About Defining Machine Kinematics

Rules that must be considered when validating the inverse kinematics of a machine are described below.

Once you have assembled a product to build a machine and created joints to fix these products to the NC resource, you can validate the inverse kinematics of the machine. Respecting the rules below will result in the successful assignment of the automatic inverse kinematics solver. For Inverse kinematics to work correctly, While defining the joint, moving part of the joint should be selected as Child(or Outer) part. The Stationary part of the joint should be selected as Parent(or Inner) part. This Parent/Child rule applies for Rigid joint also.

  • Machines can be built as a single chain or as a maximum of two chains. For a machine that has two chains, if one chain contains the spindle then the other must have the table.
  • At least one prismatic connection is necessary to complete the NC resource kinematics definition.
  • The direction of the prismatic command can be modeled along any direction and need not necessarily be along the three principal directions.
  • One of the following combinations of rotary and prismatic commands is necessary to complete the automatic assignment of inverse kinematics.
    • Up to two rotary commands without any prismatic commands. If there are two rotary commands, their axes of rotation must not be parallel.
    • Up to three prismatic commands without any rotary commands. If there are multiple prismatic commands located on the same chain, their axes must not be parallel. If a parallel axis exists on the same chain, one of the parallel axes must be locked in the program using Machine Instruction. The axes can be parallel only if the commands are located on separate chains.
    • Three prismatic and up to two rotary commands, with the same restrictions as noted above.
  • The axis of rotation of the revolute connection can be along any direction in space.
  • There cannot be more than two revolute connections on the NC resource.
  • The rotary joints can be located anywhere in a chain.
  • The mount points (workpiece and tool) must be defined for the automatic inverse kinematics solver to work correctly.
  • If a machine consists of a chain in which a number of parts are joined together, then:
    • In a bifurcated chain, the mount points must be located on the last part of the chain which belongs to the last connection.
    • In a single-chain machine, the workpiece mount point can be located on the fixed part, while the tool mount point can be located on the last joint part of the chain.
  • Inverse kinematics is also supported for a machine consisting of:
    • two prismatic joints on one chain, and
    • one rotary joint on the other chain, with the axis of rotation parallel to one of the prismatic joints
    The linear motion required along the normal to the two prismatic commands is made using the rotation of the part in the second chain.
  • For interchangeable heads, up to only two rotary joints are supported for simulation. Linear joints are not supported.
  • During simulation, the milling machine and interchangeable head, together, should have only up to three linear and two rotary joints. Further all rotary joints must be part of either milling machine or interchangeable head.