Use Equations and Parameters
You can use equations wherever you can enter a numeric value. For example, you can write equations in the Edit Dimensions dialog box, feature dialog boxes, and the Parameters dialog box. Equations can vary in complexity, and you can use them to calculate feature sizes, calculate assembly constraints offsets or angles, or simulate motion among several components.
Equations can be simple or contain many algebraic operators, prefixes, and functions. For example, here is a simple equation:
2 ul *(6+3)
The following complex equation uses internal parameters such as pi:
(PI rad/5 ul +(25 deg *PI rad)/180 deg))
Algebraic operators
The following table lists the algebraic operators supported by Autodesk Inventor.
Operator | Meaning |
+ | addition |
- | subtraction |
% | floating point modulo |
* | multiplication |
/ | division |
^ | power |
( | expression delimiter |
) | expression delimiter |
; | delimiter for multi-argument functions |
Unit prefixes
The following table lists the unit prefixes supported by Autodesk Inventor.
Prefix | Symbol | Value |
exa | E | 1.0e18 |
peta | P | 1.0e15 |
tera | T | 1.0e12 |
giga | G | 1.0e9 |
mega | M | 1.0e6 |
kilo | k | 1.0e3 |
hecto | h | 1.0e2 |
deca | da | 1.0e1 |
deci | d | 1.0e-1 |
centi | c | 1.0e-2 |
milli | m | 1.0e-3 |
micro | micro | 1.0-6 |
nano | n | 1.0-9 |
Pi co | p | 1.0e-12 |
femto | f | 1.0-15 |
atto | a | 1.0e-18 |
When you use unit prefixes in an equation, enter the prefix symbol. Do not enter the prefix itself. For example, an equation that includes the unit "nanometer" might look like this equation: 3.5 ul * 2.6 nm.
When you add the unit prefix for name to the meter unit, your equation is calculated based on the length of 2.6 nanometers.
Functions
The following table lists the supported functions.
Syntax | Returns Unit Type | Expected Unit Type |
cos(expr) | unitless | angle |
sin(expr) | unitless | angle |
tan(expr) | unitless | angle |
acos(expr) | angle | unitless |
asin(expr) | angle | unitless |
atan(expr) | angle | unitless |
cosh(expr) | unitless | angle |
tanh(expr) | unitless | angle |
acosh(expr) | angle | unitless |
asinh(expr) | angle | unitless |
sqrt(expr) | unit^1/2 | any |
sign(expr) | unitless | any (Return 0 if negative, 1 if positive.) |
exp(expr) | unitless | any (Return exponential power of expression: for example, return 2 for 100, 3 for 1000, and so on.) |
floor(expr) | unitless | unitless (Next lowest whole number.) |
ceil(expr) | unitless | unitless (Next highest whole number.) |
round(expr) | unitless | unitless (Closest whole number.) |
abs(expr) | any | any |
max(expr1;expr2) | any | any |
min(expr1;expr2) | any | any |
ln(expr) | unitless | unitless |
log(expr) | unitless | unitless |
pow(expr1;expr2) | unit^expr2 | any and unitless, respectively |
random(expr) | unitless | unitless |
isolate(expr;unit;unit) | any | any |
Reserved system parameters
The following table lists the reserved system parameters supported by Autodesk Inventor.
Parameter | Value |
PI | 3.14159265358979323846264338328 |
E | 2.71828182845904523536 |
Unit types
The unit type that you use with an equation depends on the type of data that you are evaluating. For example, to evaluate a linear or angular value, you typically use a unit type of millimeters, inches, or degrees (mm, in, or deg).
Some equations must return a unitless value, for example, an equation to solve the number of occurrences in a pattern. You designate a unitless value with the characters ul. For example, 5 ul means that the equation has been evaluated and returned the number 5, as in the number of occurrences in a pattern.
isolate(Width;mm;ul)
The number of Occurrences value in a dialog box requires a unitless (ul) result, but you are referencing the unit width, which is a linear value. Convert the Width parameter to a unitless value.