Using Equations  Part 2
In our September Tip of the Month we began a discussion
about using equations in relations. As promised, we have the answers to the questions,
as well as a continuation of our discussion on using equations.
First, answers to September questions:
1. 
The cross members in the September
Figure 2 are a pattern, and the design intent is to define these as
being central along the main beams. Can you write the equations for
this? 

/* MAKE CROSS MEMBERS EQUAL DISTANT FROM ENDS OF I BEAM
D8:1=(D4:02*D7:1)/(P0:11) 
2. 
For the same cross members in the September
Figure 2, the length of the protrusion must be controlled by the distance
between the main beams. Can you write the equation? 

/* MAKE LENGTH FIT DISTANCE BETWEEN BEAMS
CROSS_MEMBER_LENGTH:8=D6:1I_WEB_THICKNESS:0 
3. 
When relations are used
in an assembly for component features, where are the relations stored? 

This was perhaps a trick question  because you can define it.
Select RELATIONS in the ASSEMBLY menu, then in the MODEL
REL menu just above he RELATIONS menu, you have the choices
for where the relations are stored. If you choose ASSEM REL,
the relations are stored with the Assembly; if you choose PART REL,
the relations are stored with the part.
TIP: It is usually a good
idea to store the relations with the model which contains the controlled
dimensions  in this case, with the part having the clearance holes.
Why? When you modify these dimensions later, it will tell you they are
controlled by a relation, and the relation will be right there to look
at. Also, if the part is used without the assembly in session, the
dimension will still know it is controlled by a relation. 
4. 
Were you successful with the UDF
exercise? If not, keep trying, and Good luck. 
Sketcher Relations:
Sketcher relations are handled much the same as Part or Assembly relations,
except that the focus is within the section. For instance, the relation
sd1=sd0*3/2 will make the one side
of the rectangle in Figure AA 50% longer than the other.

Figure AA
Can sketcher relations reference dimensions that are not within the sketch?
Yes. The relation sd1=d52
is valid, though I would use caution in making relations this way because
it can be hard to troubleshoot problems where they are mixed. It
might be better to put this one in the regular part relations.
Now we come to the really fun and powerful part of using sketcher relations
 that of using them to control VARIABLE SECTION SWEEPS. See
our June 1999 Tip of the Month for a great
example of using section relation equations to drive a sweep. (Also
see November 1998 Tip of the Month for more
general information on Variable Section Sweeps.)
Because Variable Section Sweeps evaluate the section all along the trajectory,
we get the unique opportunity to allow Pro/E to change the section as it
moves along. We can do that in several ways including, of course,
equations.
These equations, if selected correctly, can build shapes that would
be difficult or impossible without. Figures B1 & B2 are a good
example.
Figure B1 shows the sweep without the equation, Figure B2 shows the
sweep after the equation is added. What equation will set tangency
at both ends?
. . .
Think about the functions that are available.
. . .
Here is the equation used:
/* CONTROL BAGEL SHAPE WITH RELATION EQUATION
sd4=20+4*sin(360*trajpar)
/* WHERE sd4 IS THE DIAMETER OF THE SECTION
TIP: A little thought before hand
can produce beautiful and complex shapes quite simply.
Good Luck with all your equations.
See you Next Month.
