Purpose

This paper aims to address the problem of uncertain product quality in digital light processing (DLP) three-dimensional (3D) printing, a scheme is proposed to qualitatively estimate whether a layer is printed with the qualified quality or not cured .

Design/methodology/approach

A thermochromic pigment whose color fades at 45°C is prepared as the indicator and it is mixed with the resin. A visual surveillance framework is proposed to monitor the visual variation in a period of the entire curing process. The exposure region is divided into 30 × 30 sub-regions; gray-level variation curves (curing curves) in all sub-regions are classified as normal or abnormal and a corresponding printing control strategy is designed to improve the percentage of qualified printed objects.

Findings

The temperature variation caused by the releasing reaction heat on the exposure surface is consistent in different regions under the homogenized light intensity. The temperature in depth begins to rise at different times. The temperature in the regions near the light source rises earlier, and that far from the light source rises later. Thus, the color of resin mixed with the thermochromic pigment fades gradually over a period of the entire solidification process. The color variation in the regions with defects of bubbles, insufficient material filling, etc., is much different from that in the normal curing regions.

Originality/value

A temperature-sensitive organic chromatic chemical pigment is prepared to present the visual variation over a period of the entire curing process. A novel 3D printing scheme with visual surveillance is proposed to monitor the layer-wise curing quality and to timely stop the possible unqualified printing resulted from bubbles, insufficient material filling, etc.

中文翻译：

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用于监控 DLP 3D 打印中分层固化质量的视觉呈现

目的

本文针对数字光处理（DLP）三维（3D）打印中产品质量不确定的问题，提出了一种定性判断某一层打印质量是否合格或未固化的方案。

设计/方法/方法

制备在 45°C 褪色的热致变色颜料作为指示剂，并将其与树脂混合。提出了一种视觉监控框架来监控整个固化过程中某个时期的视觉变化。曝光区域分为30×30个子区域；将所有子区域的灰度变化曲线（固化曲线）划分为正常或异常，并设计相应的打印控制策略以提高合格打印对象的百分比。

调查结果

在均质光强下，不同区域因曝光表面释放反应热而引起的温度变化是一致的。深度的温度在不同的时间开始上升。靠近光源的区域温度上升较早，远离光源的区域温度上升较晚。因此，与热致变色颜料混合的树脂的颜色在整个固化过程的一段时间内逐渐褪色。存在气泡、材料填充不足等缺陷的区域的颜色变化与正常固化区域的颜色变化大不相同。

原创性/价值

制备一种对温度敏感的有机彩色化学颜料，以呈现整个固化过程中一段时间​​的视觉变化。提出了一种具有视觉监控的新型3D打印方案，以监控分层固化质量，并及时阻止因气泡、材料填充不足等可能导致的不合格打印。