Appliance assembly lines are long, manual and heavy. A refrigerator or washing machine is a large, awkward unit, and the difference between models can be a few centimetres or a completely different cabinet. Flexibility is not a single feature; it is a set of decisions across the line.
Key takeaways
- Sequence models to balance work content, not to minimise changeover alone.
- Use a common carrier and model-specific nests rather than a new carrier for every model.
- Material presentation must change with the model, or the operator will pick the wrong part.
- Buffers absorb the takt difference between models.
Sequence before fixture
The sequence of models determines the work content at each station. If a large model follows a small one, the station may need more time for the larger unit. A sequence that alternates large and small models can smooth the load, but it may increase changeover frequency. Find the sequence that meets the output with the least variation.
Use a sequencing rule based on work content, not on customer order sequence. The line controller can reorder units within a window if the material and the label allow it.
Common carrier, model-specific nests
A common carrier with a model-specific nest is cheaper and faster than changing the whole carrier. The carrier provides the transport and the locating features; the nest provides the product-specific support. The nest should be light enough for one person to change and should locate on the carrier without adjustment.
For large appliances, the carrier often runs on a chain plate conveyor or a roller conveyor with a pallet. The pallet should be designed for the heaviest model and should have soft surfaces to protect the finish.
| Model change | What changes | Target time |
|---|---|---|
| Same platform, different trim | Parts, label, test program | <1 cycle |
| Different cabinet size | Nest, fixture width, material | 1–3 cycles |
| Different platform | Nest, tooling, test, maybe carrier | 5–15 minutes |
Material presentation
In a mixed-model line, the operator must know which part to pick for the current unit. Use a pick-to-light system, a sequenced kit or a model-specific bin that is presented at the station. A label on the unit is not enough if the parts are in the same bin.
Sequence the material to the line in the same order as the units. A kit cart that follows the unit through the line is a simple solution for high-value or high-variety parts.
Takt variation and buffers
Different models have different work content. If the line is balanced for the average, the large model will be over takt and the small model under takt. A buffer before and after the mixed-model section absorbs the difference. The buffer size should cover the largest difference in work content, typically 2–5 units.
Alternatively, use a small number of model-specific stations that can be bypassed for some models. A bypass is cheaper than balancing every station for every model.
Testing and packing
Test programs and packing materials change with the model. The test station should read the model from the unit and load the correct program automatically. The packing station should present the correct carton and foam, ideally from a sequenced dispenser.
Do not rely on the operator to select the test program. A wrong program can pass a faulty unit or fail a good one, and the record will be wrong.
Frequently asked questions
How many models can one line handle?
It depends on the differences. A line can handle many trim variants, but a limited number of platform variants. Beyond that, a second line or a cell is usually better.
What is a realistic changeover time?
For a nest and material change, 1–3 cycles is realistic. For a platform change, 5–15 minutes is typical.
Should the line be balanced for the largest model?
Balance for the largest model if it dominates the mix; otherwise balance for the average and use buffers for the difference.
Send your model matrix and output target to our engineers through the contact page; we will help design the carrier and the changeover sequence.
