OMRON CK3W-AX Multi axis Control Selection

OMRON CK3W-AX Axis Interface Unit: Complete Guide to Multi Axis Motion Control System Design and Wiring

In the field of modern precision motion control, multi axis synchronous control, high-speed encoder feedback, and flexible driver interfaces are the core of equipment performance. OMRON's CK3W-AX series axis interface unit, as an important component of the CK3M/CK5M series programmable multi axis controllers, provides engineers with a highly integrated and scalable axis control solution. A single CK3W-AX unit can control up to 4 axes, support analog command servo drivers and DirectPWM servo drivers, and can connect multiple types of position feedback encoders. This article will systematically analyze the model selection, system configuration, dedicated cable wiring, signal definition, and debugging points of CK3W-AX unit from the perspective of engineering practice, to help engineers quickly build a reliable multi axis motion control system.

Product Overview and Core Features

The CK3W-AX unit is a shaft interface module designed specifically for the CK3M/CK5M series motion controllers. It is located in the CPU rack or expansion rack and communicates with the CPU unit through unit side connectors. Each unit can handle up to 4 servo axes.

Core features:

Multi axis capability: 4 channels per unit, suitable for independent devices with less than 4 axes, or extended to more axes through multi unit cascading.

Flexible driver interface:

Analog output type: Supports filtered PWM or true DAC output, suitable for traditional ± 10V analog command servo drivers.

DirectPWM type: Directly outputs PWM pulse signals, which can be combined with intelligent servo drivers (such as CK3A-G3L) that support PWM interfaces to achieve higher bandwidth current loop control.

Rich encoder interfaces:

Digital Orthogonal Encoder (A/B/Z Differential Signal)

Serial encoder (contact OMRON to confirm specific protocol)

Sine encoder (1 Vpp SIN/COS)

Hall sensor (U/V/W/T signal)

Built in I/O: Each unit comes with 16 point digital input and 16 point digital output (NPN or PNP type), as well as dedicated flag inputs (HOME, positive limit, negative limit, user input) and an EQU output for each axis.

These characteristics make the CK3W-AX unit particularly suitable for applications that require high real-time and precision, such as high-speed surface mount machines, semiconductor equipment, laser processing, and precision inspection.

Model Classification and Selection Guide

CK3W-AX is divided into multiple sub models based on the type of output circuit and encoder interface. The correct selection is the first step in system design. The following table summarizes the main models and their key differences:

Model Output Type Encoder Interface Universal I/O Polarity Description

CK3W-AX1313N DirectPWM Digital Orthogonal/Serial NPN Low cost, High speed PWM Output

CK3W-AX1313P DirectPWM Digital Orthogonal/Serial PNP Same as above, PNP Type I/O

CK3W-AX1414N filtered PWM digital orthogonal/serial NPN analog instruction output, 1 point/channel

CK3W-AX1414P Filtered PWM Digital Orthogonal/Serial PNP Same as above, PNP Type I/O

CK3W-AX1515N True DAC Digital Orthogonal/Serial NPN True ± 10V Analog Output, 2 Points/Channel

CK3W-AX1515P True DAC Digital Orthogonal/Serial PNP Same as above, PNP Type I/O

CK3W-AX2323N DirectPWM sine/serial NPN supports 1 Vpp sine encoder

CK3W-AX2323P DirectPWM sine/serial PNP as above, PNP type I/O

2.1 Selection of Output Types

DirectPWM (AX1313/AX2323): Output as differential line drive pulses (PULSE+DIR or phase difference form), with a maximum frequency of 10 MHz. Suitable for intelligent servo drives that accept PWM control signals, such as OMRON CK3A-G3L. Due to the elimination of D/A conversion, the delay is lower, making it suitable for high dynamic response applications.

Filtered PWM (AX1414): The output is a low-pass filtered PWM signal, with each channel providing a differential analog output pair (DACA+/-). Output range ± 20 V (± 10 V to ground), suitable for traditional ± 10V command servo.

True DAC (AX1515): Each channel provides two independent analog outputs (DACA+/- and DACB+/-), which is a true bipolar digital to analog conversion with higher accuracy and linearity. Suitable for advanced applications that require simultaneous output of speed/torque commands or dual closed-loop control.

2.2 Selection of Encoder Interface

Digital Orthogonal Encoder: Supports A/B/Z differential signals (RS-422), with a maximum response frequency of 10 MHz. Combined with CK3W-CAED03A dedicated cable, it can be connected to incremental grating rulers or rotary encoders.

