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Free-form concrete panels (FCPs) require precise lower-shape implementation because lower-shape errors directly affect thickness quality, geometric accuracy, and constructability. Although previous studies have developed several lower-mold systems, the sectional behavior of lower-shape errors and their deformation tendencies under concrete load have not been sufficiently clarified. Therefore, this study investigates the sectional shape error characteristics of the lower silicone mold (LSM) before casting and of the lower shape of the FCP after casting under combined curvature and thickness conditions. Single-curved FCPs were designed with curvatures of 20, 25, and 30 mm and thicknesses of 20, 30, and 40 mm. The lower geometry was divided into middle and edge sections, and statistical analyses were conducted to examine curvature-dependent deformation and load-induced error behavior. Before casting, the mean error of the LSM increased from 0.289 mm to 0.345 mm and 0.425 mm as curvature increased. After casting, the lower-shape error of the manufactured FCPs ranged from 0.313 mm to 0.444 mm. Under the 30 mm curvature and 20 mm thickness condition, the error decreased after casting, indicating partial load compensation, whereas manufacture was not possible under the 30 mm curvature and 40 mm thickness condition because of excessive side-mold displacement. These results provide quantitative evidence for deformation behavior under load and support the need for FCP-specific quality criteria.

Free-form concrete panel production requires an increasing amount of manpower because the molds cannot be reused. There are many limitations when it comes to reproducing accurate forms due to the many manual processes. Therefore, the current study developed side mold control equipment that can automatically fabricate molds for free-form concrete panels. The equipment is capable of molding various shapes and sustainable operation. However, there may be errors as it automatically produces various shapes. Therefore, it is necessary to check the errors between manufactured shapes and designed shapes. The shape created using the side mold control equipment showed less than 0.1° error in side angle and ±3 mm error in side length. Therefore, the equipment manufactured a precise shape. Based on the findings of the study, the side mold control equipment will be used to produce accurate shape of free-form concrete panels automatically.

Free-form concrete panel (FCP) molds require precise manufacturing because each mold demands a unique shape. Therefore, automation technology for producing these molds is being developed. However, when concrete is cast in a free-form mold and subjected to the impact of compaction to distribute it, deformation occurs in the precisely designed form. Consequently, free-form molds are often produced manually, which results in bugholes on the surface of FCPs. These bugholes lead to quality issues in the panels, including deterioration in aesthetics and strength. This study aims to develop a magnetic compaction technology that installs an object which rotates due to magnetic force inside a free-form mold and applies magnetic force from the bottom to perform compaction according to the free form. By comparing a control group using the existing manual FCP production method and an experimental group using magnetic compaction, strength was measured and bughole incidence was verified. As a result, although the experimental group was subjected to rotary motion, no material separation or deterioration in strength occurred. Furthermore, a similar standard deviation of 62.23 mm2 and a mean difference of 187.42 mm2 were observed between the control group and the experimental group. The results of the t-test showed that at a 95% confidence level, the t-value was −16.35 and the p-value was 0.00. This confirms that the incidence of bugholes was reduced in the experimental group where magnetic compaction was applied. This research may contribute to reducing the occurrence of bugholes in existing free-form concrete panels and securing both aesthetics and strength.

FCP (Free-form Concrete Panel) is used to easily realize the huge and complex curved surfaces of free-form buildings, and research on FCP manufacturing technology is being conducted. However, as the concrete was extruded manually into the manufactured mold, the precision of the FCP was lowered and errors occurred. Therefore, this study developed concrete extrusion equipment that includes a nozzle part, an open/close part, and a control part, according to the required performance derived from previous research analysis. The mixing ratio of concrete was selected at an appropriate value of W/C 38% and extruded uniformly with a width of 60 mm and a thickness of 22 mm. Depending on the opening/closing function, it was possible to open and close at the desired position. The concrete extrusion nozzle for FCP production is the basic equipment, and miniaturization and automation of the nozzle are required in the future. This is expected to contribute to the development of new free-form construction technology and equipment.

FCPs (free-form concrete panels) can be made using reusable and easily customizable silicone molds tailored to the unique shape of each panel. CNC (Computer Numerical Control)-type rods move vertically to press the silicone plate and shape the lower curved surface. Silicone caps are attached to the ends of the rods to facilitate the formation of smooth curves. However, there is currently no fixing method for the silicone caps and the silicone plate, which makes them vulnerable to the lateral pressure exerted during concrete pouring. Therefore, the current study used magnetic force to improve the lower shape of free-form molds. To this end, a neodymium silicone cap was designed by adding a neodymium magnet to the upper surface of the silicone cap. Moreover, two types of silicone plates were developed for fixing: one type is IS-LSM (Iron Sheet–Silicone Mold), which includes an iron sheet, while the other type is IP-LSM (Iron Powder–Silicone Mold), which is made by mixing iron powder. To verify these two techniques, FCP manufacturing experiments were conducted. The experimental results indicated that IS-LSM had a broader error range than existing techniques, thus rendering it unusable, while IP-LSM yielded significant values. Consequently, a t-test was conducted to validate the data for IP-LSM at 30%, 50%, and 70%, and it was confirmed that the difference in error data was significant at a 95% confidence level. Future research in this area should investigate the addition of iron powder to the silicone plate and a side fixing method for the silicone mold. Such research would help advance the production technology of free-form concrete panels.

