the holes will all be normal to the faces they are
placed on, including on non-planar faces.

- Using the sketch "step and repeat" patterns always kills speed. I avoid
this like the plague.

- If you have a single fillet feature with 100 edges selected, it is faster
than having 100 fillet features with 1 edge selected. Of course this is
assuming that the two would give you equivalent geometry.

matt
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by Sean-Micha » Wed, 18 May 2005 13:07:48

Another thing that might be useful is the Feature Statistics, if speed
is an issue.

I played around with this a bit and it can tell you where your
"fattest" features are.

I made a simple model with Sketched Vs. Feature Fillets and found that
they took an identical amount of time. My example was simple, but it
should tell us what techniques are bad or good (performance wise).

I think that the problem that comes in is when someone really goes at
modeling in a round about way - there are many stylistic differences
and I simply say "it's not what I would have done, but it's not wrong
either" - other times you just shake your head and know that it is
wrong - no discussions. I have seen point sketches premade for hole
wizard features right on top of the pre-sketched points in a subsequent
sketch. Some seem to only start any model with a cube and whittle away
at it as if they we doing machining. I have seen people mate a hundred
screws in an assembly seemingly unaware that patterning is even an
option, not even using mate reference for screws - like it's easier to
do it the "easy way" than to force ourselves to learn anything new.

In any case, the feature statistic tool will be a fine helper if one
lets it.

Later,

SMA

(Slightly OT: I also wanted to mention that anyone who uses google to
read mail might really like their new toolbar - it spell checks when
you post or in any other web form. Take a look if you use google - its
nice)
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by John Eric » Wed, 18 May 2005 13:47:08

Unfortunately, your question may not have a simple answer since its probably
varies from case to case. Nonetheless, I will offer my observations.

Generally, I prefer to not get too complex with each feature to make future
editing more manageable, particularly if someone else is editing my
projects. On the other hand, I do leverage some of the tools in SolidWorks
to speed up design. Talking about holes, I will sometimes create several
sets of holes in a single feature - particularly if they are somehow
related. I try to avoid creating so many holes in a single feature that the
sketch gets hard to understand. For example, I would hate to edit a single
sketch that defined the position of 100 holes with X-Y coordinates.

Having said that, I have seen indications that more complex features offer
improved performance. I should state that these observations were made in
SolidWorks 2004 and I haven't repeated the following tests in 2005. Our
local users group had one evening in which everyone was invited to model the
same part using their preferred method. During the meeting, we reviewed
each model looking at construction techniques, degree of complexity, and
rebuild time. The fastest rebuild times were associated with the parts
built using the most complex sketches and features. For example, the
inclusion of sketch fillets was better than adding fillets as separate
features. This result came as a surprise to many of us in attendance. It
would be very interesting to repeat this experiment using 2005.

Is anyone interested in participating in such an experiment? This could be
done in an online version to look at performance issues and the submitted
models could be posted on a web site for download and review.

--

- John

John Eric Voltin
Mechanical Engineer
Agile Technology
512-633-0394
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by <<>> » Thu, 19 May 2005 00:01:56

As far as I can tell you cannot use a feature pattern to drive another
feature pattern.

You can use a feature pattern to drive a component pattern, but that's
it.
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by <<>> » Thu, 19 May 2005 00:06:13

I think that this would be a fun thing to do and a great way to talk
directly about modeling practices, everyone would probaly learn
something. Any suggestions on what would be a good part to model?
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by John Eric » Thu, 19 May 2005 12:16:25


In my opinion, just about any part that has a variety of features would be
interesting. I definitely would include some fillets and possibly at least
one rotational feature.

--

- John

John Eric Voltin
Mechanical Engineer
Agile Technology
512-633-0394
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by Bria » Thu, 19 May 2005 22:29:26

This reminded me of a challenge they were always having on the inventor
discussion. Go to http://www.yqcomputer.com/
There is a monthly challenge to quickly and accurately model a part. It
is mainly designed to challenge inventor users, but could also be done
by SW users. It would be a good head to head competition of Inventor vs. SW

Brian
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by John Eric » Sat, 21 May 2005 06:56:15

I went to the following web site, but its unclear how someone participates.
Can you point me to a page with contact and sign-up information?

--

- John

John Eric Voltin
Mechanical Engineer
Agile Technology
512-633-0394
 
 
 

Better to have multiple simple features, or 1 complex feature?

Post by John Eric » Sun, 22 May 2005 23:50:56

just took some time to perform some simple tests in SolidWorks 2005. I
created a rectangular block with four filleted edges so that I could create
it using sketch fillets in the extrude sketch or by adding fillets as a
separate feature. Here are the results as determined with Feature
Statistics:

Extrude the block and add fillets as a separate feature - 0.06 seconds

Extrude a filleted block with sketch fillets in the sketch - 0.03 seconds

Apparently, using a more complex sketch is more efficient (by a factor of 2)
than having a separate feature for adding fillets in this situation.

I also created a cylindrical part with fillets on the ends by rotating a
rectangular sketch and adding the fillets as a second feature.
Additionally, I created the same part using a single revolve feature that
incorporated the fillets in the sketch. Here are the results from Feature
Statistics:

Revolve a rectangular sketch and add fillets as a separate feature - 0.01
seconds

Revolve a filleted rectangular sketch - 0.03 seconds

In this case, the more complex sketch requiring a single feature has a much
longer rebuild time.

Although all of these times are very short and the difference would be
undetectable when hitting rebuild, such a difference is quite informative
and may prove to be very important when working on more complex parts.
Unfortunately, the cause of the differenes between these cases is unclear
and additional testing/research would be required to determine the most
efficient approach to modeling various parts.

If I have some more spare time, I will do some more experiments in the
future and report back to the group.

--

- John

John Eric Voltin
Mechanical Engineer
Agile Technology
512-633-0394

"John Eric Voltin" < XXXX@XXXXX.COM > wrote in message
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Better to have multiple simple features, or 1 complex feature?

Post by John Eric » Sun, 22 May 2005 23:58:12

was wondering about the inconsistent results I reported a few minutes ago,
so I went back and reviewed the Feature Statistics again. Upon reviewing
everything a second time, the 0.01 second rebuild time I reported for
revolving a rectangular sketch and adding fillets as a separate feature is
incorrect. SolidWorks is now giving me a rebuild time of 0.03 seconds. Its
possible that I mis-read the result the first time. Nonetheless, adding
fillets as a separate feature no longer improves the efficiency in my test
cases.

--

- John

John Eric Voltin
Mechanical Engineer
Agile Technology
512-633-0394

"John Eric Voltin" < XXXX@XXXXX.COM > wrote in message
news:kVHje.104564$ XXXX@XXXXX.COM ...