Minimizing the Negative Effects of Coolant Channels on the Torsional and Torsional-Axial Stiffness of Drills

Coolant channels allow internal coolant delivery to the cutting region and significantly improve drilling, but these channels also reduce the torsional and torsional-axial stiffness of the drills. Such a reduction in stiffness can degrade the quality of the drilled holes. The evacuation of cutting chips and the delivery of the cutting fluid put strict geometrical restrictions on the cross-section design of the drill. This necessitates careful selection and optimization of features such as the geometry of the coolant channels. This paper presents a new method that uses Prandtl’s stress function to predict the torsional and torsional-axial stiffness values. Using this method drills with one central channel are compared to those with two eccentric coolant channels, which shows that with the same cross-section area, the reduction of axial and torsional-axial stiffness is notably smaller for the design with two eccentric channels compared to a single central channel. The stress function method is further used to select the appropriate location of the eccentric coolant channels to minimize the loss of torsional and torsional-axial stiffness. These results are verified by comparison to the results of three-dimensional finite element analyses.

Viability of Cryogenic Cooling to Reduce Processor Power Consumption

Through the application of cryogenic cooling via liquid nitrogen (LN2), the power consumption of a CPU was substantially reduced. Using a digitally controlled solenoid valve and an additively manufactured cold plate, the manual process of LN2 cooling was automated for precise control of cold plate temperature. The power consumption and frequency relationship of the processor was established across three different thermal solutions to determine the effect of temperature on this relationship. It was found that power consumption of the processor decreased at lower temperatures due to a reduction in current leakage and the core voltage necessary for stable operation. This culminated in a reduction of up to 10.6% in processor power consumption for the automated solution and 20.8% for the manual LN2 solution when compared to the air cooled baseline. Due to the binary nature of the solenoid valve, flow rate was tuned via an in-line needle valve to increase thermal stability. It was found that for lower flow rates, approximately 5.0 g/s, temperatures oscillated within a range of +/- 11.5°C while higher flow rates of 10 to 12 g/s generated amplitudes as small as +/-3.5°C. Additionally, several tests measured the rate of LN2 consumption and found that the automated solution used 230% to 280% more coolant than the manual thermal solution, implying there is room for improvement in the cold plate geometry, LN2 vapor exhaust design, and coolant delivery optimization.

The effect of high-speed dental handpiece coolant delivery and design on aerosol and droplet production

Objectives: High-speed dental instruments produce aerosol and droplets. The objective of this study was to evaluate aerosol and droplet production from a novel electric micromotor handpiece (without compressed air coolant) in real world clinical settings. Methods: 10-minute upper incisor crown preparations were performed in triplicate in an open-plan clinic with mechanical ventilation providing 3.45 air changes per hour. A 1:5 ratio electric micromotor handpiece which allows water coolant without compressed air (Ti-Max Z95L, NSK) was used at three speeds: 60,000 (60K), 120,000 (120K), and 200,000 (200K) revolutions per minute. Coolant solutions contained fluorescein sodium as a tracer (2.65 mmol L−1). High-speed air-turbine positive control, and negative control conditions were conducted. Aerosol production was evaluated at 3 locations (0.5 m, 1.5 m and 1.7 m) using: (1) an optical particle counter (OPC; 3016-IAQ, Lighthouse) to detect all aerosol; and (2) a liquid cyclone air sampler (BioSampler, SKC Ltd.) to detect aerosolised fluorescein, which was quantified by spectrofluorometric analysis. Settled droplets were detected by spectrofluorometric analysis of filter papers placed onto a rig across the open-plan clinic.Results: Local (within treatment bay) settled droplet contamination was elevated above negative control for all conditions, with no difference between conditions. Settled droplet contamination was not detected above negative controls outside the treatment bay for any condition. Aerosol detection at 1.5 m and 1.7 m, was only increased for the air-turbine positive control condition. At 0.5 m, aerosol levels were highly elevated for the air-turbine, minimally elevated for 200K and 120K, and not elevated for 60K. Conclusions: Electric micromotor handpieces which use water-jet coolant alone without compressed air, produce localised (within treatment bay) droplet contamination but are unlikely to produce aerosol contamination beyond the immediate treatment area (1.5 m), allowing them to be used safely in most open-plan clinic settings.

