High-speed Tapping Research Articles

Wear mechanisms of TiN coated tools during high-speed tapping of GGG50 nodular cast iron

Ductile irons are among the most used materials in the automotive industry. One of the critical problems during manufacturing of powertrain components is the fast wear of cutting tools because it can lead to defects in the part. This work investigates the wear mechanisms of TiN coated high-speed steel (HSS) taps when machining GGG50 cast iron under high-speed conditions. SEM images and EDS analysis at the chamfered and cylinder teeth demonstrate that adhesion of iron to the cutting tool is the dominating wear mechanism. Fatigue-fracture and coating removal were also observed in many zones of the tap surface. Furthermore, wear progression is reflected on the evolution on the tapping torque with hole number. An on-line monitoring of this variable could be useful to detect an excessive wear of the tap and prevent the loss of tolerances in the threads.

Research on the wear mechanisms during the high-speed tapping in 316L stainless steel

Internal threads are present in all mechanical assemblies in modern industry. Independent of diameter, geometry or threaded length, internal threads are regions that provide extreme flexibility, safety and precision in the mounting of the industrial products. The modern industry has many engineering material options used to manufacture thousands of different products. Among these materials is the stainless steel, which shows several applications in products since medical components, devices used to produce food until aerospace components. In this work, metric threads were manufactured in square plate stainless steel aiming to know the tool wear with high-speed cutting. The experimental methodology was carried out, in dry and emulsion condition, allowing the analysis of the tool wear and thread profile every 28 threaded holes. The tool wear was analysed in an optical microscope and the thread profile in the scanning electron microscopy. The results demonstrated that for dry tapping tests, almost 250 threaded holes were manufactured, on the other hand, when coolant in emulsion condition was used, 600 threaded holes were manufactured. It can be concluded that although tool wear showed a significant difference, considering the cooling system, the tool wear had not proved to be a determining factor in defining tool life. This situation occurred because the tapping process carried out with high-speed cutting showed a random behaviour with the non-occurrence of wear in all cutting edges.

Wear-Based Assessment of the Life of High-Speed Taps

It is of interest to assess the life of high-speed taps in machining structural-steel workpieces. A general multiparametric formula is derived for the permissible wear. By that means, the tool life may be effectively utilized, and the metal removal in regrinding may be standardized.

Thread Quality Control in High-Speed Tapping Cycles

Thread quality control is becoming a widespread necessity in manufacturing to guarantee the geometry of the resulting screws on the workpiece due to the high industrial costs. Besides, the industrial inspection is manual provoking high rates of manufacturing delays. Therefore, the aim of this paper consists of developing a statistical quality control approach acquiring the data (torque signal) coming from the spindle drive for assessing thread quality using different coatings. The system shows a red light when the tap wear is critical before machining in unacceptable screw threads. Therefore, the application could reduce these high industrial costs because it can work self-governance.

12 Gbit/s three‐tap FFE half‐rate transmitter with low jitter clock buffering scheme

A 12 Gbit/s feed-forward equalisation (FFE) transmitter has been designed in 65 nm CMOS process. The three-tap/half-rate highspeed tap signal generation technique for the segmented FFE driver is presented. A clock buffer scheme to make the equivalent signal transition for each segmented unit contributes to a low jitter performance. The measurement results show 9.31 ps RMS jitter at 12 Gbit/s after equalisation and the horizontal eye-opening is 0.204 UI at 10 -12 BER. The prototype transmitter occupies 0.042 mm 2 and consumes 1.58 pJ/bit.

Wear Performance Evaluation of Tungsten Carbide Taps in Blind Hole Tapping Cast Iron

The engineblock and cylinderhead of automobile are usually made of cast iron, and tapping of blind holes is one of the most demanding operations. As usual, tapping is the final process for an engineblock, and the failure of taps can disable the engineblock possibly. The productivity is restricted because of the low cutting speed and poor wear resistance of high speed steel (HSS) taps. Thereby, according to the demand on high speed cutting and low tact time of modern engine production lines, several new typical special tungsten carbide taps are developed and their cutting performance are evaluated in comparison with the commercial taps. In the process of tapping blind holes in gray cast iron and ductile cast iron, several aspects are studied comparatively such as wear mechanism of the first complete and the last incomplete tooth, tap structure, wear of TiCN coating and effects of coolant on cutting performance of taps. This study indicates that straight coated taps with fewer flutes are suitable for high speed tapping of cast iron.

A Compound Vibratory Mode in High Speed Vibratory Tapping

Based on the investigation of two traditional vibratory modes, this paper puts forward a novel vibratory mode in high speed tapping. Vibratory tapping on stainless steel with all kinds of vibratory modes is carefully studied. Experimental results show that the new vibratory mode not only preserves the machining effect of the separable vibratory tapping, but also increases the life of tap. Therefore this study provides a new solution to increase the performance of high speed vibrat- ion tapping.

Tool wear aspects when applying high-speed tapping on grey cast iron

Tool wear is a very important subject affecting the economics of machining, especially in tapping, since it is one of the last operations to be performed within most operation sequences. In the present study, some aspects of tapping such as the mechanisms and types of wear were investigated in taps working at conventional and high-speed cutting (HSC). Additionally, different types of coatings and cooling/lubrication conditions were used. The tapping operation (M8 × 1.25) was performed in through holes with two cutting speeds (30 and 60 m/min) in grey cast iron GG25. Lubrication conditions tested were dry and with minimal quantity of lubricant. Tap materials were manufactured by powder metallurgy and coated with (TiAl)N and with TiCN. A go—non-go gauge criterion was used to assess tool life. The wear and surface aspects of the tools and workpiece were evaluated by scanning electron microscopy and energy dissipation spectroscopy. Torque signals were also measured during the tests. The main wear mechanism observed was adhesion, although some abrasion and diffusion may also have occurred, and the main type of wear was flank wear. The adhesion of workpiece material on the tool was the main and decisive factor ending tool life. Tool coatings proved to be an efficient way to minimize adhesion. Torque signals followed the same pattern as the flank wear and no significant change was observed when the cutting speed was increased.

