diff --git a/plugins/CuraEngineBackend/StartSliceJob.py b/plugins/CuraEngineBackend/StartSliceJob.py
index 1a51f9201f..2041c45ef5 100644
--- a/plugins/CuraEngineBackend/StartSliceJob.py
+++ b/plugins/CuraEngineBackend/StartSliceJob.py
@@ -1,21 +1,25 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import numpy
 from string import Formatter
 from enum import IntEnum
 import time
+from typing import Any, Dict, List, Optional, Set
 import re
+import Arcus #For typing.
 
 from UM.Job import Job
-from UM.Application import Application
 from UM.Logger import Logger
+from UM.Settings.ContainerStack import ContainerStack #For typing.
+from UM.Settings.SettingRelation import SettingRelation #For typing.
 
 from UM.Scene.Iterator.DepthFirstIterator import DepthFirstIterator
-
+from UM.Scene.Scene import Scene #For typing.
 from UM.Settings.Validator import ValidatorState
 from UM.Settings.SettingRelation import RelationType
 
+from cura.CuraApplication import CuraApplication
 from cura.Scene.CuraSceneNode import CuraSceneNode
 from cura.OneAtATimeIterator import OneAtATimeIterator
 from cura.Settings.ExtruderManager import ExtruderManager
@@ -35,19 +39,19 @@ class StartJobResult(IntEnum):
     ObjectsWithDisabledExtruder = 8
 
 
-##  Formatter class that handles token expansion in start/end gcod
+##  Formatter class that handles token expansion in start/end gcode
 class GcodeStartEndFormatter(Formatter):
-    def get_value(self, key, args, kwargs):  # [CodeStyle: get_value is an overridden function from the Formatter class]
+    def get_value(self, key: str, *args: str, **kwargs) -> str: #type: ignore # [CodeStyle: get_value is an overridden function from the Formatter class]
         # The kwargs dictionary contains a dictionary for each stack (with a string of the extruder_nr as their key),
         # and a default_extruder_nr to use when no extruder_nr is specified
 
         if isinstance(key, str):
             try:
-                extruder_nr = kwargs["default_extruder_nr"]
+                extruder_nr = int(kwargs["default_extruder_nr"])
             except ValueError:
                 extruder_nr = -1
 
-            key_fragments = [fragment.strip() for fragment in key.split(',')]
+            key_fragments = [fragment.strip() for fragment in key.split(",")]
             if len(key_fragments) == 2:
                 try:
                     extruder_nr = int(key_fragments[1])
@@ -74,25 +78,25 @@ class GcodeStartEndFormatter(Formatter):
 
 ##  Job class that builds up the message of scene data to send to CuraEngine.
 class StartSliceJob(Job):
-    def __init__(self, slice_message):
+    def __init__(self, slice_message: Arcus.PythonMessage) -> None:
         super().__init__()
 
-        self._scene = Application.getInstance().getController().getScene()
-        self._slice_message = slice_message
-        self._is_cancelled = False
-        self._build_plate_number = None
+        self._scene = CuraApplication.getInstance().getController().getScene() #type: Scene
+        self._slice_message = slice_message #type: Arcus.PythonMessage
+        self._is_cancelled = False #type: bool
+        self._build_plate_number = None #type: Optional[int]
 
-        self._all_extruders_settings = None # cache for all setting values from all stacks (global & extruder) for the current machine
+        self._all_extruders_settings = None #type: Optional[Dict[str, Any]] # cache for all setting values from all stacks (global & extruder) for the current machine
 
-    def getSliceMessage(self):
+    def getSliceMessage(self) -> Arcus.PythonMessage:
         return self._slice_message
 
-    def setBuildPlate(self, build_plate_number):
+    def setBuildPlate(self, build_plate_number: int) -> None:
         self._build_plate_number = build_plate_number
 
     ##  Check if a stack has any errors.
     ##  returns true if it has errors, false otherwise.
-    def _checkStackForErrors(self, stack):
+    def _checkStackForErrors(self, stack: ContainerStack) -> bool:
         if stack is None:
             return False
 
@@ -105,28 +109,28 @@ class StartSliceJob(Job):
         return False
 
     ##  Runs the job that initiates the slicing.
-    def run(self):
+    def run(self) -> None:
         if self._build_plate_number is None:
             self.setResult(StartJobResult.Error)
             return
 
-        stack = Application.getInstance().getGlobalContainerStack()
+        stack = CuraApplication.getInstance().getGlobalContainerStack()
         if not stack:
             self.setResult(StartJobResult.Error)
             return
 
         # Don't slice if there is a setting with an error value.
-        if Application.getInstance().getMachineManager().stacksHaveErrors:
+        if CuraApplication.getInstance().getMachineManager().stacksHaveErrors:
             self.setResult(StartJobResult.SettingError)
             return
 
