Written by In a custom machine project, maintenance is often discussed after the main design is complete. By that stage, access panels, component locations and service procedures may already be difficult to change. A better approach is to treat maintainability as a design requirement from the beginning.
Designing for maintainability does not mean adding access doors wherever space is available. It means making routine inspection, fault finding, cleaning, adjustment and part replacement predictable and safe. This article explains the main decisions that help engineering teams create custom machines that are easier to support throughout their operating life.
Start with maintainability requirements
Maintainability should be included in the technical specification alongside output, cycle time, product quality and safety requirements. The specification should describe how the machine will be serviced, not only what it must produce.
Useful questions include:
- Which components require regular inspection, lubrication, cleaning or adjustment?
- Which wear parts are expected to be replaced during the machine’s service life?
- Which areas need access during a fault, setup change or format change?
- Can technicians reach the service points without removing unrelated equipment?
- What information must be visible to operators and maintenance personnel?
- Which tasks can be completed while the rest of the line remains protected and secured?
These questions turn a general expectation such as “the machine must be easy to maintain” into design inputs that can be reviewed. A structured technical specification can also clarify responsibilities between the machine builder, production team and maintenance function.
Map maintenance tasks before finalizing the layout
A practical method is to create a maintenance task list during concept design. List the actions that technicians may need to perform and place each action on the machine layout. This reveals conflicts before frames, guarding and cable routes become fixed.
Separate routine and corrective access
Routine tasks may include visual checks, cleaning, lubrication, sensor inspection and the replacement of standard consumables. Corrective tasks may involve changing a cylinder, servo motor, valve, gripper, drive, sensor or electrical component.
Both categories need access, but they do not always require the same type of opening. Frequently used service points should be accessible without extensive disassembly. Less frequent interventions may use removable panels or modular assemblies, provided the removal process is clear and safe.
Check the technician’s working position
Access is more than an opening in a panel. The technician needs enough room to see the component, use the required tools, disconnect energy sources and remove the part without damaging adjacent equipment. A component may be technically reachable but practically unserviceable if a hand cannot be positioned correctly or a removed part has no route out of the machine.
During design reviews, inspect the machine from the viewpoint of the person carrying out the task. Consider reach, visibility, lighting, tool clearance and the weight or size of the part being handled.
Use modular assemblies to shorten interventions
Custom machines often contain repeated stations, tooling units or functional modules. Separating these assemblies logically can make troubleshooting and replacement more manageable.
Examples include:
- A removable gripper or fixture assembly with defined locating surfaces.
- A valve or pneumatic preparation module grouped in an accessible location.
- An electrical panel layout that separates power, control and field connections clearly.
- A drive or actuator unit that can be removed without dismantling the complete station.
- A test module that can be isolated for calibration or fault investigation.
Modularity should not be confused with adding more connectors or interfaces without a plan. Each module needs repeatable positioning, clear identification and connections that reduce the risk of incorrect assembly. Mechanical interfaces, pneumatic tubing, electrical plugs and software addressing should be considered together.
Make components visible and identifiable
Good maintainability depends on fast orientation. Operators and technicians should be able to understand the machine’s main functions without relying entirely on personal experience.
Component identification can include durable labels, terminal references, pneumatic circuit references, sensor numbers and clear cabinet documentation. Labels should remain readable after cleaning and normal industrial use. The naming used on the physical machine should agree with electrical drawings, the control software and the spare-parts list.
Where several similar sensors or actuators are installed, identification should make their position and function unambiguous. This is particularly important in assembly lines with multiple stations that use similar mechanisms.
Design diagnostics into the control system
Maintenance-friendly hardware can still be difficult to support if the control system provides little information. Fault messages should help users understand what the machine detected, where it occurred and what basic check is appropriate.
Use specific fault messages
A message such as “station fault” gives limited direction. A more useful message identifies the station, device and condition, for example a gripper not reaching its expected position or a safety circuit requiring attention. Messages should be written in language that operators can understand while retaining the technical reference needed by maintenance personnel.
Show relevant diagnostic states
Depending on the application, the interface may show input and output states, actuator positions, cycle-step information, alarm history and the status of communication with field devices. Diagnostics should support investigation rather than encourage bypassing safety functions or operating the machine outside its intended conditions.
Control architecture decisions influence how much diagnostic information is available and how consistently it can be presented. The choice of PLC and field equipment should therefore be considered together with service requirements, not only initial functionality. The article on selecting PLC and field equipment provides a related design perspective.
Plan safe access and energy isolation
Maintainability and machine safety are closely connected. A technician should not need to defeat a guard, reach through a hazardous area or improvise an isolation method to perform a normal service task.
Access doors, interlocks, emergency stops and isolation points should be evaluated as part of the overall safety concept. Pneumatic, electrical, mechanical, gravitational and stored-energy hazards may all need consideration. Components that can move or retain pressure after shutdown should be identified in the service procedure.
Maintenance access must not be treated as an exception to the safety design. For a practical review of hazards that can be overlooked during machine development, see machine safety risk assessment and practical checks.
Control contamination, wear and adjustment needs
Machine layout affects how quickly contamination reaches sensitive components and how easily it can be removed. Cable carriers, sensors, guides, grippers, fixtures and test connections should be positioned with the process environment in mind.
Where dust, oil, chips, moisture or production residue is expected, design reviews should address shielding, drainage, cleaning access and material compatibility. Avoid creating pockets where contamination accumulates or areas that cannot be inspected without major disassembly.
Adjustment points also require attention. If a sensor or stop must be adjusted, the adjustment should be accessible and the reference position should be defined. Mechanical stops, scales, locating features or documented setup values can reduce repeated trial and error. Adjustability is useful only when the intended range and method are clear.
Prepare documentation while the design is developing
Documentation should not be postponed until shipment. As the machine changes, maintainability information should develop with it. A useful documentation package may include:
- Maintenance intervals or task-based inspection instructions.
- Lubrication points and the applicable lubricant information.
- Spare-parts lists with clear component references.
- Pneumatic and electrical schematics that match the installed machine.
- Removal and replacement instructions for major assemblies.
- Fault-finding guidance linked to alarms and physical locations.
- Recommended checks after adjustment, replacement or intervention.
The exact content depends on the machine and the customer’s maintenance system. The important principle is consistency: drawings, labels, software messages and instructions should describe the same machine in the same terms.
Validate maintainability before handover
Maintainability should be checked during design reviews, assembly, factory testing and site commissioning. A simple validation exercise can ask a technician who was not involved in the design to perform representative tasks using the available documentation.
Observe where the person hesitates, reaches for an unsuitable tool, removes unnecessary parts or needs verbal explanations. These observations are valuable design feedback. They can lead to changes in access panels, fasteners, labels, component positioning, diagnostics or documentation before the machine enters routine production.
It is also useful to review maintainability after the first operating period. Repeated minor interventions may reveal that a sensor is exposed, a cleaning point is poorly located or a fault message is too general. Such findings can inform design updates and future machine projects.
Conclusion
Maintainability is not a final checklist item. It is a design discipline that connects mechanical layout, automation, safety, documentation and production support.
For a custom machine, the most effective approach is to define maintenance tasks early, provide realistic working access, use logical modules, identify components consistently, build useful diagnostics into the control system and validate service procedures before handover. These decisions do not remove every possible failure, but they can make inspection, troubleshooting and recovery more controlled and predictable.