Four-Pass Additive Fusing for Amorphous Polymer Ductility
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Solution Overview
Problem
Additive manufacturing techniques face challenges in achieving high ductility and low brittleness in plastic objects due to crystallization and edge curl issues during the fusing process.
Innovation Solution
A four-pass fusing process is employed, where build material is preheated, treated with a liquid fusing agent, and irradiated with light to maintain a molten state for reptation, then rapidly cooled below the crystallization temperature to lock polymers in an amorphous state, inhibiting crystallization and edge curl.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional single-pass fusing process is used, then manufacturing simplicity is maintained, but polymer crystallization occurs causing edge curl and reduced ductility
Solution Approach 1:
The fusing process is divided into four distinct passes: first pass applies fusing agent to green part, second pass fuses current layer, third pass fuses previous layer, and fourth pass cools and consolidates. This segmentation allows precise control of polymer structure at different stages, preventing crystallization while maintaining manufacturing feasibility.
Solution Approach 2:
The fusing agent is applied to the green part before the fusing process begins (first pass). This preliminary action prepares the polymer for controlled fusing and prevents crystallization by maintaining the polymer in an amorphous state before heat application, thereby improving subsequent manufacturing precision.
2Strength
If rapid cooling is applied to lock polymers in amorphous state, then ductility is improved, but cooling rate control complexity increases
Solution Approach 1:
The cooling process is implemented as periodic action within the fourth pass, where cooling is applied after fusing to lock polymers in amorphous state, then heating is applied in the first pass of the next layer to prevent edge curl. This periodic heating and cooling cycle achieves ductility improvement without requiring complex continuous cooling control systems.
Solution Approach 2:
The process utilizes parameter changes by controlling temperature transitions between passes. Rapid cooling in the fourth pass locks polymers in amorphous state for ductility, while subsequent heating in the first pass of the next layer prevents edge curl. This parameter control achieves improved strength without complex cooling systems.
3Stability of the object's composition
If fusing temperature is maintained for extended period to achieve reptation, then polymer chain entanglement improves, but energy consumption increases
Solution Approach 1:
The fusing agent is applied in advance (first pass) before the actual fusing process (second pass). This preliminary action reduces the energy required during fusing by preparing the polymer for easier chain entanglement and reptation, achieving stable polymer composition with lower energy consumption.
Solution Approach 2:
The fusing process maintains continuous useful action by keeping the polymer above crystallization temperature throughout passes two and three, allowing continuous polymer chain entanglement and reptation. This continuous process achieves stable polymer composition efficiently without requiring extended high-temperature maintenance.
4Manufacturing precision
If next layer is spread over hot build material to rapidly cool it, then crystallization is inhibited, but edge curl may occur
Solution Approach 1:
The process uses periodic action where rapid cooling by spreading the next layer occurs in the fourth pass to inhibit crystallization, followed by heating in the first pass of the next layer to warm the underlying fused material and prevent edge curl. This periodic cooling and heating cycle resolves both crystallization control and edge curl prevention.
Solution Approach 2:
The process utilizes parameter changes by rapidly cooling the fused material below crystallization temperature in the fourth pass to inhibit crystallization, then heating in the first pass of the next layer to warm the underlying material and prevent edge curl. These controlled parameter changes achieve both crystallization control and shape stability.
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 process enhances the ductility and reduces brittleness of plastic objects by maintaining polymers in an amorphous structure, improving the mechanical properties compared to traditional additive manufacturing methods.
Implementation Method 1
Light absorbing components in the fusing agent absorb light energy to help heat the patterned build material above the fusing temperature, to sinter, melt or otherwise fuse the build material
Implementation Method 2
exposing the patterned area to fusing light. Light absorbing components in the fusing agent absorb light energy to help heat the patterned build material
Implementation Method 3
build material on which the fusing agent has been dispensed is irradiated with a fusing light to heat the build material above the fusing temperature to form fused build material
Implementation Method 4
irradiating build material treated with fusing agent as well as untreated build material
Implementation Method 5
the fused build material is cooled rapidly below the crystallization temperature by spreading the next layer of unfused build material over the hot build material
Implementation Method 6
cooled rapidly below the crystallization temperature by spreading the next layer of unfused build material over the hot build material
Implementation Method 7
Preheating the new layer of unfused build material in the first carriage pass warms the underlying fused build material above the crystallization temperature to limit the duration of 'extreme' cooling and thus inhibit crystallization
Data Source
AI summary
In one example, a processor readable medium having instructions thereon that when executed cause a fusing system for an additive manufacturing machine to, during a first carriage pass, preheat build material in a layer of unfused build material; during the first carriage pass and/or during a second carriage pass, dispense a liquid fusing agent on to preheated unfused build material in the layer and then, during the second carriage pass, irradiate build material in the layer on which the fusing agent has been dispensed with a fusing light; and during a third carriage pass, irradiate the fused build material with the fusing light; and during a fourth carriage pass, irradiate the fused build material with the fusing light and then actively cool the fused build material.