Development of a novel control strategy for a highly segmented injection mold tempering for inline part warpage control

Hopmann, Christian; Kahve, Cemi; Schmitz, Mauritius

doi:10.1002/pen.25481

Cited by 15 publications

(10 citation statements)

References 13 publications

(19 reference statements)

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“…This work therefore aims modify local temperatures, such that melt properties can be homogenized to reduce stresses, eliminating part warpage for different materials. In our previous works, we demonstrated that a model predictive control yielded parts with significantly higher control accuracy and reproducible part warpage compared to a PID-controller [14,15]. Since the model predictive control is based on a self-developed simulation of the part temperature (based on Fourier's law in one dimension), the same input parameters always result in the same output parameters for the power to control the temperature (see discussion in Section 2.3).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a self‐optimizing local mold temperature control for inline warpage reduction of injection molded parts

Hopmann,

Kahve,

Fritsche

et al. 2024

Materialwissenschaft Werkst

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Dimensional accuracy is a highly important quality criterion for injection molded parts and due to the decreasing tolerance criteria an ongoing issue for mold makers, part designers and manufacturers. Variations in the molding process regarding temperature, pressure and thus the specific volume are leading to inner stress distributions within the part, which ultimately cause warpage. To reduce warpage, a homogenization of the local melt properties, such as the temperature, cooling rate or specific volume is necessary. To be able to manipulate these melt properties locally, a mold with a highly segmented temperature control, consisting of 18 heating ceramics and carbon dioxide expansion chambers was designed. This work seeks to reduce warpage using a newly developed control loop that adjusts target values for the upcoming molding cycle while considering the control error of the previous cycle. The self‐optimizing control loop‐ aiming to homogenize the local mold temperatures over multiple cycles‐ was evaluated in experimental trials. Test specimens were produced, and measured for warpage. Compared to the reference (no control), the warpage of a plate‐shaped geometry was reduced by 10 % with the mold temperature homogenization approach.

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Section: Introductionmentioning

confidence: 99%

Evaluation of a self‐optimizing local mold temperature control for inline warpage reduction of injection molded parts

Hopmann,

Kahve,

Fritsche

et al. 2024

Materialwissenschaft Werkst

Self Cite

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show abstract

“…[1][2][3] More than 30% of plastic parts are molded by the IM process. [4,5] The repeatability accuracy of the part weight is a comprehensive evaluation standard reflecting the performance of an IMM. The injection velocity, pressure, temperature, and other machine parameters of modern IMMs today can be controlled and characterized by high accuracy and repeatability.…”

Section: Introductionmentioning

confidence: 99%

Self‐optimization of the V/P switchover and packing pressure for online viscosity compensation during injection molding

Xie

et al. 2022

Polymer Engineering & Sci

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Injection molding (IM) is one of the essential forming methods for thermoplastic polymers, which is widely used in modern industries such as automobiles, electronics, and medical industries. At present, the machine parameters of the IM machine (IMM) have achieved sufficient high control accuracy and repeatability. However, the viscosity of thermoplastic melt is still easily influenced by the external environment, such as the fluctuations in batches, the compounding in recycled materials, and so on. Conventional IM equipment cannot sense and conduct adjustments correctly, which leads to the production of rejects. A real-time monitoring and controlling model employed for viscosity compensation was established in this article, which could monitor viscosity fluctuations and implement self-adjustment in the IM process. Three kinds of polypropylenes (PP) with different viscosity and materials with different percentages of recycled pellets were randomly added into the barrel for comparison. The results revealed that the pressure integral relative to time is able to monitor the melt viscosity and illustrate the IMM to optimize the V/P switchover and packing pressure in the current molding cycle. The part weight could achieve a higher stability and the model could bring about a decrease in weight fluctuations of 50% to 70%.

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“…Injection molding (IM) is one of the most suitable methods for the mass production of plastic parts with complicated shapes. [ 1, 2 ] During the injection molding process, the molten plastic flows into the mold cavity and then cools and solidifies. Considering its importance in a molding machine, the clamping unit requires a high clamping force (CF) to firmly hold the mold halves to withstand the plastic melt pressure inside the mold cavity.…”

Section: Introductionmentioning

confidence: 99%

A novel strategy to determine the optimal clamping force based on the clamping force change during injection molding

Liu

Dang

et al. 2021

Polymer Engineering & Sci

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Injection molding machines are widely used to fabricate plastic products with complex geometries and structures. They consist of an injection unit and a clamping unit. To withstand the pressure of the mold cavity, the clamping unit needs a high clamping force to hold the mold halves. Unfortunately, the clamping force is among the overlooked parameters of the injection molding parameters. Setting the clamping force at max is needed in practice to avoid flash defects for most operators. However, excessive clamping force creates problems for the machine. This study proposes a verification method for determining optimal clamping force based on the clamping force change ΔCF. When ΔCF becomes zero, the current set value of the clamping force is appropriate. A positive and negative ΔCF corresponds to an excessive and insufficient set value of the clamping force, respectively. Verification experiments are implemented on an electric injection molding machine with polypropylene (PP). The experimental results show that the novel strategy can basically calculate and identify the optimal clamping force with iteration method. The optimal clamping force value for current working conditions (620kN) is acquired after several automatic molding trials, which provides a direction for further research.

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Development of a novel control strategy for a highly segmented injection mold tempering for inline part warpage control

Cited by 15 publications

References 13 publications

Evaluation of a self‐optimizing local mold temperature control for inline warpage reduction of injection molded parts

Evaluation of a self‐optimizing local mold temperature control for inline warpage reduction of injection molded parts

Self‐optimization of the V/P switchover and packing pressure for online viscosity compensation during injection molding

A novel strategy to determine the optimal clamping force based on the clamping force change during injection molding

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