Update PurgeLinesAndUnload.py

This change adds a setting for "minimum Z height" for the "nail down the string" moves.

Update PurgeLinesAndUnload.py

Bug fix.  The prime blob code didn't account for the retraction at the end.  This adds an 'unretract' to compensate.

plugins/PostProcessingPlugin/scripts/PurgeLinesAndUnload.py

@@ -163,11 +163,21 @@ class PurgeLinesAndUnload(Script):
                 "move_to_start":
                 {
                     "label": "Circle around to layer start  ⚠️​",
-                    "description": "Depending on where the 'Layer Start X' and 'Layer Start Y' are for the print, the opening travel move can pass across the print area and leave a string there.  This option will generate an orthogonal path that moves the nozzle around the edges of the build plate and then comes in to the Start Point.  || ⚠️​ || The nozzle will drop to Z0.0 and touch the build plate at each stop in order to 'nail down the string' so it doesn't follow in a straight line.",
+                    "description": "Depending on where the 'Layer Start X' and 'Layer Start Y' are for the print, the opening travel move can pass across the print area and leave a string there.  This option will generate an orthogonal path that moves the nozzle around the edges of the build plate and then comes in to the Start Point.  || ⚠️​ || The nozzle can drop to Z0.0 and touch the build plate at each stop in order to 'nail down the string'.  The nozzle always raises after the touch-down.  It will not drag on the bed.",
                     "type": "bool",
                     "default_value": false,
                     "enabled": true
                 },
+                "move_to_start_min_z":
+                {
+                    "label": "    Minimum Z height ⚠️​",
+                    "description": "When moving to the start position, the nozzle can touch down on the build plate at each stop (Z = 0.0).  That will stick the string to the build plate at each direction change so it doesn't pull across the print area.  Some printers may not respond well to Z=0.0.  You may set a minimum Z height here (min is 0.0 and max is 0.50).  The string must stick or it defeats the purpose of moving around the periphery.",
+                    "type": "float",
+                    "default_value": 0.0,
+                    "minimum_value": 0.0,
+                    "maximum_value": 0.5,
+                    "enabled": "move_to_start"
+                },
                 "adjust_starting_e":
                 {
                     "label": "Adjust Starting E location",
@@ -254,7 +264,9 @@ class PurgeLinesAndUnload(Script):
             self.prime_blob_distance = self.getSettingValueByKey("prime_blob_distance")
         else:
             self.prime_blob_distance = 0
-
+        # Set the minimum Z to stick the string to the build plate when Move to Start is selected.
+        self.touchdown_z = self.getSettingValueByKey("move_to_start_min_z")
+        
         # Mapping settings to corresponding methods
         procedures = {
             "add_purge_lines": self._add_purge_lines,
@@ -385,7 +397,7 @@ class PurgeLinesAndUnload(Script):
         def add_move(axis: str, position: float) -> None:
             moves.append(
                 f"G0 F{self.speed_travel} {axis}{position} ; Start move\n"
-                f"G0 F600 Z0 ; Nail down the string\n"
+                f"G0 F600 Z{self.touchdown_z} ; Nail down the string\n"
                 f"G0 F600 Z2 ; Move up\n"
             )
 
