A machine that runs badly is not always a machine that is broken. Vibration, noise, heat and drift are the early signals, and they are cheap to fix right up until they are not.
What the trade covers
Industrial millwrights install, align, maintain and repair the mechanical side of production equipment: conveyors, gearboxes, pumps, fans, blowers, chain and belt drives, bearings, couplings, frames and guarding. Where an electrician owns the power and a controls tech owns the logic, the millwright owns everything that physically moves.
The work splits into roughly four buckets: installation and alignment, planned maintenance, breakdown repair, and modification - improving a machine that was designed badly or has been pushed past its original duty.
The five failures that cause most downtime
1. Misalignment
Shaft misalignment between a motor and a gearbox or pump is the most common cause of premature coupling, bearing and seal failure. It is also the cheapest to prevent. A laser alignment check takes under an hour and routinely doubles the life of a bearing set.
Two things make it worse than it needs to be: coupling wear hiding the true offset, and "soft foot" - a motor foot that does not sit flat, so the machine changes shape when you tighten the bolts. Both are found in minutes with the right tools and missed entirely with a straight edge.
2. Bearing failure
Bearings rarely fail from age. They fail from misalignment, contamination, inadequate lubrication, or excessive load. The failure mode tells you the cause: a worn outer race path usually means misalignment, spalling in the load zone usually means overload, and discolouration means heat.
If you are replacing the same bearing every eight months, the bearing is a symptom. Fix the cause or keep buying bearings.
3. Belt, chain and coupling wear
Tension, sheave alignment and wear. An over-tensioned belt destroys bearings; an under-tensioned one slips and glazes. A worn coupling introduces backlash that shows up as a positioning error the controls tech gets blamed for.
4. Gearbox problems
Oil condition, oil level, breather blockage, seal leakage and heat. Gearboxes die quietly from contaminated oil far more often than from overload. A yearly oil sample costs less than a rebuild and tells you more than listening to it.
5. Structural and guarding issues
Cracked welds, loose anchor bolts, fatigued frames, guards that vibrate loose. These are the findings that matter most because the consequence is not downtime, it is injury.
When the fault is actually mechanical, not electrical
This is the expensive confusion. A machine that trips its overload, loses position, or faults on overtorque is often reporting a mechanical problem through an electrical symptom.
- Motor draws high current with no load. Mechanical binding, failed bearing, or a phase problem - not a program bug.
- Servo faults on following error. Often a worn ball screw, a dry linear guide, or a loose coupling, not a tuning problem.
- Machine drifts out of position over a shift. Backlash, slipping coupling, or a worn belt - the encoder is telling the truth.
- Intermittent stops with no alarm. Loose mechanicals causing vibration that opens a connection, or a sensor target moving out of range.
Chasing these in the PLC first is common, and it is backwards. Check the mechanicals, then the wiring, then the logic.
What planned millwright work looks like
- Vibration route. Monthly readings on critical machines, trended. A rising trend is a work order; a step change is a call.
- Lubrication schedule. The right grease, the right amount, the right interval. Over-greasing a bearing is a real failure mode, especially on high-speed motors.
- Alignment and tension checks after any motor change, coupling replacement or foundation work.
- Thermal check on gearboxes and bearings during normal running.
- Fastener torque audit on vibrating equipment - conveyors, screens, shakers, presses.
None of that is glamorous. All of it is cheaper than a Saturday breakdown call with production waiting.
Shutdown work: how to not overrun
Mechanical shutdowns overrun for predictable reasons: parts not on site, the machine is worse than expected once opened, and the sequence was never written down. Three habits fix most of it.
- Open the machine before the shutdown if you can. Inspect, measure, order.
- Sequence the work by dependency, not by preference. Cleaning before inspection, inspection before reassembly, alignment last.
- Book the alignment and commissioning resource before the shutdown starts, not when you get there.
Mechanical and controls, one crew
Most of our break-fix calls turn out to be two faults wearing one coat: a worn mechanical part masking itself as an electrical fault, or a controls change that pushed a mechanism past what it was built for. Having mechanical and controls capability on the same job means one diagnosis instead of two, and a fix that survives the next production run rather than just clearing the alarm.