Many studies have been conducted for the accuracy of free-form concrete panel fabrication, but there still are errors in the process of fabrication. This study developed a connection technology of detachable shape part that can be applied to the existing multi-point Computer Numerical Control (CNC) to enhance the accuracy of fabrication. The detachable type can place a silicone plate on top of the rod without additional fixtures. The accuracy of the technology was verified by curvature test and free-form concrete panel fabrication test. Three curves were created to compare the discrepancies between the designed shapes and the fabricated shapes through quality test. As a result, the detachable type decreased the error by up to 2 mm. In addition, a panel was fabricated to analyze the error to verify the rigidity of the developed molds. The error caused by concrete deflection under load or the error caused by repeated fabrication was about 0.5 mm. The shape error was within 3.5 mm. This small error proved greater accuracy compared to the existing technology.

Maintaining shape accuracy in the production of concrete panels of free-form buildings is time-consuming and costly. In addition, disposable molds used for free-form panels are not sustainable. Such problems can be solved by developing a suitable computerized numeric control (CNC) machine that can produce an accurately shaped reusable form for free-form concrete materials in a short period of time. This project develops a production technology of quality free-form concrete panels using a CNC machine and verifies the shape quality through an experiment. We designed a multi-point press CNC machine and verified its quality. The CNC machine implements a smooth free-form shape by changing the shape of the silicon plate by movement of the rods. The silicone plate for the CNC machine generates a slight error due to the elastic cover and mechanical clearance. The mean error rate was within 3%, based on the thickness of the panels, at the 95% confidence level. Verification of these errors will provide meaningful information to a similar type of machine development. In addition, the project results will be helpful in technological development for the production of free-form concrete panels of uniform quality, whose shape accuracy is not influenced by the skills and competence of the workers producing the panels.

Errors that occur on the side shape of Free-form Concrete Panels (FCP) can cause errors in the FCP construction stage. Therefore, the error generated in FCPs must be reduced. Accordingly, side mold development and research are being carried out. However, in the case of studies using side silicone molds, there was no detailed information about the specifications and application methods of molds, and there was no support between molds. When producing FCPs with the method stated above, there is a high possibility for the mold to be pushed due to the side pressure of concrete, which can cause errors on the side shape of FCPs. Therefore, two new types of side silicone molds were developed in this study. In order to verify the performance difference between the newly developed mold and existing molds, FCP production tests and error analysis were performed. In result, the developed mold decreased the average error difference of the FCP side by 3–5 times compared to the existing mold. In addition, the significance of the average error difference with the produced FCP was verified, and results showed that the difference of the average error was significant at a 95% confidence level.

Free-form molds are used for one-time curve configuration, and because they are produced through manpower, they have issues with reduced precision and the occurrence of errors. In this study, 3D printing technologies were used to ensure precision, and polylactic acid and reusable eco-friendly materials to develop free-form assembly-type side-mold production technologies. In verifying the side mold, a free-form concrete panel was produced to check whether deformation occurs due to lateral pressure. Therefore, in this study, to verify this, a free-form concrete panel was produced and 3D-scanned to analyze the error at the side mold and the cause of the error to confirm the performance of the mold. The results showed that the error at each part was small, with a standard deviation of 1.627 mm, and there was little error at the panel joint part, around 1°. Such research is expected to be used in studies related to mold production technologies using 3D printers and on the production of free-form side molds.

With the increase of free-form architecture, many studies have been conducted for producing free-form Concrete Panels (FCP), but there are still areas that are lacking in terms of the technological aspect. In particular, as free-form panels are produced by hand, the precision of the shapes is low and cost and time are high. FCP production equipment was developed to resolve this. In this study, the variable side mold for FCP production used in side control equipment among FCP production equipment was developed. Variable side mold is equipment that satisfies five requirements to configure the form of FCPs. The variable side mold is made with steel plates so that it can withstand the side pressure of concrete. As a result, the material has a uniform thickness throughout and is molded to the desired shape. Therefore, in order to verify this, the panel was manufactured as a variable side mold to compare the side form with the designed form through 3D scanning and quality inspection to check for errors. As a result, there was a 0.276 mm mean difference for both ends of the panel and the central part, and it was therefore verified through t-test that errors occurred within the allowed margin of 95% confidence level.