Machine vision / Article
Off-the-shelf AOI vs custom-built: why catalogue machines fail on odd parts
A catalogue AOI machine is built around a flat, board-shaped part, conveyor-fed in a known orientation, with features inside a narrow height range. If your part matches those assumptions, buy the catalogue machine, because it is cheaper, faster to deploy and easier to support. If your part is tall, curved, reflective, multi-surface or awkward to hold, a standard system runs out of geometry rather than resolution, and no sensor upgrade fixes that. This article marks the line between the two, with the height and imaging limits that decide it.
The numbers at a glance
01 / The assumptions
What a catalogue machine assumes about your part
A standard AOI system is an excellent machine for the part it was designed around. That part is flat, roughly board-shaped, arrives on a conveyor in a repeatable orientation, presents its features to a fixed camera from above, and keeps everything important inside a limited height band. Every element of the machine, the frame, the lighting geometry, the handling, the defect library, is optimised for that case, which is exactly why it is cost-effective.
The limits are published, not hidden. Standard AOI equipment measures up to 5 mm in height, while systems designed for tall components and odd-form parts support up to 25 mm. Programming assumes a reference too: AOI requires initial programming with golden samples, and unprogrammed defects may go undetected, particularly in highly variable production. Read those two sentences against your own part before you read any brochure.
02 / Where it breaks
Five places standard systems run out of room
These are geometry and physics problems, not software problems. If your part hits two or more of them, a bigger sensor will not rescue the project.
03 / The honest case
When off-the-shelf is enough
Most inspection problems do not need a custom machine, and it would be dishonest to imply otherwise. If your part is a populated PCB or a similarly flat and standardised item, running at a normal SMT takt, with defects that sit inside the machine's own library, a catalogue system is the better buy on every axis: lower capital, faster deployment, documented programming, spare parts on a shelf, and operators who can be trained from a manual.
Standard machines are also getting better at the boundary cases. Mixed-technology lines benefit from equipment supporting a 25 mm measurement range, which allows through-hole, odd-form and SMD components to be inspected in a single program. Check that range against your part before assuming you need bespoke engineering. Buying a custom cell for a standard board is money that should have gone into the station that is actually leaking, and our breakdown of where AOI and manual inspection costs actually sit is the right place to check that.
04 / What custom means
Not a bigger camera. A different machine
Custom-built AOI is often misread as premium hardware. In practice it means the mechanical and optical arrangement is designed around your part instead of the reverse. A custom AOI system integrates imaging, lighting technique, defect detection and mechanical and electrical arrangements to automate inspection of complex parts, and that usually means several specific things: lighting designed per surface, motorised camera positioning to reach each feature, robotic or cobot handling to present the part, and encoders synchronising acquisition with motion so defect capture stays accurate even at high speed.
What you gain is a machine whose blind spots you chose. What you accept is that the design is specific, so the vendor relationship matters more than it does with a catalogue purchase. The question to settle before signing is not how sophisticated the cell is, but who can modify it in two years when your product changes. That is the same argument as the choice between measuring and photographing a defect, which we cover in 2D vs 3D AOI.
05 / Built in-house
AONIA is designed, built and supported here
AONIA is our optical inspection machine, and it is designed, built and supported in-house in Malaysia. That is a practical position rather than a marketing one. Because we build the machine, the optics, the lighting geometry, the handling and the defect model are all variables we can move for your part, instead of constraints you have to design your part around. Where a catalogue system asks whether your part fits the frame, we start from the part and the defect and work outwards.
It also fixes the support answer. The team that designed your inspection cell is the team that retunes it when a material finish changes or a variant enters the line, working from Shah Alam in Selangor and Batu Kawan in Penang rather than a regional office abroad. Defect models are trained on your real defect images, and where those are too few, NVIDIA defect image generation for AOI expands the set. CODETRACE is a member of the NVIDIA Inception program.
06 / Where to start
Measure your part against the frame
You can settle this in an afternoon with a caliper and a defect box. Write down the tallest feature you must inspect, the number of faces that carry a defect you care about, whether the part can be held in a repeatable orientation, and whether any surface is polished. Then compare that to the standard machine's height range and its single fixed viewpoint. If the part fits, buy the catalogue system. If it does not fit on two or more counts, custom engineering is not a luxury, it is the only configuration that can see the defect.
Either way, prove it before capital release. Run the real parts, including the rejects you have kept, and ask for the false-call rate next to the detection rate. Inspection sits inside factory automation, so handling and rejection belong in the same design conversation as the camera, and the six inspection jobs a vision station can actually do are set out in what AOI actually does. Bring us the part nothing else could inspect. We will tell you honestly whether it needs a custom machine.
A catalogue machine inspects a catalogue part.
FAQ / Off-the-shelf vs custom AOI
Questions, answered.
01When do I need a custom AOI machine instead of an off-the-shelf one?
When your part breaks one of the assumptions a catalogue machine is built on. Standard AOI equipment expects a flat, board-like part, conveyor-fed in a known orientation, with features inside a limited height range. Once the part is tall, curved, reflective, multi-surface, awkward to hold, or has to be inspected from angles a fixed camera cannot reach, a standard system runs out of geometry rather than resolution. That is the point where custom optics, custom handling or a purpose-built cell becomes the cheaper answer.
02What are the height limits of a standard AOI system?
Standard AOI equipment measures up to about 5 mm in height, while systems designed for tall components and odd-form parts support up to about 25 mm. If your assembly carries connectors, shielding cans or tall capacitors, or if the feature you care about sits outside that range, a catalogue machine will either miss it or force you to inspect in multiple passes. Check the measurement range against your tallest and your most critical feature before comparing prices.
03Why do catalogue AOI machines fail on odd-shaped parts?
Because non-uniform and intricate designs make it difficult to capture images from all angles with a standard AOI system, and standard systems are built around simple, flat surfaces. Reflective and multi-surface parts add a second problem: a single fixed lighting geometry that reveals a defect on one face will wash out or shadow another. Medical implants, turbine blades and automotive gears are the usual examples, and none of them can be solved by buying a better sensor.
04When is an off-the-shelf AOI system good enough?
More often than a custom vendor will admit. If your part is a populated PCB or a similarly flat, standardised item, moving down a conveyor at a normal SMT takt with defects that fall inside the machine standard library, a catalogue system is faster to deploy, cheaper to buy, easier to staff and simpler to support. Buying custom engineering for a standard part is a waste of money, and the honest recommendation in that case is the catalogue machine.
05What does CODETRACE build in-house?
AONIA, our optical inspection machine, is designed, built and supported in-house in Malaysia. That means optics, lighting, part handling and the defect model can each be changed for your part rather than configured around a fixed frame, and the team that designed the cell is the team that retunes it. Models are trained on your real defect images. Engineering and support are based in Shah Alam, Selangor and Batu Kawan, Penang, and CODETRACE is a member of the NVIDIA Inception program.
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