-        if Application.getInstance().getBuildVolume().hasErrors():
+        if CuraApplication.getInstance().getBuildVolume().hasErrors():
             self.setResult(StartJobResult.BuildPlateError)
             return
 
         # Don't slice if the buildplate or the nozzle type is incompatible with the materials
-        if not Application.getInstance().getMachineManager().variantBuildplateCompatible and \
-                not Application.getInstance().getMachineManager().variantBuildplateUsable:
+        if not CuraApplication.getInstance().getMachineManager().variantBuildplateCompatible and \
+                not CuraApplication.getInstance().getMachineManager().variantBuildplateUsable:
             self.setResult(StartJobResult.MaterialIncompatible)
             return
 
@@ -141,7 +145,7 @@ class StartSliceJob(Job):
 
 
         # Don't slice if there is a per object setting with an error value.
-        for node in DepthFirstIterator(self._scene.getRoot()):
+        for node in DepthFirstIterator(self._scene.getRoot()): #type: ignore #Ignore type error because iter() should get called automatically by Python syntax.
             if not isinstance(node, CuraSceneNode) or not node.isSelectable():
                 continue
 
@@ -151,7 +155,7 @@ class StartSliceJob(Job):
 
         with self._scene.getSceneLock():
             # Remove old layer data.
-            for node in DepthFirstIterator(self._scene.getRoot()):
+            for node in DepthFirstIterator(self._scene.getRoot()): #type: ignore #Ignore type error because iter() should get called automatically by Python syntax.
                 if node.callDecoration("getLayerData") and node.callDecoration("getBuildPlateNumber") == self._build_plate_number:
                     node.getParent().removeChild(node)
                     break
@@ -159,7 +163,7 @@ class StartSliceJob(Job):
             # Get the objects in their groups to print.
             object_groups = []
             if stack.getProperty("print_sequence", "value") == "one_at_a_time":
-                for node in OneAtATimeIterator(self._scene.getRoot()):
+                for node in OneAtATimeIterator(self._scene.getRoot()): #type: ignore #Ignore type error because iter() should get called automatically by Python syntax.
                     temp_list = []
 
                     # Node can't be printed, so don't bother sending it.
@@ -185,7 +189,7 @@ class StartSliceJob(Job):
             else:
                 temp_list = []
                 has_printing_mesh = False
-                for node in DepthFirstIterator(self._scene.getRoot()):
+                for node in DepthFirstIterator(self._scene.getRoot()): #type: ignore #Ignore type error because iter() should get called automatically by Python syntax.
                     if node.callDecoration("isSliceable") and node.getMeshData() and node.getMeshData().getVertices() is not None:
                         per_object_stack = node.callDecoration("getStack")
                         is_non_printing_mesh = False
@@ -212,12 +216,12 @@ class StartSliceJob(Job):
                 if temp_list:
                     object_groups.append(temp_list)
 
-            extruders_enabled = {position: stack.isEnabled for position, stack in Application.getInstance().getGlobalContainerStack().extruders.items()}
+            extruders_enabled = {position: stack.isEnabled for position, stack in CuraApplication.getInstance().getGlobalContainerStack().extruders.items()}
             filtered_object_groups = []
             has_model_with_disabled_extruders = False
             associated_siabled_extruders = set()
             for group in object_groups:
-                stack = Application.getInstance().getGlobalContainerStack()
+                stack = CuraApplication.getInstance().getGlobalContainerStack()
                 skip_group = False
                 for node in group:
                     extruder_position = node.callDecoration("getActiveExtruderPosition")
@@ -231,7 +235,7 @@ class StartSliceJob(Job):
 
             if has_model_with_disabled_extruders:
                 self.setResult(StartJobResult.ObjectsWithDisabledExtruder)
-                associated_siabled_extruders = [str(c) for c in sorted([int(p) + 1 for p in associated_siabled_extruders])]
+                associated_siabled_extruders = {str(c) for c in sorted([int(p) + 1 for p in associated_siabled_extruders])}
                 self.setMessage(", ".join(associated_siabled_extruders))
                 return
 
@@ -284,11 +288,11 @@ class StartSliceJob(Job):
 
         self.setResult(StartJobResult.Finished)
 
-    def cancel(self):
+    def cancel(self) -> None:
         super().cancel()
         self._is_cancelled = True
 
-    def isCancelled(self):
+    def isCancelled(self) -> bool:
         return self._is_cancelled
 
