Mill Performance Research Articles

Performance of Multilayer Coated and Cryo-Treated Uncoated Tools in Machining of AISI H13 Tool Steel—Part 1: Tungsten Carbide End Mills

This paper focused on the performance of tungsten carbide end mills in machining of AISI H13 hot work tool steel under dry and wet conditions. The tool performance was evaluated in terms of resultant cutting force (Fc), average surface roughness (Ra) and tool life. In the milling tests, four categories of end mills were used: untreated (U), cryo-treated (CT), cryo-treated and tempered uncoated (CTT) and TiAlN/TiN multilayer coated (MLC). The tests were performed at four cutting speeds (80, 100, 120, 140 m/min), three feeds (0.08, 0.12, 0.16 mm/rev) and a depth of cut (2 mm). The test results showed that the lowest values of Fc and Ra were obtained with the use of MLC end mills. However, the cryogenic treatment was also effective on decreasing Fc and Ra. In addition, while the CTT end mills provided a slight improvement in tool life under dry conditions, they showed a remarkable improvement of 126.1% in comparison with the untreated ones under wet conditions. Although the CTT end mills exhibited a superior performance to U and CT ones, the MLC end mills were much more resistant to abrasive wear. This study is organized into two parts (WC-Co and HSS) to observe the effects of deep cryogenic treatment on performance of two different tool materials and to compare cryo-treated end mills with multilayer coated ones. This part is related to the cryogenic treatment of tungsten carbide end mills, whereas part two is regarding cryo-treated HSS end mills.

Role of microstructural factor in wear resistance and cutting performance of high-speed steel end mills

The present paper describes the wear of high-speed steel (HSS) end mills with special emphasis on the influence of microstructural features, primarily the spatial distribution of eutectic carbides, on wear resistance. Hence, the wear resistance and performance of three HSSs of the same chemical composition but manufactured in three different ways, i.e. gravity casting, vacuum casting and a conventional metallurgical route, were compared. It was shown that the character of eutectic carbide spatial distribution in the HSS plays a major role in its wear performance, and, at the same hardness, it is independent of bending strength and impact toughness. For the studied range of eutectic carbide spatial distributions, tool life could differ up to 65 %. At both cutting speeds, 26 m/min and 40 m/min, the lowest wear resistance was determined for the end mills manufactured from the wrought HSS with uniformly distributed single particles of the dispersed eutectic carbides, and hence significantly higher values of bending strength and impact toughness. In contrast, the end mills manufactured from the as-cast material with coarser eutectic carbide networks along the primary matrix grain boundaries, and therefore worse mechanical properties exhibited the best wear resistance to abrasive and oxidational wear.

Effects of oblong-hole screen and round-hole screen on the performance of hammer mill

Hammer mills are widely used for grinding grain products. Screens are one of the important machine components that affect the performance of hammer mills. Generally, round-hole screens are used in hammer mills. In this study, the effects of oblong- and round-hole screens on hammer mill performance were investigated. The results showed that the mean geometric diameter, geometric standard deviation, specific surface area grinding capacity and specific energy consumption varied with the screen type, screen hole size and hammer tip speed. The particle size distribution with the oblong-hole screen was more stable, and its grinding capacity (1.481 t/h) was higher than that of the round-hole screen (1.220 t/h). The specific energy consumption of the oblong-hole screen was lower than that of the round-hole screen. The lowest specific energy consumption (2.805 kWh/t) was measured at a hammer tip speed of 60 m/s for the oblong-hole screen with a hole size of 19.8 × 2.5 mm.

