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(Usually referred to as the A axis when it is set up to rotate along the X axis)

Indexing mode: is when the 4th axis rotary table is used for point to point positioning of the workpiece. No cutting happens until the 4th axis has stopped. For example, indexing 90 degrees to drill holes on four sides of a rectangular part.


Continuous mode: is when machining happens as the workpiece is being rotated by the 4th axis rotary table. For example, Z axis slowly feeds into the outer diameter of a cylindrical part with a ball end mill as the rotary table (A axis) slowly rotates while the X axis also slowly feeds creating a spiral or helical groove that get deeper towards the end of the move. 


4th Axis Ready: is when the CNC machine has everything needed to plug in the 4th axis rotary table and is ready to use. The parts needed to be 4th axis ready usually include the amplifier and all the cables needed to power the motor, provide feedback to and from the encoders and control brake functions, etc. The cables from inside the CNC control cabinet most often lead to bulkhead connectors in the top sheet metal of the machine enclosure where the rotary table cables are then connected.


Single Axis Control Box: This box, when connected to the 4th axis rotary table is usually the most economical route when your machine is not 4th axis ready and you do not need to run in continuous mode. The different methods to interface the box to your machine are explained on the next page. Although you can theoretically rotate the part while feeding another axis, the timing can be tricky and it is not considered to be true synchronous interpolation.


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Index Designs rotary tables can be connected to nearly any type of CNC or manual machine using one of three conventional interface methods outlined below. The first one requires the CNC machine be 4th axis ready. The other two require the use of the Index Designs single axis control box. 

1. True 4th axis servo control

By far, the most popular interface option is true 4th axis servo control. This allows for use in either indexing or continuous mode. This provides the most integrated control method by using an amplifier built into the host machine. The A axis rotary table is programmed and controlled along with X, Y and Z axis commands. This method of integration is the most flexible as it allows either indexing for simple point to point part positioning or very sophisticated synchronous contouring for creating complex surfaces that are otherwise very difficult or impossible to produce. 


2. M Function Control

The programmable single axis control box can store a series of moves within the memory and have those moves incremented one by one with the closure of an M-function from the host machine. A pulse from the host machine commands the control box to move the 4th axis to the next position from within the program. Upon completion of each move, the control box signals back with a cycle complete pulse so the host machine knows the 4th axis is in position and can proceed with the next operation. A spare M-function is required on the host machine and interfaced with a simple 4 wire connection with two wires used for cycle start and the other two for cycle finish. The single axis control box comes with 15’ of cable and a 4 pin DIN connector that plugs into the back of the controller. . 


3. RS-232 Serial port control

Serial control of a 4th axis can be achieved by having the host machine send move and feed information via a standard RS-232 connection. Many CNC’s have the ability to accommodate print statements within their programs which send move data out the control’s serial port. The Index Designs Programmable Control Box reads these instructions and positions the 4th axis accordingly. An M-function interface is required to coordinate cycle start and finish of these moves so the CNC and Control Box are in sync with each other.  




The Index Designs programmable single axis control box connected to a rotary table is a cost efficient solution that provides indexing or semi 4th axis capability to machines that are not 4th axis ready. The control box can be set-up and utilized by various methods. The first is to program the indexing moves from the front panel. Easily key in a program to rotate the spindle in either direction in step sizes from 0.001˚ to 999.999˚. Step sizes of up to 30,000˚ can be executed if run off of a file on a USB key. If a CNC is capable of DNC operation, the Index Designs Programmable Control Box can accept full 4th axis programs generated by CAD/CAM systems and drip feed the program. When the Control Box reads a 4th axis move, it does not send the CNC additional information until the line preceding the A move is completed. An M-function is auto inserted and sent serially to the machine. The CNC will generate a pulse which signals the Control Box/USB that it is safe to execute the 4th axis move. The Control Box will resume sending machine data after it has finished the 4th axis move. This method simplifies the task of a programmer by allowing them to program A axis moves as if they were being done on a CNC with integrated 4th axis control. Even when not functioning as an indexer, the Control Box is capable of uploading, downloading and DNC programs from a USB key to just about any CNC machine tool with a serial port.

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• Easy installation

• G code compatible

• Accepts serial input commands for positioning  

• Accepts USB keys of any size

• Capable of loading, storing or drip feeding files from USB key


When ordered with a rotary table, the package comes with the control box and all cables including the 4-pin DIN connector and cable for interfacing to M-code.