• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.184-187
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• 2000

This paper describes action of synchronous error between z axis and spindle axis on rigid tapping. Because rigid tapping cuts the threads synchronizing the movement of z axis to spindle rotation, synchronous error between z axis and spindle is very important. Increase of synchronous error degrades the accuracy of thread and crushes the tap in worst case. So we developed the realtime measurement system of synchronous error in order to know the action of synchronous error on rigid tapping. In result, we have known that synchronous error was increased according to rise of spindle speed and z axis speed. And because the cutting torque(M3-30Ncm∼M10-300Ncm) on rigid tapping are less than maximum motor torque(3500Ncm), it specially doesn't affect the synchronous error. The most important parameter which has affected the increase of synchronous error was acceleration/deceleration time. On worst case, spindle motor was tripped because of the excess of synchronous error. Because the acceleration/deceleration time ocuupies the most of the total cutting time, in order to move on the high speed rigid tapping, the acceleration/deceleration time of spindle must be remarkably reduced.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.29-34
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• 2012

This paper reports some experimental results in high speed rigid tapping of magnesium alloy(AZ91D). M3 spiral tap and high speed spindle tapping center of gantry type were used in experiments and thrust forces were measured. The experimental results indicate that the thrust forces are proportional to the spindle speed and depth of cut. The thrust forces increase as the depth of cut increases. M3 Tapping was achieved at the spindle speed of 10,000rpm, depth of cut of 1.5D and total stroke of 32mm.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.221-227
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• 2002

Tapping is a machining process that makes a female screw on parts to be assembly together. Recently, as the number of small and compact products increases the radius of tap as small as 1 mm is not unusual and more accurate tapping is needed. In complying with those needs, some high-speed tapping machines with synchronizing function have been developed. This paper describes the development of an ultra high-speed tapping machine up to 10,000rpm. The key factors in the tapping speed are the acceleration/deceleration and the synchronizing errors between spindle motor and fred motor. To minimize the acceleration/deceleration time, a low inertia spindle with a synchronous built-in servo motor was developed. To minimize the synchronizing errors, the tapping cycle algorithm was optimized on an open architecture CNC. The developed tapping machine has the acceleration/deceleration time of 0.13sec/10,000rpm for rigid tapping and the synchronizing error below 4.4%. The cycle time for tapping a female screw of M3 and depth 2 times diameter was 0.55sec.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.4
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• pp.391-401
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• 2009

The successful outcome of dental implants is mainly the result of intial implant stability following placement. The aim of this study was to investigate the effect of a self-tapping blades and implant design on initial stability of two tapered implant systems in poor bone quality. The two different implant systems included one with self-tapping blades and one without self-tapping blades. D4 bone model using Solid Rigid Polyurethane Form was used to simulate poor bone densities. The insertion torque during implant placement was recorded. Resonance frequency Analysis (RFA), measured as the implant stability quotient (ISQ), was assessed immediately after insertion. Finally, the implant-bone specimen was transferred to an Universal Testing Machine to measure the axial pull-out force. Insertion torque values and maximum pull-out torque value of the non self-tapping implants were significantly higher than those in the self-tapping group (P = 0.008). No statistically differences were noted between the two implant designs in RFA. Within the each implant system, no correlation among insertion torque, maximum pull-out torque and RFA value could be determined. Higher insertion torque of the non-self-tapping implants appeared to confirm higher clinical initial stability. In conclusion, implants without self-tapping blades have higher initial stability than implants with self-tapping blades in poor bone quality.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.660-663
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• 1996

There has been many activity to increase accuracy in machining center by reducing tracking error. The tracking error can cause bad effect in high speed rigid tapping in which syncronization servo motor with spindle is relatively important. To reduce tracking error, feed forward control has been used, but no method is provided knowing motor dynamics, force variation, etc. In this paper, we observe that, despite of tracking error of relevant axis, high speed tapping could be possible by reducing contour error of axis to be syncronized. We present the method to increase accuracy in high speed tapping to minimize contour error by automatically fitting gains of servo and spindle.

