M. Fahrur Rozy Hentihu

PT X has consistently implemented Total Productive Maintenance (TPM) to improve operational efficiency and company productivity. On the other hand, the concept of Six Big Losses is very closely related to TPM. Thus, this research aims to evaluate the application of the Six Big Losses concept in factory management, focusing on case studies at PT X and using fishbone diagrams to identify the root causes of problems. Data from the breakdown that happened in March was analyzed, highlighting the damage caused by Pal Teflon in factory operations. The research results show that through this approach, companies can identify and handle operational problems more effectively, reflected in decreased breakdown values after corrective action. These findings emphasize the importance of implementing Six Big Losses as an effective management tool in increasing factory efficiency and productivity. The practical implication of this research is that companies can use the same approach to optimize their operations, with a focus on identifying root causes and implementing appropriate corrective actions.

A complete denture, consisting of teeth and a gum base, is a standard device used to restore masticatory and esthetic functions in patients with complete edentulism. The different colors and mechanical properties for teeth and the gum base mean a complete denture is manufactured using two materials with different mechanical properties. This study proposes a method to make a complete denture using a laboratory-developed, multiresin additive manufacturing (MRAM) system with two resins and different mechanical properties. A tenon joint is used to create the bottom of the teeth that fit into the gum base, ensuring automatic alignment and higher bending strength. The mechanical properties, material waste, fabrication time, and effect of the tenon joint on the bending strength of a complete denture printed using the MRAM system are compared with the values for a computer-aided design and computer-aided manufacturing (CAD/CAM) system. Experimental results show that the printed denture is manufactured 3 times faster and produces 14 times less material waste, but is 35.08% less inaccurate than one produced using a CAD/CAM system. The proposed tenon joint increases the bending strength by 31.94%. The MRAM system is applicable for printing a complete denture.

This study proposes an innovative three-dimensional printing technology with submersion-light apparatus. A zirconia powder with an average particle size of 0.5 µm is mixed with 1,6-Hexanediol diacrylate (HDDA) and photo-initiator to form a slurry. The weight percentage of zirconia powder to HDDA is 70:30 wt.%. A light engine box is submerged in a slurry and emits a layered pattern to induce photopolymerization and transform a slurry into a printed green body. Green body sintering parameters for the first and second stages are 380 °C with a holding time of 1.5 h and 1550 °C with a holding time of 2 h. The sintered parts’ length, width, and height shrinkage ratios are 29.9%, 29.7%, and 30.6%. The ball milling decreases the powder particle size to 158 ± 16 nm and the mean grain size of the sintered part is 423 ± 25 nm. The sintered part has an average hardness of 1224 (HV), a density of 5.45 g/cm³, and a flexural strength of 641.04 MPa. A three-unit zirconia dental bridge also has been fabricated with a clinically acceptable marginal gap.

Vat photopolymerization is one of additive manufacturing and also known as photo-curable three-dimensional printing technology. It uses light energy with the proper wavelength to expose on the liquid photo-curable resin inducing the photopolymerization process and resulting in solidification layer-by-layer. The building method is classified into two ways: free-surface and constrained-surface. The advantage and disadvantage of both methods are described and analysed according to the different material property and requirement. The basic composition for photo-curable resin consists of photo-initiator and monomer. Adding powder into photo-curable resin makes the photo-curable slurry. Literatures report that high density powder such as zirconia oxide or Inconel 718 is suitable for free-surface building method because of poor suspension. However, the volume percentage in the slurry is less than 50% causing the higher shrinkage ratio and inaccuracy after sintering process. The coupling agent may increase the suspension of powder in slurry but experimental result shows that it still cannot improve the success rate in the constrained-surface building method. Therefore, this study proposes a combination method to overcome the difficulty of making high density ceramic or metal part. In addition, the sintering process is a key factor to obtain the high dense part with no crack occurrence and desirable microstructure. The optimized sintering parameters for zirconia oxide and Inconel 718 are also introduced.