The building was a leased warehouse with a 6-metre ceiling and columns every 8 metres. The customer needed 80,000 orders a day at peak, with a 4-hour cut-off for same-day dispatch. The layout had to work around the columns, not over them.
The order profile
The orders were 92% parcels under 400 mm, 6% between 400 and 800 mm, and 2% oversized. The parcel weight was under 5 kg for 85% of the volume. The peak hour was 4,800 parcels, with a burst of 6,000 for 20 minutes.
The original plan was a cross-belt sorter with 180 chutes. The layout could not fit 180 chutes around the sorter, so we reduced to 120 chutes and added a second sort for the overflow. The second sort runs after the first wave, using the same chutes.
Induction
We used four induction stations: two automatic singulators for regular cartons and two manual stations for soft bags and oversized parcels. The automatic stations handle about 70% of the volume; the manual stations handle the rest.
Each induction station has a pre-scan conveyor that creates a 150 mm gap before the scan tunnel. The gap control was the most important detail; without it, the no-read rate was 3.5% in the first trial.
| Element | Specification |
|---|---|
| Sorter | Cross-belt, 120 chutes |
| Induction | 2 automatic, 2 manual |
| Peak rate | 6,000 parcels/hour |
| Scan read rate | 99.6% |
| Chute capacity | 40 parcels average |
| Building | 4,200 m², 6 m ceiling |
Chutes and packing
The chutes were designed for the parcel mix, with a 15° slope and a soft stop at the end. Each chute had a full sensor and a light that indicated when the packing station was ready. The packing stations were arranged in two rows, with a 1.2 m aisle between them.
The chute capacity was 40 parcels on average, but the fast-moving chutes needed 60. We used a double-depth chute for the top 20 SKUs, which reduced the number of chute full stops by about 30%.
Columns and structure
The columns were the main layout constraint. We routed the conveyor around them with a 1.2 m clearance, which allowed maintenance access. The sorter was placed in the centre of the building, with the induction on one side and the chutes on the other.
The mezzanine for the packing stations was built over the chutes, which used the 6-metre ceiling without blocking the sorter. The mezzanine structure was independent of the conveyor, so vibration did not affect the sorter.
What we would change
We would add a third automatic induction station. The two automatic stations were at 92% utilisation at peak, which left little margin for a stoppage. A third station would have cost about 8% more but would have removed the bottleneck.
We would also add a buffer before the sorter. The induction stations fed directly into the sorter, and a stoppage at one station reduced the feed to the sorter. A 200-parcel buffer would have smoothed the flow.
Frequently asked questions
Why not a tilt-tray sorter?
A cross-belt sorter was better for the parcel mix because it can handle soft bags and irregular shapes without them rolling. A tilt-tray would have required a more restricted parcel profile.
How was the 20-minute burst handled?
The buffer before the sorter and the second sort absorbed the burst. The induction stations ran at 110% of nominal for the burst, which was within the design margin.
What was the building height constraint?
The 6-metre ceiling limited the mezzanine height. The packing mezzanine was 2.4 metres above the floor, which left enough clearance for the sorter and the chutes.
If you are planning a sorting hub in an existing building, send the layout and parcel profile to our engineers through the contact page.
