Glossary

Here are key terms and dimensions used in the FireStep wiki:

Term	Definition
arm	refers to one of the two arms for a delta machine axis: pulley arm or effector arm. Most commonly refers to the pulley arm.
arm angle	refers to the pulley arm angle in degrees from the base plane down to the ball stud axis
arms level	refers to the arms in the 0-degree position with arm "elbows" in the base plane
ball stud axis	the rotational axis common to a pair of ball studs
base plane	refers to the horizontal plane defined by the three pulley axes
bed plane	refers to horizontal Z-plane of the FPD work surface
bx	bed plane X scale
by	bed plane Y scale
bz	bed plane Z offset
delta dimension	refers to any of: f, e, rf, re, gear ratio, home angle, latch backoff
effector plane	refers to the horizontal plane defined by the effector ball stud axes
effector	refers to the triangular head attached to the bottom of the effector arms
effector arm	refers to the lower arm attached to the end effector
e	side length of base plane equilateral triangle whose vertices touch the pulley arm axes
f	side length of effector plane equilateral triangle whose vertices touch the effector ball stud axes
gear ratio	is the ratio of the pulley arm pitch length circumference to the stepper gear pitch length circumference.
home angle	the negative angle above the base plane at which arm motion stops at the limit switch
latch backoff	is the microstep distance to "back off" after tripping the optical limit switch. Latch backoff is used to comopensate for individual differences in arm home angle and is used to equalize the three arm home angles.
microsteps	pulses per stepper step (typically power of 2)
pulley	refers to the sliced drive pulley driven by the GT2 belt
pulley arm	refers to the upper arm attached to the drive pulley
pulley arm axis	refers to the pulley arm rotation axis, which is always in the base plane
re	effector arm length in mm between top and bottom ball stud axes
rf	pulley arm length in mm between ball stud axis and pulley arm axis
steps360	stepper steps per revolution
Z-plane	a horizontal plane parallel to the base plane or the bed plane (note that the base/bed planes are ideally parallel but almost never parallel in reality)
SPE Angle	Sliced-Pulley-Error critical angle
SPE Ratio	Sliced-Pulley-Error compensation