Multiaxis Posting

Angle Pair

For many 5-axis machines there are two possible solutions to any point in a toolpath. The solution here refers to the angles used for each rotational axis. The following images show a part with the two possible Angle Pair solutions (this is the tool orientation for the toolpath starting point). The tool orientation to the part is the same in each situation; however, the table is rotated 180 degrees. The Angle Pair options control which solution is used. The purpose of the Auto Angle Pair is to use the solution that creates the least amount of tool-axis orientation change from the previous toolpath position. Keep in mind that some machines can't use both pairs based on rotational limits.

 

Two Solutions

 

There are two main ways to set the Angle Pair settings: Automatic Angle Pair or Manual Angle Pair. These options are explained next.

 

Automatic Angle Pair

When the Automatic Angle Pair option is selected, the following parameters become available.

 

• Select Among Solutions

  When selecting this option, the software attempts to use the angle pair that provides the least amount of machine movement (from the start of the toolpath or previous operation). You can select First Solution and allow the software to calculate the angles. If this setting does not provide the desired results, you can change it to Other Solution to use the other possible angle pair values.
  
  

• First Solution - sets the solution to one of the two possible angle pairs.
  
  
• Other Solution - sets the solution opposite to that of the first solution.
  
  
• Solution Closest to 0 - looks at the two possible solutions and the angle pairs of each. This option looks at the sums of each possible angle pair and gives the result whose sum is closest to zero.
  
  
• Solution not Closest to 0 - looks at the two possible solutions and the angle pairs of each. This option looks at the sums of each possible angle pair and gives the result whose sum is largest.

 

Note: Instead of using Select Between Two Solutions, you can provide a preferred first or second rotation Angle, and the software selects the solution closest to that value. Positive and Negative values can be used and the solution that is closest to the Provided Rotation Angle is used. For example, if you set the First Rotation Angle to 80 degrees, and the two possible solutions are: C = 90 degrees or C = -90 degrees, the post uses C = 90 degrees.

 

• Provide 1st Rotation Angle

Select this option to make the angle box become available so you to type the preferred rotation angle for the first rotary axis. The software uses the closest possible value to the angle you enter.

 

• Provide 2nd Rotation Angle

Select this option to make the angle box become available so you to type the preferred rotation angle for the second rotary axis. The software uses the closest possible value to the angle you enter.

 

Note: There is one more Automatic Angle Pair option that depends on the currently selected Pole Handling option. When you set the Pole Handling option to Force Table Rotation, the following option becomes available under Automatic Angle Pair.

 

• Provide Translation Axis

This option allows you to select the preferred translation axis that you want to use. The software uses the closest possible solution based on the axis you select. You can select the positive or negative direction for any of the three linear axes: 1st Linear Axis [+], 1st Linear Axis [-], 2nd Linear Axis [+], 2nd Linear Axis [-], 3rd Linear Axis [+], or 3rd Linear Axis [-]. What is important to understand is that these labels correspond to the linear axes defined in the machine definition. Generally, for most machines, the first linear axis is the X-axis, second is the Y-axis, and third is the Z-axis.

 

Manual Angle Pair

The Manual Angle Pair options provide another way for you to set the angle pair used for the machine.

 

• Solution 1 or Solution 2

After selecting the Manual Angle Pair option, you can select Solution 1, or Solution 2. If you are unsure which setting to use, leave the default and post the code. If this does not provide the desired solution, change to the other option.

Angle Pair (4 Axis Machines)

When a four-axis machine is selected, the Angle Pair settings change to an optimized set that apply to these machine types. These options are explained next.

 

• Auto
  This setting allows the software to automatically calculate the appropriate angle to use for the rotary axis.

 

• Provide Rotation Angle
  This setting allows you to type the preferred rotation angle in the angle box. The software uses the closest possible value to the angle you type.

 

• Provide Translation Axis
  This option is unavailable until the Pole Handling setting is Force Table Rotation. This option allows you to select the preferred translation axis that you want to use. The software uses the closest possible solution based on the axis you select. You can select the positive or negative direction for any of the three linear axes: 1st Linear Axis [+], 1st Linear Axis [-], 2nd Linear Axis [+], 2nd Linear Axis [-], 3rd Linear Axis [+], or 3rd Linear Axis [-]. What is important to understand is that these labels correspond to the linear axes defined in the machine definition. Generally, for most machines, the first linear axis is the X-axis, second is the Y-axis, and third is the Z-axis.

 

Machine Limits

The Machine Limits are used to confirm that the machine limits are not exceeded. When a program exceeds the set limits, it does not post. To set the Machine Limits, select a limit group from the Limits box and then type values for the following two parameters.

