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原位收缩传感器在注塑模具英文文献和中文翻译

时间:2017-08-10 18:00来源:毕业论文
Dimensional consistency is a critical attribute for injection molded part quality and is highly dependent on the polymer mor-phology, the thermal expansion, and various processing param-eters. The dimensional shrinkage can be estimated by kn
Dimensional consistency is a critical attribute for injection molded part quality and is highly dependent on the polymer mor-phology, the thermal expansion, and various processing param-eters. The dimensional shrinkage can be estimated by knowing the pressure-volume-temperature behavior of the polymer but with limited accuracy. There are various process monitoring systems available in the market; none of which has the capability of di-rectly monitoring and controlling the real time shrinkage and part dimensions online. With a view to measuring in-mold shrinkage, abutton cell type in-mold shrinkage sensor was developed, vali-dated, and compared against the traditional shrinkage prediction
and estimation methods. The shrinkage sensor consists of an elas-
tic diaphragm instrumented with strain gages connected in a full
bridge circuit. The sensor is placed beneath the movable pin that
is protruded into the mold cavity and remains in contact with the
sensor diaphragm. The sensor diaphragm is deflected due to the
melt pressure acting on the pin into the mold cavity and is re-
tracted back toward its original position as the melt solidifies and
shrinks away from the mold cavity wall. The sensor signals ac-
quired during each molding cycle were analyzed to validate the
sensor performance in a design of experiments as a function of
packing pressure, melt temperature, cooling time, and coolant
temperature. The regression results indicate that the shrinkage
sensor outperforms cavity pressure transducers and other methods
of predicting the in-mold shrinkage. For polypropylene, the
shrinkage sensor is able to measure the shrinkage to an average
accuracy of 0.01 mm for a molded part with a nominal thickness
of 2.5 mm. The coefficient of correlation, R2
, between the sensor’s
final positions to the final part thickness was 0.921 for the in-mold
shrinkage sensor. Other dimension prediction methods had lower 源自六/维"论\文|网.加7位QQ3249"114 www.lwfree.cn
correlation coefficients. DOI: 12352
1 Introduction
The dimensional and aesthetic quality of injection molded parts
is directly influenced by tool design, material characteristics, and
process induced effects like “shrinkage.” The shrinkage mainly
depends on polymer morphology, thermal expansion, the cooling
rate of the polymer melt to the solid state, especially for semic-
rystalline materials, the temperature difference between the melt
and the solid state temperature, and process parameters during the
processing 1–3. The shrinkage values for many plastic materials
are high relative to dimensional tolerances, and the shrinkage is
not always isotropic in nature. Shrinkage varies with the part ge-
ometry and processing conditions and is commonly assumed to be
known during part and mold design. As a result, errors in shrink-
age can limit the achievable part tolerances, require increasedcycle time, and produce excessive rejection rates. Anisotropic
shrinkage behavior can also lead to a degree of warpage out-of-
plane distortion or internal stresses 4–7.
Due to continuing demand for higher quality requirements with
fewer rejections and faster process cycle time, the plastics indus-
try has produced continual innovations in injection molding tech-
nology 8–10. One of the recent trends is online process moni-
toring to achieve more robust process control. But still, there is no
technology or research available to directly monitor the shrinkage
online during production in order to improve, optimize, and con-
trol the part dimensions. This article describes the design and
implementation of a button cell type sensor that can be placed
underneath the ejector pin within the ejector assembly in order to
monitor and measure the in-mold shrinkage during the injection 原位收缩传感器在注塑模具英文文献和中文翻译:http://www.lwfree.cn/fanyi/20170810/12088.html
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