BLU

BASIC LENGTH UNIT

LEADSCREWS

Leadscrew

Pitch

NutConverting the rotational motion of the motors to a linear motion.

pitch (p): the distance between adjacent screw threads The number of teeth per inch (n):

n = 1 / pBLU: Basic Length Unit (machine resolution)

BLU = p / N

ExampleA machine has 1 BLU = 0.001".To move the table 5"

on X axis at a speed (feed rate) of 6 ipm. Calculate pulse rate and pulse count.

• pulse rate = speed/BLU = 6 /0.001

• = 6,000 pulse/min

• pulse count = distance/BLU

= 5/0.001 = 5,000 pulses

Open Loop vs. Closed Loop controls

Advantages of CNC

- Easier to program;- Easy storage of existing programs;- Easy to change a program- Avoids human errors- NC machines are safer to operate- Complex geometry is produced as cheaply as simple ones- Usually generates closer tolerances than manual machines