diff --git a/FlatCAMApp.py b/FlatCAMApp.py
index 06ffbc72..3574dcfa 100644
--- a/FlatCAMApp.py
+++ b/FlatCAMApp.py
@@ -1002,6 +1002,10 @@ class App(QtCore.QObject):
             # Align Objects Tool
             "tools_align_objects_align_type": 'sp',
 
+            # Invert Gerber Tool
+            "tools_invert_margin": 0.1,
+            "tools_invert_join_style": 's',
+
             # Utilities
             # file associations
             "fa_excellon": 'drd, drl, exc, ncd, tap, xln',
@@ -1666,6 +1670,10 @@ class App(QtCore.QObject):
             "tools_punch_rectangular": self.ui.tools2_defaults_form.tools2_punch_group.rectangular_cb,
             "tools_punch_others": self.ui.tools2_defaults_form.tools2_punch_group.other_cb,
 
+            # Invert Gerber Tool
+            "tools_invert_margin": self.ui.tools2_defaults_form.tools2_invert_group.margin_entry,
+            "tools_invert_join_style": self.ui.tools2_defaults_form.tools2_invert_group.join_radio,
+
             # Utilities
             # File associations
             "fa_excellon": self.ui.util_defaults_form.fa_excellon_group.exc_list_text,
diff --git a/README.md b/README.md
index 6ef6dff6..374c683c 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@ CAD program, and create G-Code for Isolation routing.
 
 - adjusted the UI for Excellon and Geometry objects
 - added a new FlatCAM Tool: Gerber Invert Tool. It will invert the copper features in a Gerber file: where is copper there will be empty and where is empty it will be copper
+- added the Preferences entries for the Gerber Invert Tool
 
 13.02.2020
 
diff --git a/flatcamGUI/PreferencesUI.py b/flatcamGUI/PreferencesUI.py
index eeeb413a..df1c0021 100644
--- a/flatcamGUI/PreferencesUI.py
+++ b/flatcamGUI/PreferencesUI.py
@@ -252,6 +252,9 @@ class Tools2PreferencesUI(QtWidgets.QWidget):
         self.tools2_punch_group = Tools2PunchGerberPrefGroupUI(decimals=self.decimals)
         self.tools2_punch_group.setMinimumWidth(220)
 
+        self.tools2_invert_group = Tools2InvertPrefGroupUI(decimals=self.decimals)
+        self.tools2_invert_group.setMinimumWidth(220)
+
         self.vlay = QtWidgets.QVBoxLayout()
         self.vlay.addWidget(self.tools2_checkrules_group)
         self.vlay.addWidget(self.tools2_optimal_group)
@@ -269,6 +272,7 @@ class Tools2PreferencesUI(QtWidgets.QWidget):
 
         self.vlay4 = QtWidgets.QVBoxLayout()
         self.vlay4.addWidget(self.tools2_punch_group)
+        self.vlay4.addWidget(self.tools2_invert_group)
 
         self.layout.addLayout(self.vlay)
         self.layout.addLayout(self.vlay1)
@@ -8239,6 +8243,62 @@ class Tools2PunchGerberPrefGroupUI(OptionsGroupUI):
         self.layout.addStretch()
 
