8 Basic CNC Programming
8.4 NC Codes
119
Calculating L
If you know the chord length you would like used when approximating an arc or circle, calculate the
angle L as follows:
Calculation: Calculating the Value of L
Calculation
Where:
𝐿 =
360 ∙ 𝑐
2𝜋 ∙ 𝑅
c is the desired chord length.
R is the arc or circle radius.
Example
To calculate the L value for a chord length of 0.001" and a radius of 0.5", you would write the
equation as:
𝐿 =
360 ∙ 𝑐
2𝜋 ∙ 𝑅
=
360 ∙ (.001)
2𝜋 ∙ .5
= 0.1146°
Negative L Values
A negative value for L will generate a normalized L factor, calculated as:
Angle {degrees} = L / Radius { inches}
For example, with the default L factor of -1:
Calculation: Calculating the Angle of Arc when Using Normalized L of -1
Radius
L Value
Calculation
Result
0.5 inch
-1
Angle = L/0.5 = 1/1
The arc will have line segments approximating every 2 degree of
the arc.
1 inch
-1
Angle = L/R = 1/1
The arc will have line segments approximating every 1 degree of
the arc.
2 inches
-1
Angle = L/2 = 1/2
The arc will have line segments approximating every 0.5 degrees of
the arc.
