SBN250 NG Buffer Conveyor — Keep Good Boards Flowing When Inspection Fails One

Inline PCB buffering is one of the most overlooked elements of a productive SMT or THT line. When an AOI or SPI machine rejects a board, when a downstream machine pauses, or when two stations run at different cycle times, the whole line can stall — unless a buffer is in place. The SBN250 NG buffer conveyor from Southern Machinery (also known as the SPI vertical buffer) absorbs that variation automatically, so good boards keep moving and failed boards are stored for rework without stopping production.

The cost of no buffer between stations

Without an inline buffer, any mismatch in station speed or any single NG board becomes a line-stop event:

A slow inspection step stalls everything upstream. When AOI or SPI runs slower than placement, the line backs up and the placement head idles.
NG boards mix with OK boards. Failed boards that are not separated physically end up re-inspected or, worse, escape into the next stage.
Manual handling returns. Operators carry boards between stations, adding dropped-board, ESD and labor risk.
Traceability breaks. Without controlled flow (FIFO/LIFO), lot sequencing and quality records become guesswork.

The SBN250 is built to the same standard as the rest of the line: SMEMA-compatible, ESD-safe and simple to operate.

The NG/OK Buffer Check

Score your board flow before you quote. The check uses your own line:

Find the speed mismatch. Identify the station that runs slower than the rest (usually AOI/SPI or a manual rework bench).
Count mixed-lot events. How often do NG boards sit among OK boards waiting for a decision?
Measure idle from waiting. How many minutes per shift does the placement head or reflow oven spend idle because a board is stuck downstream?
Confirm transport height. Standard 900 mm ±20 mm; the SBN250 matches it in L-to-R or R-to-L transfer.

The check does not tell you to buy. It sizes the stoppages your line suffers today from takt-time imbalance.

The machine: how the SBN250 buffers

The SBN250 temporarily stores PCBs inline between process stations. Its most common application is after an AOI or SPI step: boards that pass (OK) continue downstream immediately, while boards that fail (NG) are diverted into the vertical buffer and held until an operator or rework station removes them.

Three modes — FIFO, LIFO and pass-through — so you control exactly how boards release.
12-PCB capacity standard (custom capacity available) with a cycle time of about 10 seconds, keeping steady flow even when inspection or rework is slower than the rest of the line.
Vertical buffer design — boards stored on levels, with an upper level available for inspection or rework.
Takt-time decoupling — absorbs speed differences between stations so a slow step does not stop the whole line.
ESD round belt transport moves boards without damaging sensitive components; leadscrew width adjustment keeps both rails parallel and square to the board path.
No air required on the standard version; AC 110 V or 220 V single-phase, 250 VA maximum.

For simple accumulation without NG separation, the related S-350C PCB Board Buffer Conveyor (widths up to 500 mm, 0–2 m/min, SMEMA signal plug) is a lower-cost alternative in the same family.

Where it fits on the line

The SBN250 is an inline machine designed to sit between standard SMT/THT equipment, connecting through the SMEMA interface at 900 mm ±20 mm transport height:

After AOI (post-reflow): OK boards proceed; NG boards are buffered for re-inspection.
After SPI (post-print): paste inspection results are separated before placement, protecting the pick-and-place and reflow processes.
Between THT insertion and wave soldering: buffers absorb differences in insertion and soldering cycle times.
Before or after manual stations: keeps a small work-in-progress bank so operators never wait for boards.

See the machine run: SMT PCB NG/OK Buffer Conveyor and How the Dual-Lane NG-OK Buffer Conveyor Works.

Make it a recurring part of line design

Station speeds drift as you add products and inspection steps. Re-run the NG/OK Buffer Check when you add an AOI, slow a process for quality, or see idle time accumulate after a changeover — the buffer size that looked adequate may bottleneck as volume grows. Treat buffering as line infrastructure reviewed on the same cadence as your conveyor layout.

Your next step

Send your board dimensions and line layout to info@smthelp.com or WhatsApp +86 136 0256 2576. The team returns a buffer configuration and quotation matched to your board sizes and where the bottleneck actually sits. Choosing the right buffer comes down to board sizes, line height, and where the stoppage lives.

FAQ

What is a PCB buffer conveyor? An inline board-handling machine that temporarily stores PCBs between process stations. It absorbs differences in station speed and holds boards — for example NG boards after inspection — so the line does not stop.

How does an NG/OK buffer conveyor work after AOI or SPI? The inspection machine sends its result with the board. OK boards pass through and continue downstream; NG boards are diverted into the buffer's storage levels and can be sent to an upper level for re-inspection or rework, all without stopping the line.

What is the difference between a buffer conveyor and a shuttle or turn conveyor? A shuttle moves boards sideways between parallel lanes or machines; a turn conveyor rotates boards 90 degrees. A buffer conveyor stores boards vertically for a period — its job is accumulation and separation, not direction change.

Can it connect to my existing SMT line? Yes. The SBN250 is SMEMA-compatible, uses the standard 900 mm transport height, and is available in L-to-R or R-to-L, so it inserts into most existing lines. Width adjustment is via leadscrew for fast changeover.

What board sizes can the SBN250 handle? PCBs from 50×50 mm to 330×250 mm, thickness 0.6–4 mm. The larger SBN330 handles up to 460×330 mm. Custom capacities and sizes can be confirmed with Southern Machinery.

What support does Southern Machinery provide? Global support, spare parts, training and after-sales service from Shenzhen, China, serving 237+ customers worldwide since 2011.

Jason Wu

Founder & CEO, Southern Machinery (Shenzhen Southern Machinery Sales and Service Co., Ltd.)

Email: jasonwu@smthelp.com / info@smthelp.com

WhatsApp: +86 13602562576

Catalog & manuals: file.autoinsertion.com | Machine photos: ph.smthelp.com

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