Wear resistance and cutting performance of high-speed steel ball nose end mills related to the initial state of tool surface

The wear resistance and cutting performance of uncoated and coated high-speed steel ball nose end mills were investigated. A fine-scale multi-component B–C–N diffusion coating was produced on AISI M35 steel substrate at 580 °C for 1 h. The surface and the cross-sections of the samples were subjected to detailed characterisation focusing on a surface condition of the uncoated and coated tools. It was shown that after grinding operation certain surface defects are observed in the steel matrix as well as in the exposed carbides in the case of the uncoated tool. In contrast, the microstructure of the surface of the coated tool appeared to be more uniform and without any visual surface defects. In general, the results established that there are two aspects to the wear behaviour of the coating, its main ability to resist plastic deformation during abrasive wear, which was in line with the results of the nanoindentation test, and secondly to recovering the surface defects of the ground surface thus enhancing the surface integrity. As a consequence, the lifetime of the coated tool was 2.5 times greater.

Nature instigated Grey wolf algorithm for parametric optimization during machining (Milling) of polymer nanocomposites

The new era of engineering society focuses on the utilization of the potential advantage of carbon nanomaterials. The machinability facets of nanocarbon materials are passing through an initial stage. This article emphasizes the machinability evaluation and optimization of Milling performances, namely Surface roughness (Ra), Cutting force (Fc), and Material removal rate (MRR) using a recently developed Grey wolf optimization algorithm (GWOA). The Taguchi theory-based L27 orthogonal array (OA) was employed for the Machining (Milling) of polymer nanocomposites reinforced by Multiwall carbon nanotube (MWCNT). The second-order polynomial equation was intended for the analysis of the model. These mathematical models were used as a fitness function in the GWOA to predict machining performances. The ANOVA outcomes efficiently explore the impact of machine parameters on Milling characteristics. The optimal combination for lower surface roughness value is 1.5 MWCNT wt.%, 1500 rpm of spindle speed, 50 mm/min of feed rate, and 3 mm depth of cut. For lower cutting force, 1.0 wt.%, 1500 rpm, 90 mm/min feed rate and 1 mm depth of cut and the maximize MRR was acquired at 0.5 wt.%, 500 rpm, 150 mm/min feed rate and 3 mm depth of cut. The deviation of the predicted value from the experimental value of Ra, Fc, and MRR are found as 2.5, 6.5 and 5.9%, respectively. The convergence plot of all Milling characteristics suggests the application potential of the GWO algorithm for quality improvement in a manufacturing environment.

Determining Optimum Productivity of a Ball Drum Mill When Milling Brown Coals

Ball drum mills (BDM) are one of the main types of coal-grinding equipment in Russia. A significant drawback of BDM is high power consumption (a significant part of the TPP’s own needs). With a huge scale of production, reducing these costs even by a few percent gives a significant economic effect. The problem of minimizing the specific energy consumption for grinding and transporting Azean coal in an ShK-32 ball drum mill is considered. For moist brown coals, the efficiency of grinding and transport of coal dust is usually achieved in the mode of equality of the grinding and drying capacities of the mill. The implementation of this regime is a necessary but insufficient condition. A system of equations is obtained that describe the processes of grinding and transport of coal dust. The analysis of the equations shows that the specific energy consumption for grinding is inversely proportional to the air consumption, and the specific costs for the transport of the dust and gas flow are proportional to the square of the air consumption. This fact ensures the presence of a minimum specific energy consumption for pulverization. A comparison is made of the estimated consumption of specific energy for pulverizing in an ShK-32 ball drum mill with experimental results obtained during routine commissioning tests of the dust system of the Irkutsk CHPP-9. The average deviations of the calculation results from the experimental data are in the range of ±10%. Comparison of the calculated and experimental data indicates that the mathematical model of the mode of equality of the grinding and drying capacities of the BDM adequately describes the processes occurring during the preparation of fuel for combustion. It is shown that an increase in the efficiency of dust systems with BDM can be achieved only after a detailed study of the transport of coal dust. In the proposed method for determining the optimal performance of the ball mill, the effect of the polydispersity of coal dust on the aerodynamic resistance of the mill is consistently taken into account.

