Feeder Setup: Peeling Force and Pickup Reliability

A tape feeder is a mechanical device expected to present a component within a few hundredths of a millimetre, thousands of times a shift, from a carrier tape it did not manufacture. The settings that make that possible are the peel, the index and the pickup height, and all three drift with wear.

What the Feeder Has to Deliver

The feeder has to advance the tape by exactly one pocket, hold the pocket at the pickup point, peel the cover tape away without lifting the component and allow the nozzle to take the part without touching the pocket walls. Each of those is a separate adjustment, and a fault in any one of them appears as a placement error.

The index accuracy is the one that gets measured, because it is the easiest to check with a gauge, but peel force and pickup height cause more of the intermittent faults that are blamed on the machine’s vision system. A placement accuracy study that ignores the feeder is measuring only half of the system.

Tape and Reel Specification

Carrier tape and cover tape are made to EIA-481, which fixes the pocket dimensions, the pitch, the sprocket hole size and the cover tape peel strength. The peel figure is specified as a range of about 0.1 to 1.0 newtons measured at a defined angle and speed, and a tape outside that range is not a feeder problem.

Pocket size relative to the component matters as much as the pitch, because a component that can move inside its pocket arrives at the pickup point at a random angle. The pocket is specified with a clearance, and the clearance is why a part can be placed straight from a tape that has been shaken in transit.

Peeling Force and How It Is Measured

The peeling force is measured by pulling the cover tape away from the carrier at about 165 to 180 degrees and at a speed of around 300 millimetres per minute, and recording the force over the length of the pull. The figure quoted is usually an average with a peak limit, because a single high peak lifts the component out of its pocket.

The feeder’s own peel mechanism adds to the tape’s figure, and a worn peel bar or a mis-set angle can double the force without changing the tape. That is why the measurement is repeated with the tape in the feeder when a pickup problem is being investigated.

Feeder Adjustment and Wear

The moving parts are the sprocket, the index lever, the tape guide and the peel blade, and each of them wears in a way that changes the presentation of the pocket. A sprocket that has worn on one side advances the tape with a slight rotation, and the error is a fraction of a millimetre at the pickup point.

Wear is managed by a maintenance interval that is based on the number of index cycles rather than on the calendar, and by keeping a record of the feeder’s life. A feeder that is used for the same 0402 part every day wears faster than one that sees a mixture of jobs, so the interval follows the duty.

Pickup Height and Nozzle Contact

The pickup height is the distance the nozzle descends below the top of the tape, and it is set so that the tip touches the component without pressing it into the pocket. A height that is too shallow leaves the part behind when the vacuum is applied, and one that is too deep pushes the part against the pocket floor and can crack a chip capacitor.

The height is taught from the tape surface and is typically 0.05 to 0.15 mm below it, with a dwell set long enough for the vacuum to build. Where the tape sits differently in a different feeder, the height is re-taught rather than copied, because the two feeders do not present the tape at the same level.

Placement Error That Comes From the Feeder

The errors that originate in the feeder are rotation and offset in the pocket, and both are best seen by placing a row of components onto a glass plate or a paste-free board and measuring them. A pattern in which every tenth part is rotated points to the tape, while a random scatter points to the vision or the nozzle.

Static is the other feeder-related error, because a cover tape that is peeled quickly can charge the pocket and move a light component as it is picked. Where 0201 or 01005 parts are being placed, the tape path is grounded and the peel speed is reduced to keep the charge below the level that moves the part.

Changeover and Verification

A changeover is where most feeder faults are created, because the settings are changed by hand and verified by eye. The setup sheet names the feeder, the tape, the index pitch and the pickup height, and the first board is inspected for placement before the build is released.

The verification that catches the most faults is a run of the first ten placements onto double sided tape, measured under a microscope. It takes a few minutes, and it finds the feeder that is indexing one tooth short before the board is populated with it; our AOI notes describe what the inspection station can and cannot see.

Maintenance, Records and Feeder Life

The maintenance record should carry the feeder number, the cycle count, the last service and the parts it has been used for. A feeder is a tool with a life, and a line that tracks that life replaces feeders before they start producing intermittent faults.

The record also allows a fault to be traced to a feeder rather than to the machine, which matters because the same machine may run ten feeders. Our production floor zoning notes describe how feeders and tools are stored and staged so that a feeder is identified with the job it belongs to.

The feeder’s own peel mechanism adds to the tape’s figure, and a worn peel bar or a mis-set angle can double the force without changing the tape. That is why the measurement is repeated with the tape in the feeder when a pickup problem is being investigated.

FAQ

Can peel force be adjusted on the feeder? On most feeders the peel angle and the blade position can be set, and both change the force the tape sees. The tape’s own specification sets the range, and the feeder is adjusted to keep the combined force inside it.

Why does a part occasionally come out rotated? Usually because it can move in its pocket, and the rotation happens as the tape is indexed or as the cover tape is peeled. A pocket that is at the loose end of its tolerance is the first thing to check.

How often should pickup height be re-taught? Whenever a feeder is loaded with a different tape and whenever a feeder is serviced. Copying the height from another feeder is the commonest cause of a shallow pickup that leaves parts behind on the tape.