“The feeder is unreliable” is not a specification. Tape advance is. It takes a few minutes to measure, and it turns feeder condition from an opinion into a number you can put on a purchase order.
What tape advance actually is
Tape advance is the distance the feeder moves the carrier tape in one index cycle, relative to the nominal pocket pitch. If it drifts long or short, the component no longer sits centred under the nozzle, and the pick either misses or clips the part. The machine may still report a successful pick — or it may report an error you attribute to the nozzle.
Why feders drift
- Sprocket wear — the pin teeth round off and the engagement point shifts.
- Belt stretch — small, cumulative, and invisible until it is not.
- Tension spring fatigue — the tape is held less firmly and creeps between indexes.
- Cover-tape drag — a worn peel path pulls the tape back slightly after each advance.
- Contamination — adhesive residue on the sprocket changes effective pitch.
How to measure it
- Load a full reel of known-good carrier tape, ideally the same part the feeder will run in production.
- Index the feeder 20 cycles, discard the first few, then measure the total travel against the expected travel for 20 pockets.
- Express the result as a deviation in millimetres and, more usefully, as a percentage of pitch.
- Repeat at two or three points along the cycle count — drift that grows with cycle count points at the drive, not the tape.
Record the number for each feeder and keep it with the feeder. A feeder with a logged advance measurement is a known quantity; a feeder without one is a surprise waiting for a production day.
What to put on a purchase order
When you buy refurbished feeders — from us or anyone else — ask for the advance measurement for the specific units, the components renewed during refurbishment, and whether any functional warranty applies. Three lines. It separates a tested unit from a cleaned one.
Maintenance that actually buys you uptime
- Clean the sprocket and peel path on a fixed interval — weekly on high-usage feeders.
- Replace tension springs as a consumable, not on failure.
- Rotate feeders between high-use and low-use positions so wear is spread.
- Re-measure after any refurbishment and after the first month in service.