Perbedaan Distribusi Kekerasan Metode Minimum Quantity Lubrication (MQL) dan Metode Wet Machining Pada Material Al-Zn

This study aims to determine the influence of three different coolant delivery methods, namely dry machining, Minimum Quantity Lubrication (MQL), and wet machining. This is quantitative research with the use of experimental methods. Data were collected through observation. Data analysis techniques being used was descriptive statistics. In MQL methods, the use of coolant is minimized by mixing it with high-pressurized air. It is shown from the obtained data that the use of MQL methods is not as good as the wet machining. The hardness distribution of wet machining method is lower than the MQL. This was observed from the machining chips of the two methods. The chips from the MQL method were darker than the wet machining method. This finding showed that the heat generated from the MQL was higher than that of wet machining. The Al and Zn bonds in the MQL method is considered to be denser.Penelitian ini bertujuan untuk mengetahui seberapa besar pengaruh penggunaan metode pemberian coolant yang berbeda, 3 metode yang digunakan adalah metode dry machining, Minimum Quantity Lubrication (MQL), dan wet machining. Penelitian ini termasuk jenis penelitian kuantitatif dan menggunakan metode eksperimen. Untuk teknik pengumpulan data menggunakan metode observasi dan teknik analisis data menggunakan teknik analisis statistik deskriptif. Metode MQL merupakan metode yang digunakan untuk meminimalisir penggunaan coolant dengan mencampurkannya dengan udara bertekanan tinggi. Data yang didapat menunjukkan bahwa penggunaan metode MQL belum sebaik penggunaan metode wet machining. Distribusi kekerasan metode wet machining lebih rendah daripada MQL. Hal tersebut dapat terlihat dari geram yang dihasilkan oleh kedua penggunaan metode tersebut, geram yang dihasilkan dari metode MQL lebih gelap daripada metode wet machining. Hal tersebut menunjukkan bahwa, panas yang dihasilkan dari metode MQL lebih tinggi daripada panas yang dihasilkan dari metode wet machining panas tersebut mempengaruhi ikatan Al dan Zn pada metode MQL menjadi lebih rapat.

Investigation of Metal Air-Cooling Process as An Element of Thermal Processing

<p>Background: Nowadays on metal tempering and annealing its air cooling (AC) is realized inside furnace with forced coolant delivery. Scientific tools lack for metal AC study and design is substantiated. The aim of this work is to investigate technological and design furnace parameters influence on metal AC duration, as well as disclosure of metal AC heat engineering regularities. Materials and method: For study mathematical model of metal AC is used. It bases on solving the differential non-stationary heat conductivity equation in one-dimensional form for cylindrical ingots and lining. Results: For three lining design types and different technological parameters operation acceleration possibility due to lining design change was studied. It is found that with ceramic fibers on walls and roof acceleration is 31-45% and with all lining made of ceramic fiber it is 44-52% as compared with fireclay brick lining. For a furnace with hearth of fireclay bricks and ceramic fiber on the walls and roof, convective component varies from 10 to 30%; for lining completely consisting of ceramic fibers it is 10 - 25%. When using fireclay brick lining parts their inner temperature is higher than for ceramic fiber up to 50 °C. Conclusions: Significant furnace lining materials type influence on metal AC intensity is proved. Heat removal mechanism on metal AC in furnace is disclosed, by establishing heat proportion directly removed from metal by convection. It is found that radiant heat transfer between metal and fireclay brick part of lining goes less intensively than with ceramic fiber part. </p>

Evaluation of Performance of Various Coolant Grades When Turning Ti-6Al-4V Alloy With Uncoated Carbide Tools Under High-Pressure Coolant Supplies

This work presents the evaluation of three commercially available coolant grades (dicyclohexylamine-based coolant, a triethanolamine-based coolant, and an ester-based coolant) when machining Ti-6Al-4V alloy with high-pressure coolant delivery. The evaluations were based on tool life, tool failure modes, surface integrity, and chip formation. The dicyclohexylamine-based coolant was the more effective coolant when machining at the highest pressure of 20.3 MPa due to its stability at elevated temperature, whereas the triethanolamine-based coolant performed effectively at a pressure of 11 MPa due to its low surface tension properties. Deterioration of the ester-based coolant was found in almost all coolant pressures due to its low resistance to oxidation. Surfaces generated when machining with all coolants grades were generally acceptable with negligible physical damage.