• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.491-497
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• 2016

This study aims to develop a vision inspection system for screw threads. To inspect external defects in screw threads, the vision inspection system was developed using front light illumination from which bright images can be obtained. The front light system, however, requires multiple side images for inspection of the entire thread surface, which can be performed by omnidirectional optics. In this study, an omnidirectional optical system was designed to obtain annular images of screw threads using an image sensor and two reflection mirrors; one large concave mirror and one small convex mirror. Optical simulations using backward and forward ray tracing were performed to determine the dimensional parameters of the proposed optical system, so that an annular image of the screw threads could be obtained with high quality and resolution. Microscale surface defects on the screw threads could be successfully detected using the developed annular inspection system.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.261-268
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• 2014

Precision screws have a wide range of industrial applications such as electrical and automotive products. To produce screw threads with high precision, not only high precision manufacturing technology but also reliable measurement technology is required. Machine vision systems have been used in the automatic inspection of screw threads based on backlight illumination, which cannot detect defects on the thread surface. Recently, an omnidirectional inspection system for screw threads was developed to obtain $360^{\circ}$ images of screws, based on front light illumination. In this study, the illumination design for the omnidirectional inspection system was modified by adding a light shield to improve the image uniformity. Optical simulation for various shield designs was performed to analyze image uniformity of the obtained images. The simulation results were analyzed statistically using response surface method, from which optical performance of the omnidirectional inspection system could be optimized in terms of image quality and uniformity.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.80-86
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• 2011

This study compared and analyzed manual tapping and automatic tapping regarding tapping process characteristics of titanium hard-to-cut-material. Tapping process characteristics of titanium hard-to-cut-material are evaluated as the quality of a screw, wear of a tap, economic analysis, and cycle time etc. The type of screw threads after manual tapping is formed as an irregular type of screw threads, and perfect screw threads are created after automatic tapping. In addition, the chip type after manual tapping process is formed as the discontinuous chip due to work hardening, and the powder type of chip after automatic tapping process is created. In terms of cycle time, an automatic tapping process is shortened by 70% compared to manual tapping process. Insert tip wear of an automatic tapping shown in the process of 5-hole tapping is not found, but hand tap wear for finish cutting is most severe.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.94-99
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• 1998

The CAD system which enables to design and draw the screw thread gauges was developed and constructed. This system was proposed based on Visual C++ Version 5.0. Even beginner can get drawings as well as concerned data for the manufacturing of screw thread limit gauges by selecting the input data. This system was constructed from relevant standards and regulations (based on the Korean Standard and referred to ISO and JIS), handbooks and textbooks. The system shall provide more powerful and user friendly tool for design and drawing for screw thread gauges such as metric fine and coarse threads, unified fine and coarse threads, Parallel and taper pipe threads. The results of this system are proved to be in good agreement with concerned standards and regulations.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.85-91
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• 1998

The CAD system which enables to design and draw the screw thread gauges was developed and constructed. This system was proposed based on Visual C++ Version 5.0. Even beginners can get drawings as well as concerned data for the manufacturing of screw thread limit gauges by selecting the input data. This system was constructed form relevant standards and regulations and was developed based on the Korean Standard and referred to ISO, JIS, handbooks and textbooks. This system shall provide more powerful and user friendly tool for design and drawing for screw thread gauges such as metric fine and coarse threads, unified fine and coarse threads, parallel and taper pipe threads. The results of this system are proved to be in good agreement with concerned standards and regulations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1003-1007
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• 1997

This study is na introduction of ADS in which we have written out programs which can design three-dimensional machine parts and reduce the required time for design them comparing with other CADs. Among the machine parts, screws are commonly used in joining one part to another because of easy handling but welding and rivet are used to join permanently them even thought hard operation. Consequently, w have developed the screw for permanent fixing using stairs type screw threads, which is considered as the main machine parts in joining. For that, we designed permanent fastened screws according to the different rotation angle using VisualLISP and transferred it to ANSYS, structural solution program, to find out allowance load, maximum equivalent stress and where it occur.