• Journal of Korean Dental Science
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• v.4 no.2
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• pp.52-58
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• 2011

Purpose: Modifications of implant design have been related to improving initial stability. The purpose of this study was to investigate their respective effect on initial stability between two tapered implant systems (self-tapping vs. non-self-tapping) in medium density bone using three different analytic methods. Materials and Methods: Self-tapping implant (GS III$^{(R)}$; Osstem Implant Co., Busan, Korea) and non-self-tapping implant (Replace Select$^{(R)}$; Nobel Biocare, G$\H{o}$teborg, Sweden) were investigated. In Solid rigid polyurethane blocks of artificially simulated Quality 2 bone, each of the 5 implants was inserted according to the manufacturer's instructions for medium-bone drilling protocol. Evaluation of initial stability was carried out by recording the maximum insertion torque (IT) and performing the resonance frequency analysis (RFA), and the pull-out test. Results: The IT and RFA values of self-tapping implant were significantly higher than those of non self-tapping implant (P=.009 and P=.047, respectively). In the pull-out values, no significant differences were found in implants between two groups (P=.117). Within each implant system, no statistically significant correlation was found among three different outcome variables. Conclusions: These findings suggest that design characteristics of implant geometry significantly influence the initial stability in medium bone density.

• Journal of Korea Entertainment Industry Association
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• v.13 no.4
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• pp.369-375
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• 2019

This study looked at the effects of teratainment taping and footpad exercise on the improvement of flat foot in a university student. We divided it into flexible flat foot taping group(n=13), flexible flat foot exercise group(n=14), rigid flat foot taping group(n=12), rigid flat foot exercise group(n=13) through a navicular drop test. After one hour's application of teratainment taping and footpad exercise, the height change of navicular, balancing ability and postural stability were evaluated. Change in the height of the navicular was measured before and after intervention, and the balancing ability was measured timed up & go test, and the postural stability ability was evaluated for stability limits in shoulder-width double leg stance, narrow base double leg stance, tandem stance. According to result, there was a statistically significant difference in the left and right foot of the flexible tapping group, right foot of the flexible tapping group, right foot of the rigid tapping group in the change in the height of the navicular in comparison pre- and post- intervention(p<0.5). There were no statistically significant differences in pre- and post- intervention comparisons intragroup and intergroup in balancing ability. There was a statistically significant difference in flexible flat foot exercise group and rigid flat foot taping group in tandem stance in comparison pre- and postintervention in the postural stability(p<0.5). And there was a statistically significant difference in tendem stance of the flexible flat foot exercise group compared to the rigid flat foot exercise group(p<0.5). The results of this study show that teratainment taping and footpad exercise have a significant effect on the improvement of flat foot in adults. Therefore, it is recommended to apply teratainment taping and footpad exercise to improve flat foot.

• Archives of Plastic Surgery
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• v.36 no.3
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• pp.318-321
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• 2009

Purpose: The bony mallet finger injury is generally managed by conservative treatments, but operative treatments are needed especially when the fractures involve above 30% of articular surface or distal phalanx is accompanied by subluxation in the volar side. This is the reason they often result in chronic instability, articular subluxation and unsatisfactory cosmetic. In this report, We describe new method using the hook plate as an operative treatment of Mallet finger deformity. Methods: Among 13 patients with Mallet finger deformity who came from February 2006 to February 2008, six patient were included in surgical indication. Under local anesthesia, H or Y type incision was made at the DIP joint area. After the DIP joint extension, the hook plate was put on the fracture line, and one self tapping screw was used for fixation. 2 hole plate which was one of the holes in 1.5 mm diameter was cut in almost half and bended through approximately $100^{\circ}$. Results: In all six cases which applied the hook plate, complications such as loss of reduction or nail deformity were not seen. In only one patient, hook pate was removed due to inflammatory reaction after surgery. At 2 weeks after operation, active motion of DIP joint was performed. The result was satisfactory not only cosmetically but also functionally. At 6 weeks after operation, the range of motion of DIP joint was average $64^{\circ}$. Conclusion: The purpose of the operative treatment for mallet finger deformity using the hook plate is to provide anatomical reduction with rigid fixation and to prevent contracture at the DIP joint. While other operations take 6 weeks, the operation using the hook plate begins an active motion at 2 weeks after operation. Complication rate was low and the method is rather simple. Thus, the operation using the hook plate is recommended as a good alternative method of the mallet finger deformity treatment.