Printing Machine Workpiece Clamping for Variable Thickness Control

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Solution Overview

Problem

Industrial screen-printing machines face challenges in maintaining optimal print gap due to variations in workpiece thickness, leading to poor control over the printing process and potential damage, as thicker workpieces result in large variations that cannot be accommodated by traditional negative print gap methods.

Innovation Solution

The implementation of an overdriving step in the workpiece clamping process, controlled through measurement of relative heights of clamping and rail brackets, allows for adaptive gripping of workpieces of varying thickness by lifting the clamping brackets away from the rails, ensuring consistent contact with the printing screen.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional top clamping with pneumatic cylinders is used, then workpiece gripping is achieved, but variations in workpiece thickness cannot be accommodated leading to poor print gap control

Engineering Contradiction:

Improveadaptability to workpiece thickness variationVSAvoidprint gap control

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The system transitions from a static clamping height to a dynamic adjustable height mechanism. The tooling table can be raised to different heights to accommodate varying workpiece thicknesses, and the overdriving feature dynamically adjusts the clamping position by lifting the clamping brackets away from the rails by a predetermined amount, enabling the system to adapt to thickness variations while maintaining consistent print gap control

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the height parameter of the tooling table and the relative position parameter between clamping brackets and rails. By adjusting the tooling table height to lift the workpiece off the conveyors and applying overdriving to lift the clamping brackets away from the rails by a predetermined amount, the system modifies these parameters to accommodate different workpiece thicknesses while maintaining optimal print gap control

Inventive Principle:

Principle #35Parameter changes

2Reliability

If negative print gap is used to accommodate thickness variation, then contact between workpiece and printing screen is ensured, but large thickness variations cannot be accommodated and may cause damage

Engineering Contradiction:

Improvecontact between workpiece and printing screenVSAvoiddamage to workpiece or printing screen

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary action by raising the tooling table height to lift the workpiece off the conveyors before the printing operation begins. This preliminary positioning ensures the workpiece is at the correct height, and the overdriving feature further preliminarily positions the clamping brackets by lifting them away from the rails by a predetermined amount, preventing potential damage while ensuring proper contact during printing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The overdriving feature acts as a cushioning mechanism by creating a predetermined lift distance between the clamping brackets and rails. This cushioning distance accommodates thickness variations without transmitting excessive force to the workpiece or printing screen, preventing damage while maintaining reliable contact during the actual printing operation

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Manufacturing precision

If workpiece is overdriven into stencil to ensure gasket formation, then small thickness variations are accommodated, but large thickness variations result in poor yield

Engineering Contradiction:

Improvegasket formation controlVSAvoidyield

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

Instead of overdriving the workpiece into the stencil to ensure gasket formation, the invention inverts the approach by overdriving the tooling table upwards to lift the workpiece off the conveyors and lifting the clamping brackets away from the rails. This reverse approach achieves proper gasket formation and thickness accommodation without compromising yield, as the predetermined lift distance ensures appropriate positioning for all thickness variations

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11787000B2Method for gripping variable thickness workpieces in a printing machine

Publication Date: 2023.10.17 ASMPT SMT SINGAPORE PTE LTD

AI summary

A method of gripping a substantially planar workpiece while providing compensation for variations in thickness is described. During the process, the workpiece is overdriven into a clamping member before clamping force is applied, and the positions of the clamping member before and after application of the clamping force are measured. These measurements are then used to control a compensating movement of the tooling table and optionally a final lift of the conveyance rails.