US20060118459A1

US20060118459A1 - System and method for locating components on a tray

Info

Publication number: US20060118459A1
Application number: US11/007,501
Authority: US
Inventors: David Christensen
Original assignee: Peak Plastic and Metal Products International Ltd
Current assignee: Peak Plastic and Metal Products International Ltd
Priority date: 2004-12-07
Filing date: 2004-12-07
Publication date: 2006-06-08

Abstract

A system and method for precisely locating the position of a component in a tray. The tray is a unitary structure having a plurality of protrusions on at least one side. A robot relies on the protrusions to locate pockets adjacent to each protrusion. An end effector reaches for a component in each pocket. The degree of accuracy of locating a component in a tray is enhanced by employing the plurality of protrusions and by following the method of the present invention.

Description

FIELD OF INVENTION

This invention pertains to improving the accuracy of locating a component during an automation process. More specifically, the invention pertains to providing datums on an automation tray for more precisely locating the presence of a component within a specific pocket of the tray.

BACKGROUND OF THE INVENTION

In automated assembly lines, process trays with a single datum are known. The single datum is located in the center of the tray and acts as a point of reference for a robot that moves in increments across the top surface of the tray. The robot preferably contacts the center top surface of the component and lifts the component out of its pocket to another location. The robot determines where it is by computing the distance between its current location and the datum. As the robot moves further away from the central reference point its degree of accuracy in identifying component locations decreases.
In reference to FIG. 1, the prior method of locating a specific area will be described. In the prior art, use of a central datum was adequate for components close to the center of the tray. The degree of accuracy in locating a specific area on a tray is affected by the molding compound and the mold used to mold the tray. Each molding compound has a tolerance standard that ranges between 0.001-0.005 inches/inch. The accuracy of the mold itself also has an effect on the tolerance, or level of certainty, in identifying a specific location on a tray decreases as the distance from a reference point increases. The overall tolerance for a tray that uses a single reference marker is illustrated in FIG. 1. The tolerance is determined by considering the case of two pockets separated from each other.
The degree of accuracy of pocket 20A is determined by the distance from reference 25 to the center of pocket 20A multiplied by the tolerance standard. Using a tolerance standard of 0.005, the tolerance of pocket 25 is 4.0311 multiplied by 0.005 or 0.020 inches. Thus an end effector will locate a component to within 0.020 inches of accuracy.
Possible errors from relying on a single reference point include inaccurate detection of a component location, failure to pick up a component, and needless disposal of functional parts. During automation, a robot is programmed to pick up components in the center of their top surface and then transfer the component to hardware. If a component is picked up off center it will be put down in an off center position. The likelihood that the component will be improperly installed into hardware is increased as a result of the inaccurate pick up by the robot.
As electronic components shrink in size it becomes more desirable to increase the precision of locating components on a tray. In addition, the industry is approaching the technological limits of the precision that can be maintained with the current molding materials, tools, and molding processes. Therefore, the need exists for a method and system that improves the accuracy of locating components on a tray.

