diff --git a/CHANGELOG.md b/CHANGELOG.md
index 66b50c65..9a237dbe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,13 +7,18 @@ CHANGELOG for FlatCAM beta
 
 =================================================
 
+21.07.2021
+
+- when using the NCCAD9 preprocessor (for Kosy machines) at GCode save the .knc extension will be automatically preselected
+- added a preprocessor for Roland MDX-540
+
 20.07.2021
 
 - in ParseDXF file fixed import of module due of changes in the latest version of ezdxf module
 - changes in Milling Plugin in the selection in the Tools Table
 - some updates of milling data structure
 - changes in handling the tool shape due of moving the parameter from the tool table in the tool parameters section
-
+a
 18.07.2021
 
 - modified the Geometry UI tools table. Replaced the comboboxes with labels.
diff --git a/appObjects/FlatCAMCNCJob.py b/appObjects/FlatCAMCNCJob.py
index ca27a7a2..2d5ab838 100644
--- a/appObjects/FlatCAMCNCJob.py
+++ b/appObjects/FlatCAMCNCJob.py
@@ -656,6 +656,8 @@ class CNCJobObject(FlatCAMObj, CNCjob):
 
         if 'Roland' in self.pp_excellon_name or 'Roland' in self.pp_geometry_name:
             _filter_ = "RML1 Files .rol (*.rol);;All Files (*.*)"
+        elif 'nccad' in self.pp_excellon_name.lower() or 'nccad' in self.pp_geometry_name.lower():
+            _filter_ = "KOSY Files .knc (*.knc);;All Files (*.*)"
         elif 'hpgl' in self.pp_geometry_name:
             _filter_ = "HPGL Files .plt (*.plt);;All Files (*.*)"
         else:
diff --git a/app_Main.py b/app_Main.py
index 300fa32c..c731d9d9 100644
--- a/app_Main.py
+++ b/app_Main.py
@@ -7780,7 +7780,7 @@ class App(QtCore.QObject):
             if len_objects == cnt:
                 # all selected objects are of type CNCJOB therefore we issue a multiple save
                 _filter_ = self.defaults['cncjob_save_filters'] + \
-                           ";;RML1 Files .rol (*.rol);;HPGL Files .plt (*.plt)"
+                           ";;RML1 Files .rol (*.rol);;HPGL Files .plt (*.plt);;KNC Files .knc (*.knc)"
 
                 dir_file_to_save = self.get_last_save_folder() + '/multi_save'
 
@@ -9116,7 +9116,7 @@ class MenuFileHandlers(QtCore.QObject):
 
         # https://bobcadsupport.com/helpdesk/index.php?/Knowledgebase/Article/View/13/5/known-g-code-file-extensions
         _filter_ = "G-Code Files (*.txt *.nc *.ncc *.tap *.gcode *.cnc *.ecs *.fnc *.dnc *.ncg *.gc *.fan *.fgc" \
-                   " *.din *.xpi *.hnc *.h *.i *.ncp *.min *.gcd *.rol *.mpr *.ply *.out *.eia *.sbp *.mpf);;" \
+                   " *.din *.xpi *.hnc *.h *.i *.ncp *.min *.gcd *.rol *.knc *.mpr *.ply *.out *.eia *.sbp *.mpf);;" \
                    "All Files (*.*)"
 
         if name is None:
diff --git a/preprocessors/NCCAD9.py b/preprocessors/NCCAD9.py
index 5177598d..8758ea87 100644
--- a/preprocessors/NCCAD9.py
+++ b/preprocessors/NCCAD9.py
@@ -104,7 +104,7 @@ class NCCAD9(PreProc):
         gcode += ';X range: ' + '{: >9s}'.format(xmin) + ' ... ' + '{: >9s}'.format(xmax) + ' ' + units + '\n'
         gcode += ';Y range: ' + '{: >9s}'.format(ymin) + ' ... ' + '{: >9s}'.format(ymax) + ' ' + units + '\n\n'
 
