What Happens When the Person Who Understands Your Legacy Machine Leaves?
What Happens When the Person Who Understands Your Legacy Machine Leaves?
Legacy equipment rarely becomes difficult to support overnight. More often, the machine keeps running while the people who understand its history gradually change. After years of repairs and modifications, one or two employees may become the people everyone relies on to explain why the controls behave a certain way or where to start when something goes wrong.
Some of that knowledge may be documented, but much of it comes from years of working with the equipment and understanding its quirks firsthand. That makes knowledge transfer increasingly important as experienced manufacturing employees leave the workforce. In 2025, roughly one in four people working in U.S. manufacturing was age 55 or older, underscoring the need for manufacturers to prepare for continued workforce turnover and retirement.
When an experienced employee leaves or is unavailable during a breakdown, the machine itself may not have changed, but the plant’s ability to support it has. That knowledge dependency should be considered alongside the condition and long-term supportability of the technology itself.
How One Person Becomes the Legacy Machine Expert
No one plans to make one employee the only person who can support a machine. It happens as equipment is repaired, modified, upgraded, and adapted to changing production needs over many years. The person who is present for those changes keeps accumulating jotted-down notes that newer employees never had the opportunity to see firsthand.
That creates a gap between the documented machine and the machine that exists on the plant floor. The drawings may show how it was originally wired, and the PLC program may show how the controls currently operate, but an experienced technician may be the only person who understands why the differences exist.
That missing context matters most when something goes wrong. A technician familiar with the system may recognize a problem quickly, while someone new to the machine first has to determine what has changed, whether the available documentation is current, and how the system is supposed to behave. The repair itself may not be complicated, but reconstructing information the plant once knew can add significant time to the troubleshooting process.
Would Your Team Be Able to Support the Machine Tomorrow?
A practical way to evaluate risk is to imagine that the person who normally handles the machine is unavailable tomorrow. The question is not whether another technician could eventually figure it out, but if the organization has enough information and experience to respond without starting from scratch.
Consider whether your team can answer the following questions:
- Can another qualified person access the PLC and HMI programs?
- Do you know where the current program backups are stored and whether they match what is running?
- Do the electrical drawings reflect the equipment as it exists today?
- Can more than one person explain the normal operating and recovery sequence?
- Does the team know the machine’s recurring failure points and major past modifications?
- Are the required software, hardware information, and system access details available to the appropriate people?
- Does the plant know who can provide outside support if the internal team cannot resolve an issue?
- Do you have legacy software that requires the old Windows XP laptop to be dusted off, hoping that the battery didn’t die?
A few gaps do not necessarily mean the legacy machine is in immediate trouble, but they do show where support still depends on individual memory rather than information the broader team can use.
Reducing the Dependency Before It Becomes an Emergency
This challenge is not unique to older controls systems. PMMI’s 2025 research into knowledge transfer among packaging and processing companies found that 74% of surveyed CPG and OEM respondents considered knowledge transfer among machine operators a very or extremely significant problem. The issue becomes especially important on equipment where years of practical experience have never been fully documented
Start with the machines where lost knowledge would create the most disruption. Equipment with incomplete documentation, older controls, significant production impact, limited OEM support, or a long history of modifications deserves more attention than a lower-risk system that several people already understand.
Capture the information while the people who know the system are still available. Review:
- How the machine operates
- Which failures occur repeatedly
- What has been changed
- How recovery works
- Where the controls architecture has quirks that aren’t obvious to someone new
NIST’s Manufacturing Extension Partnership recommends documenting institutional knowledge and cross-training employees as part of succession planning so operations are not critically tied to one person.
Existing documentation also needs to be verified rather than simply collected. A backup is useful only if the team knows it is current and can open it with the available software. Electrical drawings should be compared with the actual machine, configuration files should be located, and hardware versions should be recorded where they matter for support.
Another qualified technician or engineer should also have opportunities to navigate the program, review schematics, and participate in troubleshooting. Documentation provides a reference, but hands-on experience helps another person understand how the pieces work together. Plants with limited internal controls coverage should also establish an outside support path before a serious outage so a controls partner is not learning the machine for the first time while production is waiting.
Does the Machine Need to Be Replaced?
A knowledge gap by itself does not mean an older legacy machine needs to be replaced. If the controls are still supportable and the equipment continues to meet production needs, better documentation, cross-training, updated backups, or targeted engineering cleanup may address much of the risk.
Other systems may need more work. Years of modifications can leave a machine with outdated drawings, inconsistent code, poor diagnostics, or components that are becoming difficult to support. In that situation, targeted updates may improve maintainability without requiring a complete rebuild.
If the machine also depends on obsolete hardware, unavailable software, increasingly scarce replacement components, or a controls platform that limits reasonable changes, a planned upgrade may be the better long-term path. Identifying the knowledge risk early gives the plant more time to decide what response makes sense before a breakdown or staffing change forces the issue. The condition of the system, the availability of support, and the needs of production should ultimately determine what happens next.
Make Your Legacy Machines Easier for the Next Person to Support
Experienced technicians and engineers will always carry knowledge that is difficult to capture completely. Their familiarity with a machine is especially valuable in custom industrial environments where years of changes can make one system very different from another. Problems begin when the organization cannot reasonably support the equipment without that one person present.
A maintainable automation system should give another qualified person enough information to understand how the machine operates, where to start when it stops, and what has changed over time. If a critical machine depends heavily on one employee’s memory, identifying that dependency now gives the team a chance to document the system and decide whether the controls need additional work.
Cleveland Automation Systems helps manufacturers assess, troubleshoot, document, upgrade, and support existing automation systems. When the supportability of a legacy machine is unclear, CAS can review the controls environment and help determine whether the next step should be better documentation, targeted engineering improvements, or a planned system upgrade.
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About the Author: Rylan Pyciak
Rylan Pyciak, CEO of Cleveland Automation Systems™, is a Systems and Control Engineering graduate from Case Western Reserve University. With expertise in PLCs, robotics, and industrial engineering, Rylan leads CAS in delivering innovative automation solutions. Passionate about mentoring future trades professionals, he combines technical knowledge with a commitment to fostering sustainable growth in manufacturing.