PA calibration: lower test flow for TPU/TPE

_PA_CFG.material_max_volumetric lowers MAX_VOLUMETRIC for materials that
cannot extrude 25 mm3/s (tpu, tpe, flex: 8). The calibration line shows
the flow used.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

macros/pressure_advance/bd_pa_spoolman.cfg

@@ -191,6 +191,10 @@ variable_fallback_nozzle_temp: 260
 # bd_pressure PA_CALIBRATE parameters -- tune to your printer/filament.
 # See https://pandapi3d.cn/bdpressure/home for guidance on these values.
 variable_max_volumetric: 25
+# Lower test flow (mm3/s) for materials that cannot extrude max_volumetric:
+# soft TPU buckles or slips in the extruder at 25. A key contained in the
+# lane's material (any case) applies; with several matches the lowest wins.
+variable_material_max_volumetric: {"tpu": 8, "tpe": 8, "flex": 8}
 variable_acc_wall: 5000
 variable_travel_speed: 300
 variable_acc_to_decel_factor: 50
@@ -452,8 +456,15 @@ gcode:
             {% set lane_temp = lane_obj.extruder_temp|default(0, true)|float %}
             {% set target = printer.extruder.target|default(0)|float %}
             {% set nozzle_temp = lane_temp if lane_temp > 0 else (target if target > 0 else cfg.fallback_nozzle_temp|float) %}
+            {% set material = lane_obj.material|default("", true)|string|lower %}
+            {% set vol = namespace(max=cfg.max_volumetric|float) %}
+            {% for key, flow in cfg.material_max_volumetric.items() %}
+                {% if key in material and flow|float < vol.max %}
+                    {% set vol.max = flow|float %}
+                {% endif %}
+            {% endfor %}
 
-            {action_respond_info("Calibrating PA for %s (spool %d) at %.0fC..." % (lane, spool_id, nozzle_temp))}
+            {action_respond_info("Calibrating PA for %s (spool %d) at %.0fC, %g mm3/s..." % (lane, spool_id, nozzle_temp, vol.max))}
             M117 Calibrating PA: {lane}
 
             G1 Z50 F3000
@@ -462,7 +473,7 @@ gcode:
             G4 P400
             G1 Z0 F3000
             G4 P400
-            PA_CALIBRATE NOZZLE_TEMP={nozzle_temp} MAX_VOLUMETRIC={cfg.max_volumetric} ACC_WALL={cfg.acc_wall} TRAVEL_SPEED={cfg.travel_speed} ACC_TO_DECEL_FACTOR={cfg.acc_to_decel_factor}
+            PA_CALIBRATE NOZZLE_TEMP={nozzle_temp} MAX_VOLUMETRIC={vol.max} ACC_WALL={cfg.acc_wall} TRAVEL_SPEED={cfg.travel_speed} ACC_TO_DECEL_FACTOR={cfg.acc_to_decel_factor}
 
             # IMPORTANT: we do NOT read printer.extruder.pressure_advance
             # here. Klipper fully evaluates a macro's Jinja2 template