Retrofitting a machine means replacing its control system (PLC, operator panel, drives and wiring) while keeping the mechanics. It pays when the mechanics are in good condition, the process will not change and the problem is a lack of spares or diagnostics. Replacement is better when the mechanics are worn, capacity is short or safety requires rebuilding the whole machine.
What is replaced in a retrofit?
- The PLC and its input and output cards.
- The operator panel, with clear messages and an alarm log.
- Motor drives and starters, if discontinued.
- Deteriorated sensors and wiring.
- The electrical cabinet, in whole or in part, with new drawings.
- The mechanics, frame and pneumatic or hydraulic parts are kept.
When does a retrofit pay and when should you replace?
We give no saving percentages: the cost difference between the two options depends on each machine. The comparison is made with two quotes on the table and the cost of each day of downtime.
| Situation | Retrofit | Replace |
|---|---|---|
| Condition of the mechanics | Good, with play within tolerance | Worn or with repeated mechanical faults |
| Control spares | Discontinued or very expensive | Not a factor |
| Production capacity | Enough for the coming years | Insufficient even when running well |
| Process and product | Stay the same | Change significantly |
| Available stop | Days or a few weeks | The new machine can be installed in parallel |
| Safety | Can be upgraded with limited changes | Requires redesigning the machine |
What about safety and CE marking?
In Spain, a machine in use must meet the minimum safety provisions for work equipment (Real Decreto 1215/1997). Replacing a PLC with an equivalent one does not, in principle, alter its conformity. It is different if the modification introduces a new hazard or increases a risk: the EU Machinery Regulation 2023/1230, applicable from January 2027, treats whoever carries out a substantial modification as the manufacturer, with the obligations that entails.
That is why it is wise to assess the risks before starting and to record in writing what is changed and what is not. Safety functions are handled with dedicated components, separate from production control.
How is it planned to keep downtime to a minimum?
- Recover the documentation: drawings, program and signal list. If they do not exist, they are drawn up on site.
- Agree in writing what the machine must do, including any improvements to be added.
- Build and test the new cabinet in the workshop, before touching the machine.
- Make the change in a planned stop, keeping the old cabinet available in case of rollback.
- Commission with product and with the operators, and hand over drawings, program and backup.