Influence of 3D printing properties on relative dielectric constant in PLA and ABS materials

Nowadays, it is well known that on the ship, free space is at a premium. Unfortunately, every part on the ship has its duration before the failure, and the spare parts occupy the space. The broken part must be replaced when the failure occurs to maintain the ship's operation. Developing 3D printer technology and particular material technology, it has become possible to print a spare part that can replace broken. However, due to hazardous environments (salt, humidity, vibrations, etc.), printed parts change their properties. Electrical capacity and further dielectric permittivity is a parameter or metric that has to be monitored since it directly influences the printed part material structure. Therefore, this paper aims to research the impact of relative dielectric constant in additive manufacturing on printed ship's spare parts since infill patterns and density were changed due to a hazardous environment. The experiment, in which the three shaped material samples are created, consists of the following equipment, the Ultimaker S5 3D printer, Polylactic Acid (PLA) and Acrylonitrile-Butadiene-Styrene (ABS) materials, and LC HM 8018 m. Results show relative dielectric constant changes between 1.7778 and 2.8141 for PLA and between 2.1979 and 2.9989 for ABS, depending on infill density and pattern. ANOVA test for ABS is performed to investigate how the calculated dielectric constant relates to the infill density for various infill shapes. Scores are: F = 154.3773, Fcrit = 5.1432, and p = 6.9269·10-6. ANOVA test for PLA resulted in scores F = 18.911, Fcrit = 5.1432, and p = 0.0022.

Dynamic repair priority rule based on remaining useful life predictions

In this paper, we propose a novel repair priority rule for spare parts in a repair station with limited repair capacity to minimize total inventory cost per time unit. Inventory cost is composed of holding costs and backorder costs. The proposed rule uses Remaining Useful Life (RUL) predictions of functioning machines obtained from a Prognostics and Health Monitoring (PHM) system. An inventory system comprising a finite number of machines, one warehouse, and one single-server repair station is considered. Numerical experiments were conducted to compare the performance of the proposed model with the performance of three existing priority rules: a first-come, first-served (FCFS) rule, a static priority rule, and a dynamic priority rule. A testbed with 20 instances of the problem was considered. The results showed that the proposed PHM-based rule consistently reduces the inventory system cost.

Classification and clinical evaluation of "spare parts" procedures in mutilating hand injuries

Mutilating hand injuries are common, and reconstruction should be tailored to each case. The "spare parts" concept relies on harvesting tissues for reconstruction from amputated or non-salvageable parts that are being discarded. This study sought to evaluate the outcomes of "spare parts" procedures in mutilating hand injuries and to propose a classification of "spare parts" types. This study included 28 patients with mutilating hand injuries undergoing surgery using "spare parts" for tissue reconstruction either at the time of trauma or later on. A total of 31 "spare parts" procedures were performed on the 28 patients. The outcomes were assessed in terms of reconstruction success, Disabilities of the Arm, Shoulder, and Hand (DASH) score, grip strength, and an overall patient satisfaction score that we designed. Reconstruction using "spare parts" was successful in 25 patients (89%). The mean DASH score was 8.45 ± 4.74, the mean grip strength was 24.57 ± 2.73 kg, and overall patient satisfaction was 3.32 ± 0.77 out of 5. Specific outcomes were assessed using case-specific measures. Based on these data, a hand-specific classification of "spare parts" procedures was designed to be taken into consideration when managing mutilating hand injuries. Besides direct digital replantation and tissue harvesting from different donor sites, the "spare parts" concept is an important tool for a hand surgeon. Its different types should always be taken into consideration when managing mutilating hand injuries to avoid additional donor site morbidities and to achieve a high level of overall patient satisfaction. We propose adding a "patient satisfaction with hand appearance" item to the DASH and QuickDASH score.

Preservation of lower extremity spare parts using the University of Wisconsin solution

The management of a mangled limb is a challenging endeavor. With the advancement in microsurgery, spare parts surgery (fillet flaps) has gained recent interest. In the context of lower extremity amputation secondary to trauma, viable spare parts can provide stump soft tissue coverage, potentially preserving critical length and obviating above-knee amputations. Commonly, spare parts surgery is performed in the acute setting but tissue preservation is sometimes necessary. The authors report their experience preserving a fillet flap of a mangled lower extremity for 48 h using the University of Wisconsin solution. A sole fillet flap and a split-thickness skin graft were harvested and preserved from the amputated lower extremity (based on the posterior tibial artery and vein). Stump coverage was achieved by anastomosing the fillet flap to the proximal posterior tibial artery and vein. This solution has not been previously described for preservation of fillet flaps.

Medial forefoot fillet flap for primary closure of transmetatarsal amputation: A series of four cases

Amputation of the forefoot is a salvage procedure for several forefoot acute or chronic infection. A good, sensate and durable skin cover is important for quicker and better rehabilitation. The use of filleted flaps (or "spare parts technique") has been published in the past as a creative technique. The purpose of this article is to introduce a reproducible, pre-planned, technique that requires less creativity for the use of the "spare parts". The authors describe a case series of 4 patients with deep infection and osteomyelitis of the forefoot, without involvement of the medial skin that underwent two staged procedure for transmetatarsal amputation with medial forefoot fillet flap. The first procedure was amputation of the 4 lesser metatarsal and the wound was left open. After a few days the second operation was done with amputation of the first metatarsal bone and using the filleted medial skin and subcutaneous tissue for closure of the wound. In conclusion the medial fillet flap is an effective method of covering large wounds after partial, lateral forefoot amputation. This method shortens the healing time of the patient, and in hospital stay. The authors recommend using the staged method when dealing with diabetic patients with partial, central and lateral forefoot deep infection and/or necrosis.

Vascularized Spare Parts Reconstruction of Hand Gunshot Injury

Reconstruction of extensive traumatic bone and soft tissue deficits in the hand often presents a significant challenge. We present a case of a gunshot wound managed with a resourceful "vascularized spare parts" reconstruction in which a single compromised digit provided two separate vascularized tissue transfers. A rarely reported pedicled phalanx restored osseous stability, a digital fillet flap achieved soft tissue coverage, and the flexor tendons reanimated the hand. An excellent functional and cosmetic result was obtained and the patient was able to return to manual labor within six months of injury.