Margin Wear Research Articles

プリント配線板の小径穴あけ加工における工具摩耗が加工穴品質におよぼす影響

In the current manufacturing of printed circuit boards (PCBs), micro-drills are generally used to make smaller diameter through-holes in PCBs. The purpose of this paper is to clarify the effect of flank wear and margin wear on drilled hole quality. Series of PCBs drilling tests are carried out to investigate hole quality, hole location accuracy and hole wall roughness. The cutting torque and cutting force are measured by Kistler 9329 and 9257B respectively. Detailed observation of drilled hole surface is made by SEM. The hole location accuracy does not get worse with increasing flank wear of drill. On the other hand, the hole location accuracy becomes worse with increasing margin wear of drill. The hole wall roughness when using the margin wear type drill is worse than using the flank wear type drill. In addition the cutting torque when using the margin wear type drill is larger than using the flank wear type drill.

DLCコーテッドドリルを用いたプリント配線板の小径穴あけ加工に関する研究

In recent years, needs for micro drilling are increasing, accompanying the development of higher wiring density of printed circuit board (PCB). When drilling PCB for the purpose of making the electric through holes, it has been said that the drill breakage is caused by being filled the chips of GFRP and copper of PCB in the drill flutes. The aim of this study is to clarify the effect of PCB drilling using DLC coated drill on tool wear, chip evacuation and cutting torque. Series of drilling tests of PCB have been carried out to investigate the amount of drill wear, the chips evacuation behavior out of drilled hole with the drill, the shape of chips produced and the cutting torque using DLC-coated drill and non-coated drill. The chips evacuation behavior out of drilled hole with the drill is filmed by a high-speed motion camera and the shape of chips produced is observed by a microscope. The cutting torque is measured by a dynamometer; Kistler 9329A. The amounts of drill flank wear and margin wear using DLC-coated drill and non-coated drill are almost the same. The chips of GFRP using DLC-coated drill are shorter and smaller than those using non-coated drill. The chips evacuation out of drilled hole with the drill using DLC-coated drill is better than those using non-coated drill, and cutting torque using DLC-coated drill is lower than those using non-coated drill.

Effect of Tool Wear on Hole Quality in Drilling of Carbon Fiber Reinforced Plastic–Titanium Alloy Stacks Using Tungsten Carbide and Polycrystalline Diamond Tools

This paper reviews the nature of hole defects and postulates the cause of hole defects resulting from the drilling process of carbon fiber reinforced plastic–titanium alloy stacked panels (CFRP–Ti stacks) using tungsten carbide (WC) and polycrystalline diamond (PCD) twist drills. The parameters that describe the hole quality of the CFRP–Ti stacks include CFRP entry hole delamination, hole diameter and roundness, inner hole surface roughness, CFRP hole profile, CFRP–Ti interplate damage, and Ti exit burr. They are caused by heat generation during drilling as well as hot Ti chips and adhesion, Ti burr formation, tool instability, and tool geometry change due to tool wear. For the WC drills, large flank wear and margin wear occurred at the high spindle speed condition, resulting in a reduction of the hole size and an increase of the hole roundness and CFRP–Ti interface damage. At the low spindle speed condition, tool geometry was changed due to the large edge rounding. This resulted in large fiber pull-out at the CFRP hole surface. Ti entry burrs caused damage associated with fiber removal and matrix discoloring at the bottom of the CFRP panel and this interplate damage was observed to increase with tool wear. When compared with the WC tool at the same speed condition, the PCD drill maintained relatively small hole defects under all parameters.