SUMMARY OF THE INVENTION

The invention is directed to a method for moving a component from a pocket of a tray, by providing a plurality of datums on the tray; and surrounding each datum with a pocket cluster. An end effector of a robotic system locates a central datum on the tray; and then reaches for a component from each pocket in the cluster surrounding the central datum. Thereafter the end effector locates a new datum and resets the zero point of the tray at the location of the new datum. The end effector reaches for a component from each pocket in the cluster associated with the new datum and then the robot proceeds to sequentially target each pocket cluster, until every pocket on the tray has had its component transferred to hardware.
In another embodiment, the invention is directed to a system for locating a component position on a tray wherein the system comprises a mechanical member that is programmed to sequentially move from one central datum to another on the same tray; a sensor that detects datums; a reset mechanism for establishing the new datum as a zero point on the tray; and an arm connected to the mechanical member that reaches for a component in each pocket of a cluster associated with the datum.
The tray of the invention comprises a unitary structure having more than one pocket for storing components; a central datum on the tray and external to the pockets; and additional datums external to the pockets, distributed throughout the tray. Each datum enables a detector to precisely identify the location of components stored within the tray.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a tray in accordance with the prior art.
FIG. 2 illustrates a tray in accordance with the present invention.
FIG. 3 is a flow chart that summarizes the various steps for implementing the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention enhances the accuracy of locating a component on a tray by providing multiple datums, or reference points, on a tray. In a preferred embodiment the datums are located on only one side of the tray. However, datums can be placed on any side which has pockets for carrying components.
This invention may be applied to automation trays of various dimensions. FIG. 2 illustrates a tray 200 with a central datum 22 and supplemental datums 15. The precise position of each locating datum molded on the tray is known. The supplemental datums 15 are equally spaced on tray 200. A cluster of pockets 35 surround each datum shown. An example of how the method of the invention is implemented is discussed below.
A robot in an automated assembly works has a robotic arm with an end effector attached to it. The end effector may be a gripper or a vacuum suction device that reaches for a component from each pocket in a cluster. The end effector relies on datums to locate components in a pocket cluster.
A sensor detects the datums and relays the datum location to the end effector. The robot is programmed to start at a specific point on a tray, such as the central datum 22. The first datum 22 is then used by the end effector to find supplemental datums 15. When the end effector reaches a supplemental datum 15, the robot re-zeros itself at the location of datum 15. Then, the new zero position is used to find supplemental datum such as 15B or 15C for example.
The robot places its end effector over the central datum 22 on a 10-inch tray, and uses it as a 0,0 reference point to sequentially find additional datums 15 on tray 200. The robot is programmed to move from central datum 22 down 3.0 inches and then left 3.0 inches to locate supplemental datum 15D. After the end effector has targeted pocket cluster 45 it will move to datum 15E, and re-zeroes at 15E and then begins targeting the pockets in cluster 47. After the end effector has targeted cluster 47, it proceeds to an adjacent cluster until all the pocket clusters have been targeted and the tray is ready to be advanced to a stacking area.
Suitable datums for this invention may include a protrusion having the form of an L, an X or a +. For a touch sensor, an “L” shaped datum is preferred. The sensor would move up until it hits the bottom leg of the “L” and that position would be the zero for the Y direction. Then it would move until it finds the vertical portion of the “L” and set that as the X zero point. For a vision system, an “X” is preferred to be used to mark the 0,0 location. The protrusion is molded in the same mold as the tray. The trays of this invention are preferably injection molded with a thermoplastic polymer and have a unitary structure.
The component in pocket 30 is closer to datum 15D than it is to central datum 22. Since the robot knows the precise location of datum 15D, the degree of accuracy of locating a component in pocket 15D is enhanced. In other words, the proximity of pocket 30 to datum 15B allows the robot to more precisely locate a component in pocket 30 than if the robot relied on central datum 22 alone to locate the component in pocket 30. Once a datum is located, the end effector reaches for a component in each pocket of the cluster closest to that datum. The robotic gripper moves the component to hardware such as a circuit board, a disk drive, or any other type of electronic hardware.
When an end effector approaches a new datum, the robot will re-zero itself on the new datum and thereby reduce the overall uncertainty in locating components within pockets that are clustered around the new datum. It is not necessary to include any inserts in the tray in order to benefit from the precision characteristics of the method of this invention.
FIG. 2 illustrates the tolerance of a specific tray in accordance with the present invention where multiple datums are placed on tray 200. FIG. 2 shows that in each pocket cluster 35 the distance from the center of one pocket to an adjacent pocket in the cluster is 0.75 inches. Hence, the tolerance for any one pocket in a cluster is 0.0038 inches [0.75×0.005 (tolerance standard)]. By adopting the method of the present invention, the degree of accuracy improves more than five-fold from 0.020 inches to 0.0038 inches.
FIG. 3 is a flowchart that illustrates the various steps of the invention. A handler positions a tray at an assembly station. The robot moves to a central datum and targets components in the pocket cluster associated with central datum 22. Components are targeted when the robot's mechanical member reaches for a component from each pocket and transfers the component to a desired hardware. The mechanical member may make a transferring motion even if a component has not picked up from a specific pocket. The robot stores to memory each pocket that has been targeted. Consequently, when the robotic memory bank indicates that all pocket clusters have been targeted, the handler advances the tray to a stacking area. At this point, the automation system is ready to receive a new tray loaded with components.
The examples of the system and method described herein are solely representative of the present invention for locating a component. It is understood that various modifications may be made to the foregoing examples and methods of operation without departing from either the spirit or scope of the invention. It is therefore the intent that the scope of the invention is to be defined by the appended claims.

Claims

1. A method for moving a component from a pocket of a tray, the method comprising:

(a) providing a plurality of datums on the tray;

(b) providing a pocket cluster around each datum;

(c) moving an end effector to a first datum on the tray;

(d) manipulating the end effector to reach for a component from one or more pockets in the cluster surrounding the first datum;

(e) manipulating the end effector to locate a supplemental datum on the tray;

(f) resetting the end effector at the supplemental datum to zero; and

(g) manipulating the end effector to reach for a component from one or more pockets in a cluster surrounding the supplemental datum.

2. The method of claim 1, further comprising repeating steps (e)-(g) until the end effector has attempted to move a component from each pocket in the tray.

3. The method of claim 1, wherein the location of a component is determined within 0.0030-0.010 inches of accuracy.

4. The method of claim 1, wherein the step of reaching for a component comprises retrieving the component and inserting it into hardware.

5. The method of claim 1, wherein the datum is located by a touch or vision sensor.

6. The method of claim 1, wherein the tray is advanced to a stacking area after the robot has targeted all of the pocket clusters in the tray.

7. A system for locating a component position on a tray in an assembly line, the system comprising:

a. a mechanical member that is programmed to move a predetermined distance from a first datum on a tray to a new datum on the same tray;

b. a sensor on the mechanical member that detects the new datum;

c. a reset mechanism within the mechanical member for establishing the new datum as a zero point on the tray;

d) a lever arm connected to the mechanical member that reaches for a component in one or more pockets of a cluster associated with the datum when a sensor detects a new datum.

8. The system of claim 7, wherein the datums comprise a protrusion having an x- and a y-axis.

9. The system of claim 8, wherein the datums comprise a protrusion shaped in the form of an L, an X, or a +.

10. The system of claim 8, wherein each datum is surrounded by a cluster of pockets.

11. A tray for storing components in an automation assembly line, said tray comprising:

a) a unitary structure having more than one pocket for storing components;

b) a first datum on the tray and external to the pockets; and

c) additional datums external to the pockets, distributed throughout the tray, wherein each datum enables a detector to precisely identify the location of components stored within the tray.

12. The tray of claim 11, wherein the additional datums surround the central datum,

13. The tray of claim 11, wherein each datum is a protrusion.

14. The tray of claim 13, wherein the protrusion comprises an L, an X or a + shape that is molded together with the tray.