Most of the production lines we are asked to look at are not worn out. They are unsupportable. The mechanics are sound, the frame is rigid, the tooling is fine — but the PLC went end-of-life in 2016, the drives are no longer stocked, and nobody left in the plant can edit the ladder logic.
That is a control problem wearing a mechanical problem's clothing, and it is usually the cheapest kind of problem to fix.
The four questions we ask first
- Is the mechanical structure still within tolerance? A geometry survey answers this in a day, and it is the only question that can rule a retrofit out outright.
- Has the required output changed? Retrofits restore a line; they rarely lift its ceiling by more than 10–15%. If you need double the throughput, you need a new line.
- How long is the available shutdown? A control retrofit is realistic in five to seven days. A mechanical rebuild is not.
- Who will maintain it afterwards? Standardising on the same controls platform as the rest of the plant is often worth more than any single technical gain.
A worked example
A food packaging client came to us with a 2007 line running at 71% OEE, losing most of it to unplanned stops nobody could diagnose. Replacement quotes came in around 14 billion VND with a nine-month lead time.
We retrofitted the controls over a Tết shutdown: new PLC and drives, new safety circuit to ISO 13849 PL d, servo replacement on two axes, and instrumentation that finally made stoppage causes visible. Cost landed near 18% of the replacement quote. OEE settled at 89% within six weeks, and — more usefully — the maintenance team can now see why the line stops.
“The goal is not to make an old line look new. It is to make it supportable, safe and legible to the people who run it every day.”
When we say no
We turn down roughly one retrofit enquiry in five. Usually it is because the frame has lost rigidity, the product itself has changed enough that the line's format range no longer fits, or the required capacity increase is simply beyond what better controls can deliver. Saying so early is cheaper for everyone than discovering it during commissioning.