Clinical performance of chairside CAD/CAM restorations

The CEREC system (Sirona Dental Systems GmbH, Bensheim, Germany) is marking its 20th year of clinical service. The author reviews the literature on the effectiveness of this chairside CAD/CAM system. The author identified and reviewed clinical studies from 1985 through 2006 that included CEREC-generated inlays, onlays or crowns. These studies were conducted in both private practice and university settings. The author summarized the findings as they relate to postoperative sensitivity, restoration fracture, color match, margin adaptation and clinical longevity. Although postoperative sensitivity was reported, it was due to mainly occlusal interferences. Long-term postoperative sensitivity was not a reported problem. Similar to other ceramic restorations, restoration fracture is the primary mode of failure for CEREC-generated restorations. Although margin wear is detected consistently, consequences of the wear leading to restoration failure were reported rarely. The survival probability of CEREC-generated restorations was reported to be approximately 97 percent for five years and 90 percent for 10 years. The low rate of restoration fracture and long-term clinical survivability document the effectiveness of the CEREC system as a dependable, esthetic restorative option for patients.

O.173 A new concept of positioning the proximal segment of the mandible: Upper vs lower alignment

The CEREC system (Sirona Dental Systems GmbH, Bensheim, Germany) is marking its 20th year of clinical service. The author reviews the literature on the effectiveness of this chairside CAD/CAM system.The author identified and reviewed clinical studies from 1985 through 2006 that included CEREC-generated inlays, onlays or crowns. These studies were conducted in both private practice and university settings. The author summarized the findings as they relate to postoperative sensitivity, restoration fracture, color match, margin adaptation and clinical longevity.Although postoperative sensitivity was reported, it was due to mainly occlusal interferences. Long-term postoperative sensitivity was not a reported problem. Similar to other ceramic restorations, restoration fracture is the primary mode of failure for CEREC-generated restorations. Although margin wear is detected consistently, consequences of the wear leading to restoration failure were reported rarely. The survival probability of CEREC-generated restorations was reported to be approximately 97 percent for five years and 90 percent for 10 years.The low rate of restoration fracture and long-term clinical survivability document the effectiveness of the CEREC system as a dependable, esthetic restorative option for patients.

ＰＷＢ加工におけるＣＶＤダイヤモンドドリルの摩耗挙動

Wear performances of CVD (Chemical Vapor Deposition) diamond films caused by PWB (Printed Wiring Board) drilling were investigated. For glass epoxy resin boards, only major cutting edge wear occurred, and chisel edge wear, margin wear, and face wear were very little. By the wear of CVD diamond films, major cutting edge showed knife edge shape. These phenomena are very characteristic as compared to carbide drills. On the other hand, for paper phenol resin boards, almost all wear didn't occur. It is considered that the main influence factor for wear of CVD diamond films is not abrasive but thermal. Chipping of major cutting edge was triggered by appearance of substrate followed by the extension of major cutting edge wear. Wear performances were affected by a film thickness and cutting conditions. It was revealed that there were critical thickness for chipping of major cutting edge, and low feed rates accelerated wear progress.

Application of Self-Learning for Tool Failure Diagnosis in Robotic Drilling System

The effort in monitoring tool condition for fully automatic drilling processes has resulted in the development of an intelligent drilling machine to work with industrial robots. This computer-controlled drilling machine has five built-in sensors. Based on the pattern recognition of sensor outputs with sets of algorithms, an intelligent diagnostic system has been developed for on-line detection of and pin-pointing of anyone of the nine drill failures: chisel edge wear, margin wear, breakage, flank wear, crater wear, lip height difference, corner wear and chipping at lips. Many inherent factors affecting the criteria for the judgement of drill wear/breakage, such as drill size, drill material, drill geometry, workpiece material, cutting speed, feed rate, material microstructure, hardness distribution, etc. is avoided by implementing, a self-learning system.

Performance and failure of high speed steel drills related to wear

Three high speed steel grades, representing low, medium and high contents of alloying elements, were investigated in a comparative drill performance test using two different work materials. The results are discussed with reference to the observed wear mechanisms. Since drill performance is usually expressed as number of holes to failure, relationships between gradual wear and final failure of the drills are emphasized. The performance tests resulted in chisel edge, crater, flank and margin wear. The corresponding wear mechanisms were studied with the aid of scanning electron and light optical microscopy. The most important mechanisms are (1) abrasive wear for drilling in a plain carbon steel and (2) adhesive wear for drilling in a quenched and tempered steel.