 
+class Tools2InvertPrefGroupUI(OptionsGroupUI):
+    def __init__(self, decimals=4, parent=None):
+
+        super(Tools2InvertPrefGroupUI, self).__init__(self)
+
+        self.setTitle(str(_("Invert Gerber Tool Options")))
+        self.decimals = decimals
+
+        # ## Subtractor Tool Parameters
+        self.sublabel = QtWidgets.QLabel("<b>%s:</b>" % _("Parameters"))
+        self.sublabel.setToolTip(
+            _("A tool to invert Gerber geometry from positive to negative\n"
+              "and in revers.")
+        )
+        self.layout.addWidget(self.sublabel)
+
+        # Grid Layout
+        grid0 = QtWidgets.QGridLayout()
+        grid0.setColumnStretch(0, 0)
+        grid0.setColumnStretch(1, 1)
+        self.layout.addLayout(grid0)
+
+        # Margin
+        self.margin_label = QtWidgets.QLabel('%s:' % _('Margin'))
+        self.margin_label.setToolTip(
+            _("Distance by which to avoid\n"
+              "the edges of the Gerber object.")
+        )
+        self.margin_entry = FCDoubleSpinner()
+        self.margin_entry.set_precision(self.decimals)
+        self.margin_entry.set_range(0.0000, 9999.9999)
+        self.margin_entry.setObjectName(_("Margin"))
+
+        grid0.addWidget(self.margin_label, 2, 0, 1, 2)
+        grid0.addWidget(self.margin_entry, 3, 0, 1, 2)
+
+        self.join_label = QtWidgets.QLabel('%s:' % _("Lines Join Style"))
+        self.join_label.setToolTip(
+            _("The way that the lines in the object outline will be joined.\n"
+              "Can be:\n"
+              "- rounded -> an arc is added between two joining lines\n"
+              "- square -> the lines meet in 90 degrees angle\n"
+              "- bevel -> the lines are joined by a third line")
+        )
+        self.join_radio = RadioSet([
+            {'label': 'Rounded', 'value': 'r'},
+            {'label': 'Square', 'value': 's'},
+            {'label': 'Bevel', 'value': 'b'}
+        ], orientation='vertical', stretch=False)
+
+        grid0.addWidget(self.join_label, 5, 0, 1, 2)
+        grid0.addWidget(self.join_radio, 7, 0, 1, 2)
+
+        self.layout.addStretch()
+
+
 class FAExcPrefGroupUI(OptionsGroupUI):
     def __init__(self, decimals=4, parent=None):
         # OptionsGroupUI.__init__(self, "Excellon File associations Preferences", parent=None)
diff --git a/flatcamTools/ToolInvertGerber.py b/flatcamTools/ToolInvertGerber.py
index 8d96419e..df1af676 100644
--- a/flatcamTools/ToolInvertGerber.py
+++ b/flatcamTools/ToolInvertGerber.py
@@ -8,14 +8,12 @@
 from PyQt5 import QtWidgets, QtCore
 
 from FlatCAMTool import FlatCAMTool
-from flatcamGUI.GUIElements import FCButton, FCDoubleSpinner
+from flatcamGUI.GUIElements import FCButton, FCDoubleSpinner, RadioSet
 
-from shapely.geometry import Polygon, MultiPolygon, MultiLineString, LineString, box
-from shapely.ops import cascaded_union
+from shapely.geometry import box
 
-import traceback
 from copy import deepcopy
-import time
+
 import logging
 import gettext
 import FlatCAMTranslation as fcTranslate
@@ -30,7 +28,7 @@ log = logging.getLogger('base')
 
 class ToolInvertGerber(FlatCAMTool):
 
-    toolName = _("Invert Tool")
+    toolName = _("Invert Gerber Tool")
 
     def __init__(self, app):
         self.app = app
@@ -56,7 +54,7 @@ class ToolInvertGerber(FlatCAMTool):
                         """)
         self.tools_box.addWidget(title_label)
 
-        # Form Layout
+        # Grid Layout
         grid0 = QtWidgets.QGridLayout()
         grid0.setColumnStretch(0, 0)
         grid0.setColumnStretch(1, 1)
@@ -70,7 +68,7 @@ class ToolInvertGerber(FlatCAMTool):
         self.gerber_combo.setRootModelIndex(self.app.collection.index(0, 0, QtCore.QModelIndex()))
         self.gerber_combo.setCurrentIndex(1)
 
-        self.gerber_label = QtWidgets.QLabel('%s:' % _("Gerber Object"))
+        self.gerber_label = QtWidgets.QLabel('<b>%s:</b>' % _("GERBER"))
         self.gerber_label.setToolTip(
             _("Gerber object that will be inverted.")
         )
@@ -78,6 +76,13 @@ class ToolInvertGerber(FlatCAMTool):
         grid0.addWidget(self.gerber_label, 1, 0, 1, 2)
         grid0.addWidget(self.gerber_combo, 2, 0, 1, 2)
 
+        grid0.addWidget(QtWidgets.QLabel(""), 3, 0, 1, 2)
+
+        self.param_label = QtWidgets.QLabel("<b>%s:</b>" % _("Parameters"))
+        self.param_label.setToolTip('%s.' % _("Parameters for this tool"))
+
+        grid0.addWidget(self.param_label, 4, 0, 1, 2)
+
         # Margin
         self.margin_label = QtWidgets.QLabel('%s:' % _('Margin'))
         self.margin_label.setToolTip(
@@ -89,18 +94,35 @@ class ToolInvertGerber(FlatCAMTool):
         self.margin_entry.set_range(0.0000, 9999.9999)
         self.margin_entry.setObjectName(_("Margin"))
 
