VERICUT Users' Forum

BillH

VERICUT Specialist

From: Irvine, CA

Registered: 2004-10-08

Posts: 146

Website

Possible failure to detect a vector programming error

Attention VERICUT users simulating 5-axis milling NC programs that use vector programming!
(i.e. NC programs that use IJK vectors to turn rotary axes to orient the tool axis)

A specific vector position could be incorrectly simulated in VERICUT 6.1.2 (and earlier versions) on specific 5-axis machine configurations. The simulated motion could appear ok, but the actual machine tool motion could cause a collision.
   
Specifically, when the tool axis is aligned with the rotation axis of the parent rotary, then the angular position of that rotary is undefined by the tool axis vector. In this case VERICUT correctly assumes the angular position of the parent rotary does not change for that motion. However, if the tool axis orientation is incorrectly inverted from its current orientation, either due to a fault in the NC path or the post-processor, VERICUT will not detect the tool axis change.

For example, on a machine with an A-Axis on C-Axis rotary head (C is the parent axis):

•    With A at 0 degrees (and C at any angle) the tool axis orientation vector (IJK) specified in the NC program is 0,0,1.
•    Because the tool axis is aligned with C’s rotation axis, the C-Axis angular position is undefined, and maintained at its current position.
•    If the NC program then incorrectly inverts the tool axis orientation vector (IJK) to 0,0,-1, VERICUT does not detect this change and incorrectly maintains the A and C axes at their current positions.
•    In a recent case, the machine attempted to rotate the tool to the invalid 0,0,-1 orientation, which caused a crash on the machine.

The problem is not specific to A/C configurations and can occur with any rotary configuration where the tool axis can be aligned with the parent rotary. The problem only occurs if using vector programming, typically on either a Siemens 840D or Heidenhain iTNC530 control. The problem does not occur if tool axis orientation is programmed via axis angles (either real or virtual angles).

This problem has been fixed for all vector-programming rotary configurations in a pre-release VERICUT 5.4.6 and 6.1.3 version. A production 6.1.3 release will follow soon.

Zip files containing a pre-release update are available at:

ftp://ftp.cgtech.com/Download/pointrel/windows/

Contact CGTech technical support for specific file information and the zip file password.

Note: These updates should only be used to address this specific problem.

VERICUT has been simulating CNC programs that use vector programming for nearly 7 years, and this is the first occurrence of this situation. The chance of this specific condition happening is low. However, it is a critical condition and if you are using vector programming and your machine kinematics could encounter the problem condition described above, you should update to these latest versions, or at least be aware of the situation.