Efficiency is a plant-level property
A plant is more than a set of machines. Material has to arrive, work has to be scheduled, products have to be checked and shipped, and equipment has to be maintained. Efficiency at the plant level depends on how smoothly these parts work together. A single fast machine in a poorly coordinated plant does not make the plant efficient.
This is why the biggest losses are often found between steps rather than inside them. Automation can help with those gaps, but only if they are identified first.
Three common sources of loss
Idle time
Idle time means that equipment or people are available but not producing. Causes include waiting for material, waiting for instructions, waiting for a previous step, and waiting for repair or a changeover. A plant might have a machine capable of high output that actually produces for only part of the scheduled time.
Automation addresses idle time by:
- detecting a shortage or fault immediately and signaling the right person, rather than waiting for someone to walk past
- feeding and unloading machines automatically so that they do not wait for an operator
- coordinating machines through controllers so each starts when the previous one finishes
- logging the reasons for stops, which makes the biggest causes visible
The last point is often the most valuable. Many plants discover that their assumptions about why a line stops are wrong once stops are recorded automatically.
Rework
Rework includes correcting defective products, redoing paperwork and repeating steps. Rework consumes labor and machine time, and it can hide in normal-looking shifts. Automated checks at the point of work can reduce it, for example by verifying that the correct component is installed before moving on. Repeatable machine actions also tend to reduce errors of variation. Where rework continues, it is worth tracing the source instead of only fixing the symptoms; the root cause analysis approach is well suited to this.
Manual handoffs
A handoff occurs when work or information passes from one person or system to another. Examples are a supervisor writing a work order that an operator reads, or a quality result copied into a spreadsheet. Each handoff introduces delay and potential error. Automatic data transfer between machines, supervisory software and planning systems cuts out much of this. The physical equivalent, moving materials between areas, can be reduced by conveyors, automated carts or better layout.
Looking across the plant
Take a hypothetical plant with a machining area, an assembly area and a packing area. Suppose machining runs well, but assembly often waits for parts because transport between areas relies on someone noticing a full bin. Assembly output drops, packing is starved, and overtime is used to catch up. A fix at the machining stage would not help. A simple signal that tells the transport worker when a bin is full, or an automated transfer, could reduce the waiting for far less than a new machine would cost. This example is invented to show the reasoning and does not reflect any real facility.
The general lesson is to follow the flow of material and information through the whole plant, and put effort where the flow is interrupted.
Practical steps
- Measure where time goes. Record, for a few weeks, the major reasons for stops and the amount of rework by area. Even a simple tally is a start; automatic logging is better.
- Rank the losses. Concentrate on the largest, not the most visible.
- Choose the right fix. Not every loss needs automation. Better scheduling, clearer instructions or an adjusted layout may be cheaper and as effective.
- Automate selectively. Use automation where the task is repeatable, the problem is verified and the benefits can be measured.
- Check for side effects. Removing one loss may move the constraint elsewhere.
- Sustain the gain. Keep monitoring, and keep the maintenance and training that the new systems need.
Limits to keep in mind
Efficiency gains from automation depend on the plant’s starting point; a well-run plant has less to gain than a disorganized one, though even a well-run plant may find specific losses. Costs, complexity and the need for skilled maintenance have to be weighed against the benefits. Some inefficiencies are structural, such as long supplier lead times, and cannot be fixed on the plant floor.
Also, efficiency is not the only goal. A plant needs resilience, including some spare capacity and trained people who can act when automation fails. A system with no slack and no manual fallback can be efficient on a good day and fragile on a bad one.
Safety changes associated with new equipment must be reviewed by trained personnel, following manufacturer manuals and local regulations. This article is general information and not engineering advice.