• The Journal of Advanced Prosthodontics
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• v.8 no.1
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• pp.62-69
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• 2016

PURPOSE. The purpose of this study was to evaluate the effects of abutment screw length and cyclic loading on the removal torque (RTV) in external hex (EH) and internal hex (IH) implants. MATERIALS AND METHODS. Forty screw-retained single crowns were connected to external and internal hex implants. The prepared titanium abutment screws were classified into 8 groups based on the number of threads (n = 5 per group): EH 12.5, 6.5, 3.5, 2.5 and IH 6.5, 5, 3.5, 2.5 threads. The abutment screws were tightened with 20 Ncm torque twice with 10-minute intervals. After 5 minutes, the initial RTVs of the abutment screws were measured with a digital torque gauge (MGT12). A customized jig was constructed to apply a load along the implant long axis at the central fossa of the maxillary first molar. The post-loading RTVs were measured after 16,000 cycles of mechanical loading with 50 N at a 1-Hz frequency. Statistical analysis included one-way analysis of variance and paired t-tests. RESULTS. The post-loading RTVs were significantly lower than the initial RTVs in the EH 2.5 thread and IH 2.5 thread groups (P<.05). The initial RTVs exhibited no significant differences among the 8 groups, whereas the post-loading RTVs of the EH 6.5 and EH 3.5 thread groups were higher than those of the IH 3.5 thread group (P<.05). CONCLUSION. Within the limitations of this study, the external hex implants with short screw lengths were more advantageous than internal hex implants with short screw lengths in torque maintenance after cyclic loading.

• Journal of Korean Neurosurgical Society
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• v.37 no.5
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• pp.345-349
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• 2005

Objective: Anterior screw fixation provides the best anatomical and functional results for type II odontoid process fracture (type II-A, II-N, and II-P) with intact transverse ligament. The purpose of this study is to evaluate the usefulness of the 4.5mm diameter, cannulated Herbert screw in anterior screw fixation. Methods: From Jan. 2003 to Feb. 2004, consecutive 10cases of type II odontoid process fractures were treated with anterior screw fixation using a Herbert screw. The Herbert screw has double threads, with different pitches on the distal and proximal ends. It has no head, so it can be inserted through articular cartilage and buried below bone surface. It was originally developed for treating scaphoid fractures. Results: There were 8male and 2female patients whose ages ranged from 15 to 67years (mean 42.1years). The fracture type was type II-A in 4patients, II-N in 3 patients, and II-P in 3 patients. The fracture line was oblique downward and backward in 6cases, oblique downward and forward in 1 case, and horizontal in 3cases. The range of follow-up was 5 to 18months (mean 12months). Bone fusions were achieved in all cases without any instrumental failures or postoperative complications. Conclusion: The Herbert screw is very useful in anterior fixation for type II odontoid process fracture. This series showed successful results also in type II-A odontoid fracture when treated with the Herbert screw, but further more studies are required.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.139-145
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• 1996

Tapping is one of the most widely used machining operations. There are several methodes of producing external screw threads, e.g. turning, milling with single or multiple cutter, rolling, and grinding, but the methods available for cutting enternal threads are less numerous, and for threads in small holes, tapping is employed almost exclusively. In this study, the tap with the various geometry has been developed in order to tap special workmaterial at considerably higher cutting speed than that of the conventional HSS tap. The experimental tests are run with various cutting speed by using a piezo type tool dynamometer to measure tapping torque. Tapping torque is affected by the design of the tap, which seems to be due to internal friction and shearing of the metal. It is clarified that the process of chip formation strongly depends on rake angle, relief angle, angle of twist.

• Clinics in Shoulder and Elbow
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• v.20 no.4
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• pp.236-239
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• 2017

After dual plating with a locking compression plate for comminuted intraarticular fractures of the distal humerus, the incidence of ulnar nerve injury after surgery has been reported to be up to 38%. This can be reduced by an anterior transposition of the ulnar nerve but some surgeons believe that extensive handling of the nerve with transposition can increase the risk of an ulnar nerve dysfunction. This paper reports ulnar nerve injuries caused by the incomplete insertion of a screw head in dual plating without an anterior ulnar nerve transposition for AO/OTA type C2 distal humerus fractures. When an anatomical locking plate is applied to a distal humeral fracture, locking screws around the ulnar nerve should be inserted fully without protrusion of the screw because an incompletely inserted screw can cause irritation or injury to the ulnar nerve because the screw head in the locking system usually has a slightly sharp edge because screw head has threads. If the change in insertion angle and resulting protruded head of the screw are unavoidable for firm fixation of fracture, the anterior transposition of the ulnar nerve is recommended over a soft tissue shield.