Pulse Cure UV Materials Depth of Cure
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Solution Overview
Problem
Existing UV curable composite materials face challenges with insufficient depth of cure, which limits the size and quality of additively manufactured objects and dental composites.
Innovation Solution
A pulse cure technique is employed, involving an iterative ultraviolet cure sequence with adjustable parameters such as emitted irradiance, exposure time, and break time, to optimize the curing process and achieve deeper penetration of UV light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional continuous UV curing is used, then the curing process is simple and fast, but the depth of cure is insufficient
Solution Approach 1:
The patent applies periodic action by implementing a pulse cure technique where UV irradiation is delivered in repeated cycles with exposure time followed by break time, rather than continuous irradiation. This periodic on-off cycling allows UV light to penetrate deeper into the material during exposure phases while preventing surface crust formation during break phases, thereby increasing the depth of cure beyond what conventional continuous curing achieves.
2Length of stationary object
If UV intensity is increased to cure deeper materials, then the depth of cure improves, but surface curing becomes excessive and causes crust formation
Solution Approach 1:
The pulse cure technique uses periodic action to alternate between high-intensity UV exposure (which enables deep penetration) and zero-intensity break periods (which prevent excessive surface curing). This cycling allows the bulk material to receive sufficient energy for deep cure while the surface has periodic rest periods that prevent crust formation, thus resolving the contradiction between depth of cure and surface curing quality.
Solution Approach 2:
The break time in the pulse sequence serves as a preliminary action that prevents crust formation before it can occur. During the break period, the surface material has time to relax and remain uncured, preparing it for the next exposure cycle without having formed a blocking crust layer, thereby maintaining surface quality while enabling deeper overall cure.
3Productivity
If continuous UV irradiation is applied, then the curing process is simple, but the exposure time required is excessive
Solution Approach 1:
The pulse cure technique improves curing efficiency by delivering UV energy in concentrated exposure pulses rather than diluted continuous irradiation. During exposure time, full UV intensity is applied to maximize polymerization rate, while break time periods are non-productive but necessary to prevent crust formation. The overall process achieves deeper cure in less total time compared to continuous irradiation at lower effective intensities.
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
The pulse cure technique significantly increases the depth of cure, reduces exposure time, and improves material quality and consistency, enabling larger print sizes and better dental composite performance.
Implementation Method 1
Ultraviolet (UV) curing uses ultraviolet light to initiate a photochemical reaction in a material that contains a photo-initiator. Essentially, polymerization is initiated by breaking down the photo-initiator into functional groups through absorption of UV light.
Data Source
AI summary
A process for curing an ultraviolet curable material comprises setting initial conditions, such as an emitted irradiance of an ultraviolet source, an initial value for an exposure time, an initial value for a break time, a stopping condition, combinations thereof, etc. The process repeatedly performs an ultraviolet cure sequence to cure a material until the stopping condition is met, where each iteration in the ultraviolet cure sequence comprises irradiating the material with the ultraviolet source at the emitted irradiance for the exposure time, and resting for the break time with no irradiation applied to the material. In some embodiments, the process adjusts a value of at least one of the emitted irradiance, the exposure time, or the break time in at least one iteration of the ultraviolet cure sequence. For instance, in some embodiments, the exposure time is adjusted, e.g., by a fixed amount, according to a gradient, etc.