Lesson 12 - Specialist Finishing

Objectives

• Explore a series of finishing toolpaths.

Plane Projection Exercise

All five Projection Finishing strategies can be used to machine undercut

features if used with suitable tooling such as Disc or Spherical. The following
example shows an undercut application using the Plane Projection strategy

• Open Project…\PMData\Projects\Heatsink

• Save Project as:

…\COURSEWORK\PMProjects\ Heatsink-EX1

• Open Block Editor in Home > Setup and recalculate to Defined by Box
and Type Model.

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• From Simulation > Simulation Path select the Entity as NC Program

then from the Entity pull-down menu Entity select NC Program 1

Turn on ViewMill and in Mode select Rotatable Followed Shiny from the
Shading option. Turn on the Auto-draw tool option and play at full
speed

• From Simulation > ViewMill select Mode and select No Image .

Store the current state of viewmill model and Suspend

viewmill from the toolpath simulation

• Deactivate NC Program 1

Deactivating the NC Program will prevent any new toolpaths from being
added to that NC Program

• Activate Toolpath D25TR3-RGH1 to reinstate the original setup, then turn

off the toolpath

• Activate the D75-H6-T2 tool

• Open Block Editor and lock the X and the Z limits. In the Expansion field
enter 40.0. Calculate and Accept form

The Y limits for the Block have increased an equal distance of 20mm per side

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 Next will create a semi finishing toolpath to remove access material from the inside
faces of the ribs

• From Toolpath > Create select the Projection Plane finishing strategy.

• Rename Toolpath as Projection Plane

• Select Plane Projection from the explorer and enter the following values
for the Location: -75.0, -150.0, -77.0

Select the preview button to display the start point of the Projection plane

• Set the Direction to Outwards, The Tolerance to 0.1, the Thickness to 0.5
and the Step over to 0.5

• Select Pattern from the explorer

• Fill in the following in the Pattern section: Pattern direction U, Ordering

One way, Sequence None

Now set the end point for the Projection plane in the Limits section

• Set the Start Height as 0.0 the End Height as 37.0

• For the Width make the Start 0.0 and the End 150.0

• Select Preview.

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• Calculate and Close

To prevent a tool collision when tool rapid moves in Z to return to the next start
position we must add some extension moves.

• From Toolpath Edit select Toolpath Connections

• Select lead ins followed by 1st Choice > Extended move. Enter a length
of 40.0 and Apply lead ins

• Apply the same to the lead Outs

• Run a Verification check with Holder clearance of 3mm and Shank 1mm.

• Run Viewmill simulation on toolpath D75-H6-T2-SEM1-Ucut and save

current state of model.

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• Save Project but do not close

Summary
in this exercise, we have created a plane projection toolpath by setting up a
plane with a width and height to cover the area that is required to be
machined.

Surface Projection Finishing

Surface Projection will be used for the finishing strategy as it will provide a
consistent stepover within the undercut regions. To allow this a specially created,
single, reference surface will be imported (To create this surface the user would
require the services of a suitable CAD package such as PowerSHAPE). The reference
surface does not necessarily have to represent the true shape of the finished
component. In practice it could be positioned inside, outside, or flush with the actual
model surfaces to be machined. In this example the reference surface is not flush
with the existing model.

• Right mouse click on Models in the PowerMill explorer and select Import
Reference Surfaces.

• Select model:
…\PMData\models\heatsink-ref.dgk

By importing a model with this method, the surfaces can only be used for a
reference and will not be machined.

• Open the View tab and select Command Window from User

Interface menu.

• Enter the following in the window:

EDIT SURFPROJ AUTORANGE OFF (return key)

EDIT SURFPROJ RANGEMIN -1 (return key)
EDIT SURFPROJ RANGE MAX 1 (return key)

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 This is to restrict the tool projection distance to within 0.5mm of the reference
surface. Otherwise it would be projected from infinity onto non-undercut faces on
the outside of the model.

The default setting is restored by typing: -

• EDIT SURFPROJ AUTORANGE ON

• In PowerMill explorer select the reference surface.

• In the Finishing strategy selector, choose Projection Surface Finishing.

• Rename Toolpath Projection Surface.

• Select Surface projection from the explorer and in Projection field select
the direction to Inwards

• Set Tolerance to 0.01 and a Stepover of 0.5

• From Pattern in the explorer, set the following: Pattern U, Ordering One
Way and leave the rest as default

• Calculate and Close

• Save Project and close.

Summary
In the exercise just completed we have imported a reference model that
was used to generate a consistent pattern to be projected onto the model

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Line projection Exercise

• Open Project…\PMData\Projects\Undercut Projection

• Save Project as:

…\COURSEWORK\PMProjects\Line-Projection

The imported Project (Undercut Projection) contains a Model, Tooling, Roughing,

and Semi-Finishing strategies with 1 and 0.3 thickness values respectively. The undercut
regions have not yet been machined.

• Activate the toolpath (Rough) to reinstate the settings and then simulate
both existing toolpaths in ViewMILL and Store the result.

• Turn of image and Disconnect the ViewMILL session and select a View
from Top (Z).

• Turn on Cross hair and position on the lower left corner of the model. In the
ordinate windows the values display are 50 80 0

• Activate the TD30 cutting tool.

• From the Toolpath strategies dialog, select Projection Line Finishing.

• Open the Line Projection page, set the Style to Circular and enter the
values that we recorded with the cursor into the Location field. Set the
Direction to Inwards, Tolerance (0.01), Thickness (0.0), Stepover (0.5).

