The customer made board-to-board connectors in a plant where the assembly bay was 19 metres long and 6 metres wide. The target was 300,000 units per day on two shifts, with a takt of 12 seconds. The existing line was a manual bench layout with no conveyor.
The constraint
The bay length ruled out a conventional speed chain line with a 600 mm pitch and 20 stations: the line alone would have been 12 metres, leaving no space for the infeed, the test area or the packing station. The product was small, 18 × 6 mm, and the fixtures were correspondingly small.
The customer also needed accumulation at every station because the operators also performed visual inspection, which varied with the part. A line without accumulation would have transferred every inspection delay to the next station.
The layout decision
We reduced the carrier pitch to 320 mm and used a 160 mm wide carrier. The line was configured as a U-shape with 14 stations on two sides, which allowed the same 14 stations to fit in 9.6 metres of line length. The U-shape also put the line leader in the middle, where both sides were visible.
The test station was placed at the end of the U, with a 6-position buffer before it. The packing station was adjacent, so a passed unit moved one metre to the box.
| Parameter | Value |
|---|---|
| Line length | 18 m of chain, 9.6 m of floor |
| Stations | 14, double-sided |
| Carrier pitch | 320 mm |
| Takt | 12 s |
| Output | 300,000 units/day, two shifts |
| Accumulation | 3 carriers per station |
Accumulation and inspection
Each station had three carrier positions: one at work, one waiting and one as a buffer. The accumulation was controlled, with a pneumatic stop at each position, so the carriers did not touch. This was important because the connectors were presented in an open tray and contact between carriers could dislodge them.
The inspection station used a camera and a monitor. The operator placed the carrier in a nest, and the camera checked the connector position and the presence of the latch. The inspection time was 8 seconds, leaving 4 seconds for handling.
What was difficult
The small pitch made the line sensitive to carrier wear. A worn carrier could tilt by 0.5 mm, which was enough to misalign the connector in the inspection nest. We specified hardened carrier pins and a weekly carrier check, and the problem disappeared.
The second difficulty was static. The connectors were supplied in tape and reel, and the tape generated charge when peeled. We added ionisers at the two stations where the tape was opened, and grounded the carriers through the chain.
What we would do differently
We would specify a larger buffer before the test station. The 6-position buffer was adequate for normal variation, but a 10-minute test stoppage emptied it. A 10-position buffer would have covered the stoppage without stopping the line.
We would also add a carrier return lane inside the U, rather than returning carriers on the floor. The floor return worked, but it added a manual handling step that the customer later automated.
Frequently asked questions
Why a speed chain line rather than a belt?
The line needed accumulation at every station and a stable carrier for the inspection nest. A belt would have required a separate pallet system and would not have accumulated without pressure.
How was the 12-second takt verified?
We ran a 30-cycle simulation with the actual station times and a ±10% variation, then measured the first 100 cycles on the line. The measured takt was 11.8 seconds at the bottleneck station.
What was the payback?
The line replaced 18 manual benches and reduced labour by 11 operators per shift. The customer reported a payback of 14 months.
If you have a constrained bay and a tight takt, send the layout and product drawing to our engineers through the contact page. We will check whether a U-shape or a shorter pitch can fit the line.
