Tray Design Recommendations for Automation
January 2, 2012
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There are two principal methods to automatically feed trays:
– Drop-style (rotary screw or alternating gate) and vacuum (pick n’ place). Drop-style feeding allows for high-speed applications, however the tray design including thickness of material must support this.
– Vacuum Pick n’ Place feeding at slightly slower speeds provides the most flexibility in tray design.
The following information will apply to both methods, however our emphasis will be on tray design that supports the Vacuum Pick n’ Place method. There are three main types of Vacuum Pick n’ Place automated tray feeding. In most cases, the trays are stacked in a magazine with the tray cavity forward or toward the vacuum cups.
– Standard Reciprocating Motion: The vacuum cups contact the bottom of the tray near the lower sidewall. Flat areas of about 1 1/2″ in diameter must be provided to give a good sealing surface for the vacuum cups.
– Straight-line Motion: This is the most forgiving motion as it relates to tray design (can handle the toughest trays). Flat spots must be located on the tray bottom near the corner where each sidewall meets the bottom of the tray.
– Sidewall Denesting Motion: This is used when the tray material is very thin or no flat spot is provided on the bottom of the tray. Tray sidewalls must be flat (smooth).
– Bottom Pick Motion: Trays are loaded in the magazine with bottom of the tray facing the vacuum cups (opposite of all other styles) and the vacuum cups contact the bottom of the tray when picking. These applications are unique and least used. The instances when this is required are (1) No good flange to clip on (2) Light tray material so bottom of the tray is flimsy (3) Prohibited from making contact with the inside of the tray. Flat spots must be located on the bottom of the tray.
Denesting lugs are a necessary feature to allow for automated tray feeding. Lugs allow for separation of the tray and permits the insertion of a hold back clip between trays when needed.
– Standard / Alternating Lugs: The lug from one tray sits atop the flange of the next. Design of each lug is same, but lug location on each tray varies so that the lug from one tray does not line up with the next. This requires trays be manufactured on a multiple head die and collated in sequence so the lugs do not line up.
– Reverse Lug: Similar to Standard Lugs, each lug sits on the flange of the next tray. These lugs are more difficult to produce because lugs are created by notching the mold in an opposite draft angle from the rest of the tray. This can make the tray difficult to release from the mold. As for the positives, these can be made on a one-up mold. Since each tray is the same, no collation sequence is required.
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