Milling Performance of Fluorinated Surfactants-Based Coating Tools in Processing Particleboard

To investigate the cutting performance of tools with fluorinated surfactant-based coatings, the milling performance of melamine-coated particleboard was characterized by means of the cutting force, tool wear and surface quality. A scanning electron microscope (SEM) and a three-dimensional super field microscope were used to observe the morphologies of coated and uncoated tool wear and machined surfaces. The results showed that (1) the surface wettability of the coated tool is lower than that of the uncoated tool; (2) the main wear mechanisms for tools with a fluorinated surfactant-based coating are abrasive wear and microchipping. The fluorinated surfactant-based coating acts as a solid lubricant, which can obviously reduce adhesion wear; (3) the surface roughness obtained by machining using coated tools is much smaller than that found for uncoated tools.

Roller milling performance of dry yellow split peas: Mill stream composition and functional characteristics

AbstractBackground and objectivesYellow split pea flour is a growing trend in the food sector as a functional ingredient. The aim here was to analyze the milling performance and composition of dry yellow split peas on a pilot roller mill and determine whether there were differences in pea cotyledon fractionation.FindingsDry yellow split peas were efficiently roller milled with complete recovery in nine mill streams; over half of the flour was produced on two. All streams except 4th Midds had a high proportion of particles <125 μm, starch damage levels similar to wheat flour, and similar protein, pasting, and solvent retention capacities. The 4th Midds represented only 1% of the total flour.ConclusionThis study shows that dry yellow split peas can be efficiently milled on a wheat roller mill to a small particle size. In contrast to wheat, split peas are fairly uniform in composition with modest differences among mill streams. Flour recovery was essentially 99%.Significance and noveltyTo serve as a food ingredient, dry split peas must first be reduced to small particles. Roller milling, though not a traditional method, was shown to be highly efficient. Unlike wheat, pea flour streams were rather similar in composition and functionality.

Study of new solid end mill for side milling of Ti-6Al-4V with improved cooling efficiency

In the present work, machining performance of a new solid carbide end mill has been investigated during side milling of Ti-6Al-4V. It is observed that adding cooling grooves on the clearance side of the cutting tool improves the tool performance by decreasing tool wear. Tool temperature measurements by infrared camera showed that these grooves decreased the tool temperature during the machining process. In order to understand the mechanisms behind this improvement, simulations of the coolant flow around the tool with and without these grooves are performed. Modelling and simulation results showed that these cooling grooves lead to an increase in the velocity of fluid at the head of the tool, which results in more efficient cooling and consequently the temperature along the cutting edge is decreased.

Review on vertical roller mill in cement industry & its performance parameters

India is the world's second largest producer of cement and produces more than 8 per cent of global capacity. Due to the rapidly growing demand in various sectors such as defense, housing, commercial and industrial construction, government initiative such as smart cities & PMAY, cement production in India is expected to touch 550–600 million tones per annum (MTPA) by the end of year 2025. With recent growth and success journey there is also a threat approaching to cement industry that its input cost is increasing. Power cost, fuel cost, raw material cost have doubled up in recent years whereas cement price has not hiked in that fashion. Also 40% of the cement production costs are energy costs out of which more than 60% of the total electricity is used in grinding circuits. In order to survive and sustain in the market they need to increase their profitability which can only be achieved by increasing productivity and reducing power consumption. High productivity and low power costs can be achieved by increasing output, lowering breakdowns and optimizing the energy consuming grinding process. The objective of the study, is to draw attention to the need of Cement grinding process optimization to minimize power consumption and achieve higher productivity. In the study the advantages of vertical roller mill are discussed over ball mills. VRM construction, its process and parameters which affects the performance and productivity of vertical roller mill are discussed. Also the consequences of variations in parameter explained. With proper optimization of these parameters, the productivity of vertical roller mill can be improved and performance stability can be achieved by addressing root causes.. This study can benefit the organizations using VRM and are not able to utilize its full productivity due to some bottlenecks or constraints.