@@ -494,6 +506,9 @@ class PurgeLinesAndUnload(Script):
                 # Travel to the purge start
                 purge_str += f"G0 F{self.speed_travel} X{self.machine_left + self.border_distance} Y{self.machine_front + 10} ; Move to start\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{self.machine_left + self.border_distance} Y{y_stop} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{self.machine_left + 3 + self.border_distance} Y{y_stop} ; Move over\n"
@@ -513,6 +528,9 @@ class PurgeLinesAndUnload(Script):
                 # Travel to the purge start
                 purge_str += f"G0 F{self.speed_travel} X{self.machine_right - self.border_distance} ; Move\nG0 Y{self.machine_back - 10} ; Move\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{self.machine_right - self.border_distance} Y{y_stop} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{self.machine_right - 3 - self.border_distance} Y{y_stop} ; Move over\n"
@@ -533,6 +551,9 @@ class PurgeLinesAndUnload(Script):
                 # Travel to the purge start
                 purge_str += f"G0 F{self.speed_travel} X{self.machine_left + 10} Y{self.machine_front + self.border_distance} ; Move to start\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{x_stop} Y{self.machine_front + self.border_distance} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{x_stop} Y{self.machine_front + 3 + self.border_distance} ; Move over\n"
@@ -554,6 +575,9 @@ class PurgeLinesAndUnload(Script):
                 purge_str += f"G0 F{self.speed_travel} Y{self.machine_back - self.border_distance} ; Ortho Move to back\n"
                 purge_str += f"G0 X{self.machine_right - 10} ; Ortho move to start\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{x_stop} Y{self.machine_back - self.border_distance} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{x_stop} Y{self.machine_back - 3 - self.border_distance} ; Move over\n"
@@ -575,6 +599,9 @@ class PurgeLinesAndUnload(Script):
                 # Travel to the purge start
                 purge_str += f"G0 F{self.speed_travel} X{self.machine_left + self.border_distance} Y{self.machine_front + 10} ; Move to start\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{self.machine_left + self.border_distance} Y{y_stop} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{self.machine_left + 3 + self.border_distance} Y{y_stop} ; Move over\n"
@@ -594,6 +621,9 @@ class PurgeLinesAndUnload(Script):
                 # Travel to the purge start
                 purge_str += f"G0 F{self.speed_travel} X{self.machine_right - self.border_distance} Z2 ; Move\nG0 Y{self.machine_back - 10} Z2 ; Move to start\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{self.machine_right - self.border_distance} Y{y_stop} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{self.machine_right - 3 - self.border_distance} Y{y_stop} ; Move over\n"
@@ -613,6 +643,9 @@ class PurgeLinesAndUnload(Script):
                 # Travel to the purge start
                 purge_str += f"G0 F{self.speed_travel} X{self.machine_left + 10} Z2 ; Move\nG0 Y{self.machine_front + self.border_distance} Z2 ; Move to start\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{x_stop} Y{self.machine_front + self.border_distance} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{x_stop} Y{self.machine_front + 3 + self.border_distance} ; Move over\n"
@@ -633,6 +666,9 @@ class PurgeLinesAndUnload(Script):
                 purge_str += f"G0 F{self.speed_travel} Y{self.machine_back - self.border_distance} Z2; Ortho Move to back\n"
                 purge_str += f"G0 X{self.machine_right - 10} Z2 ; Ortho Move to start\n"
                 purge_str += f"G0 F600 Z0.3 ; Move down\n"
+                if self.prime_blob_enable:
+                    purge_str += f"G1 F{self.retract_speed} E{self.retract_dist} ; Unretract\n"
+                    purge_str += "G92 E0 ; Reset extruder\n"
                 # Purge two lines
                 purge_str += f"G1 F{self.print_speed} X{x_stop} Y{self.machine_back - self.border_distance} E{purge_volume} ; First line\n"
                 purge_str += f"G0 X{x_stop} Y{self.machine_back - 3 - self.border_distance} ; Move over\n"
@@ -945,7 +981,7 @@ class PurgeLinesAndUnload(Script):
         blob_string = "G0 F1200 Z20 ; Move up\n"
         blob_string += f"G0 F{self.speed_travel} X{blob_x} Y{blob_y} ; Move to blob location\n"
         blob_string += f"G1 F{speed_blob} E{self.prime_blob_distance} ; Blob\n"
-        blob_string += f"G1 F{self.retract_speed} E-{self.retract_dist} ; Retract\n"
+        blob_string += f"G1 F{self.retract_speed} E{self.prime_blob_distance - self.retract_dist} ; Retract\n"
         blob_string += "G92 E0 ; Reset extruder\n"
         blob_string += "M300 P500 S600 ; Beep\n"
         blob_string += "G4 S2 ; Wait\n"