9-Point Checklist for Retrofitting PLCs, Drives and Motors

When buying a PLC, drive or motor to retrofit an existing machine, it is important to consider compatibility with existing equipment, features needed for the application, capacity and power factor requirements, brand and supplier reputations, cost, technical support provided, safety standards met, and potential integration with other control systems such as SCADA. Consulting with the manufacturer or a qualified engineer is strongly recommended to ensure compatibility and safety. If you need further details, please contact us.

Compatibility: Make sure the PLC drive is compatible with your existing equipment and control systems. This includes checking for compatibility with the voltage, current, and communication protocols used by your equipment as well as the physical compatibility of the pins and connectors.

Features: Consider the features that are important for your application, such as software features, speed control, torque control, and energy efficiency.

Capacity: Make sure the PLC drive has the capacity to handle the power requirements of your equipment. This includes checking for compatibility with the voltage, current, and power factor of your equipment.

Brand and supplier: Consider the reputation and reliability of the brand and supplier of the PLC drive. Look for reviews and feedback from other users, and make sure the supplier is able to provide technical support and service.

Product life cycle: Where the current models of PLCs, drives and controllers are compatible with your machine, retrofit with them rather than older series, so that replacement parts stay available for longer.

Cost: Compare the cost of the PLC drive with the cost of other retrofit options, such as replacing the entire system. Consider the long-term cost savings that the PLC drive may provide, such as energy efficiency and maintenance savings.

Technical Support: Ensure that the manufacturer or supplier of the PLC drive provides adequate technical support and documentation that will help you with the installation, setup, and maintenance of the drive.

Safety: Make sure the PLC and drive meet the safety standards and certifications that apply to your industry or application, such as CE marking or relevant IEC/ISO standards.

Control: Check if the PLC drive can be integrated with other control system, such as SCADA, or any other building management system.

Consult with our engineers to ensure the compatibility and safety of the retrofit PLC drive with your system. We are happy to help.

Survey the Existing Machine First

Most retrofit problems come from information that was not collected before ordering. Before you request quotes, record:

• Make, model and serial number of the existing PLC, drives, motors and HMI, with photos of each nameplate.
• Supply voltage, number of phases and control voltages (for example 415 V AC, 230 V AC, 24 V DC).
• Motor rated power, current, speed and torque, flange size, shaft diameter and key, and encoder type.
• I/O count and type: digital, analog, high-speed counter and positioning outputs, with spare capacity.
• Communication links to the HMI, SCADA or other machines.
• A backup of the existing PLC program, drive parameters and HMI project, where they can still be read.
• The electrical drawings, even if they are out of date.

This survey also tells you whether a like-for-like replacement is possible or a full upgrade is needed.

Common Retrofit Pitfalls

• Mismatched servo pairs: a servo motor normally has to be used with a drive from the same family. Plan to change both together.
• Encoder differences: a new motor may use a different encoder protocol or resolution, which affects homing and machine parameters.
• Panel space and heat: new drives may need different mounting space, braking resistors and ventilation.
• Lost program logic: if the old PLC program cannot be read, the sequence must be rewritten from the machine's behaviour, which takes time.
• Earthing and EMC: modern VFDs and servo drives need shielded motor cables and proper earthing to avoid noise problems.
• Commissioning time: allow time for tuning, testing interlocks and training operators.

EKA CNC has experience re-engineering and retrofitting Siemens, Fanuc, Mitsubishi and Heidenhain machines and building custom control panels. See CNC retrofitting and repair.

Frequently Asked Questions