Modelling of the High-Energy Ball Milling Process

In this paper, the milling parameters of high energy ball mill (Fritsch Pulverisette 7) like vial geometry, number and size of balls and speed of the mill were modelled and discussed. Simulations through discrete element method (DEM) provide correlation between the milling parameters. A mathematical model is used to improve and develop this process. The results show that the loss of powder mass can remarkably improve the performance of milling. The balls made of stainless-steel have a positive effect on the milling efficiency. The simulation shows that the high ball milling velocities can contribute to faster particle size reduction.

Optimizing grinding mill performance using extremum seeking control

Optimizing grinding mill performance using extremum seeking control

The researches concern the influence of the helix angle on the composite machining process

Magnesium oxide-reinforced wood fiber composites (MgO/WF) are a new type of multifunctional material, which can be used in different occasions, such as shopping malls, hotels, and residential buildings. Referring to the relevant literature, there is no research on the milling performance of MgO/WF. In order to better understand the relevant knowledge of the processability of MgO/WF, three cutters with different helix angles were used in this experiment to carry out the cutting of MgO/WF, and the variation trend of its cutting force, tool wear, and surface roughness was measured. The results are as follows: First, under the same cutting parameters, the resultant force decreases with the increase of helix angle. Second, with the increase of helix angle, the tool wear was slightly improved. Third, the surface roughness (Ra) showed an increasing trend with the decrease of helix angle. In the end, when milling MgO/WF, better machined surface quality and less tool wear can be obtained by selecting the tool with larger helix angle.

Determination of the ball mills performance, taking into account the particle size of the finished product

The article discusses the issue of determining the newly formed specific surface of the cement clinker taking into account the lateral surface of the seal area. When developing this technique, the assumption that the newly formed particles have a shape close to spherical, has been made. The obtained ratio determines the work that considers the formation of thecement clinker material new surface, depending on the size of the original and newly formed material. An arithmetic expression is given, defined as the minimum amount of energy that must be introduced into the deformation zone for the destruction of a cement clinker particle to occur. The presented technique is specified taking into account the fact that defects are introduced into the crushed material particle. Taking into account the fact that the grinding ball makes an impact in one cycle of its movement, the value of the newly formed surface of the material in the ball mill is determined in one hour of its operation.

锤片式粉碎机参数优化与试验研究

Low productivity and high electricity consumption are considered problems of the hammer mill, which is widely used in current feed production. In this paper, the mechanical properties of corn grain ground by a hammer mill were analysed, and the key factors affecting the performance of the hammer mill were determined. The single-factor experiment and three-factor, three-level quadratic regression orthogonal experiment were carried out with the spindle speed, corn grain moisture content and number of hammers as experimental factors and the productivity and electricity consumption per ton as evaluation indexes. The results showed that the order of influence on the productivity was spindle speed > corn grain moisture content > number of hammers and that the order of influence on the electricity consumption per ton was corn grain moisture content > spindle speed > number of hammers. The parameters were optimized based on the response surface method with the following results: the spindle speed was 4306 r/min, the corn grain moisture content was 10%, and the number of hammers was 24. The validation experiment was carried out with the optimal parameters’ combination. The productivity and electricity consumption per ton were 988.12 kg/h and 5.37 kW·h/t, respectively, which were consistent with the predicted results of the model.

Effect of cooling strategies on performance and mechanism of helical milling of CFRP/Ti-6Al-4 V stacks

