Delta Tau GEO BRICK LV User Manual

 

 

In operation, Turbo PMAC starts from the uncompensated X, Y, and Z-axis positions for each end-point 
programmed while 3D compensation is active.  Then two offsets are applied to the X, Y, and Z-axis 
positions.  The first offset is taken along the surface-normal vector, of a magnitude equal to the tip radius.  
The second offset is then taken toward the center of the tool, in the plane containing both the surface-
normal vector and the tool-orientation vector, perpendicular to the tool-orientation vector, of a magnitude 
equal to the cutter radius minus the tip radius. 

Once the modified end-point is calculated, the move to that end-point is calculated just as it would be 
without compensation.  If the program is in LINEAR mode, it will be linearly interpolated.  If the 
program is in CIRCLE mode (not advised), arc interpolation will be applied. 
Because the offset to the end-point is directly specified for each move, there are no intersection points for 
Turbo PMAC to compute using the equations for the next move.  This means there are no special 
lookahead or single-step execution considerations, as there are in 2D compensation. 

All moves in 3D compensation are directly blended together.  There are no special considerations for 
outside corners, as there are in 2D compensation.  Also, there are no special considerations for the lead-in 
and lead-out moves.  The lead-in move is an interpolated move from the last uncompensated position to 
the first compensated position.  The lead-out move is an interpolated move from the last compensated 
position to the first uncompensated position. 

TR

CP

PP

PP: Programmed Position
CP: Compensated Position
N: Surface-Normal Vector
T: Tool-Orientation Vector
CCR: Cutter’s End Radius
TR: Tool Shaft Radius

N

T

TR-CC

R

C

C

R

 

Turbo PMAC can perform highly sophisticated lookahead calculations on programmed trajectories to 
ensure that the trajectories do not violate specified maximum quantities for the axes involved in the 
moves.  This permits writing the motion program simply to describe the commanded path.  Vector 
feedrate becomes a constraint instead of a command; programmed acceleration times are used only to 
define corner sizes and minimum move block times.  Turbo PMAC will control the speed along the path 
automatically (but without changing the path) to ensure that axis limits are not violated. 

Lookahead calculations are appropriate for any execution of a programmed path in which throughput has 
been limited by the need to keep execution slow throughout the path because of the inability to anticipate 
the few sections where slow execution is required.  The lookahead function’s ability to anticipate these 
problem areas permits much faster execution through most of the path, dramatically increasing 
throughput.