 

• Angle Tolerance For Using Machine Limits - type a value from which the selected Machine Limits can vary. If you set Machine Limits for an axis between 0 and 90 degrees and set an Angle Tolerance of 2, then the possible range becomes -2 to 92 degrees.
  
  
• Angle Change Limit - type a value in degrees to limit the amount of angle change from one toolpath position to the next. If an angle change exceeds this limit, then a retract move is applied in the post.
  
  
• Limits - select one of the following options to be affected by the Angle Tolerance and Angle Change Limit parameters:
  
  
  • No Limits
    
    
  • Translational Limits
    
    
  • Rotational Limits
    
    
  • All Limits

 

Pole Handling

When a five axis machine is used to run a 3-axis toolpath, there are certain situations that make the C-axis value arbitrary. What this means is that by changing the X- and Y-axis values appropriately, any C-axis value used creates the same results. For example, when a cylinder is located in the center of the table, depending on the machine, there are multiple ways to cut the profile of the cylinder. The rotation axis can be fixed while the linear axes are used to cut the part. On the other hand, the linear movements can be fixed, while the table is allowed to rotate in order to cut the part. This situation where the C-value is arbitrary, because the spindle direction and the table direction are collinear, is called a singularity or pole. The Pole Handling options are used to control these situations as follows.

• Freeze Angle Around Pole - fixes the rotational axis in order to use the linear axes movements.
  
  

• Linear Interpolation of Rotation Angle Around Pole - calculates rotational axis values to make the changes from one value to the next in a linear fashion. The linear distribution is based on the tool tip position from one toolpath point to the next. This is useful when a 3-axis toolpath is converted to a 5-axis toolpath. For example, when a toolpath transitions from linear motions to rotational motions (from 3-axis to 5-axis), an abrupt change can result because of the conversion. This option is used to avoid these abrupt changes by setting a constant (linear) rate of change for the rotational axis.

 

Without Linear Interpolation	With Linear Interpolation

 

• Smooth Interpolation of Rotation Angle Around Pole - similar to Linear Interpolation, this option also manipulates the table rotation speed to create a more fluent transition.

 

Without Smooth Interpolation	With Smooth Interpolation

 

• Force Table Rotation - uses table rotation moves instead of linear moves when a multiaxis toolpath approaches 3-axis positioning.
  
  

 

• Pole Angle Tolerance - controls how far from the main spindle direction the tool axis can tilt and still be considered parallel, in order to be used as a pole.
  
  

Tool Repositioning

In certain scenarios, when machine limits are reached, a retract move is needed. Tool Repositioning affects the retract move.

 

• Retract Tool To Maximum
  
  Select the check box to retract the tool to the maximum distance set for the machine.
  
  Clear the check box to type a retract distance in the Tool Retract box.
  
  
  • Tool Retract - type a value for the tool retract distance when the Retract Tool to Maximum check box is cleared.

 

Point Interpolation

• Interpolation Type - select one of the two following options.
  
  
  • By Vectors - creates the interpolation between the two endpoints of a toolpath segment in the shortest possible way. The movement happens in a flat plane.
    
    
  • By Machine Angles - creates the interpolation between the two endpoints of a toolpath segment gradually with respect to the machine kinematics. The movement does not necessarily happen in a flat plane.
    
    

 

 

Retract and Rewind

Some machines have rotational limits that cannot be exceeded. In this situation, the machine must retract the tool and rewind the rotation axis to avoid exceeding the limits. The retract and rewind options determine how the machine handles exceeded rotation limits.

 

• Retract and Rewind
  
  Select the check box to have the machine perform a retract and rewind move to avoid exceeding rotational limits.
  
  Clear the check box if you don't want to generate a retract when the machine needs to rewind (this may result in collisions depending on the part and machine).
  
  
  • Angle
    
    Select the check box to specify an angle step for the retract moves that are used with the Retract and Rewind option. This determines the amount of rotation between possible retract moves. A large value results in less moves and a smaller value may result in more moves.
    
    Clear the check box to allow only a single retract position to be utilized for the retract and rewind moves. All retract moves use the same location to move to clearance.

 

Machine Definition Zero

• Real Machine Zero - the posted NC program uses the actual machine zero location.
  
  
• Work Offset Position - the posted NC program uses the location defined by the work offset.

 

Move List Writer

The Move List Writer options control what appears in the posted NC program. These options are used to set machine limits that are not exceeded in the posted NC program. Some machines don't have rotational limits, and some don't except large angle values. You can limit the angle values used.

 

• 1st Rot Axis Angle Limit - limits the values used for the first rotational axis. Select: No Limits, Limit Between 0 and 360 degrees, or Limit Between -180 and 180 degrees.
  
  
• 2nd Rot Axis Angle Limit - limits the values used for the second rotational axis. Select: No Limits, Limit Between 0 and 360 degrees, or Limit Between -180 and 180 degrees.