We'll spend some time on this area. The concepts are straightforward. If you can drive a dimension with geometry, why not drive geometry with dimensions? Not possible before computers, different paradigm.
Why not then drive dimensions with equations?
As we'll see later, most of the obfuscation is about 2D. All 3D VDD Systems today are history based.
All simple stuff -- basic geometry. For instance, this is how to specify a line:
Method 1: 2 end points (x1, y1, z1) AND (x2, y2, z2)
Method 2: start point, angle, length; (x1, y1, z1, alpha, L)
Some systems assume constraints.
For example, if d3 were 90 deg, some don't allow a change
Some systems mark the constraints on the sketch.
Design Rules:
For bolts with shank length > 6" , thread length = 2D + 1/4"
For bolts with shank length < 6", thread length = 2D + 1/2"
For bolts with shank length
< 6", where the formula , thread length = 2D + 1/2"
,will exceed the shank length, threads extend to within 2-1/2
threads of the head.
Except for implied closures
No. G can move left and
right, need radius of D.
Suppose we decide later
to move G?
Suppose we change C so its not horizontal?
We reviewed dimensional
Now look at equational
L1=3*L4
L2=sqrt(*2)*L3+cos(angles L3/L4)
Both of the above are single
line non-conditional, also need multiline equations
L1=3: if(L4+L7)<=9;
else L1=5
L1=if(L4+L7<=9) then 3 else 5
if expression in parens is true then 3
if expression in parens is false then 5
Multi line expressions
Importing from spread sheets
Tables
Entity naming
Display appearance of names
Single or multiple line
Logical if-then-else statements
Inequalities
Concentric, parallel, tangent, etc.
How are constraints presented visually?
How to imply constraints on this shape?
What if we change?
Can the system auto build constraints?
How useful is this? Can we change them?