Tutorials:-Working with Power MILL "PART V" Toolpath Leads and Links


Z Heights

Skim and Plunge distance provide variable control of rapid move heights within a component. These operate in conjunction with Safe Z and Start Z to minimize slow and unnecessary movement of the tool in fresh air while machining the component form.

Skim distance – An incremental distance above the model at which rapid moves occur from the end of one tool track to the start of the next. The tool rapids across the model clearing the highest point along its route by the Skim value.

Plunge distance – An incremental distance above the local component surface where a downward rapid movement of a tool changes to plunge rate.

  1. Step 1:

    Lead In/Lead out Moves

    Lead In controls the tool movement onto the start of a tool track and Lead Out the movement away from the end of a tool track. Lead In moves available include None, Vertical Arc, Horizontal Arc, Horizontal Arc Left, Horizontal Arc Right, Extended Move, Boxed and Ramp. The same options exist for Lead Out moves apart from the omission of Ramp.

    Leads and Links are effectively extensions to tool tracks and as result must be gouge protected. To prevent gouging, the Gouge Check flag should be ticked (default) on the Toolpath Leads and Links Form. Any Lead that would result in a gouge will not be created. The following examples illustrate different leads and links, and unless otherwise stated, Gouge Check should always be set.
    If any instances occur where the 1st Choice cannot be applied then the software will apply the 2nd Choice. If neither option is valid under gouge check conditions then the Lead will be locally applied as None.
    The Current settings of Leads and Links are included in the creation of new machining strategies. Alternatively they can be applied later to the Active toolpath in the explorer.

  2. Step 2:

    •Edit the toolpath with Limit to a Plane with an X value of 74 leave all other options as default.

    The new Active toolpath has Lead In and Lead Out set to None (default). With the limited toolpath 1_1.

    •Right click on the Toolpath 1_1 and select Edit  Copy Toolpath.
    •Activate the copied toolpath 1_1_1.

  3. Step 3:

    Vertical Arcs

    •In the Toolpath Leads and Links Form, select the Lead In tab.
    •Select Vertical Arc with a Radius 5 and Angle 90 and press Apply

    Vertical arcs Leads creates a circular movement downward at the start and upward at the end of each tool track.

  4. Step 4:

    There is now a Vertical Arc leading into each tool track. If the required Lead Out is to be exactly the same as the Lead In and vice versa the Edit option allows easy copying of the settings between the two.

    •Select the Lead Out tab.
    •Select the Copy from Lead in button.
    •Apply the form to modify the active toolpath.

  5. Step 5:

    Horizontal Arc

    This produces circular leads on the horizontal plane, and the Radius and Angle value is similar to that for Vertical Arc. This type of lead is frequently used for toolpaths running at constant Z, or with only small changes in Z height.
    •Change the Lead Out to None.
    •Change the Lead In to be Horizontal Arc with Radius 5 and Angle 90 and select Apply.

    The Horizontal Arcs have been generated on all tool tracks. With Horizontal Arc set PowerMILL makes its own mind up which direction the arcs are given. They are also calculated to comply with the Gouge Check flag. If it is not possible to apply the specified lead due to a gouge situation it will remain as the default vertical move (unless the Gouge Check flag is

    •Change the Lead In to be Horizontal Arc Right, so that it performs a right hand arc move on to the cutting direction and press Apply.

  6. Step 6:

    •Select the Copy to Lead Out button and Apply.

    All but one of the Leads has been applied. By default PowerMILL will not apply Leads and Links where gouge would occur. To apply a Horizontal Lead Out to this tool track a different Lead option will be applied to the 2nd Choice area of the form.

    •In the Lead Out 2nd Choice area select Horizontal Arc with Angle 90 and Radius 5 then Apply.

    PowerMILL has applied a 1st Choice, Horizontal Arc to all parts of this tool track where it can do so as a gouge free move.
    At this position the 2nd Choice - Lead Out has been applied in preference to the 1st Choice - Lead Out due to the latter being a potential gouge situation.
    As long as the Gouge Check flag is ticked, if both 1st and 2nd Choice options would result in a gouge then a direct Z move will be applied instead.

  7. Step 7:

    It is essential to keep the Gouge Check flag on. There are however certain specialised applications where the desired results can only be achieved if Gouge Check is switched off. These mainly include undercut and multi-axis machining where alternative gouge checking and removal procedures are applied.

  8. Step 8:

    Extended Move

    Extended Move inserts a linear, tangential move on to or off the end of a tool track. When selected, the Distance box becomes highlighted ready for the insertion of a suitable value.

  9. Step 9:

    Set the Lead Out 1st and 2nd Choices to None.

    •Change the Lead In to an Extended Move with Distance 10 as shown and Apply.

    The Lead In to each tool track is modified as shown below.

  10. Step 10:


    An Extension is an additional part of geometry to be added to the start or end of a Lead. For example, a Straight Extension could be added to a Circular Lead In/Out where a machine tool cannot apply cutter compensation on the arc move. The relevant adjustment will occur during the linear extension move.

    The geometry options for Extensions are exactly the same as for Leads.

    •Activate the toolpath 1_1_1.
    •Set the Lead In as Vertical Arc with a Distance of 0, Radius of 5 and an Angle of 45 degrees.
    •Select the Copy to Lead Out button.
    •Open the Extensions tab and set values as shown and press Apply.

    Extensions running tangential to the original vertical arc leads are created and can be quite useful to allow an approach from outside of the component surfaces.

    •Set the Extensions Inward and Outward to Straight with the values shown.
    The Angle in the Straight Extension area is calculated from the direction of the Lead In. To confirm this we can change the angle and view the results.

  11. Step 11:

    •Set a view in Z and change the Inward Straight Angle to 45 Degrees then Apply.

    The approach angle is clearly seen to be at 45 degrees from the direction of the Lead In.

    •Set both Inward and Outward - Extensions back to None.


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