The result of material processing with a laser beam depends primarily on the interaction time with the material. It is for this reason that laser material processing systems must be equipped with a dynamic single-axis or multiple-axis control. In addition, the control must account for additional functions, so-called M functions, for laser control. Ideally, the controller should allow constant surface speeds, irrespective of the contour. Due to the required calculating time as well as the inertia of the follow-up system, controllers with an older design have a disadvantage that the actual position of the laser beam always lags behind the theoretical position. The distance between the theoretical and the actual position is the “trailing distance”. Novel controllers allow highly dynamic acceleration of the axis drives, combined with the required change of direction in the axis movements. They also allow synchronization with the laser power control without noticeable trailing faults. For this reason, only slight deviations from the theoretical track speed and the theoretical track contour are possible.

CNC controls function as follows:

1. Preparation of the programmed control data for the track movement.
2. Determination of the theoretical positional values for the individual drive axes using an interpolator.
3. Determination of the positional deviation by comparison of the theoretical positional values for the individual axes with the corresponding actual value.
4. Specification of the theoretical speed and optimization of positional control and dynamics by the so-called Kv factor. The Kv factor is an indication of the circuit amplification of the entire closed-loop control circuit.
5. Derivation of the required speeds for the drive motors.
   The most important parameter to describe the capacity of a given controller is the block cycle time. This time period is needed to process an NC data record. Modern controllers realize short access times to the machine system, for instance by fast M functions.

Modern controllers are equipped with a servo processor used exclusively to process the required interpolations. To this end, the CNC data records are initially prepared by a basic processor. The processor is responsible for keyboard entries as well as other preliminary program tasks. It is only when a buffer installed between the basic processor and the servo processor is filled with the feed commands of several CNC data records that the servo processor starts to output the desired values for the positioning control circuit. Thus, the block cycle time may be reduced to a few milliseconds only.

During laser material processing, the laser power must be adapted to the constantly changing process conditions, for example contour-related speed reduction via a corresponding power control system. The following control options are available:

• Speed-related (proportional) ramp functions, and
• Path-controlled or time-controlled functions.

Three different types of interpolation are available for the connection of programmed interpolation points:

• Linear interpolation,
• Circular interpolation, and
• Spline interpolation.

Due to the connection of points by a 5th degree polynomial, positioning in accordance with the spline function may lead to collisions between the machining head and the workpiece. This type of interpolation is therefore not always very useful in controlling a machining head. Today, the motion information is usually programmed directly by keyboard entry on an operator’s panel, or by “teach-in”. Teach-in means moving the system to a certain sequence of interpolation points and then entering these data in the CNC. Another option involves off-line programming where the corresponding track information is derived from the CAD data of a given component.