diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b84bdfa..5c1bb89e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -27,6 +27,8 @@ CHANGELOG for FlatCAM beta
 - on tab close in Notebook the tool_shapes are deleted (shape markings used by some of the App Tools) therefore part fo the clean-up
 - added some protections in case the Editors could not start such that the app is not crashed
 - fixed wrong display of editor actions in the Editor toolbar at the first start of the app
+- fixed missing import in the preprocessors
+- deleted the Toolchange_custom preprocessor because it is no longer used
 
 26.11.2020
 
diff --git a/appPreProcessor.py b/appPreProcessor.py
index 96ea1921..955ee910 100644
--- a/appPreProcessor.py
+++ b/appPreProcessor.py
@@ -9,6 +9,7 @@
 from importlib.machinery import SourceFileLoader
 import os
 from abc import ABCMeta, abstractmethod
+import math     # keep this. it is used in preprocessors
 
 # module-root dictionary of preprocessors
 
diff --git a/preprocessors/Toolchange_Custom.py b/preprocessors/Toolchange_Custom.py
deleted file mode 100644
index 457a2d7f..00000000
--- a/preprocessors/Toolchange_Custom.py
+++ /dev/null
@@ -1,209 +0,0 @@
-# ##########################################################
-# FlatCAM: 2D Post-processing for Manufacturing            #
-# http://flatcam.org                                       #
-# File Author: Marius Adrian Stanciu (c)                   #
-# Date: 3/10/2019                                          #
-# MIT Licence                                              #
-# ##########################################################
-
-from appPreProcessor import *
-
-
-class Toolchange_Custom(PreProc):
-
-    include_header = True
-    coordinate_format = "%.*f"
-    feedrate_format = '%.*f'
-
-    def start_code(self, p):
-        units = ' ' + str(p['units']).lower()
-        coords_xy = p['xy_toolchange']
-        end_coords_xy = p['xy_end']
-        gcode = ''
-
-        xmin = '%.*f' % (p.coords_decimals, p['options']['xmin'])
-        xmax = '%.*f' % (p.coords_decimals, p['options']['xmax'])
-        ymin = '%.*f' % (p.coords_decimals, p['options']['ymin'])
-        ymax = '%.*f' % (p.coords_decimals, p['options']['ymax'])
-
-        if str(p['options']['type']) == 'Geometry':
-            gcode += '(TOOL DIAMETER: ' + str(p['options']['tool_dia']) + units + ')\n'
-            gcode += '(Feedrate_XY: ' + str(p['feedrate']) + units + '/min' + ')\n'
-            gcode += '(Feedrate_Z: ' + str(p['z_feedrate']) + units + '/min' + ')\n'
-            gcode += '(Feedrate rapids ' + str(p['feedrate_rapid']) + units + '/min' + ')\n' + '\n'
-            gcode += '(Z_Cut: ' + str(p['z_cut']) + units + ')\n'
-            if p['multidepth'] is True:
-                gcode += '(DepthPerCut: ' + str(p['z_depthpercut']) + units + ' <=>' + \
-                         str(math.ceil(abs(p['z_cut']) / p['z_depthpercut'])) + ' passes' + ')\n'
-            gcode += '(Z_Move: ' + str(p['z_move']) + units + ')\n'
-
-        elif str(p['options']['type']) == 'Excellon' and p['use_ui'] is True:
-            gcode += '\n(TOOLS DIAMETER: )\n'
-            for tool, val in p['exc_tools'].items():
-                gcode += '(Tool: %s -> ' % str(tool) + 'Dia: %s' % str(val["tooldia"]) + ')\n'
-
-            gcode += '\n(FEEDRATE Z: )\n'
-            for tool, val in p['exc_tools'].items():
-                gcode += '(Tool: %s -> ' % str(tool) + 'Feedrate: %s' % \
-                         str(val['data']["tools_drill_feedrate_z"]) + ')\n'
-
-            gcode += '\n(FEEDRATE RAPIDS: )\n'
-            for tool, val in p['exc_tools'].items():
-                gcode += '(Tool: %s -> ' % str(tool) + 'Feedrate Rapids: %s' % \
-                         str(val['data']["tools_drill_feedrate_rapid"]) + ')\n'
-
-            gcode += '\n(Z_CUT: )\n'
-            for tool, val in p['exc_tools'].items():
-                gcode += '(Tool: %s -> ' % str(tool) + 'Z_Cut: %s' % str(val['data']["tools_drill_cutz"]) + ')\n'
-
-            gcode += '\n(Tools Offset: )\n'
-            for tool, val in p['exc_cnc_tools'].items():
-                gcode += '(Tool: %s -> ' % str(val['tool']) + 'Offset Z: %s' % \
-                         str(val['data']["tools_drill_offset"]) + ')\n'
-
-            if p['multidepth'] is True:
-                gcode += '\n(DEPTH_PER_CUT: )\n'
-                for tool, val in p['exc_tools'].items():
-                    gcode += '(Tool: %s -> ' % str(tool) + 'DeptPerCut: %s' % \
-                             str(val['data']["tools_drill_depthperpass"]) + ')\n'
-
-            gcode += '\n(Z_MOVE: )\n'
-            for tool, val in p['exc_tools'].items():
-                gcode += '(Tool: %s -> ' % str(tool) + 'Z_Move: %s' % str(val['data']["tools_drill_travelz"]) + ')\n'