Hole-making for Carbon Fiber Reinforced Plastics (CFRP)/Ti-6Al-4 V stacks is crucial for the assembling strength of aircraft structure parts. This work carried out experimental work for helical milling (HM) of the stacks with sustainable cooling/lubrication (dry, MQL and cryogenic) conditions. Cutting forces and temperatures at the CFRP layer, Ti-6Al-4 V layer and the interface of stacks were obtained by a developed measuring system. The temperatures in CFRP machining at cryogenic condition varied from −167 °C to −94 °C, which were much lower than those at dry and MQL conditions. The maximum temperature near the interface of stacks for the ninth hole was higher than 240 °C due to heat conduction from Ti-6Al-4 V layer. The hole quality, hole diameter and tool wear mechanism at different cooling/lubrication conditions were presented and discussed. MQL condition generated mainly extrusion fracture for the fibers, due to the reduced friction effect compared with dry condition. MQL was helpful to reduce the feed mark at the hole surface of Ti-6Al-4 V alloy. The flank wear of cutting edge at MQL condition was better than those at dry and cryogenic conditions. Cryogenic cooling contributed to better CFRP surface with smaller delamination and hole entrance damage due to the increased resin strength and fiber brittleness. The damage near the entrance of CFRP were analyzed by the contact state of cutting edges and fibers. Additionally, hole diameters near the exit of CFPR layer were larger than other test positions. This work provided feasible processes for improving hole quality and tool life in hole-making of CFRP/Ti-6Al-4 V stacks.

Performance of stereolithography and milling in fabricating monolithic zirconia crowns with different finish line designs

Subtractive manufacturing has become the dominant method in fabricating zirconia dental restorations while additive manufacturing is emerging as a potential alternative. The aim of this in vitro study was to investigate the performance of stereolithography (SLA) and milling in fabricating monolithic zirconia crowns with different finish line designs. Full-contour crowns with three finish lines (chamfer, rounded shoulder, knife-edge) were designed and fabricated by SLA and milling. Fabrication accuracy was accessed by 3D deviation analysis and margin quality was characterized under microscopes. The obtained root mean square value was significantly influenced by finish line design (P < 0.05) but not by fabrication method (P＞0.05). However, the color-difference map showed crowns fabricated by SLA and milling had different error distribution in external surfaces. SLA-printed crowns exhibited margins of rounded line angle and without small flaws, although large chippings were found in knife-edged crowns. In milling group, crowns showed margins of sharp line angle and with separate chippings. More and larger margin chippings were found in knife-edged crowns by milling. The results indicate that SLA and milling can fabricate monolithic zirconia crowns of comparable accuracy and knife-edged crowns are prone to large margin chippings by either of the two manufacturing methods.

Conventional milling into CNC machine tool remanufacturing: Sustainability modeling

Aims: Sustainability modeling for conventional milling into CNC machine tool remanufacturing-upgrading. Study design: Remanufacturing-upgrading of conventional milling into CNC machine in its mechanical part, it is merely traditional remanufacturing process of conventional milling where gearbox can be eliminated due to use of motorized axes. Lead screws can be replaced with motorized ball screws. Heavy parts of machine bed such column, knee and saddle are reused. A group of criteria are selected to conduct comprehensive sustainability assessment of remanufacturing-upgrading process include: 1. Remanufacturing cost: It is the cost of milling remanufacturing into CNC machine. 2. Remanufacturing time: It is the duration of time required for milling remanufacturing into CNC machine. 3. Accuracy: It is an expected technical performance of remanufactured milling into CNC machine. 4. Reliability: It is an expected technical performance of remanufactured milling into CNC machine. 5. Processing efficiency: It is the man-hour based productivity efficiency of a remanufactured milling into CNC machine. 6. Processing range: It is the flexibility of remanufactured machine tool into CNC machine. 7. Ergonomics: It is the interaction among operator, remanufactured milling into CNC machine tool and other system unit through the cell of manufacturing. Conventional machine tool into CNC machine remanufacturing-upgrading experience is used to project the suitable literature comparatively to construct sustainability assessment model. Sustainability assessment models in field of remanufacturing-upgrading are reviewed and modified to accommodate new changes that accompany the current case study.&#x0D; Place and Duration of Study: Middle Technical University, Institute of Technology-Baghdad, Mechanical Techniques Department, between February 2020 and July 2020. Methodology: Literature survey in area of remanufacturing assessment and remanufacturing sustainability assessment. Comparative literature based assessment application. Classification of literature sample. Re-representation of discussions and conclusions. Graphical representation of results. Isolation of criteria. Case study definition. Weighting of criteria. Triangular fuzzication of criteria. Weighting of satisfaction. Global weights calculation. Sustainability Index weight calculation. Results: Summation of sub-sustainabilities index weights is within limit of consistency. Environmental sustainability literature is predominated to be followed by economic and technical sustainbilities literature. Conclusion: Economic, environmental and social sub-sustainabilities are of good performances and directed toward sustainability. Social and management sustainability are interlinked and require more studies to be directed toward sustainability.

