add comments and constants + fix tiprack lid pickup height.

Author: vegano1

api/src/opentrons/drivers/flex_stacker/driver.py

@@ -33,10 +33,10 @@
     StackerAxis.X: {
         "home": MoveParams(
             StackerAxis.X,
-            max_speed=10.0,
-            acceleration=100.0,
-            max_speed_discont=40,
-            current=1.5,
+            max_speed=10.0,  # mm/s
+            acceleration=100.0,  # mm/s^2
+            max_speed_discont=40,  # mm/s
+            current=1.5,  # mAmps
         ),
         "move": MoveParams(
             StackerAxis.X,

api/src/opentrons/hardware_control/modules/flex_stacker.py

@@ -55,6 +55,9 @@
 OFFSET_MD = 10.0
 OFFSET_LG = 20.0
 
+# height limit in mm of labware to use OFFSET_MD used when storing labware.
+MEDIUM_LABWARE_Z_LIMIT = 20.0
+
 
 class FlexStacker(mod_abc.AbstractModule):
     """Hardware control interface for an attached Flex-Stacker module."""
@@ -344,7 +347,7 @@ async def store_labware(self, labware_height: float) -> bool:
         await self._prepare_for_action()
 
         # Move X then Z axis
-        offset = OFFSET_MD if labware_height < 20 else OFFSET_LG * 2
+        offset = OFFSET_MD if labware_height < MEDIUM_LABWARE_Z_LIMIT else OFFSET_LG * 2
         distance = MAX_TRAVEL[StackerAxis.Z] - (labware_height / 2) - offset
         await self._move_and_home_axis(StackerAxis.X, Direction.RETRACT, OFFSET_SM)
         await self.move_axis(StackerAxis.Z, Direction.EXTENT, distance)