Nozzle Center of Rotation Measurement Using Collimated Laser Shadow

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Solution Overview

Problem

Current pick and place machines face challenges in achieving precise component placement due to mechanical tolerances and variations during operation, leading to errors in component alignment and size measurement, especially with the decreasing size of electronic components and increasing interconnection density.

Innovation Solution

A method is developed to automatically measure and update the Center of Rotation (COR) of a nozzle in a pick and place machine using a laser-based alignment sensor, which calculates the true COR by performing single-edge and two-edge measurements on a round artifact, minimizing measurement bias and allowing for accurate alignment and placement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If laser-based alignment sensors are used to measure component position and orientation, then placement accuracy is improved, but measurement bias due to mechanical tolerances and nozzle variations persists

Engineering Contradiction:

Improvecomponent placement accuracyVSAvoidmeasurement bias from mechanical variations

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system performs automated measurements of the nozzle's center of rotation using a round artifact, calculates the actual center position, and feeds this information back to correct subsequent component measurements. This feedback loop eliminates measurement bias by continuously updating the reference frame based on actual nozzle position.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The nozzle itself serves as the measurement reference by measuring its own center of rotation position. The system uses the nozzle's geometric features (via the round artifact) to self-calibrate its positioning, eliminating the need for external calibration references and compensating for mechanical tolerances.

Inventive Principle:

Principle #25Self-service

2Device complexity

If the nozzle center of rotation is assumed to be fixed at nominal position, then device complexity is reduced, but manufacturing precision deteriorates due to mechanical tolerances

Engineering Contradiction:

Improvesensor calibration complexityVSAvoidcomponent alignment precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The system performs a preliminary measurement of the nozzle's center of rotation position before actual component placement. By measuring the nozzle's actual position in advance using the round artifact and storing this information, the system prepares correction data that eliminates the need for complex real-time calibration during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system creates a digital copy or model of the nozzle's actual position and orientation characteristics. This digital representation is stored and used to correct subsequent measurements, replacing the need for physical adjustment or complex mechanical calibration mechanisms.

Inventive Principle:

Principle #26Copying

3Measurement precision

If separate motion to fixed alignment sensor is used, then measurement accuracy is improved, but productivity decreases due to additional motion time

Engineering Contradiction:

Improvealignment measurement accuracyVSAvoidcomponents placed per hour

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The alignment measurement function is merged with the existing nozzle motion system. The nozzle moves directly to the component position while the laser sensor simultaneously measures the nozzle's center of rotation, eliminating the need for separate motion to a fixed sensor and combining positioning and measurement in a single integrated operation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system transitions from a static fixed sensor to a dynamic measurement system where the sensor moves with the nozzle. This allows measurements to be taken during the nozzle's natural motion cycle, eliminating additional motion time and maintaining high productivity while preserving measurement accuracy.

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables precise and accurate alignment of components by correcting for mechanical errors and variations, improving placement accuracy and reducing operational errors, thereby enhancing the efficiency and reliability of pick and place machines.

Implementation Method 1

Edges of a shadow cast by the rotating artifact are detected and used to calculate error of a coordinate of the center of rotation of the nozzle

Methodology Applied

Scientific EffectShadow: Shadow

Implementation Method 2

A substantially collimated laser beam is directed at the artifact

Methodology Applied

Scientific EffectCollimated beam:

Data Source

PatentUS7746481B2Method for measuring center of rotation of a nozzle of a pick and place machine using a collimated laser beam

Publication Date: 2010.06.29 CYBEROPTICS CORP

AI summary

A method of measuring and storing a center of rotation of a nozzle in a pick and place machine is provided. The method includes coupling an artifact to the nozzle. A substantially collimated laser beam is directed at the artifact, which is rotated while the collimated laser beam is energized. Edges of a shadow cast by the rotating artifact are detected and used to calculate error of a coordinate of the center of rotation of the nozzle. A coordinate of the center of rotation of the nozzle is calculated based upon a previous coordinate of the center of rotation and the error. The calculated coordinate of the center of rotation is stored for subsequent measurements.