-        gcode += ';Spindle Speed: %s RPM)\n' % str(p['spindlespeed'])
+        gcode += ';Spindle Speed: %s RPM\n' % str(p['spindlespeed'])
 
         gcode += ('G20' if p.units.upper() == 'IN' else 'G21') + "\n"
         gcode += 'G76 ;Reference-travel to the endswitches'
diff --git a/preprocessors/Roland_MDX_540.py b/preprocessors/Roland_MDX_540.py
new file mode 100644
index 00000000..b20c35c7
--- /dev/null
+++ b/preprocessors/Roland_MDX_540.py
@@ -0,0 +1,128 @@
+# ##########################################################
+# FlatCAM: 2D Post-processing for Manufacturing            #
+# http://flatcam.org                                       #
+# File Author: Marius Adrian Stanciu (c)                   #
+# Date: 3/10/2019                                          #
+# MIT Licence                                              #
+# ##########################################################
+
+from appPreProcessor import *
+
+
+# for Roland Preprocessors it is mandatory for the preprocessor name (python file and class name, both of them must be
+# the same) to contain the following keyword, case-sensitive: 'Roland' without the quotes.
+class Roland_MDX_540(PreProc):
+
+    include_header = False
+    coordinate_format = "%.1f"
+    feedrate_format = '%.1f'
+    feedrate_rapid_format = '%.1f'
+
+    def start_code(self, p):
+        gcode = ';;^IN;' + '\n'
+        gcode += '^PA;'
+        return gcode
+
+    def startz_code(self, p):
+        return ''
+
+    def lift_code(self, p):
+        if p.units.upper() == 'IN':
+            z = p.z_move / 25.4
+        else:
+            z = p.z_move
+        gcode = self.feedrate_rapid_code(p) + '\n'
+        gcode += self.position_code(p).format(**p) + ',' + str(float(z * 100.0)) + ';'
+        return gcode
+
+    def down_code(self, p):
+        if p.units.upper() == 'IN':
+            z = p.z_cut / 25.4
+        else:
+            z = p.z_cut
+        gcode = self.feedrate_code(p) + '\n'
+        gcode += self.position_code(p).format(**p) + ',' + str(float(z * 100.0)) + ';'
+        return gcode
+
+    def toolchange_code(self, p):
+        return ''
+
+    def up_to_zero_code(self, p):
+        gcode = self.feedrate_code(p) + '\n'
+        gcode += self.position_code(p).format(**p) + ',' + 0 + ';'
+        return gcode
+
+    def position_code(self, p):
+        if p.units.upper() == 'IN':
+            x = p.x / 25.4
+            y = p.y / 25.4
+        else:
+            x = p.x
+            y = p.y
+        return ('Z' + self.coordinate_format + ',' + self.coordinate_format) % (float(x * 100.0), float(y * 100.0))
+
+    def rapid_code(self, p):
+        if p.units.upper() == 'IN':
+            z = p.z_move / 25.4
+        else:
+            z = p.z_move
+        gcode = self.feedrate_rapid_code(p) + '\n'
+        gcode += self.position_code(p).format(**p) + ',' + str(float(z * 100.0)) + ';'
+        return gcode
+
+    def linear_code(self, p):
+        if p.units.upper() == 'IN':
+            z = p.z / 25.4
+        else:
+            z = p.z
+        gcode = self.feedrate_code(p) + '\n'
+        gcode += self.position_code(p).format(**p) + ',' + str(float(z * 100.0)) + ';'
+        return gcode
+
+    def end_code(self, p):
+        if p.units.upper() == 'IN':
+            z = p.z_end / 25.4
+        else:
+            z = p.z_end
+        gcode = self.feedrate_rapid_code(p) + '\n'
+        gcode += self.position_code(p).format(**p) + ',' + str(float(z * 100.0)) + ';'
+        return gcode
+
+    def feedrate_code(self, p):
+        fr_sec = p.feedrate / 60
+
+        # valid feedrate for MDX20 is between 0.1mm/sec and 15mm/sec (6mm/min to 900mm/min)
+        if p.feedrate >= 900:
+            fr_sec = 15
+        if p.feedrate < 6:
+            fr_sec = 6
+        return 'V' + str(self.feedrate_format % fr_sec) + ';'
+
+    def z_feedrate_code(self, p):
+        fr_sec = p.z_feedrate / 60
+
+        # valid feedrate for MDX20 is between 0.1mm/sec and 15mm/sec (6mm/min to 900mm/min)
+        if p.z_feedrate >= 900:
+            fr_sec = 15
+        if p.z_feedrate < 6:
+            fr_sec = 6
+        return 'V' + str(self.feedrate_format % fr_sec) + ';'
+
+    def feedrate_rapid_code(self, p):
+        fr_sec = p.feedrate_rapid / 60
+
+        # valid feedrate for MDX20 is between 0.1mm/sec and 15mm/sec (6mm/min to 900mm/min)
+        if p.feedrate_rapid >= 900:
+            fr_sec = 15
+        if p.feedrate_rapid < 6:
+            fr_sec = 6
+        return 'V' + str(self.feedrate_format % fr_sec) + ';'
+
+    def spindle_code(self, p):
+        return '!MC1'
+
+    def dwell_code(self, p):
+        return''
+
+    def spindle_stop_code(self, p):
+        return '!MC0'