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Fixed Vs flexible infrastructure – which automation style is better? 

Article by James Gore
warehouse automation

The robotics revolution keeps on rolling. Warehouse managers aren’t asking “will we automate?” anymore.

Now, the question has become “when will we automate” and even more importantly, “how will we automate?”.

Automation will always have substantial up-front costs, which means you will need to put together a plan. A plan that details timetables, scheduling, anticipated ROI, and a comparison between all the available options. For warehouses looking to automate, that means a decision between one of two possible courses: Flexible or Fixed infrastructure.

What is Fixed Infrastructure?

Shelves, tracks, cranes or any other arrangements that are static and built in place are all examples of fixed infrastructure. Automation that needs these fixed systems to work is known as fixed infrastructure automation. Sometimes this kind is known as Automated Storage and Retrieval Systems or ASRS.

What is Flexible Infrastructure?

Automation that uses flexible infrastructure means that everything moves. Nothing is bolted in its place or to the floor. Not the shelves, not the racks, definitely not the stock, and not the robots that move them all. The kinds of automation systems that use these systems are known as Automated Guided Vehicles or AGVs, and Autonomous Mobile Robots or AMRs.

Which is better?

Since most businesses won’t be able to set up a real world side by side comparison, we’ve put together this point-by-point comparison to help explain things.

Space Requirements:

Fixed – A fixed infrastructure system requires a great deal of space. ASRSs need enough space for cranes, conveyor belt systems, or tracks. Because of this, ASRSs only work in the largest warehouses, and even among those, only ones of a specific shape. Usually that shape needs to include very high ceilings. All the infrastructure that makes ASRSs work consumes space that could otherwise go to the storing of goods. ASRSs offer a trade-off that businesses need to consider. Is the efficiency of the automation worth the loss of space?

Flexible – Flexible infrastructure systems can work in spaces of any size or any shape. The robots do not need tracks or conveyor belts, meaning more warehouse space is used to store and organise goods. The only static infrastructure that AMRs/AGVs need are charging docks or battery swap stations. When comparing ASRS directly against AMRs/AGVs, you will see that the latter use more floor space but much less vertical space. This means that AMRs/AGVs can allow for high bay racking to be set aside for replenishment, and floor space can be doubled with the addition of a mezzanine floor that an ASRS would not allow.

Implementation Time:

Fixed – Fixed robotics involve installing lots of extra infrastructure. This is a long and laborious process. An empty warehouse space will need to have hardware built in place to work correctly.

Flexible – Installing flexible robotics is far faster. AMRs/AGVs are almost entirely self-contained. AGVs need coloured tape or machine-readable codes on the floor to help them stay oriented. Without the need to install substantial new warehouse infrastructure, an empty space can become a working warehouse very quickly.

Safety Requirements:

Fixed – Fixed infrastructure automation needs separate safety systems. Fences and barriers must be installed to keep manual workers away from the areas where the automated systems operate. This can further consume space that could otherwise be storing stock.

Flexible – In contrast, flexible infrastructure robots such as AGVs and AMRs are much more able to work around and alongside manual workers. Flexible systems need very little in the way of separate safety infrastructure, thanks to their on-board sensors. Instead, they can move and adapt to make safety something intrinsic, not additional. AMVs will stop in place when faced with obstructions.

Growth Possibilities:

Fixed – Once fixed infrastructure ASRS is installed, growth or expansion becomes extremely difficult. Any expansion will have to be with the specifications of the existing ASRS in mind.

Flexible – Growth is much easier when using a flexible automation system. The shape and size of the expansion matters very little for AMRs. Their flexibility means they can move and adjust to any size or shape of space, no matter how much bigger it gets.

Financial Commitment:

Fixed – Fixed infrastructure is an arrangement that has to be bought outright. This means that the ROI calculations are much starker, and a business planning to use ASRS must be much more certain in their long term viability.

Flexible – Purchase options are much more varied for flexible systems. Hiring, hire purchase, and outright purchase are all possible. This allowing for rapid ROI turnaround or temporary testing periods. You can also have automation installed on a temporary basis in just a portion of your warehouse to demonstrate its effectiveness in-situ. This is known as a proof-of-concept period, where a company can try out the robots without committing fully. Such a process is not remotely possible with fixed systems, but is the natural territory of flexible automation.

Throughput Rates

Fixed vs Flexible – A direct comparison between fixed and flexible systems here is not entirely possible. There are too many variables in terms of the SKUs size and weight, the factory size, the distance between picking stations and despatch, and so on.

However a comparison is possible in terms of projections and ability to change and adapt your systems. When it comes to choosing to installing an automation system, just how much faster your processes will move can only be estimated. If it turns out it isn’t going as quickly as you hoped, changes will need to be made.

Making changes to a fixed system like an ASRS is very difficult indeed. Existing infrastructure will need to be dismantled, rearranged, and rebuilt according to new specifications. This involves a lot of downtime, and substantial costs.

By contrast, a flexible system can be altered with relative ease. New AGVs and AMRs can be deployed, and the positions of picking and replenishment stations can be changed. Flexible systems also make it easier to rearrange product storage. The most popular products can be kept near the picking stations, for the fastest possible fulfilment. For fixed systems, this kind of change will be a long and drawn out process. For flexible alternatives, it is much simpler.

SKU Capacity:

Fixed vs Flexible – Fixed automation dedicates substantial space to conveyance and safety, taking away space that could otherwise be used for storage. Because of this, in most cases, flexible automation systems will be able to handle greater volumes of SKUs. Flexible systems are also more suited to warehouses containing a wider variety of SKU types and sizes.

As the name suggests, flexible systems are better suited to a wider variety of situations. Flexible infrastructure can grow as you grow. More robots can be deployed as demand increases. The infrastructure’s overall shape can change as your businesses’ requirements shift and evolve.

A simple way to summarise the differences would be the following. A flexible system means the robots will adapt to your needs. With a fixed infrastructure system, it is the other way round. With fixed systems, your warehouse will remain in a singular state for the foreseeable future. Flexible robots however, allow for the kinds of changes that are very much a natural part of the warehouse marketplace. While fixed systems are valuable for certain industries in some situations, most businesses will get much more utility from a flexible automation solution.

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