-            gcode += '\n'
-
-        if p['toolchange'] is True:
-            gcode += '(Z Toolchange: ' + str(p['z_toolchange']) + units + ')\n'
-
-            if coords_xy is not None:
-                gcode += '(X,Y Toolchange: ' + "%.*f, %.*f" % (p.decimals, coords_xy[0],
-                                                               p.decimals, coords_xy[1]) + units + ')\n'
-            else:
-                gcode += '(X,Y Toolchange: ' + "None" + units + ')\n'
-
-        gcode += '(Z Start: ' + str(p['startz']) + units + ')\n'
-        gcode += '(Z End: ' + str(p['z_end']) + units + ')\n'
-        if end_coords_xy is not None:
-            gcode += '(X,Y End: ' + "%.*f, %.*f" % (p.decimals, end_coords_xy[0],
-                                                    p.decimals, end_coords_xy[1]) + units + ')\n'
-        else:
-            gcode += '(X,Y End: ' + "None" + units + ')\n'
-        gcode += '(Steps per circle: ' + str(p['steps_per_circle']) + ')\n'
-
-        if str(p['options']['type']) == 'Excellon' or str(p['options']['type']) == 'Excellon Geometry':
-            gcode += '(Preprocessor Excellon: ' + str(p['pp_excellon_name']) + ')\n' + '\n'
-        else:
-            gcode += '(Preprocessor Geometry: ' + str(p['pp_geometry_name']) + ')\n' + '\n'
-
-        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 += ('G20\n' if p.units.upper() == 'IN' else 'G21\n')
-        gcode += 'G90\n'
-        gcode += 'G17\n'
-        gcode += 'G94\n'
-
-        return gcode
-
-    def startz_code(self, p):
-        return ''
-
-    def lift_code(self, p):
-        return 'G00 Z' + self.coordinate_format % (p.coords_decimals, p.z_move)
-
-    def down_code(self, p):
-        return 'G01 Z' + self.coordinate_format % (p.coords_decimals, p.z_cut)
-
-    def toolchange_code(self, p):
-        z_toolchange = p.z_toolchange
-        toolchangexy = p.xy_toolchange
-        f_plunge = p.f_plunge
-        gcode = ''
-
-        if toolchangexy is not None:
-            x_toolchange = toolchangexy[0]
-            y_toolchange = toolchangexy[1]
-        else:
-            x_toolchange = 0.0
-            y_toolchange = 0.0
-
-        no_drills = 1
-
-        if int(p.tool) == 1 and p.startz is not None:
-            z_toolchange = p.startz
-
-        toolC_formatted = '%.*f' % (p.decimals, p.toolC)
-
-        if str(p['options']['type']) == 'Excellon':
-            for i in p['options']['Tools_in_use']:
-                if i[0] == p.tool:
-                    no_drills = i[2]
-
-            if toolchangexy is not None:
-                gcode = """
-M6
-""".format(x_toolchange=self.coordinate_format % (p.coords_decimals, x_toolchange),
-             y_toolchange=self.coordinate_format % (p.coords_decimals, y_toolchange),
-             tool=int(p.tool),
-             t_drills=no_drills,
-             toolC=toolC_formatted)
-
-            if f_plunge is True:
-                gcode += '\nG00 Z%.*f' % (p.coords_decimals, p.z_move)
-            return gcode
-
-        else:
-            if toolchangexy is not None:
-                gcode = """
-M6
-""".format(x_toolchange=self.coordinate_format % (p.coords_decimals, x_toolchange),
-             y_toolchange=self.coordinate_format % (p.coords_decimals, y_toolchange),
-             tool=int(p.tool),
-             toolC=toolC_formatted)
-
-            if f_plunge is True:
-                gcode += '\nG00 Z%.*f' % (p.coords_decimals, p.z_move)
-            return gcode
-
-    def up_to_zero_code(self, p):
-        return 'G01 Z0'
-
-    def position_code(self, p):
-        return ('X' + self.coordinate_format + ' Y' + self.coordinate_format) % \
-               (p.coords_decimals, p.x, p.coords_decimals, p.y)
-
-    def rapid_code(self, p):
-        return ('G00 ' + self.position_code(p)).format(**p)
-
-    def linear_code(self, p):
-        return ('G01 ' + self.position_code(p)).format(**p)
-
-    def end_code(self, p):
-        coords_xy = p['xy_end']
-        gcode = ('G00 Z' + self.feedrate_format % (p.fr_decimals, p.z_end) + "\n")
-
-        if coords_xy and coords_xy != '':
-            gcode += 'G00 X{x} Y{y}'.format(x=coords_xy[0], y=coords_xy[1]) + "\n"
-        return gcode
-
-    def feedrate_code(self, p):
-        return 'G01 F' + str(self.feedrate_format % (p.fr_decimals, p.feedrate))
-
-    def z_feedrate_code(self, p):
-        return 'G01 F' + str(self.feedrate_format % (p.fr_decimals, p.z_feedrate))
-
-    def spindle_code(self, p):
-        sdir = {'CW': 'M03', 'CCW': 'M04'}[p.spindledir]
-        if p.spindlespeed:
-            return '%s S%s' % (sdir, str(p.spindlespeed))
-        else:
-            return sdir
-
-    def dwell_code(self, p):
-        if p.dwelltime:
-            return 'G4 P' + str(p.dwelltime)
-
-    def spindle_stop_code(self, p):
-        return 'M05'