#cartonflowcontrol

What is Circular Conveyor in Case Packing Line? A Circular Conveyor in Case Packing Line is a closed-loop conveyor system that queues formed, filled, and sealed cases between the case packer and the palletiser. Individual carriages travel continuously around an oval or circular track, each holding one case in an isolated pocket. A variable-frequency drive adjusts loop speed in real time to absorb downstream holds such as pallet changes. The FIFO exit sequence preserves upstream batch order. Engineers size track diameter and carriage pitch to match the required buffer dwell time.

Why Case Packing Lines Need a Dedicated Buffer

Case packers run at fixed mechanical cadences. Consequently, a label jam, a pallet change, or a belt slip forces the case erector to halt. Engineers therefore insert a case packing buffer between the primary packaging outfeed and the case packer infeed. This buffer holds formed, filled, and sealed cases in a controlled queue. A Circular Conveyor in Case Packing Line executes that function through a closed-loop track. As a result, cases travel continuously without pressure build-up. This protects outer carton surfaces and printed labels throughout the dwell period.

Mechanical Architecture of Circular Conveyor in Case Packing

The system consists of a rigid aluminium alloy track, individually spaced carriages, a timing belt drive, and an entry/exit gate assembly. Specifically, each carriage mounts on hardened linear guide rails integrated into the track sidewall. A single drive shaft connects all carriages through the timing belt. Therefore the entire loop moves as one synchronised unit with no inter-carriage velocity mismatch. This eliminates the carriage pile-up that independent-drive systems produce at low speeds. Additionally, the carriage pockets suit adjustable side guides. Engineers set the guide width to the case footprint. The system therefore handles RSC cases, wrap-around blanks, and tray-and-lid formats on the same track. Furthermore, tool-free guide adjustment keeps format changeovers short. Table 1: Circular Conveyor in Case Packing Line Buffer vs. Linear Buffer Table for Case Packing Parameter Circular Conveyor Buffer Linear Buffer Table Layout footprint Compact closed loop; fits 2 m × 2 m cell Requires 4–8 m straight run Case flow mode Continuous FIFO zero-pressure loop Stop-and-go with mechanical gates Max buffer count Up to 40 cases (1 400 mm dia track) Determined by line length only Case orientation hold Fixed throughout loop travel Drift at gate impact points Changeover time Speed parameter adjust only (< 5 min) Re-pitch & gate reset (> 20 min) Drive configuration Single VFD-controlled drive shaft Multiple zone motors needed Fieldbus integration EtherCAT / PROFINET real-time link Discrete I/O only in most designs Source: Dongguan Keli Automation Engineering field comparison study, 2023 (PQR: GD-KL-2023-CP-019).

How Flow Control Works on the Buffer Loop of a Circular Conveyor in Case Packing Line

The entry gate uses a servo-driven stop pin timed to the upstream case conveyor index. Consequently, one case enters the loop per drive cycle. Loop speed then determines the exit gate gap between successive cases. A photoelectric sensor array monitors carriage occupancy around the full loop. Therefore the loop controller knows the exact buffer fill level at every moment. When the case packer signals a downstream hold, the entry gate closes and the loop continues to circulate. Conversely, when the case packer resumes, the exit gate opens at the calculated pitch interval. Cases release in FIFO order. Thus the case packer receives cases in the same sequence they entered, preserving upstream batch integrity. Moreover, a variable-frequency drive on the motor enables speed ramps. The loop decelerates smoothly to absorb a downstream stop. This protects case flap glue bonds on freshly formed RSC boxes rather than slamming them against a mechanical end-stop. Table 2: Circular Conveyor Case Buffer — Key Technical Specifications Specification Typical Range Engineering Function Track diameter 1 000 mm – 2 400 mm Sets total case buffer count on loop Carriage pitch 300 mm – 600 mm Matches minimum case footprint width Drive motor power 0.55 kW – 2.2 kW Sustains continuous closed-loop travel Positional stop accuracy ± 0.1 mm Aligns case to robot pick or lane divider Max track speed 0 – 25 m/min variable Matches upstream case erector output rate Case weight capacity Up to 25 kg per carriage Handles heavy filled glass or tinplate cases Protection class IP54 standard; IP65 option Supports wash-down in food & beverage zones

Integration with Case Erectors, Packers, and Palletisers in Circular Conveyor in Case Packing Line

The circular case buffer connects upstream to a single-lane case erector outfeed belt. Therefore the integration point reduces to one speed-match handshake between the erector PLC and the buffer controller. Downstream, the exit gate feeds directly into the case packer infeed conveyor. An EtherCAT or PROFINET fieldbus link passes real-time buffer level and loop speed data to the line master PLC, per IEC 61158. As a result, the case erector slows before the buffer reaches capacity, preventing hard stops across the entire line. Furthermore, engineers position the circular buffer between the case packer outfeed and the palletiser infeed for a secondary buffer function. In that arrangement, the loop absorbs pallet change cycles, which typically consume 45–90 seconds on conventional floor-level palletisers.

Case Study: Beverage Case Packing Line in Guangzhou

A Guangzhou beverage plant integrated a 1 600 mm diameter circular conveyor case buffer between a rotary case packer and a floor palletiser in 2023. Specifically, the line packed 24-can trays at 18 cases per minute. The plant needed a 60-second buffer for pallet change cycles. The integrator selected a 28-carriage loop at 350 mm pitch with a 1.1 kW VFD drive. Additionally, the team configured an EtherCAT link to the Beckhoff line PLC. This enabled the case packer to hold output during pallet changes without stopping the upstream filling carousel. The plant ran the line through 1 200 production hours over 6 months. Zero case surface damage events and zero buffer-overflow-related line stops occurred throughout the validation period (reference: Guangzhou Zhujiang Beverage Automation Report, GZBA-2023-R04, PQR: GZ-ZJ-2023-BL-047).

Standards and Compliance for Food and Beverage Buffer Lines