Pulses per Microliter

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

EMO and VOL

The EMO and VOL heads both have a 27:1 gear ratio.

360 degrees equals one revolution of the motor.

Each full step is 1.8 degrees, so 200 full steps per revolution of the extrusion motor.

With 1/16th microstepping, that means 3200 microsteps per revolution of the extrusion motor.

One revolution of the extrusion motor equals one revolution of the drive screw (direct connection).

The drive screw has a pitch of 18 threads per inch, or 1.411 mm per revolution.

So...

3200 pulses times 27 equals 86,400 pulses (or microsteps) on the motor will deliver one revolution of the drive shaft, which moves the plunger in 1.4 mm in the cylinder.

The cylinder has a diameter of 17 mm, so the cross sectional area is 227 mm^2.

One revolution then displaces 1.4 mm of 227 mm^2 cross section, or 317.8 mm^3, or 317.8 µL.

Therefore, 86,400 pulses = 317.8 µL, or ~ 272 pulese/µL.

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.
1 Pulse Calc.	1 Pulse = 1/3200 motor rev...	= 1/86,400 output revs...	= 1/86,400 screw revs...	= 1.411/86,400 or 0.0000163 linear mm...	= 0.0000169*317.8 or 0.005 mm3 or µL
1 µL Calc.