Warning Construction Geometry Isn't
Warning Construction Geometry Isn't
(OP)
Just a note so others don't have the same problem I ran into yesterday.
After getting far into a complex cabinet assy I found that the 19" rack mount section was the wrong size.
Traced it down to some reference lines. Turns out that all CONSTRUCTION GEOMETRY is in centerline format (not changeable as far as I could find). So, when I dimensioned other lines from the construction lines it introduced a midpoint relationship so that when I typed in 1.75" spacing, it actually spaced the new lines at .875".
Big cabinet, and until I zoomed in later I couldn't tell that the dimension was not between the 2 lines as I thought, but between the line and a point in space 1/2 way beyond the construction line.
This was for the 2nd of many features added to the cabinet. By the time I moved all the child features to where they should have been in the first place I ended up with a model with 12 solid bodies instead of 1.
Anyway, just a friendly warning. Construction Geometry isn't really just "reference geometry" like with most software. It's a centerline, and there may be hidden relationships (ie diameter dimensioning) that you're not aware of and are undesirable, so be careful.
After getting far into a complex cabinet assy I found that the 19" rack mount section was the wrong size.
Traced it down to some reference lines. Turns out that all CONSTRUCTION GEOMETRY is in centerline format (not changeable as far as I could find). So, when I dimensioned other lines from the construction lines it introduced a midpoint relationship so that when I typed in 1.75" spacing, it actually spaced the new lines at .875".
Big cabinet, and until I zoomed in later I couldn't tell that the dimension was not between the 2 lines as I thought, but between the line and a point in space 1/2 way beyond the construction line.
This was for the 2nd of many features added to the cabinet. By the time I moved all the child features to where they should have been in the first place I ended up with a model with 12 solid bodies instead of 1.
Anyway, just a friendly warning. Construction Geometry isn't really just "reference geometry" like with most software. It's a centerline, and there may be hidden relationships (ie diameter dimensioning) that you're not aware of and are undesirable, so be careful.






RE: Warning Construction Geometry Isn't
Best Regards,
Heckler
Sr. Mechanical Engineer
SW2005 SP 4.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NIVIDA Quadro FX 1400
o
_`\(,_
(_)/ (_)
"There is no trouble so great or grave that cannot be much diminished by a nice cup of tea" Bernard-Paul Heroux
RE: Warning Construction Geometry Isn't
I also deliberately use the construction geometry as a centerline for dimensions. It's strange to dimension a radius of something with a diameter of 0.375"--especially when you create this as a revolve where all the geometry is to one side of a centerline. So this action as a centerline is useful unless you're not expecting its effect.
Jeff Mowry
www.industrialdesignhaus.com
Reality is no respecter of good intentions.
RE: Warning Construction Geometry Isn't
1) Clicking between the two lines will give a direct distance between them.
2) Clicking on the side of the construction line away from the solid line, will create a "doubled" dimension. This is suitable when using the sketch to create a revolved feature. When the dimension is inserted into a drawing view, it comes in as a diameter.
Making the best use of this Forum. FAQ559-716
How to get answers to your SW questions. FAQ559-1091
Helpful SW websites every user should be aware of. FAQ559-520
RE: Warning Construction Geometry Isn't
Flores
RE: Warning Construction Geometry Isn't
There is an icon that allows you to change a Construction line to sketch line and back. Look under your Sketch tools toolbar, for the icon. I would post image, but I don't have access anymore.
This is also in the help listed as Construction geometry. "When in doubt use the help"
Anytime you are in a sketch or you make other sketches after another one and you use points, lines, Construction geometry (centerlines) etc... then you will have child relationships and you need to be aware that this happens.
Most users I believe understand this concept.
Regards,
Scott Baugh, CSWP
www.scottjbaugh.com
FAQ731-376
RE: Warning Construction Geometry Isn't
I'd find it more useful to be able to create ACTUAL construction lines. If I WANT a centerline, I'll draw a centerline.
I WANTED 'construction geometry'. You know lines that showed me where the edges of the cabinet were even when the solid bodies were hidden, but didn't do ANYTHING else. Reference Geometry (not centerlines). I'll NEVER want a diameter relationship when drawing a rectangular box, or on reference lines I use to show where interior components or mounting surfaces are.
What I got was interactive geometry that DID do something else, and WASN'T 'construction geometry', regaurdless of what it's called.
Since this isn't documented in the help section, I'd call it a bug. (Sorry old joke: What's the difference between a feature and a bug? A feature is documented).
RE: Warning Construction Geometry Isn't
A layout sketch is only used to create converted entities in other sketches ... never directly with a feature.
This way you will place a centreline (albeit still a construction line) only where & when you want, for use with a feature. A construction line in a layout sketch does not allow its use as a centreline in another sketch.
Making the best use of this Forum. FAQ559-716
How to get answers to your SW questions. FAQ559-1091
Helpful SW websites every user should be aware of. FAQ559-520
RE: Warning Construction Geometry Isn't
You can draw solid lines, or you can draw centerlines. You can convert them back and forth with the touch of A button, but you CANNOT draw construction lines, so be CAREFUL.
I hope this tip saves someone else from messing their models up.
RE: Warning Construction Geometry Isn't
Chris
Sr. Mechanical Designer, CAD
SolidWorks 05 SP3.1 / PDMWorks 05
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Warning Construction Geometry Isn't
The centerline is construction geometry unless you otherwise use it as a centerline. This cuts down on feature and toolbar clutter simply by knowing under which conditions a given line is construction geometry (completely benign) or a centerline (acting as an axis for a dimension, sketch, or feature). Perhaps we could request an enhancement that would automatically denote when construction geometry is being used as a centerline--different dash pattern, color, whatever.
Jeff Mowry
www.industrialdesignhaus.com
Reality is no respecter of good intentions.
RE: Warning Construction Geometry Isn't
Fill what's empty. Empty what's full. And scratch where it itches.
RE: Warning Construction Geometry Isn't
Flores
RE: Warning Construction Geometry Isn't
Jeff Mowry
www.industrialdesignhaus.com
Reality is no respecter of good intentions.
RE: Warning Construction Geometry Isn't
ongybill,
It seems that what you want would be called a layout sketch. Create a sketch of what you want to see, and close it without using it to create a feature.
Move to the top of the tree and you will see it ALL the time until you choose to hide it.
Remember...
"If you don't use your head,
your going to have to use your feet."
RE: Warning Construction Geometry Isn't
Actually, now that I know to be careful with the pretend construction lines I shouldn't have any more problems. If I ever reference from one again I'll make VERY sure it dimensions properlly.
I have found that it's very useful to use construction lines to show where something inside a complex assy or part is. Particularly if I'm going to hide the solids while sketching.
While in sketch mode rotate around so you can see the location of an interior mounting surface for example. Select it and convert the edges, then change them to construction lines. When you convert the edges SW puts lines on the plane you're sketching on that are aligned with the interior surface/feature/part. Now if you hide things you still know where they are. Very useful feature.
Just something I find useful, perhaps some other newbies will as well.