Sine encoder (1 Vpp): Supports SIN/COS differential signals and is suitable for high-resolution sine and cosine encoders (such as some models of Heidenhain). CK3W-CAEA03A cable is required, and an INDEX pulse is provided.

Serial encoder: Supports multiple serial protocols (specific protocols need to be consulted with OMRON). Can connect absolute encoders such as BISS and EnDat, using CK3W-CAES03A cable.

Hybrid interface: Some cables support simultaneous transmission of digital orthogonal signals and UVW Hall signals, or simultaneous transmission of sine signals and serial data, making it easy to integrate brushless motors with commutation sensors.

2.3 Universal I/O Polarity

NPN type: Input common terminal is 0V, output is low level effective. Suitable for commonly used logic in Japanese PLCs.

PNP type: Input common terminal is 24V, output is high level effective. Suitable for European and American control habits.

Engineering suggestion: When selecting, it is necessary to confirm the type of command signal received by the servo drive and the type of encoder feedback. If using a third-party servo, pay attention to signal level matching (differential/single ended) and voltage range.

System configuration and rack installation

The CK3W-AX unit must be used on the rack of the CK3M/CK5M motion controller. The system consists of a CPU rack and an optional expansion rack.

3.1 CPU Rack Configuration

The CPU rack shall at least include: power unit, CPU unit End Cover。 On the right side of the CPU unit, it can be connected in sequence:

Up to 4 CK3W units (but up to 2 CK3W-AX units, the rest can be MD/AD/ECS/GC, etc.).

To connect the expansion rack, the expansion main unit CK3W-EXM01 must be installed adjacent to the right side of the CPU unit before connecting other units.

If the extended main unit is not adjacent to the right side of the CPU unit, the CK3WConfigErr in the Sys. Status register will display error code "5".

3.2 Expansion Rack Configuration (CK5M/CK3M)

CK5M CPU supports up to 3 expansion racks; The CK3M CPU supports up to one expansion rack.

Each expansion rack requires a power unit, as well as an expansion slave unit located immediately to the right of the power unit:

The extension in the middle position uses CK5W-EXS01 from the unit (only supported by CK5M).

The farthest (last) expansion rack uses CK3W-EXS02.

Use a dedicated extension cable CK3W-CAX003A (30 cm) to connect the expansion master unit and the expansion slave unit.

Attention: The CPU rack and expansion rack must be powered by the same 24V power supply to avoid communication abnormalities caused by potential differences.

3.3 Unit Installation and Address Setting

Each CK3W-AX unit has an address switch (0-F) on the front panel for setting the Gate3 index. In the IDE of Power PMAC, this address will be used to access the register mapping of the axis interface. Within the same rack, the addresses of each unit must be unique.

Detailed explanation of dedicated cables and wiring

To ensure signal integrity, OMRON provides various specialized shielded cables for CK3W-AX units, with lengths mostly up to 3 meters (some options include 0.9/1.8/3.6 meters). It is not recommended to make cables by oneself, as differential signals have strict matching requirements for impedance and shielding structures.

4.1 Encoder side cable

Encoder type, cable model, length description

Digital orthogonal encoder CK3W-CAED03A 3 m supports A/B/Z differential and end scatter

Sine encoder CK3W-CAEA03A 3 m SIN/COS/INDEX, end scattered line

Serial encoder CK3W-CAES03A 3 m CLK/DAT differential, end scattered

Digital orthogonal+UVW/serial CK3W-CAEW03A 3-meter two cable combination (see manual line sequence)

Sine+UVW/Serial CK3W-CAEAW03A 3 m Two Cable Combination

Wiring points:

All cable shielding layers are connected to the outer casing (FG) of the encoder connector. For sine encoder cables, there is also a twisted pair shielding layer connected to the encoder power GND pin.

When connecting G5 series servo drives, specific pins (such as 1-5, 6-10) need to be short circuited to disable the serial DAT terminal resistor, and OutFlagD=1.

The encoder power supply (5V) has a maximum of 500 mA per channel, and the total output of the entire unit is ≤ 1 A. If the encoder current requirement is high, an external power supply should be considered.

4.2 Amplifier side cable

4.2.1 Analog output type (AX1414/AX1515)

Use CK3W-CAA03A (3m) cable with loose ends. The signals include:

Analog output A+/- (DACA), analog output B+/- (DACB, only valid for AX1515)

Pulse output+/- (PULSE)

Directional output+/- (DIR)

Fault input

Amplifier Enable NO/NC and Common Terminal

Wiring suggestion: Connect the analog output "analog GND" to the signal ground of the servo driver at a single point; It is recommended to use shielded twisted pair cables for pulse/direction signals.

