A Factory Acceptance Test is one of the few moments you get to evaluate a systems integrator under real conditions: before the equipment ships, before your team owns the problems, and before production pressure makes everything harder to fix. The machine will either work or it won't. The more revealing part is how the integrator handles the process.
Here are nine green flags that separate solid partners from the ones who will cost you time and money later. If you are still choosing an integrator, it also helps to ask the right questions up front.
1. They give you all the time you need
A good FAT is not a rushed demo. The integrator should build the schedule around your questions, not force you to fit their timeline. If they keep glancing at the clock or try to move you along, treat that as information.
2. Full documentation is ready before the FAT
Electrical drawings, mechanical assemblies, I/O lists, control narratives, alarm lists, and spare parts lists should already be in your hands (or at least staged and accessible). Waiting until the FAT to "pull the docs together" is a sign the project is still disorganized.
3. Safety systems are fully active and shown to you
Guards, light curtains, e-stops, interlocks, and safety PLCs should be live and demonstrated. You should see the machine stop when it is supposed to stop, and you should understand the restart sequence. Safety that is "temporarily bypassed for the test" is a red flag, not a convenience. OSHA's machine guarding guidance and hazardous energy control rules are a good baseline for what you should expect to see, and we cover common gaps in 5 mistakes we see in machine safety retrofits.
4. They explain how every system works
The people running the FAT should be able to walk you through the sequence, the logic, the sensors, the actuators, and the operator interface without constantly deferring to "the guy who programmed that." Knowledge should be distributed, not locked in one person's head.
5. The machine is tested with your real parts or system
Running the equipment on generic or ideal parts only proves it can run. Testing with your actual parts, fixtures, materials, or upstream/downstream interfaces shows whether it will work in your process. If they cannot or will not do this, ask what assumptions they are making.
6. Issues get fixed before the FAT, not "on-site later"
Open punch-list items that are deferred to site installation almost always grow. The better integrators treat the FAT as the last major chance to close technical issues while the equipment is still in their facility and their people are available. "We'll handle that during installation" is usually optimistic.
7. They trigger faults and show recovery
Anyone can run a machine in happy-path mode. Ask them to force common faults (sensor failures, part jams, air loss, communication drops) and then demonstrate how an operator recovers. If the recovery process is unclear or undocumented, your team will discover the gaps on the night shift.
8. Performance stays consistent across repeated runs
One or two good cycles are not enough. The machine should hold cycle time, quality, and reliability across multiple runs under realistic conditions. Drift, intermittent faults, or "it usually does that" are problems you want to see (and fix) now.
9. Your team leaves confident
By the end of the FAT, the people who will own the equipment should understand how it works, how to run it, how to recover it, and what remains open. Confidence is not the same as optimism. It comes from having seen the machine perform, having asked hard questions, and having received clear answers.
Don't trade a few weeks now for months of pain later
Deadline pressure is real, and there will always be a reason to "just ship it." The cost of fixing problems on your floor (lost production, expedited parts, extra engineering time, operator frustration, and delayed ramp-up) almost always exceeds the cost of taking the time to get it right at the factory. A well-run FAT is one of the highest-leverage checkpoints in the entire project.
Use these nine points as a checklist the next time you walk into an integrator's facility. The machine matters. How the integrator behaves around it matters just as much. The Control System Integrators Association is also a useful place to find integrators who hold themselves to a published standard of practice.
Your FAT checklist
- They give you all the time you need
- Full documentation is ready before the FAT
- Safety systems are fully active and shown to you
- They explain how every system works
- The machine is tested with your real parts or system
- Issues get fixed before the FAT, not "on-site later"
- They trigger faults and show recovery
- Performance stays consistent across repeated runs
- Your team leaves confident
Don't let deadline pressure push you into accepting less. A few extra weeks of fixes now saves months of production losses later.
Want a second set of eyes on your next FAT? See how we've helped other manufacturers in our success stories, or book a time with our team.
