Warehouse Racking to Better Suit Automated Forklift System
Automated guided vehicles (AGV), particularly of the laser guided variety, are designed in such a way that they require a certain level of perfection from their environment. In a brownfield project this can be very difficult to achieve, and if the proper considerations aren’t made from the beginning it can lead to ongoing issues and costs.
This project concerns an existing AGV system handling palletised finished goods and raw packaging materials. The system includes both selective and drive-in racking, up to 8 meters in height.
The project launched considering three key concerns of the existing system:
The AGV system could not be relied upon to consistently place standard wooden pallets into selective racking and have them ‘lock into position’ correctly.
On rare occasions a pallet would impact racking uprights while being deposited into a rack by an automated forklift.
Given tight tolerances and inconsistencies in the system, wider materials could not be handled by the AGV system. This lead to increased requirements for manual forklifts to operate in the AGV environment.
Drive in racking after the upgrade.
Solution
A set of modifications were scoped to meet the design criteria.
70 bays AGV selective racking to have shelves installed.
30 bays AGV drive-in racking to be widened.
3 bay AGV/Manual Forklift Handover rack to be widened.
Selective Racking – ‘Locking into position’ problem
It was relatively easy to determine a few likely factors contributing to this problem. Given the issue was worse at greater heights, 8 metres being the highest pallet position, we could deduce that the vehicle has some kind of lean or flex in the mast that increases proportionally with height. If this was the case both the mast and potentially pallet weight could play a role. Pallet weight wasn’t something we could realistically control for, there would always be full and part pallets of different materials.
All the vehicles were fully calibrated and underwent a mast alignment. The mast alignment uncovered a lot of variation between the vehicles and correcting it did make a noticeable difference to the system overall by improving pallet placement – but not enough.
The other likely contributing factor was the pickup station. This rack where manual forklifts handover pallets to the automated system was scrutinised as a point where humans could introduce inconsistencies. A fair amount of work had already been done here putting guides in place. The guides would allow up to 15 mm of variation, but this didn’t really explain the 50+ mm that could be seen in the racking.
It was ultimately determined that the existing vehicles would not be able to consistently place pallets with sufficient accuracy to allow them to ‘lock in’ reliably. The factors likely causing variations were a combination of differences between vehicles. It was acknowledged that pallet quality and pickup locations could also both contribute to these variances.
To resolve this concern, all selective racking would have new shelves installed with which locking in of pallets would not be required. The shelf would be considered sufficient and stable perching despite pallet position variations.
As a bonus benefit, the design would allow the AGV’s existing ‘beam search’ sensors to operate and guarantee left-right horizontal alignment in position. Previously these positioning sensors weren’t used for the selective racking positions.
Shown above are pallets not locked in correctly, the overhang is highlighted, they may appear off balance. With the new shelves, this isn’t of concern.
Shown is the shelving installed on selective racking negating the negative impact of pallets not being locked in correctly. See that even if a pallet overhangs, it has additional support available.
Concerns about widths – Wide packaging and impacts with uprights
When the system was originally installed, the requirement for packaging materials wider than a standard Australian Chep pallet was not considered, as a result the system was not designed for or suited to such materials. Using the system with wider materials would present a risk, but not doing so presented a risk of its own – manual forklifts operating in an AGV environment.
While overlooking wider materials was a scoping gap during the original installation, it was demonstrated that even with materials conforming to standard dimensions there were rare occasions where a misalignment could result in materials impacting uprights while being loaded into racking by the automated forklifts. The frequency of this occurring was increased as levels or depth of drive-in racking increased. The likely cause was a combination of mast movement or variation, vehicle navigation issues, and floor levels – fixes for all of these issues were elusive to say the least.
The solution to this problem, perhaps predictably enough, was to widen the racking. Approximately 75% of drive-ins used for packaging materials were widened. This included 12 bays of 4 deep, 7 meter high racking where upright impacts had occurred multiple times. A set of 2 deep drive-ins were also widened solely for the purpose of catering for the wider materials.
The racking widths were increased from 1370 to 1565 mm. This increased the clearance by ~100 mm on either side of the standard Australian Chep pallet (1165 mm), to 200 mm.
One of the additional benefits to working through this process of racking modifications was the opportunity provided to review the existing racking units and their suitability based on materials used by the plant. Through a review of inventory, it was determined there was significant opportunity to make more economical use of vertical space. As a result, despite needing to remove bays to maintain our footprint, we were able to produce a net increase in pallet storage capacity by optimising the number of levels of racking available in the existing space.
Project Outcome
The project delivered on its scope of works and was well received by the site. The changes have delivered on improving confidence in the system. Nobody will need cringe again watching a pallet swing close to an upright while being stored in drive in racking, the days of checking for locked in pallets are over, and everyone from operator to manager feel far more comfortable seeing a reduction in interactions between manual and automated forklifts.
