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Black Forest
07-28-2010, 02:47 PM
Would there be any advantage of an explicit modeling program versus a parametric modeling program?

Or in what instance would it be an advantage to have explicit vs. parametric?

MuellerNick
07-29-2010, 05:46 AM
Well, not a very educated answer:
Parametric CAD allows you to give dimensions (or better constrains) that depend on other dimensions. A simple example is "Make that part half as long as this one". This feature is getting very interesting when doing assemblies and beginning to make changes. For example parts that need to be symetrical but where you have to change one dimension to make it fit. Etc.

Explicit has to give every dimension and will be a PITA when you begin making changes.


Nick

Black Forest
07-29-2010, 06:55 AM
Thank you Nick,

I have Alibre Design which is a parametric CAD program. I notice many members here use Google's Sketch-up 7.

I always have trouble with Sketch-up to resize anything after I draw it. So I never got that deep into the learning curve.

Most of what I build I don't have everything worked out as to size in the beginning and then must make changes. Parametric seems easier for this use.

What do you use Nick?

MuellerNick
07-29-2010, 08:34 AM
What do you use Nick?


A sheet of paper and a pencil. :D

I once used Catia, but that ain't affordable for a private person. A year ago, I had a look at Alibre. But I considered it absolute crap (sorry).


Nick

Black Forest
07-29-2010, 08:45 AM
Well as you know Nick, Crap and farmers go together!!!!

RB211
07-29-2010, 12:35 PM
Parametric all the way.

Dan Dubeau
07-29-2010, 02:33 PM
Both. That's why I like Mechanical desktop. The best of both worlds. Not touted as the greatest in any area, but it works for everything I need it for, and over the years I've got pretty good, and quick at it;)

MuellerNick
07-29-2010, 03:20 PM
Well as you know Nick, Crap and farmers go together!!!!

No need to get upset! If you have worked with something unaffordable, something like Alibre looks like a toy.
What I really don't understand is Alibre's pricing. They always have special offers with at least 50% off. Are they kidding me?
What I didn't like at all was the "speed" of it. It took seconds for the cursor to change.


Nick

Black Forest
07-29-2010, 04:08 PM
I haven't found anything to be slow using Alibre.

squirrel
07-29-2010, 04:58 PM
No need to get upset! If you have worked with something unaffordable, something like Alibre looks like a toy.
What I really don't understand is Alibre's pricing. They always have special offers with at least 50% off. Are they kidding me?
What I didn't like at all was the "speed" of it. It took seconds for the cursor to change.


Nick
Alibre is a toy, it cannot even handle simple splines!! I did buy a seat then realized it was a waste. I tried to save money but in the long run it just added more cost to our CAD budget because I had to buy a seat of Solidworks 2010 that performs perfectly.

Evan
07-29-2010, 06:28 PM
SketchUp is parametric. The key to working with SketchUp is using the parameter entry window and editing the entity properties window.

If for instance you need to scale something you select and then choose the appropriate scale handle. Once you have clicked on the scale handle you ignore what is happening on the screen and enter the correct scale factor(s) as desired and press enter.

loose nut
07-31-2010, 09:28 AM
Parametric models while allowing rescaling of sizes in the drawing also allow the use of formulas to generate dimensions for parts.

These can also be linked back to a spread sheet, usually Excel, there by having a table of data points and dimension that can be used to make various versions of the same part. IE: You can have a drawing of a gear with all the necessary data in the spread sheet and by changing the reference to the appropriate row in the spread sheet it changes the size of the gear.

The down side of parametric modeler, some types at least, is that if the drawing isn't made in the correct fashion (the manner in which you place a hole in a block, IE: measuring from an edge instead of from the center) then when a change is made later, in an assembly, the constraints won't work right and the drawing is "broken". This requires time spent fixing or redrawing to make it right, In a "worst" case situation, starting over at the beginning.

This is an, by necessity, oversimplified explanation so don't throw the parametric modeler out with the bath water.