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:

• Copy/Paste the left-hand program to create a new program. This method is suitable for symmetrical left-hand/right-hand parts

• Copy/Paste operations in left-hand program to create a new operations in that program. This method is suitable for a symmetrical (or nearly symmetrical) workpiece.

• perform a File>Save As of the CATProcess.

Transforming the Program and Reversing Machining Conditions

To transform the copied program (or operations):

• Use the TRACUT Operator command to create and apply a transformation in order to create a symmetrical tool path (Mirror or other suitable transformation).

  After applying the transformation to the tool path, the cutting conditions of some operations may be reversed (climb/conventional milling, for example).

• Select the Opposite Hand Machining Options command . In the dialog box that appears, select the types of operations whose cutting conditions change after a Mirror type transformation. You can now apply a Reverse Machining Conditions processing to the selected operation types. The following dialog box shows the operations supported with  Reverse Machining. The reverse cutting conditions are supported for all mill type operations. By default all buttons are enabled.

• In the specification tree, select the program (or groups of operations) whose cutting conditions have to be reversed and apply the Reverse Machining Conditions command .

If Reverse Keyword specified in the Tools > Options > Machining > Operation is _Reverse and if Reverse machining command is applied to Multi-Axis Spiral Milling. Keyword will be appended to the MO name at end and new MO name will be as shown in the image below (MO name get appended to Multi-Axis Spiral Milling_Reverse). After Reversing, a message will pop up indicating number of MO's selected, treated, and updated. Modified operations can be easily identified in the program due to the out-of-date symbol () that appear in the tree.

If any of the MOs selected are locked, the the message Some of the Operations are locked. Do you want to unlock them and apply reverse machining conditions comes. If you select Yes the Locked MOs are unlocked and Reverse condition is applied. If you select NO only the MOs which are not locked will be treated for Reversing Machining condition.

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.

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.

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.