• Open the Pattern page and set Style to Circular, Ordering to One way,
Sequence to None.

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• In the Limits > Azimuth angle set the Start to 90.0 and the End to 0.0.

• Under Height enter in the Start -10.0 and the End to -27.0.

• Preview to show pattern.

The settings we have given in the Limits and Height options denote the
travel order of the toolpath.
If we take a quick look at the image above, the Pattern has the arrow at
the top right hand side, this tells us that the toolpath will Climb mill and
start at the top.

• Add suitable Lead Ins/Outs then Calculate and verify toolpath with

Verification .

• Save Project and close.

Summary
In the exercise just completed we have chosen to use Line Projection to
produce a toolpath. This method uses a line at given point and orientation
where a pattern is anchored to.

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Point Projection Finishing

• Import Model…\PMData\Models\radknob.dgk

• Save Project as:

…\COURSEWORK\PMProjects\PointProj-ex1

• From the Workplane tab activate Workplane 1 and from the

• Edit > Workplane to open the Editor.

The workplane XY plane needs reversing to have access to machine the inner walls.

• Select Twist around X and enter 180.0 in the Twist dialog before
Accepting.

• Create an Ø16 ball nosed tool from the Database named BN16.

• Calculate a Block defined by Box and Type by Model.

• Calculate Safe Area to defaults.

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• Select Point Projection Finishing strategy and name PointProjection.

• Open Point Projection page and in Pattern Style menu select Spiral, in
Location enter the coordinates 0.0 0.0 -11.0

• from the Projection Direction menu select Outwards. Set Tolerance

(0.01), Thickness (0.0), Angular Stepover (2.0)

• Open Pattern page and select the Direction as Anticlockwise and Limits
> Elevation Angles Start 0.0 and End 90.0.

• Calculate and Close.

• Save Project and Close.

Summary

In this exercise, we have generated an internal spiral toolpath which starts

on the contact point of the tool. This was set by entering values within the
Location field.

Curve Projection Finishing

• Import Model…\PMData\Models\CurveProjection.dgk

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• Save Project as:
…\COURSEWORK\PMProjects\curveProjection-ex1

Note the model also includes a wireframe curve running centrally along the slot.

• Activate Workplane 1

• Calculate the Block using Defined by - Box and Type - Model.

• Create an Ø16 ball nosed tool from the Database named BN16.

• Calculate Safe Area to defaults.

• Turn off Model and turn on Wirefame view to display

wireframe curve.

• Select Curve.

• Select Pattern > Create to open Pattern toolbar and select Pattern
To create a new pattern

• Insert the selected wireframe curve by selecting Edit > Insert Model
to add geometry into the pattern.

• Turn off the Wireframe view and turn the Model view back on.

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• Select a Curve Projection Finishing strategy and open the Curve
Projection page.

• In the Curves definition menu select pattern 1 then select Linear from the
style menu.

• In Projection Change Direction to Outwards and then change the

Tolerance 0.01, Thickness 0, and Angular Stepover 1.5

• Open the Pattern page and in Limits change the Azimuth angle of the
Start to -75.0, and the End to 75.0

• Preview Pattern.

• Calculate and Close.

The Curve used as the basis for the strategy will in the majority of cases be created
in a CAD package as part of the Model. In these cases the imported wireframe
curve must then be inserted into a Pattern.

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• Save Project and close.

Summary
In this exercise, we have used the Curve Projection strategy, which
projects a tubular pattern onto the model, which is then machined.

Swarf Finishing

Swarf Finishing is specifically designed to machine down one or more surfaces where
a linear transition exists along the tool alignment direction. It will not work where
the transition is concave or convex.

• Open Project…\PowerMill_Data\Projects\Swarf

• Save Project as:

…\COURSEWORK\PMProjects\Swarf-Ex1

• Activate Workplane mc-Datum and Tool EM16.

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• Calculate the Block using Defined by - Box and Type - Model.

• Calculate Safe Area to defaults.

• Expand the Levels and Sets in the PowerMill explorer to list all the
levels.

• Right mouse button click on the Level Swarf-MC and from the local menu
select the option Select Surfaces.

The surfaces selected on the Level Swarf-MC are all suitable for Swarf
machining.

• Select Swarf finishing strategy from finishing selector and name

SwarfOffsetdown.

• Open the Swarf finishing page and enter Tolerance 0.01, Cut direction
Climb, Thickness 0.0.

• In the position page select Bottom from the Base positon pulldown
menu

• Open the Multiple cuts page and in the Mode menu select Offset down,
in the Maximum stepdown enter (5.0).

• Calculate and close.

The tool tracks that machine the base of the selected surfaces have
progressively offset downwards (by the stepdown value) until fragmentation occurs
when the upper edge is exceeded. This can be prevented by using, Mode Merge
instead of Offset Down.

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• Make a copy of toolpath SwarfOffsetdown and Rename
SwarfMerge. Then change the Mode to Merge in the Multiple cuts page.

Merge will use a variable stepdown to exactly track the selected surfaces,
upper and lower edges and minimize the number of lift moves.

• Calculate and close.

• Make a copy of the toolpath SwarfMerge Rename SwarfSinglePass

and change the Mode to Off in the Multiple cuts page.

• Calculate and close.

• Save project and Close

Summary
In this exercise we have created three variants of swarf machining,
including multiple and single passes.

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