Buffer & Sort Tote Shuttle
Built for sequence rather than storage. Flow-rack operation holding strict first-in-first-out while the lane is replenished behind it, feeding pick and pack stations in the order they need.
SLS900 Series · Buffer & Sort
Order matters more than volume.
Every other model in the range is measured on how much it can move. This one is measured on whether the right unit arrives next. It runs lighter loads at a lower rate because the work is sequencing, and it holds that sequence while the lane behind it is being restocked.
First-in-first-out by geometry
Stock loads at one end of the lane and leaves from the other, so the oldest unit is physically next out. The software sequences on top of a rack that already makes the wrong pick awkward.
High-density buffering
Ample buffer locations in limited space maximize buffer space utilization Fast storage/retrieval: rapid inbound and outbound shorten order processing wait times.
Multi-shuttle coordination
Parallel operation boosts overall system throughput. Intelligent diverting: goods are quickly routed based on orders, destinations, waves, and other task data.
| Movement | Bidirectional, single aisle |
|---|---|
| Payload | 3 to 20 kg |
| Throughput, per aisle | ≥540 boxes/hr |
| Continuous Runtime | Unlimited · charges on track |
| Max speed | 6 m/s |
| Position accuracy | ±3mm |
| Positioning method | DC servo + positioning photoelectric sensor + RFID |
Typical deployments
Where the SLS900 B&S excels
These are operations where getting the order right is worth more than getting more through, and where the cost of a sequencing error lands downstream rather than in the rack.
Pick-face replenishment
Keeping the face stocked without interrupting picking. The lane refills from behind while the front continues to deliver.
Order sequencing to despatch
Units arrive at pack in the order the load plan needs, so the sortation problem is solved in the rack rather than on the floor.
Date-coded stock
Food and pharmaceutical lines where rotation is a compliance question, not a preference, and the rack should make the correct pick the only convenient one.
Wave and batch staging
Holding a built wave until the truck, the lane or the labour is ready, without occupying pick locations to do it.
The complete system
The complete buffer & sort shuttle system
Tote shuttles handle every horizontal move inside the rack. Servo lifts carry cases between levels, and interface lines connect the rack to the rest of the building. Throughput is set by how many shuttles and lifts you run rather than by the structure, so density and speed are specified separately.
01 · Box shuttle
Travels the rack on rail, bidirectionally on the Standard, Variable and buffer & sort shuttles, and across aisles on the 4-Way. Positioning to ±3 mm by DC servo, photoelectric and RFID.
02 · Layer-changing lift
Servo belt drive carrying up to 100 kg across two cargo compartments, positioning to ±2 mm, at 6 m/s unloaded.
03 · Interface lines and charging
Chain in and out conveyors at the rack face, and a conductor rail running the length of the aisle. Shuttles collect power continuously as they travel, so they never stop to charge.
Specs
Buffering and sorting, in full.
| Specification | Buffer & Sort |
|---|---|
| Movement | Bidirectional, single aisle |
| Sequencing | Strict first-in-first-out |
| Rack configuration | Flow rack |
| Payload | 3 to 20 kg |
| Throughput, per aisle | ≥540 boxes/hr |
| Max speed | 6 m/s |
| Acceleration | 2 m/s² |
| Case size (L×W×H) | 200–600 × 200–400 × 150–500 mm |
| Electric roller power | 32W |
| Driving mode | poly V-belt |
| Positioning accuracy | ±3 mm |
| Continuous runtime | Unlimited · charges on track |
| Operating temperature | −25 to 45 °C |
| Specification | Buffer & Sort |
|---|---|
| Drive | Synchronous belt, electric braking |
| Travel motor | 1,000 W |
| Fork motor | 400 W |
| Positioning method | DC servo, photoelectric and RFID |
| Battery | Lithium titanate, 2.9 Ah |
| Supply voltage | DC 48 V ±10% |
| Charging style | Rail track contact line |
| Communication | 5 GHz / 2.4 GHz dual band, RS-485 |
| Structure | Q235B steel, ≥235 MPa yield |
| Certification | CE · 2006/42/EC, SGS verified |
| System availability | ≥97% to FEM 9.222 |
| Rack height range | 1 to 6 m |
| Aisle length range | Unlimited |
Safety and certification
What protects people and stock.
Obstacle detection
HWA sensors stop the shuttle before contact, whether the obstruction is a load, a person or another machine.
Anti-fall and end stops
HWA sensors and mechanical end stops hold the shuttle on rail at the limits of travel.
Emergency stop
Red emergency stop on the machine, halting the shuttle immediately.
Battery protection
Over-temperature, overcharge and over-discharge protection on the onboard lithium titanate pack.
Alarm and interference
Onboard alarm function, with dual-band wireless chosen for resistance to interference across a busy rack.
Certification
CE to Machinery Directive 2006/42/EC, verified by SGS across the shuttle, the shuttle lift and the tote AS/RS system. Manufacturing certified to ISO 14001:2015.
Frequently Asked Questions
SLS900 Buffer & Sort, specifically.
How is first-in-first-out actually enforced?
By the geometry, not by the software alone. Stock is loaded at one end of a flow lane and retrieved from the other, so the oldest unit is always the next one out. The control layer tracks and sequences on top of that, but the rack itself makes the wrong pick physically awkward rather than merely discouraged.
Why is the payload lower than the other tote shuttles?
Because the work is different. This model is optimised for high cycle counts on light totes moving between the buffer and the pick face, not for carrying the heaviest case in the range. If your buffered units run above 20 kg, the Standard or Variable is the right machine and the buffering logic moves into the software.
Can one rack both buffer and store?
Usually it should not. Buffering wants shallow, fast-turning lanes near the pick face; reserve storage wants depth and density. Most sites that do both zone the building, run this model on the buffer and a Standard or Variable behind it, and manage the whole thing as one fleet.