-        grid0.addWidget(self.margin_label, 3, 0)
-        grid0.addWidget(self.margin_entry, 3, 1)
+        grid0.addWidget(self.margin_label, 5, 0, 1, 2)
+        grid0.addWidget(self.margin_entry, 6, 0, 1, 2)
+
+        self.join_label = QtWidgets.QLabel('%s:' % _("Lines Join Style"))
+        self.join_label.setToolTip(
+            _("The way that the lines in the object outline will be joined.\n"
+              "Can be:\n"
+              "- rounded -> an arc is added between two joining lines\n"
+              "- square -> the lines meet in 90 degrees angle\n"
+              "- bevel -> the lines are joined by a third line")
+        )
+        self.join_radio = RadioSet([
+            {'label': 'Rounded', 'value': 'r'},
+            {'label': 'Square', 'value': 's'},
+            {'label': 'Bevel', 'value': 'b'}
+        ], orientation='vertical', stretch=False)
+
+        grid0.addWidget(self.join_label, 7, 0, 1, 2)
+        grid0.addWidget(self.join_radio, 8, 0, 1, 2)
 
         separator_line = QtWidgets.QFrame()
         separator_line.setFrameShape(QtWidgets.QFrame.HLine)
         separator_line.setFrameShadow(QtWidgets.QFrame.Sunken)
-        grid0.addWidget(separator_line, 4, 0, 1, 2)
+        grid0.addWidget(separator_line, 9, 0, 1, 2)
 
         self.invert_btn = FCButton(_('Invert Gerber'))
         self.invert_btn.setToolTip(
             _("Will invert the Gerber object: areas that have copper\n"
-              "will be emty of copper and previous empty area will be\n"
+              "will be empty of copper and previous empty area will be\n"
               "filled with copper.")
         )
         self.invert_btn.setStyleSheet("""
@@ -109,7 +131,7 @@ class ToolInvertGerber(FlatCAMTool):
                             font-weight: bold;
                         }
                         """)
-        grid0.addWidget(self.invert_btn, 5, 0, 1, 2)
+        grid0.addWidget(self.invert_btn, 10, 0, 1, 2)
 
         self.tools_box.addStretch()
 
@@ -161,13 +183,18 @@ class ToolInvertGerber(FlatCAMTool):
         self.app.ui.notebook.setTabText(2, _("Invert Tool"))
 
     def set_tool_ui(self):
-        self.margin_entry.set_value(0.0)
+        self.margin_entry.set_value(float(self.app.defaults["tools_invert_margin"]))
+        self.join_radio.set_value(self.app.defaults["tools_invert_join_style"])
 
     def on_grb_invert(self):
         margin = self.margin_entry.get_value()
         if round(margin, self.decimals) == 0.0:
             margin = 1E-10
 
+        join_style = {'r': 1, 'b': 3, 's': 2}[self.join_radio.get_value()]
+        if join_style is None:
+            join_style = 'r'
+
         grb_circle_steps = int(self.app.defaults["gerber_circle_steps"])
         obj_name = self.gerber_combo.currentText()
 
@@ -181,12 +208,14 @@ class ToolInvertGerber(FlatCAMTool):
             return "Could not retrieve object: %s with error: %s" % (obj_name, str(e))
 
         if grb_obj is None:
+            if obj_name == '':
+                obj_name = 'None'
             self.app.inform.emit('[ERROR_NOTCL] %s: %s' % (_("Object not found"), str(obj_name)))
             return
 
         xmin, ymin, xmax, ymax = grb_obj.bounds()
 
-        grb_box = box(xmin, ymin, xmax, ymax).buffer(margin, resolution=grb_circle_steps, join_style=2)
+        grb_box = box(xmin, ymin, xmax, ymax).buffer(margin, resolution=grb_circle_steps, join_style=join_style)
 
         try:
             __ = iter(grb_obj.solid_geometry)
diff --git a/flatcamTools/ToolPunchGerber.py b/flatcamTools/ToolPunchGerber.py
index 2a5d8ef4..282c20d4 100644
--- a/flatcamTools/ToolPunchGerber.py
+++ b/flatcamTools/ToolPunchGerber.py
@@ -515,7 +515,9 @@ class ToolPunchGerber(FlatCAMTool):
 
         punch_method = self.method_punch.get_value()
 
-        new_options = deepcopy(grb_obj.options)
+        new_options = dict()
+        for opt in grb_obj.options:
+            new_options[opt] = deepcopy(grb_obj.options[opt])
 
         if punch_method == 'exc':