Browse Prior Art Database

ISMECCA FEEDER IMPROVEMENT VIA POCKET SENSING INDEXING METHOD

IP.com Disclosure Number: IPCOM000007310D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2002-Mar-13
Document File: 2 page(s) / 141K

Publishing Venue

Motorola

Related People

Scott Potter: AUTHOR [+2]

Abstract

This paper discusses an improved method of indexing Ismecca tape reel feeders. The new method utilizes a sensor mounted beneath the feeder tape such that it can accurately detect the presence of a component pocket. The design reuses all of the orig- inal Ismecca indexing circuitry and requires only an additional $120 in sensors to rework each feeder. The new feeder is currently being used in the Jedi factory with outstanding improvements in reliabil- ity and reduction ofrequired operator assists.

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MOTOROLA Technical Developments Volume 23 October 1994

ISMECCA FEEDER IMPROVEMENT VIA POCKET SENSING INDEXING METHOD

by Scott Potter and Tom Winchell

ABSTRACT

  This paper discusses an improved method of indexing Ismecca tape reel feeders. The new method utilizes a sensor mounted beneath the feeder tape such that it can accurately detect the presence of a component pocket. The design reuses all of the orig- inal Ismecca indexing circuitry and requires only an additional $120 in sensors to rework each feeder. The new feeder is currently being used in the Jedi factory with outstanding improvements in reliabil- ity and reduction ofrequired operator assists.

buttons on the feeder to manually align the compo- nent in the tape with a target on the feeder rails. Even when the component is visually aligned with the target it may not remain correct atler the feeder is indexed due to mechanical slop hysteresis. The operator must either correctly predict the hysteresis (a difficult task) during setup or go through a repet- itive trial and error procedure until the component happens to index into the correct position. Since setup is required every time a reel runs out of parts, every time there is a feeder jam, and every time the component drifts out of alignment this becomes a frequent and time consuming non value added task.

INTRODUCTION

DISCUSSION OF SOLUTION

  Feeder indexing failures have been the single biggest problem on robots in the Jedi factory They are responsible for up to 60% of operator assist time on a robot. We currently have over 60 Ismecca feed- ers in the Jedi factory and have had overwhelming indexing and setup problems with this model feeder.

  The feeder improvements involved a redesign of the indexing feedback mechanism. Rather than monitoring the motor rotation to control indexing the new design directly monitors and controls the location of the component in the tape. This was accomplished by mounting a thru beam sensor to the feeder rails to sense the bottom side ofthe com- ponent tape at the part presentation site.

DISCUSSION OF PROBLEM

  The unaltered Ismecca feeder uses a 24V DC motor connected via gears and belt drive to a stand- ard sprocket wheel. The sprocket wheel meshes with matching sprocket holes in the component tape, and indexing is accomplished by rotation ofthe sprocket wheel. The pitch with which the tape is advanced is selected by setting DIP switches inside the feeder which control how many motor rotations will occur. The motor rotations are counted with by using a thru beam sensor which detects slots in a wheel rotated by the motor. The major problem with this design is that the indexing feedback is accomplished at the motor. This causes all gear and belt slop to directly affect indexing accuracy. Frequent feeder maintenance is required to insure that belts are tight, but even when properly adjusted the feeder has an unacceptable amount of mechanical slop. This makes setup of a component in the feeder very...