     ##  Creates a dictionary of tokens to replace in g-code pieces.
@@ -298,7 +302,7 @@ class StartSliceJob(Job):
     #   with.
     #   \return A dictionary of replacement tokens to the values they should be
     #   replaced with.
-    def _buildReplacementTokens(self, stack) -> dict:
+    def _buildReplacementTokens(self, stack: ContainerStack) -> Dict[str, Any]:
         result = {}
         for key in stack.getAllKeys():
             value = stack.getProperty(key, "value")
@@ -311,7 +315,7 @@ class StartSliceJob(Job):
         result["date"] = time.strftime("%d-%m-%Y")
         result["day"] = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"][int(time.strftime("%w"))]
 
-        initial_extruder_stack = Application.getInstance().getExtruderManager().getUsedExtruderStacks()[0]
+        initial_extruder_stack = CuraApplication.getInstance().getExtruderManager().getUsedExtruderStacks()[0]
         initial_extruder_nr = initial_extruder_stack.getProperty("extruder_nr", "value")
         result["initial_extruder_nr"] = initial_extruder_nr
 
@@ -320,9 +324,9 @@ class StartSliceJob(Job):
     ##  Replace setting tokens in a piece of g-code.
     #   \param value A piece of g-code to replace tokens in.
     #   \param default_extruder_nr Stack nr to use when no stack nr is specified, defaults to the global stack
-    def _expandGcodeTokens(self, value: str, default_extruder_nr: int = -1):
+    def _expandGcodeTokens(self, value: str, default_extruder_nr: int = -1) -> str:
         if not self._all_extruders_settings:
-            global_stack = Application.getInstance().getGlobalContainerStack()
+            global_stack = CuraApplication.getInstance().getGlobalContainerStack()
 
             # NB: keys must be strings for the string formatter
             self._all_extruders_settings = {
@@ -344,7 +348,7 @@ class StartSliceJob(Job):
             return str(value)
 
     ##  Create extruder message from stack
-    def _buildExtruderMessage(self, stack):
+    def _buildExtruderMessage(self, stack: ContainerStack) -> None:
         message = self._slice_message.addRepeatedMessage("extruders")
         message.id = int(stack.getMetaDataEntry("position"))
 
@@ -371,7 +375,7 @@ class StartSliceJob(Job):
     #
     #   The settings are taken from the global stack. This does not include any
     #   per-extruder settings or per-object settings.
-    def _buildGlobalSettingsMessage(self, stack):
+    def _buildGlobalSettingsMessage(self, stack: ContainerStack) -> None:
         settings = self._buildReplacementTokens(stack)
 
         # Pre-compute material material_bed_temp_prepend and material_print_temp_prepend
@@ -385,7 +389,7 @@ class StartSliceJob(Job):
 
         # Replace the setting tokens in start and end g-code.
         # Use values from the first used extruder by default so we get the expected temperatures
-        initial_extruder_stack = Application.getInstance().getExtruderManager().getUsedExtruderStacks()[0]
+        initial_extruder_stack = CuraApplication.getInstance().getExtruderManager().getUsedExtruderStacks()[0]
         initial_extruder_nr = initial_extruder_stack.getProperty("extruder_nr", "value")
 
         settings["machine_start_gcode"] = self._expandGcodeTokens(settings["machine_start_gcode"], initial_extruder_nr)
@@ -406,7 +410,7 @@ class StartSliceJob(Job):
     #
     #   \param stack The global stack with all settings, from which to read the
     #   limit_to_extruder property.
-    def _buildGlobalInheritsStackMessage(self, stack):
+    def _buildGlobalInheritsStackMessage(self, stack: ContainerStack) -> None:
         for key in stack.getAllKeys():
             extruder_position = int(round(float(stack.getProperty(key, "limit_to_extruder"))))
             if extruder_position >= 0:  # Set to a specific extruder.
@@ -416,9 +420,9 @@ class StartSliceJob(Job):
             Job.yieldThread()
 
     ##  Check if a node has per object settings and ensure that they are set correctly in the message
-    #   \param node \type{SceneNode} Node to check.
+    #   \param node Node to check.
     #   \param message object_lists message to put the per object settings in
-    def _handlePerObjectSettings(self, node, message):
+    def _handlePerObjectSettings(self, node: CuraSceneNode, message: Arcus.PythonMessage):
         stack = node.callDecoration("getStack")
 
         # Check if the node has a stack attached to it and the stack has any settings in the top container.
@@ -456,9 +460,9 @@ class StartSliceJob(Job):
             Job.yieldThread()
 
     ##  Recursive function to put all settings that require each other for value changes in a list
-    #   \param relations_set \type{set} Set of keys (strings) of settings that are influenced
+    #   \param relations_set Set of keys of settings that are influenced
     #   \param relations list of relation objects that need to be checked.
-    def _addRelations(self, relations_set, relations):
+    def _addRelations(self, relations_set: Set[str], relations: List[SettingRelation]):
         for relation in filter(lambda r: r.role == "value" or r.role == "limit_to_extruder", relations):
             if relation.type == RelationType.RequiresTarget:
                 continue