Use the Step cutting page to create intermediate toolpath slices to reduce terracing. It rest machines the terraces remaining from a large area clearance toolpath with the same tool in the same toolpath.
The first pass is a main slice.
The next pass is the lowest step-cutting slice.
The next pass is the next to lowest step cutting slice and so on up the part (shown by 
) until the previous main slice is reached.
The next main slice.
The main slices are cut from top to bottom as normal. The intermediate slices are cut from bottom to top. This is possible because the depth of cut is always less than the depth of cut (or Stepdown) for the main slice. This is the most efficient way of cutting the part as it reduces the number of passes and increases the depth of cut of each pass.
This page contains the following:
Step up — Enter the distance between intermediate cutting levels. The main slice clears the majority of the material. The intermediate slices remove the terraces remaining after the main slice.
Stepdown of the main slice.
Stepup of the intermediate slice.
Detect material thicker than — Enter a threshold value. PowerMill ignores rest material that is thinner than the specified threshold. This helps to avoid thin regions being rest machined, where the benefit of a second cut is negligible. These thin regions can be caused by cusps from the previous toolpath.
Expand area by — Enter the distance by which to expand the rest areas, measured along the surface. Use with the Detect material thicker than value to reduce the areas to be machined to the details (for examples, corners), and then to offset these areas slightly to ensure that all the detail (for example, on the corners) is machined. For the example below, use the Expand area by option to increase the rest area (the blue hatched area) and eliminate the undetected area (the black area).
Model
Thickness
True rest material (outlined in pink)
Actual rest material detected (blue hatched area)
Amount you need to expand the area by to include all the rest material
Undetected material (black area)
Tool
Reference tool
Constant volume removal — Select to increase the Feed rate of the intermediate slices. Because the stepdown of the intermediate slices is less than that of the main slice, you can increase the feed rate of the intermediate slices while maintaining the tool load. Each intermediate slice can have an increasing feed rate as the depth of cut gets progressively smaller. PowerMill determines the increase in feed rate for intermediate slices based on the depth of cut. So if the maximum depth of cut for an intermediate slice is half that of a main slice, the feed rate can be twice as fast. To see the effect of the varying feed rate, select Drawing Options > Draw Feeds from the individual toolpath menu.
Maximum feed rate % — Enter the maximum allowable cutting feed rate for the intermediate slices as a percentage of the base cutting feed rate specified on the Feeds and Speeds dialog. This value must be larger than 100%. A value of 300 means the cutting feed rate of the intermediate slices can be up to three times faster than the base cutting feed rate.
Maximum feed rate mm/min — Enter the maximum allowable feed rate for the intermediate slices. (Base cutting feed rate x %).
Base cutting feed rate (mm/min) — Displays the cutting feed rate as specified on the Feeds and Speeds dialog. To change this value click 
.
Feed rates — Click to display the Feeds and Speeds dialog.