Finishing is usually performed on a given surface with a single operation that uses a single part setup and a single tool approach (see Setup Axis GCDs). However, in some cases, aPriori determines that finishing a given surface is best accomplished using a combination of different tool approaches and/or a combination of different operations. This can happen when there is no single tool approach from which all the surface is accessible to finishing or side milling (using a feasible tool).

Consider, for example, the surface highlighted in yellow, below:

For a tool approaching from the top (in this picture), some of the highlighted surface is obstructed by other surfaces, and so is inaccessible; similarly, for a tool approaching from the bottom, some of the surface is obstructed and so is inaccessible. But each point on the surface is accessible from one or the other approach, so aPriori assumes that one approach is used to side mill part of the surface, and the other approach is used to side mill the rest of the surface.

Multiple approach finishing is implemented by the following operation sequences, which are available for milling processes only:

Planar Face finishing:

Curved Wall finishing:

Multiple approach sequences are generally assigned to a surface only if all the following hold:

For a surface and tool approach, The Direction Type property of the Is Accessible From relation indicates whether the approach is obstructed.

To find a surface’s accessible area for a given tool approach, find the Accessible Surface Area property of the Is Accessible From relation that relates the surface and the tool approach:

A surface’s total surface area is given by the Finished Area property of the surface:

In general, given a multi-approach operation sequence, aPriori assumes that the more efficient operation finishes all of the surface that it has access to and the other operation finishes the remainder of the surface. For Side Milling/Side Milling or Contouring/Contouring, the first operation finishes all of the surface that it has access to and the second operation finishes the remainder of the surface.

Note that it is possible in rare cases that the two approaches do not have access to the entire surface, causing aPriori to underestimate the finishing time required. This can happen, for example, when full access from the first approach is prevented by multiple distinct obstructions; the second approach may access the area blocked by one obstruction to the first approach, but nevertheless fail to access the area blocked by another obstruction.

To highlight the surfaces that are finished with multi-approach sequences, select Multi-Approach Operation in the Criterion menu of the Geometry Analysis tool.

Note that, in addition to multiple-approach finishing, aPriori supports variable-approach finishing. With variable-approach finishing, available for 5-Axis Mill and Mill Turn routings, the tool orientation varies while the tool is engaged. This allows for a single operation that combines side milling and contouring or contouring from various angles—see Allow the Use of Flank Milling in Machining Node Process Setup Options.

If Facing alone is not feasible for a planar face, and Side Milling alone, from a single approach, is also not feasible for the planar face, aPriori attempts to assign the sequence Side Milling/Facing to the surface. The illustration below shows a planar face (PlanarFace8, in yellow) to which aPriori assigns Side Milling/Facing:

For this surface, Facing alone is not feasible because the surface is partially obstructed from the approach that is normal to the surface. And Side Milling alone is not feasible for this surface, because the surface is partially obstructed from any approach parallel to the surface. But Facing and Side Milling can each access part of the surface. Therefore, aPriori assigns Side Milling/Facing to the surface.

(Note that Facing followed by Side Milling is shown as Side Milling/Facing in the Operation Sequence Selection dialog.)

In the illustration below, the yellow arrow shows the direction, SetupAxis4, from which the tool approaches for side milling. This part uses a 4-Axis Mill routing, and the upwards-pointing purple arrow shows the part setup axis, which is aligned with the machine’s axis of rotation.

Note that the Geometric Cost Drivers pane shows that the side milling tool approach has Parallel Obstructed as the Direction Type.

In the illustration below, the yellow arrow shows the tool approach, SetupAxis8, used for face milling. Note that the facing tool approach has Normal Obstructed as the Direction Type.

aPriori assumes that Facing handles all of the surface that is accessible to Facing, and that Side Milling handles the remainder of the surface.

The surface’s accessible area for the Facing tool approach (represented by SetupAxis8) is the value of the Accessible Surface Area property of the Is Accessible From relation that relates the surface and the tool approach:

The surface’s total surface area is given by the Finished Area property of the surface:

In this case, side milling is assumed to finish a surface area of 10,850.62 - 4836.52 = 6014.10mm2.

The illustration below shows another planar face (PlanarFace:2, in yellow) to which aPriori assigns Side Milling/Facing:

For this surface, Facing alone is not feasible because the surface is partially obstructed from the approach (SetupAxis:2) that is normal to the surface.

In addition, Side Milling alone is not feasible for this surface, not because of an obstruction, but because the tool reach would have to be too long compared to the tool’s diameter (see Length to Diameter Ratio Check).

But Facing and Side Milling can each access part of the surface. Therefore, aPriori assigns Side Milling/Facing to the surface.

Facing/Side Milling is available for the following processes:

The operation sequence Side Milling/Side Milling can be assigned to a planar face or curved wall that is not fully accessible to side milling from any single tool approach, but can be side milled using a combination of two approaches.

The operation sequence is used only if none of the following are feasible:

Side Milling/Side Milling can be used for the following types of GCD:

The illustration below shows a planar face (in yellow) to which aPriori assigns Side Milling->Side Milling:

For this surface, Facing alone and Facing->Side Milling are not feasible because the surface is entirely obstructed from the approach that is normal to the surface. And Side Milling alone is not feasible for this surface, because the surface is partially obstructed from any approach parallel to the surface. But Side Milling from two different approaches can access all of the surface. Therefore, aPriori assigns Side Milling->Side Milling to the surface. (Side Milling followed by Side Milling is shown as Side Milling/Side Milling in the Operation Sequence Selection dialog.)

The arrows in the image below show the two directions (SetupAxis:1 and SetupAxis:2) from which the tool approaches in order to perform side milling. Since this part uses a 3-Axis Mill machine, the two milling operations are performed using two different part setups.

Both approaches have Parallel Obstructed as the Direction Type of the Is Accessible Relation between the surface and the approach.

The illustration below shows another surface (in yellow) to which aPriori assigns Side Milling/Side Milling. In this case, the two side milling approaches are orthogonal to each other. The arrows show the two directions (SetupAxis:2 and SetupAxis:3) from which the tool approaches:

aPriori assumes that the first operation handles all of the surface that is accessible to it, and that the second operation handles the remainder of the surface.

This operation sequence is available for the following processes:

A planar face that is not fully accessible to face milling can sometimes be machined with a combination of facing and contouring. In such a case, aPriori may assign Facing/Contouring to the surface.

The operation sequence is used only if none of the following are feasible:

This operation sequence is available for the following processes:

The following illustrations show a pocket whose floor (a planar face, in yellow) is partially obstructed by an angled side wall:

Face milling can access all of the surface except the undercut edge. If this part is routed to a Mill Turn routing (which must be selected manually), aPriori assigns Facing/Contouring to the surface.

In the image below, the yellow arrow shows the direction from which the face milling tool approaches.

The Mill Turn machine can tilt the spindle and rotate the part around the turning axis so that the contoured region is accessible using the same part setup as was used for facing. aPriori assumes that Facing handles all of the surface that is accessible to Facing, and that Contouring handles the remainder of the surface.

In some cases, aPriori determines that a curved wall should be finished with contouring that uses two different tool approaches. This can happen only if none of the following are feasible:

The image below shows a part with a curved wall (in yellow), half of which is accessible from the top, and half of which is accessible from the bottom.

If this part is routed to a 3-Axis Mill, the curved wall (CurvedWall:4) is assigned Contouring/Contouring, using two different part setups.