datum plane setup question

[2ms1]

I would like to make a datum plane that is tangent to the 3D curve shown below at one of the datum points along the curve. I don't seem to be able to figure out how to do it though. What I would like even more, is to be able to make a datum plane that is tangent to the curve in two of its dimensions and then parallel to Top as its positioning in the third dimension. However, I'll be happy if I can at least get started by accomplishing the first of these two goals.

Anyone have suggestions for either or both?

View attachment 2997

side view:
View attachment 2998


top view:
View attachment 2999

 

[jeff4136]

I'm not following, exactly, but for any point on a curve there
are two vectors, tangent and normal, that can be calculated and
from those you should be able to get where you want to go.


Axis thru Pt, Tan to Crv will get one.


Using Foundation; I believe the only way* to get the normal
vector (as geometry vs. a graphic analysis display) is using a
Variable Section Sweep. Pick the curve as Origin trajectory,
expand the References tab, go into Details then Options and Trim
at Reference using the Datum Pt as reference and OK. What you
want is for the VSS to begin at the Datum Pt. Now when you go
into Sketcher either the X or Y axis will be coincident with the
curve normal vector. Sweep a line so you have an edge to use as
a normal vector reference when done.


From there, along with a curve normal plane, you should be able
to define anything you want.


> tangent to the curve in two of its dimensions
> and then parallel to Top as its positioning
> in the third dimension"


I'm not following that at all. Parellel to Top, thru Pt may, or
may not, be tangent to the curve (or even to a projection) at that
point. I'm not sure where Top is in the pics but maybe projecting
to Front then tan to crv, parallel to Top is what you want?


[* or, I should say; only way to get a parametric normal vector.
You could, of course, use Analysis function values to create an
entitiy but don't believe there's any way to create a 'live'
link to the values without some extension module (BMX?) or other.]

 

[2ms1]

Actually, sorry, I meant normal to Top. Let see, what I'm trying to do is mate a flat surface to the datum point on curve. The flat surface needs to be normal to Top, but otherwise be tangent to the curve. Does that make sense? In other words, I want to be mating on plane that is normal to Top and tangent to the curve in the plane that runs through the datum point while being parallel to Top.

 

[jeff4136]

Ah! Ok;Axis thru Pt tangent to curve, then Plane normal to Top thru Axis. Sound good?

 

[2ms1]

yup, just got it myself from what you said earlier. Hadn't thought of making datum axis first. It still irks me that have to do those kinds of intermediary unintuitive steps. To me that is not what axis are for. To me axis are for being centerlines of things, particular about which things revolve, and having to add in elements like this clutters model and causes confusion when want to work with the axis for which purpose is all their own. I wonder why there can't simply be an option for tangent constraint. Heh, thanks though

 

[jeff4136]

Wait'll you have to create a datum plane that's normal to a curve
and contains a point not on that curve.


The frustration is familiar but you're getting too wrapped up in
trivia and making too many assumptions. Gets in the way of the
real work.


I use Groups to tidy up the Model Tree. I recommend doing so
with the reservation; if you fail a member feature and Suppress
the Group it's a panic until you ferret out the recovery steps:

RMB -> Resume -> (Resolve mode) Fix Model -> Feature ->
Confirm -> Group -> Ungroup -> Failed Feat


Hiding / Unhiding them can also be irritating if you're in the
middle of a feature operation. Using the Layer Tree helps with
that. You can Cut or Remove items from Hidden Items and I usually
have and use a "Hide" layer as well.