FAT vs SAT for Feeding Systems: What Each Test Should Prove Before Production
Why FAT and SAT are not interchangeable
Factory acceptance testing and site acceptance testing both matter, but they answer different questions. FAT proves that the supplier delivered the agreed feeder concept under controlled conditions. SAT proves that the installed system still behaves correctly once it meets the customer utilities, line logic, operators, and production environment. Treating one as a substitute for the other usually creates blind spots that only appear after launch.
A strong feeder project uses FAT to reduce surprise and SAT to reduce false confidence. This article builds on our feeder acceptance test guide, site preparation checklist, and installation-readiness work before the machine reaches the floor.
How FAT and SAT divide the risk
The cleanest way to avoid duplicated effort is to assign each test stage the risks it can actually expose.
| Topic | Best checked at FAT | Best checked at SAT | Why |
|---|---|---|---|
| Basic mechanical function | Yes | Confirm only | Supplier has direct access to tooling and machine build |
| Line I/O and interlocks | Partial simulation | Yes | Real PLC and station timing exist only on site |
| Utilities and floor conditions | No | Yes | Air quality, grounding, and mounting change by plant |
| Operator workflow and refill access | Limited review | Yes | Real floor layout often changes the result |
What a good FAT should cover first
FAT is the right time to verify feed rate, orientation yield, alarm logic, reject behavior, and the physical condition of the finished build. It is also the best time to align evidence such as videos, settings, and agreed test methods while the supplier team can still modify the machine efficiently.
SAT should not repeat every FAT task mechanically. Instead, it should confirm that transport, reinstallation, local utilities, line integration, and operator use have not changed the result. A feeder can pass FAT honestly and still fail SAT because the site introduced poor air quality, different samples, awkward refill access, or unexpected machine timing.
The handoff between FAT and SAT is where many arguments start. Teams need a clear list of what was proven at the supplier and what remains open until site commissioning. Without that list, minor issues become disputes about responsibility rather than fast engineering decisions.
Decision rules for splitting FAT and SAT scope
- Keep supplier-build verification at FAT whenever practical.
- Keep plant-specific integration, utilities, and operator checks at SAT.
- Use the same pass criteria language across both stages so results stay comparable.
- Record unresolved FAT punch items before the machine ships.
What to watch after installation
At SAT, review refill behavior, machine clearances, operator access, and response to real stop-start conditions. Site layout often changes those more than expected.
Check whether the feeder still meets the agreed presentation quality once connected to the real robot, press, camera, or assembly nest. A stable standalone bowl is not the same thing as a stable cell.
If the line is complex, our PLC integration guide and cycle time balancing article help define what should be proven only after full site integration.
Acceptance checklist for project teams
- Define FAT scope before build completion, not the day testing starts.
- List SAT-only checks tied to utilities, layout, and line interfaces.
- Carry forward all settings, videos, and open points from FAT into SAT.
- Use the same product samples or clearly document any sample difference.
Huben Automation helps teams separate FAT proof from SAT proof so project responsibility stays clear and startup moves faster. If you want help structuring both stages, send us the process flow and current test checklist.
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