Weld strength evaluation of AM insert molding
Topic(s) : Manufacturing
Co-authors :
Makoto INOMOTO (JAPAN), Sae OBATA (JAPAN), Ryoji OKABEAbstract :
Composite AM (Additive Manufacturing) is a manufacturing method to create three-dimensional objects with polymer containing reinforcing materials such as short fibers and continuous fibers. Since this method can manufacture complex shapes that are not feasible by conventional manufacturing methods, it is expected to add further value to products such as weight reduction, heat insulation, sound absorption. Also, MHI group started applying it to aerospace, transportation vehicles, and industrial machinery products.
On the other hand, AM has disadvantages such as long cycle time, high material cost, and low material strength, which often becomes problem to apply AM to real part production. To solve these disadvantages and take advantage of AM, a manufacturing method combining AM and the injection molding, which are widely used as a fast and inexpensive manufacturing method, is invented by authors.
In this hybrid method, an integrated part of the AM inserts, and the injection polymer is molded by following steps: (i) hollow insert parts printed by AM are placed in the mold, and (ii) polymer is injected to the mold. The functional part having a complicated structure is manufactured by AM, and a simple shape part is filled by an injection polymer to achieve cost reduction and manufacturing speed improvement. In past study, the feasibility of this molding method is verified by designing the structure and molding conditions to prevent the AM insert parts from failure during injection molding, conducting molding tests, and inspecting quality.
On the other hand, the weld strength formed by the AM insert and injection polymer is affected by compatibility of the polymer with each other, the interfacial shape, and the molding temperature and pressure conditions, so quantitative evaluation has not yet been carried out.
Therefore, this study investigates the effects of polymer combination, interface shape, and molding conditions on interface strength, and clarifies guidelines for material selection and structural and molding condition design. The following results were obtained from this study.
- The interfacial shear strength of a combination of crystalline polymer (AM: Nylon6, Injection: Nylon9T) and amorphous polymer (AM: Ultem9085, Injection: Ultem2400) was measured.
- Several types of interface shapes were subjected to molding tests to investigate the effect of the fit structure on the interfacial shear strength.
- The sensitivity of temperature and pressure conditions to the interfacial shear strength was evaluated, and the guideline of the molding condition design was clarified.
On the other hand, AM has disadvantages such as long cycle time, high material cost, and low material strength, which often becomes problem to apply AM to real part production. To solve these disadvantages and take advantage of AM, a manufacturing method combining AM and the injection molding, which are widely used as a fast and inexpensive manufacturing method, is invented by authors.
In this hybrid method, an integrated part of the AM inserts, and the injection polymer is molded by following steps: (i) hollow insert parts printed by AM are placed in the mold, and (ii) polymer is injected to the mold. The functional part having a complicated structure is manufactured by AM, and a simple shape part is filled by an injection polymer to achieve cost reduction and manufacturing speed improvement. In past study, the feasibility of this molding method is verified by designing the structure and molding conditions to prevent the AM insert parts from failure during injection molding, conducting molding tests, and inspecting quality.
On the other hand, the weld strength formed by the AM insert and injection polymer is affected by compatibility of the polymer with each other, the interfacial shape, and the molding temperature and pressure conditions, so quantitative evaluation has not yet been carried out.
Therefore, this study investigates the effects of polymer combination, interface shape, and molding conditions on interface strength, and clarifies guidelines for material selection and structural and molding condition design. The following results were obtained from this study.
- The interfacial shear strength of a combination of crystalline polymer (AM: Nylon6, Injection: Nylon9T) and amorphous polymer (AM: Ultem9085, Injection: Ultem2400) was measured.
- Several types of interface shapes were subjected to molding tests to investigate the effect of the fit structure on the interfacial shear strength.
- The sensitivity of temperature and pressure conditions to the interfacial shear strength was evaluated, and the guideline of the molding condition design was clarified.