Breakage detection of small-diameter tap using vision system in high-speed tapping machine with open architecture controller

In this research, a vision system for detecting breakages of small-diameter taps, which are rarely detected by the indirect in-process monitoring methods such as acoustic emission, cutting torque and motor current, was developed. Two HMI (Human Machine Interface) programs to embed the developed vision system into a Siemens open architecture controller, 840D, were developed. They are placed in sub-windows of the main window of the 840D and can be activated or deactivated either by a softkey on the operating panel or the M code in the NC part program. In the event that any type of tool breakage is detected, the HMI program issues a command for an automatic tool change or sends an alarm signal to the NC kernel. An evaluation test in a high-speed tapping machine showed that the developed vision system was successful in detecting breakages of small-diameter taps up to M1.

Improving tapping mode atomic force microscopy with piezoelectric cantilevers

This article summarizes improvements to the speed, simplicity and versatility of tapping mode atomic force microscopy (AFM). Improvements are enabled by a piezoelectric microcantilever with a sharp silicon tip and a thin, low-stress zinc oxide (ZnO) film to both actuate and sense deflection. First, we demonstrate self-sensing tapping mode without laser detection. Similar previous work has been limited by unoptimized probe tips, cantilever thicknesses, and stress in the piezoelectric films. Tests indicate self-sensing amplitude resolution is as good or better than optical detection, with double the sensitivity, using the same type of cantilever. Second, we demonstrate self-oscillating tapping mode AFM. The cantilever's integrated piezoelectric film serves as the frequency-determining component of an oscillator circuit. The circuit oscillates the cantilever near its resonant frequency by applying positive feedback to the film. We present images and force-distance curves using both self-sensing and self-oscillating techniques. Finally, high-speed tapping mode imaging in liquid, where electric components of the cantilever require insulation, is demonstrated. Three cantilever coating schemes are tested. The insulated microactuator is used to simultaneously vibrate and actuate the cantilever over topographical features. Preliminary images in water and saline are presented, including one taken at 75.5 μm/s—a threefold improvement in bandwidth versus conventional piezotube actuators.

Non-linear viscoelastic models predict fingertip pulp force-displacement characteristics during voluntary tapping

We evaluated whether lumped-parameter non-linear viscoelastic models of human fingertip tissue can describe fingertip force-displacement characteristics during a range of rapid, dynamic tapping tasks. Eight human subjects tapped with their index finger on the surface of a rigid load cell while an optical system tracked fingertip position using an infra-red LED attached to the fingernail. Four different tapping conditions were tested: normal and high-speed taps with a relaxed hand, and normal and high-speed taps with the other fingers co-contracted. A non-linear viscoelastic model comprised of an instantaneous stiffness function and viscous relaxation function was capable of predicting fingertip tissue force response due to measured pulp compression under these four different loading conditions. The model could successfully reconstruct very rapid (less than 5 ms) force transients, and forces occurring over time periods greater than 100 ms, with errors of 10%. Model parameters varied by less than 20% over the four conditions, despite almost 3-fold differences in average forces and 38% differences in fingertip velocities. Energy dissipation by the fingertip averaged 81%, and varied little (<3%) across conditions, despite a 1. 5-fold range of energy input. The ability of a lumped-parameter model to describe fingertip force-displacement characteristics during a range of conditions contributes both to understanding the transmission of force through the fingertip to the musculoskeletal system and to predicting the stimulation of mechano-receptors located within the fingertip.

Effects of Synchronizing Errors on Cutting Performance in the Ultra-High-Speed Tapping

Synchronizing errors between the spindle motor and the z-axis motor directly influences the cutting characteristics in tapping, because the tapping process is accomplished by synchronizing the movement of the z-axis with the revolutionary spindle motion. The excessive synchronizing error can cause tap breakage due to the abrupt increase of cutting torque or damage the thread accuracy by overcutting the already cut threads. This paper describes the effects of the synchronizing errors on the cutting performance in the ultra high-speed tapping and presents a minimum level of synchronizing errors necessary to maintain the quality of the cut thread.

High-speed tapping mode imaging with active Q control for atomic force microscopy

The speed of tapping mode imaging with the atomic force microscope (AFM) has been increased by over an order of magnitude. The enhanced operation is achieved by (1) increasing the instrument’s mechanical bandwidth and (2) actively controlling the cantilever’s dynamics. The instrument’s mechanical bandwidth is increased by an order of magnitude by replacing the piezotube z-axis actuator with an integrated zinc oxide (ZnO) piezoelectric cantilever. The cantilever’s dynamics are optimized for high-speed operation by actively damping the quality factor (Q) of the cantilever. Active damping allows the amplitude of the oscillating cantilever to respond to topography changes more quickly. With these two advancements, 80μm×80 μm high-speed tapping mode images have been obtained with a scan frequency of 15 Hz. This corresponds to a tip velocity of 2.4 mm/s.