**5.3 Programming finishing operations**

This is an operation of three-dimensional milling, utilizing 3, 4, or 5 free axes, according to arrangement of the machine-tool. This operation is going to remove all excess material of the previous operations and finalize the operations of milling.

In the finish, the axial cut depth parameter passes the tolerance value and depending on the position of the tool-piece, this depth will not be necessarily axial, as illustrated the Figure 11. The tool parameter of geometrical cut itself maintains the same concept.

Fig. 11. Finishing depth of cut

The CAM systems present offer different algorithms to calculate machine paths for finishing. The main principles are:

a. **Parallel passes horizontally constant.** Probably this is one of the first algorithms for finish path calculation to be developed, and is widely employed. Known as

Advanced Free Form Manufacturing by Computer Aided Systems – Cax 569

influenced barely by the equal tool/piece, as is the case of the milling common, but depends strongly of the adequate utilization of the strategy of cut for a determined rank of curvature

Similar upon roughing, the operations of finish also should possess limitations of the areas

Selection of faces of the piece. Upon selecting a face of the geometry, the CAM can

 Manual creation. The user designs, in a plan 2D, the region that is going to limit to machining, that can be in the inside of the border or external, in agreement selection of

 Geometry originating from the CAD. Many times, the user has the option of extract a curve of the geometry, utilizing the CAD, and export it for the CAM, transforming it in

of machining. These borders of finish (boundaries) can be created by different ways:

There are other ways to calculate boundaries, in agreement the software CAM utilized. In many cases, the software CAM utilizes the geometry of the boundary as information help for carry out the calculations of the paths of the tool. Boundaries improperly formed can impact the quality of the machining process. It must itself consider that this boundary many times is a curve kind Spline. Inflection in this curves, which will transformed in a boundary machining are transferred for the tool paths, injuring the quality of machining. A help with the CAD in these occasions can be convenient, in agreement demand of the agreement.

Boundary

(b) Boundary created by sketch wireframe

a. **Verify undesired tool invasions into the part (gouge)**. These invasions can occur either due to error during tool path calculation (software) or by misconceptions of the user, in

of the surface and to its association with the adjacent surfaces.

**5.4 Borders of machining for finishing in specific areas** 

create a border for carry out a specific finish.

Boundary

(a) Boundary calculated by an specific surface

the user.

border of machining.

Fig. 13. Boundary for finishing

**5.5 Simulation of the machining in the CAM software**  The phase of simulation can possess different objectives:

the definitions of the movements and specific settings.

strategy in Zig-Zag or Raster. The software previously creates the parallel paths in a horizontal parametric plan, superior to the geometry it be machined, considering the value of the radial pass informed by the user. These paths, which are spaced out equally in this plan, are projected about the surface that will be machined in the finish, as illustrated it Figure 12.

(a) Preview of tool path calculus on the parametric plane

(b) Calculated tool paths on the surface

Fig. 12. Finishing milling by parallel tool paths strategy

It should be noticed that this strategy is adequate for horizontal regions of the geometry, where the distances between the passes from the tool remain constant, as in the plan parametric. In the regions where the inclination is vertical, the tool passes stay distant, having repercussions in areas that will not be machined in the finish. For motivate, the combination of different strategies in machining, the same piece, is in many ways necessary and convenient.


The CAM systems offer an amount of finishing strategies. The user should identify the adequate for each case.

The choice among the different paths of tool can represent a big influence about the necessary time for the machining, cutting tool load and superficial quality. This it is aggravated in the machining of complex surfaces, where the quality of the trial is not

finish, as illustrated it Figure 12.

(a) Preview of tool path calculus on the parametric plane

many ways necessary and convenient.

be ended up a tool of small diameter.

strategies are employed.

adequate for each case.

Fig. 12. Finishing milling by parallel tool paths strategy

strategy in Zig-Zag or Raster. The software previously creates the parallel paths in a horizontal parametric plan, superior to the geometry it be machined, considering the value of the radial pass informed by the user. These paths, which are spaced out equally in this plan, are projected about the surface that will be machined in the

It should be noticed that this strategy is adequate for horizontal regions of the geometry, where the distances between the passes from the tool remain constant, as in the plan parametric. In the regions where the inclination is vertical, the tool passes stay distant, having repercussions in areas that will not be machined in the finish. For motivate, the combination of different strategies in machining, the same piece, is in

b. **Parallel passes vertically constant.** This strategy is equivalent to previous, considering now the vertical sense. Therefore, the vertical areas of the geometry will be more beneficiary than the horizontal areas. Many times, the combination of both the

c. **Passes in three-dimensional offset.** In this algorithm the paths of the tool are calculated by offset of the contour of the geometry it be machined, maintaining the pass constant even in complex geometries. The inconvenient one of these options of paths is the

d. **Spiral passes conforming to three dimensional profiles.** There are more sophisticated algorithms, which calculate the path of the tool in spiral, following the contour of the

e. **Passes for finishing corners.** These algorithms identify corners of the geometry it will

The CAM systems offer an amount of finishing strategies. The user should identify the

The choice among the different paths of tool can represent a big influence about the necessary time for the machining, cutting tool load and superficial quality. This it is aggravated in the machining of complex surfaces, where the quality of the trial is not

marks in the surface left by the tool in the transition between the passes.

geometry. Few systems CAM has implemented this algorithm successfully.

(b) Calculated tool paths on the surface

influenced barely by the equal tool/piece, as is the case of the milling common, but depends strongly of the adequate utilization of the strategy of cut for a determined rank of curvature of the surface and to its association with the adjacent surfaces.
