Opposite Hand Machining

This document provides methodology for machining symmetrical parts and left-hand/right-hand parts. A user task showing you how to program using Opposite Hand Machining techniques is also include in this guide.

Although this is quite a flexible process, there are usually 3 steps involved:

  1. Preparing the program
  2. Transforming the machining operations and reversing the machining conditions
  3. Locally editing the transformed program.

By following this method, you will obtain a program for the symmetrical part that has the same cutting conditions as the initial part.

Preparing the Program

The following methodology assumes that a proven program already exists for one symmetrical half of a part or for one workpiece in a left-hand/right-hand pair.

Taking the example of an existing left-hand program, you should make a copy of the program (or the operations in the program) in one of the following ways:

Transforming the Program and Reversing Machining Conditions

To transform the copied program (or operations):

Modified operations can be easily identified in the program due to the update symbols () that appear in the tree. The tool paths of these operations must be computed or re-computed.

Due to the applied transformation followed by the Reverse Machining Conditions processing, the cutting conditions are now reset to the values of the initial program.  A summary of the processing appears on an information pop-up.

Note that the cutting conditions of deactivated operations () can be changed, since they can be edited. However, the cutting conditions of locked operations () cannot be changed, since they cannot be edited.

Locally Editing the Transformed Program

The program may need to be finalized by means of some local editing.

If the operations of the original program are linked one after the other, you may need to reverse the order of these operations in the processed program. This is the case, for example, if the end point of Operation1 is the start point of Operation2.

In this case, you can use the Reorder Operations List command to reverse the order of one or more groups of operations. In the example below, the groups A, B, C and E, F were selected and reversed.

Operation.A

Operation.B

Operation.C

--------------->

Operation.C

Operation.B

Operation.A

Operation.D Operation.D
Operation.E

Operation.F

Operation.F

Operation.E

Note that groups of operations must be selected one after the other in the tree and they must use the same tool. Operations in each group must be selected from top to bottom.

Similarly, it may be necessary to inverse the approach and retract macros on an operation. In this case, select the relevant operations and select the Inverse Macros command .

Operations Processed by Opposite Hand Machining

The following table summarizes the references elements that are transformed by Opposite Hand Machining. Typically, the Reverse Machining Conditions command must be applied to these operations in order to retrieve the cutting conditions of the initial program.

Operation Effect of Opposite Hand Machining
3-axis Roughing Climb and Conventional options are inverted.
Spiral Milling Climb and Conventional options are inverted.
Axial Machining Operations Order of pattern points is reversed in the tool path.
Pocketing Climb and Conventional options are inverted.
Facing Climb and Conventional options are inverted.
Profile Contouring Climb and Conventional options are inverted.
Order of multi-contour is inverted.
Start and End elements, offsets, and conditions are inverted.
Groove Milling Climb and Conventional options are inverted.
3-axis/5-axis Isoparametric Machining Order of parts is inverted.
Corners 1 and 2 are swapped.
Corners 3 and 4 are swapped.
Corresponding interpolation axes at corners are swapped.
5-axis Flank Contouring Order of drives is inverted as follows when the Close tool path check box is not selected in the operation's Machining parameters tab.
Drives A, B, C, D are machined in the order D, C, B, A.

Before Opposite Hand Machining:


After Opposite Hand Machining:

Order of drives is inverted as follows when the Close tool path check box is selected in the operation's Machining parameters tab.
Drives A, B, C, D are machined in the order A, D, C, B, A.
Drive A is the first and last machined element.

Before Opposite Hand Machining:


After Opposite Hand Machining:

Start and End elements, offsets, and conditions are inverted.
Approach and Leave distances are swapped.
Manual direction is reversed (Left / Right).
Local stopping condition and Local restarting direction are updated.

5-axis Curve Machining Climb and Conventional options are inverted.
Sign of Tilt angle is changed to invert the left/right condition.
Couple of Points limit elements are swapped.

For Tangent Axis guidance along isoparametric lines:
when machining a strip of drive surfaces, check that the reference tool axis gives the desired result for the best matching u or v isoparametric line of the first machined face.

CUTCOM You should check that the desired cutter compensation is still applied (correct side, and so on).

Typical User Scenarios

Machining of any symmetrical right part, when left part machining is already defined.
The right part does not exist as a physical model, everything is referenced on the left part.

Scenario 1: Creation

Program of left-hand part has been defined.

  1. Duplicate left-hand program (CTRL+C, CTRL+V) and rename it 'Right Program before Transform'.
  2. Use the TRACUT Operator command to manage the symmetry. You can also use another way to transform the resulting tool path. The CUTCOM syntax is not taken into account by the transformation. PQR output is taken into account by the transformation.  This may be done in a 'Final left program after symmetry'.
  3. Select the Auxiliary Operations tool bar.
  4. Check the Options command in order to select operation types for Reverse Machining Conditions processing.
  5. Select the block of operations to be processed.
  6. Select the Reverse Machining Conditions command.
  7. Compute the new tool paths.
  8. Locally edit the program, if needed (to reverse the order of operations, macros, pattern points, and so on). 

Scenario 2: Modification of the left program

Operations in left-hand program have been updated because of design changes, but the tool path was fully associative.

In this case, right-hand program is updated and is associative.

Scenario 3: Modification of the left program

Operations in left-hand program have been updated because of design changes, some operations have been edited to take new geometry into account.

  1. Delete existing old operations in the 'Right Program before Transform'.
  2. Select and duplicate the modified operations in the 'Right Program before Transform'.
  3. Do local opposite hand processing and modifications on operations.

Scenario 4: Modification of the left program

Some operations' options in left-hand program have been modified, or some operations have been added to left part.

  1. Delete existing old operations in the 'Right Program before Transform'.
  2. Select and duplicate the new and modified operations in the 'Right Program before Transform'.
  3. Do local opposite hand processing and modifications on the operations.