Mechanical Desktop

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*Pinks, Kevin
Message 1 of 6 (17 Views)

Constraining question!

17 Views, 5 Replies
04-08-2000 08:20 AM
I have read 2 different books now on the subject of constraining a
sketch.....one book says to always apply dimensional constraints to the
largest geometry first then the smaller geometry. The other book states
that smaller dimensions should be constrained first. Which is correct or
does it depend on other factors. Please help
Kev
*Wehner, Kevin
Message 2 of 6 (17 Views)

Re: Constraining question!

04-08-2000 08:20 AM in reply to: *Pinks, Kevin
I don't see how applying dimension based on the value of the dimension would
matter.
There are things that I do that seem to make a difference though. The most
significant seems to be using as many 2d constraints as possible. When I
first started using MDT, I would use a zero dimension if two lines were
collinear. Using construction geometry really helps eliminate dimensions.
After I have all the possible 2d constraints, I add the most significant
dimensions, the dimension until the sketch is fully constrained.
I do a lot of table driven parts for our parts library (cylinders, bearings,
etc.). Table driven parts need to have good sketches or you'll end up with
all sorts of odd deformities. This method has worked well with them....or I
could just be clueless and lucky.

--
=========================
Kevin Wehner
Electric Device Corporation
Mechanical Engineer
kevin.wehner@electricdevice.com
Phone: 330.533.1111 ext. 317
Fax: 330.533.2639
=========================
"Kevin Pinks" wrote in message
news:eefdc64.-1@WebX.SaUCah8kaAW...
> I have read 2 different books now on the subject of constraining a
> sketch.....one book says to always apply dimensional constraints to the
> largest geometry first then the smaller geometry. The other book states
> that smaller dimensions should be constrained first. Which is correct or
> does it depend on other factors. Please help
> Kev
>
*Keller, Kent
Message 3 of 6 (17 Views)

Re: Constraining question!

04-08-2000 10:24 AM in reply to: *Pinks, Kevin
Kevin

If you draw pretty close to actual size before profiling you will
almost never run into any problems. I agree with Kevin Wehner,
which ones first isn't a big deal as long as it doesn't deform the
sketch out of a usable shape.

Say you drew the sketch a lot bigger than what it is going to end
up like, and it looks like a U with a couple of stairs across the
top. If you dimension the width of the bottom a lot smaller than
what it currently is one of the stair sections is likely to fold
over on itself, leaving you with a mess.

__
__| |
| |
|____| something like that could end up looking like this if
you dim the bottom width first
__
__ |_ |
|__ |

Sure wish we could still do small pictures :smileysad:

--
Kent Keller
Check out the Mechanical Desktop FAQ @
http://webhome.idirect.com/~dfulford/

"Kevin Pinks" wrote in message
news:eefdc64.-1@WebX.SaUCah8kaAW...
> I have read 2 different books now on the subject of constraining
a
> sketch.....one book says to always apply dimensional constraints
to the
> largest geometry first then the smaller geometry. The other
book states
> that smaller dimensions should be constrained first. Which is
correct or
> does it depend on other factors. Please help
> Kev
>
*Fulford, Drew
Message 4 of 6 (17 Views)

Re: Constraining question!

04-08-2000 02:44 PM in reply to: *Pinks, Kevin
Kevin,

Rather than read books, just draw various sketches of no importance.
Constrain them and understand how they behave.

There is no set of rules and the way you constrain is really your
choice. In fact you need not constrain at all. the practise will teach
more than any book can. Just go to it and fiddle.

- Drew

On Sat, 8 Apr 2000 15:20:03 +0000, "Kevin Pinks"
wrote:

>I have read 2 different books now on the subject of constraining a
>sketch.....one book says to always apply dimensional constraints to the
>largest geometry first then the smaller geometry. The other book states
>that smaller dimensions should be constrained first. Which is correct or
>does it depend on other factors. Please help
>Kev
>

Drew Fulford, B.A.Sc. Systems Engineer
Solid Caddgroup Inc, Burlington, Ontario
Phone: (905) 331-9670 Fax: (905) 331-7280
Check out my MDT FAQ @ http://webhome.idirect.com/~dfulford/
*Jeffrey, Dennis
Message 5 of 6 (17 Views)

Re: Constraining question!

04-08-2000 04:53 PM in reply to: *Pinks, Kevin
If the created geometry is overly large then you should apply dimensions
from the smallest first in order to prevent the sketch from flipping
over onto itself. Otherwise, I would agree with the others here...

Remember, if you screw up and implode your sketch, there's always undo!

Dennis

Kevin Pinks wrote:
>
> I have read 2 different books now on the subject of constraining a
> sketch.....one book says to always apply dimensional constraints to the
> largest geometry first then the smaller geometry. The other book states
> that smaller dimensions should be constrained first. Which is correct or
> does it depend on other factors. Please help
> Kev

--
************************************************************
Dennis Jeffrey, Pres. Tekni Group, Inc. (219) 478-4014
Autodesk System Center and Trainer (Indiana)
Author, "Creative Design With Mechanical Desktop"
Fax: (219) 478-4118 - http://www.teknigroup.com
************************************************************
*Novara, Rick
Message 6 of 6 (17 Views)

Re: Constraining question!

04-09-2000 05:05 PM in reply to: *Pinks, Kevin
I think this applies if you draw very rough sketches.......... when you are
way off the large dims will get you........

--
Later,

-- Rick Novara --

"Kevin Pinks" wrote in message
news:eefdc64.-1@WebX.SaUCah8kaAW...
| I have read 2 different books now on the subject of constraining a
| sketch.....one book says to always apply dimensional constraints to the
| largest geometry first then the smaller geometry. The other book states
| that smaller dimensions should be constrained first. Which is correct or
| does it depend on other factors. Please help
| Kev
|
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