Will someone please explain the principle behind making a line a
"construction" line , versus a regular sketched line? What is the
actual reason for it? I see it being used as an axis for a revolve,
also I see it for the placement of text on a model.
I did read the help files on construction geometry, and I must say
that I am now more confused than before I read it. I hope it is not
just me, but it seems that the author of some of the Solidworks help
files actually takes delight in confusing the reader.
My sincere thanks to anyone who takes the time to help me on this,
Ben
A construction line will be ignored in a sketch for a feature. For example,
if you need to cut a shape out of a plate, and you want to reference
something with a dim that is tangent to an arc, or something, then you can
put in a construction line that fits the bill and it will not try to be used
as part of the outline for the cut. You use it only as a construction tool,
not a profile element.
Now, that being said, even in cases where I don't have a problem with solid
lines, I like to make them construction lines to denote that they are
reference entities, not to be used for a profile.
WT
First, you understand that for feature creation (extrusions, cuts,
revolves, lofts,..), using sketches (closed or open profiles), have to
be solid (not hidden lines) and construction lines (hidden) can not
define a profile. (and yes, a centerline or construction line also
does define a rotation center)
Think of construction lines (dashed) as reference entities within your
normal sketch (solid),.. lines, arcs, curves,.. which serve to
reference construction intent and drive your sketch entities (solid).
In your sketch, you can always toggle from hidden to solid and back
again.
The most common or simplest example of a construction line is used
with polygon sketches, such as a closed rectangle sketch, where you
apply a diagonal construction line to quickly define the center of the
rectangle, (via the mid point of the construction line) or using a
construction circle to help define the center of a hexagon.
Use construction lines to help construct of your open/close profile
sketches,...
such as,, you may want to only create a layout sketch, 2D or 3D, which
could define your profile intent or open/closed profile boundaries...
so, you may have construction entities within your layout sketch to
help with defining your open/closed boundaries.
..
One thing I like about using centerlines in solids is when doing lathe or
cylindrical work. When you dimension from a "centerline" it dimensions the
diameter. Seems to keep sketches cleaner and makes you think in ral life,
not radius numbers.
Hi Cliff,
What sounds like "Ref"
Construction lines are what they are "Constructions Lines". In
Autocadand, Pathtrace as well as Mastercam ( I think) dont want to
bother open it.
Where do use "Ref" ?
Daveb
I often find on complex profiles, that it is difficult to make a fully
defined sketch without extra construction lines beyond just
"centerlines" on the main axes.
It is very often I use a construction line between two ends of solid
profile lines to define a Mid Point between the two line ends such
that I can mirror items in a sketch or dimension to the center of a
"rib" for instance.
Lots of good uses for construction lines exist.
Bo
Ben,
In addition to all of the other reasons, construction lines can be used to
mirror sketch items about.
They can also be used to keep track of design intent. You can put
construction geometry in a sketch, then use convert edges in later sketches
to make "real" geometry.
Jerry Steiger
Tripod Data Systems
"take the garbage out, dear"
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