Pulses per Microliter

This is to explain the various gearing on our different heads.

Calculating Pulses/µL for the 27:1 EMO and VOL

The EMO and VOL heads each have:

• A 1.8° stepping motor;
  • Running in 1/16th microstep mode;
• A 27:1 planetary gear;
• A 1:1 drive screw coupling;
• A drive screw with a pitch of 18 threads per inch, or 1.411 thread per mm;
• And a reservoir with a 17 mm diameter, or 227 mm² cross section.

The table below explains how a certain number of pulses (or microsteps) on the motor will generate a certain volume displacement in the reservoir - the pulses/µL (or pulses/mm³) number that we need to control the material flow.

Flow Calculations for the 27:1 EMO and VOL Heads

Component	Motor	Gearing	Coupling	Drive Screw	Reservoir
Image
Details	This is a 1.8° stepping motor, so 200 full steps = 1 revolution. 1 pulse is a 1/16th microstep, so 3200 pulses = 1 motor rev.	27:1 planetary gear, so 27 motor revs = 1 output rev.	1:1 direct coupling, so no change is introduced.	The drive screw has a pitch of 18 threads per inch, or 1.411 mm linear travel per revolution.	The reservoir has a diameter of 17 mm, so the cross sectional area is 227 mm2. Therefore, each revolution of the drive screw displaces 1.411 x 227 or 317.8 mm3 (or 317.8 µL) of volume.
1 Rev Calc.	86,400 pulses = 27 motor revs...	= 1 output rev...	= 1 screw rev...	= 1.411 mm linear advance...	= 317.8 µL displacement.
And so:	86,400 pulses = 317.8 µL, or 271.9 pulses/µL