Oil mist concentration and machining characteristics of SiO2 water-based nano-lubricants in electrostatic minimum quantity lubrication-EMQL milling

• SiO 2 nano-lubricant droplets presented better chargeability and more likely to be affected by electrostatic force to adsorb and deposit. • SiO 2 nano-lubricant showed higher penetrability after charging compared with vegetable oil. • The adsorption quantities of the charged SiO2 nano-lubricant droplets were larger than those of the charged vegetable oil droplets. • SiO 2 nano-lubricant EMQL showed much lower oil mist concentration and alternative machining performance of traditional oil-based MQL. Minimum quantity lubrication (MQL) machining is an advanced near dry cutting technology in modern machining field. However, the cutting oil mist produced during the process of oil-based MQL affected the ambient air quality and endangered the health of employees. To avoid this drawback, a novel lubrication/cooling method called electrostatic minimum quantity lubrication (EMQL) which used SiO 2 water-based nano-lubricant as cutting fluid was proposed. The charge mass ratio, surface tension and contact angle of SiO 2 water-based nano-lubricant and vegetable oil with different charging voltages were compared, and the penetration performance of these two lubricants was analysed using capillary dynamics equation. The adsorption and deposition properties of oil mist produced by different lubrication methods were investigated, and revealed the adsorption and deposition mechanisms of the charged droplet. The influences of the charging voltage, flow rate, air pressure, spindle speed and cutting depth on PM10 and PM2.5 concentrations under different lubrication conditions were revealed. Finally, the milling performance of SiO 2 water-based nano-lubricant EMQL of stainless steels was evaluated comparatively. The results showed that SiO 2 water-based nano-lubricant presented better chargeability compared with vegetable oil, and thus displayed stronger penetrability, adsorption and deposition capacity. SiO 2 water-based nano-lubricant EMQL with -4 kV showed the lowest oil mist concentration and similar machining performances compared with the vegetable oil MQL, and the concentration values were close to the standards set by the National Institute for Occupational Safety and Health (NOISH). The charged SiO 2 water-based nano-lubricant droplets with excellent charging performance presented better adsorbability and penetrability, so that the charged droplets were prone to be electrostatic adsorbed in the machine tool and penetrated into the cutting region, which reduced the oil mist content in the machining environment and presented alternative cutting performance.

Effects of Blade Parameters on the Flow Field and Classification Performance of the Vertical Roller Mill via Numerical Investigations

The vertical roller mill is an important crushing and grading screening device widely used in many industries. Its classification efficiency and the pressure difference determine the entire producing capacity and power consumption, respectively, which makes them the two key indicators describing the mill performance. Based on the DPM (Discrete Phase Model) and continuous phase coupling model, the flow field characteristics in the vertical roller mill including the velocity and pressure fields and the discrete phase distributions had been analyzed. The influence of blade parameters like the shape, number, and rotating speed on the flow field and classification performance had also been comprehensively explored. The numerical simulations showed that there are vortices in many zones in the mill and the blades are of great significance to the mill performance. The blade IV not only results in high classification efficiency but also reduces effectively the pressure difference in the separator and also the whole machine. The conclusions of the flow field analysis and the blade effects on the classification efficiency and the pressure difference could guide designing and optimizing the equipment structure and the milling process, which is of great importance to obtain better overall performance of the vertical roller mill.