4.2.2 DirectPWM type (AX1313/AX2323)

For OMRON CK3A-G3L intelligent servo, it is recommended to use one touch installation cable:

200‑602739‑036x（0.9 m）

200‑602739‑072x（1.8 m）

200‑602739‑144x（3.6 m）

For other brands of servos, screw fixed cables can be used:

CK3W‑CAAD009A（0.9 m）

CK3W‑CAAD018A（1.8 m）

CK3W‑CAAD036A（3.6 m）

The signals transmitted by DirectPWM cables include PWM+/-, directional signals, encoder feedback (some models), etc. Specific pin allocation should refer to the servo driver manual.

Engineering Tip: When using DirectPWM mode, be sure to confirm that the input circuit of the servo driver can accept 5V differential PWM signals and correctly set the terminal resistance.

Flag signal and universal I/O

5.1 Each axis flag signal (connected through Flag terminal block)

Each channel provides the following dedicated signals:

HOME: Origin input (normally open, configurable)

PLIM: Positive limit input

NLIM: Negative limit input

User: User defined input (can be used for emergency stop, zeroing completion, etc.)

EQU: Equal position output (conducts when the actual position is within tolerance of the instruction position)

All these signals are optically isolated and require an external 24V power supply for wiring. The polarity depends on the unit model (NPN or PNP).

5.2 Universal digital I/O (via 50 pin terminal block)

Each unit provides 16 inputs/16 outputs, independent of the axis function. These I/O can be used to control peripheral devices (cylinders, sensors, indicator lights, etc.) and read and write directly through variables of Power PMAC. Typical applications: fixture control, material detection, alarm display.

Input circuit: NPN/PNP compatible (depending on the unit), response time ≤ 1 ms.

Output circuit: transistor output, maximum 50 mA per point, with short-circuit protection.

Key points for debugging and troubleshooting

6.1 Pre power on inspection

Power wiring: Confirm that the CPU rack and expansion rack are powered by the same 24V power supply, and the grounding resistance is ≤ 100 Ω.

Unit address: The address switches of all CK3W-AX units are set correctly and without conflicts.

Cable connection: Insert the encoder cable and amplifier cable tightly, and tighten the screws.

Terminal resistor: For differential numerical control signals (such as encoders A/B), check if the terminal resistor is correctly connected at the end of the cable (if the driver is built-in, it can be skipped).

I/O polarity: Confirm that the external wiring of the universal I/O matches the unit type (NPN external 0V common terminal, PNP external 24V common terminal).

6.2 Common Problems and Countermeasures

Possible causes and solutions for the phenomenon

The Amp Enable indicator light is not on. The servo drive is not ready or the fault input signal is abnormal. Check if the Fault input is low level (usually ON when normal) and check the driver alarm output

The motor does not rotate, there is no alarm, the simulated command voltage is 0, or the PWM output is disabled. Check the Motor [x]. Ctrl and motor enable positions in the Power PMAC

Encoder feedback abnormality (position jump), poor shielding of encoder cable, or reverse connection of differential signal line. Use an oscilloscope to check the A+/- signal and ensure that the shielding layer is grounded at a single point

Unit status register error (CK3WConfigErr=5) Extended main unit not adjacent to CPU unit, rearranging rack unit order to the right

Multiple units cannot be recognized due to address switch conflicts or insufficient rack power. Check the address settings and calculate the total power consumption (5V/24V)

6.3 Debugging with Power PMAC IDE

After establishing the project, set the encoder count mode and output mode for each axis on the Gate3 configuration page.

For the True DAC type (AX1515), the range of DACA and DACB can be configured separately (± 10V or ± 20V).

Utilize online monitoring function to view encoder count values, instruction tracking errors, limit status, etc. in real time.

If a sine encoder is required, SIN/COS interpolation multiplication (e.g. x4096) must be enabled in the encoder parameters to achieve high resolution.

Practical application cases and wiring suggestions

Case: 4-axis high-speed picking and placing robot

Install two CK3W-AX1414N units using a CK5M CPU and an expansion rack.

Each AX1414N controls two servo motors (4 axes in total), both using ± 10V analog commands.

The encoder uses a digital orthogonal type (10000 lines/rev) and is connected through CK3W-CAED03A cable.

Universal I/O is used to control vacuum suction cups and cylinders.

Wiring precautions:

Lay the encoder cable and power cable separately, with a spacing of ≥ 200mm.

All shielding layers are grounded on the controller side to avoid multiple grounding points forming a ground loop.

Use ferrite magnetic rings to cover the input power line of the servo driver to suppress high-frequency interference.