Description

The RELIANCE MD-D4002B​is a central processing unit(CPU)module for the Reliance Electric AutoMax Distributed Control System(DCS).This controller served as the computational heart for a generation of industrial automation systems,executing ladder logic,process control algorithms,and sequential function charts to coordinate complex manufacturing and process operations.

Application Scenarios

In a continuous steel strip galvanizing line from the late 1990s,precise control of zinc bath temperature,strip tension across multiple bridles,and synchronized drive speeds is critical for coating quality.The entire line is orchestrated by an AutoMax DCS,with several RELIANCE MD-D4002B​controllers each managing a distinct section—entry looping,cleaning,annealing,galvanizing,and exit.One controller fails,causing its section to halt.Without a compatible spare MD-D4002B,the entire multi-million dollar line stops,solidifying zinc in pots and creating hours of cleanup.The plant’s strategic stock of a tested MD-D4002B​spare allows maintenance to hot-swap the module(in a redundant rack),download the preserved application program,and restart the section in under an hour.This isn’t just fixing a computer;it’s preventing catastrophic production loss and preserving a capital-intensive control system whose functionality is deeply embedded in the plant’s operations,avoiding a multi-million dollar line modernization project ahead of schedule.

Parameter

Main Parameters

Value/Description

Product Model

RELIANCE MD-D4002B

Manufacturer

Reliance Electric(acquired by Rockwell Automation)

Product Type

AutoMax DCS Processor/Controller Module

CPU Architecture

Motorola 68000 Family Microprocessor

Memory

Configuration-dependent;typically included battery-backed RAM for user logic and volatile memory for execution.

I/O Capacity

Managed a distributed I/O network(AutoMax Remote I/O)over a proprietary bus,supporting hundreds of points.

Programming Language

Executed ladder logic,sequential function charts,and structured text(via AutoMax software suite).

Communication Ports

Included serial ports for programming terminal(RS-232)and likely a proprietary network port for peer-to-peer or supervisory communication.

Real-Time Clock

Battery-backed for time-stamping events.

Operating Mode Keyswitch

Run,Program,Test modes for safety.

Power Supply

Powered through the AutoMax rack backplane.

Operating Temperature

Designed for industrial control panel environments(0-60°C).

Technical Principles and Innovative Values

Innovation Point 1:Blurring the PLC/DCS Boundary for Manufacturing.In its era,the RELIANCE MD-D4002B​and the AutoMax platform represented a hybrid approach.It combined the modular,ladder-logic familiarity of Programmable Logic Controllers(PLCs)with the distributed,processor-heavy architecture of a Distributed Control System(DCS).This allowed a single platform to handle both discrete machine sequencing(like a PLC)and complex analog process loops(like a DCS),which was ideal for hybrid industries like metals,plastics,and automotive manufacturing where process and discrete control are intertwined.

Innovation Point 2:Deterministic,Scan-Based Execution for Predictable Performance.The controller operated on a deterministic scan cycle:read inputs,execute the entire user logic program,update outputs.This predictability was crucial for tightly synchronized multi-axis motion control and high-speed sequencing common in manufacturing.Engineers could calculate worst-case scan times and design interlocks with confidence,unlike in some modern event-driven systems where timing can be less predictable under heavy load.

Innovation Point 3:Distributed Intelligence with Centralized Management.While the MD-D4002B​was a powerful central processor for its rack,the AutoMax system excelled at distributed control.Multiple MD-D4002B​controllers could be networked,each managing a cell or process area independently but exchanging data for coordination.This provided inherent robustness—a failure in one controller did not necessarily cripple the entire plant—while still allowing for centralized programming,monitoring,and data collection from a single engineering workstation.

Application Cases and Industry Value

Case Study:Automotive Paint Shop Retrofitting.A major automotive plant’s paint shop,controlled by an aging AutoMax system,needed new robotic painters integrated.A full control system replacement would require a month-long shutdown,impossible within production schedules.The solution was to keep the core AutoMax system,including its RELIANCE MD-D4002B​controllers managing oven temperatures,conveyor tracking,and ventilation,but add new robot controllers on a separate network that communicated via discrete I/O and serial links to a specific MD-D4002B.This”controller-of-controllers”approach leveraged the existing system’s proven reliability for critical environmental and safety controls while enabling a phased modernization.The plant engineer stated that understanding the MD-D4002B’s communication capabilities and I/O capacity allowed them to extend the system’s life for seven more years,deferring a$15M overhaul and achieving a seamless integration that maintained legendary paint quality consistency.

Related Product Combination Solutions

AutoMax DCS Rack&Power Supply(e.g.,DCS-500):The chassis that housed and powered the MD-D4002B​and other modules.

AutoMax Remote I/O Scanner Modules(e.g.,DCS-502):The communication modules that linked the MD-D4002B​controller to distributed I/O drops throughout the plant.

AutoMax I/O Modules(Digital/Analog):The various input and output cards(e.g.,16-point DC input,4-20mA output)that provided the physical interface to field devices,managed by the MD-D4002B.

AutoMax Programming Software&Hardware Key:The legacy DOS/Windows-based programming environment(e.g.,AutoMax Workshop)and its associated dongle required to develop and download logic to the MD-D4002B.

Reliance/Rockwell Communications Converters:Devices to interface the AutoMax network with newer Rockwell(Allen-Bradley)networks like Data Highway Plus or ControlNet for integration into plant-wide systems.

Motorola 68000 Family MPU Sockets&Support Chips:For component-level repair of the MD-D4002B​board itself,targeting the CPU,ROM,or supporting logic chips.

Third-Party Retrofit Kits:Some specialists offer kits to replace an entire AutoMax rack(with MD-D4002B)with a modern PLC(like ControlLogix)while reusing existing field wiring and I/O bases,representing an end-of-life upgrade path.

Installation,Maintenance,and Full-Cycle Support

Installation and Commissioning:Installing a new or replacement RELIANCE MD-D4002B​required careful handling to avoid electrostatic discharge(ESD).It was inserted into a designated slot in the AutoMax rack,and the keyswitch was set to PROGRAM mode.Commissioning involved connecting a programming terminal,loading the application software from a backup,and verifying the configuration matches the I/O hardware present in the rack.A full system test,forcing I/O and verifying logic execution,was essential before placing the controller in RUN mode in a live environment.

Maintenance and Lifecycle Support:Primary maintenance involved monitoring the controller’s status LEDs,ensuring the memory backup battery was replaced proactively(every 2-5 years),and keeping the application software backups secure and version-controlled.Due to its age,support from the OEM is typically discontinued.Our role becomes critical.We provide fully refurbished and tested RELIANCE MD-D4002B​units,recovered from decommissioned systems.Each unit undergoes a rigorous burn-in test,verifying CPU operation,memory integrity,and communication port functionality.We also support the preservation of your intellectual property by assisting with software backup and migration consulting,helping you navigate the eventual transition to a modern platform while maximizing the value of your existing investment.

Contact our legacy systems specialists for immediate availability of tested RELIANCE MD-D4002B controllers and to develop a sustainable lifecycle management plan for your critical AutoMax DCS assets.

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