Ultra-high Speed Grinding Research Articles

Sustainable lubrication: low molecular weight PTFE micro-particles as extreme pressure additives for heavy duty grease applications

Purpose The purpose of this paper is to formulate heavy-duty lithium complex grease using low molecular weight poly tetra fluoro ethylene (PTFE) micro-particles as extreme pressure (EP) additive manufactured by E-beam scissoring and ultra-high speed grinding process of pre-sintered PTFE scrap. Design/methodology/approach Lithium complex grease is formulated with PTFE micro-particles, and optimum treat rate was studied by standard bench tests by ASTM D 2266 and IP-239 for tribological properties and compared with commercially available Molybdenum Di sulphide (Moly)-based lithium complex grease. The performance of the grease was further evaluated by a cyclic load test at varying speeds and loads to simulate the operational field conditions. Findings The lithium complex PTFE grease was manufactured using PTFE micro-particles as EP additive. The PTFE micro-particles dispersed in the lithium complex grease significantly improve the anti-wear performance and load bearing properties. Further, when the product was tested under a cyclic load conditions on standard tribological bench test against commercially available Moly lithium complex grease, shows stable anti-wear properties and reduced coefficient of friction. Originality/value The low molecular weight PTFE micro-particles, manufactured in the in-house electron beam (E-beam) and ultra-high speed micronizer facility from a pre-sintered PTFE scrap has been used as EP additive for grease applications for the first time. The results on the cyclic load tests indicate significant performance improvement in retaining the anti-wear and friction properties. Thus, value addition is done in formulating superior performance grease and evaluating under cyclic load conditions similar to field operating conditions and also in creating value added additives by converting the pre-sintered PTFE scarp which is environmental hazard due to poor biodegradability, creating a cyclic economy and a sustainable concept.

Flow field and cooling capacity in workpiece-tool contact zone during ultra-high speed grinding

Ultra-high speed grinding (UHSG) is a promising machining technology because it can reduce grinding force and greatly increase machining efficiency. However, a mass heat produced in the workpiece-tool contact (WTC) zone risks burning the machined surface during UHSG. Therefore, it is important to ensure timely cooling. The paper studies the flow field of the coolant and cooling capacity of WTC zone under different grinding speeds and coolant velocities by both three-dimensional (3D) finite element (FE) simulation and experiments. Results show that coolant velocity rapidly decreases after a slight initial increase with increasing the distance from the nozzle and little coolant could enter the WTC zone to cool down, which is responsible for the temperature rise in the WTC zone in UHSG. As grinding speed increases, a higher coolant velocity is needed for breaking the barrier of airflow layer to cooling. The critical coolant velocity to break the barrier and enter the WTC zone is obtained by theoretical calculation and experiment. The critical coolant velocity increases with the grinding speed, the coolant velocity needed is 19.2 m/s at the grinding speed of 120 m/s, and it rises to 30 m/s at the grinding speed of 160 m/s. This study could provide a guide to improve the cooling performance in UHSG, which is of great significance to a high-quality surface finish by UHSG.

Investigation of the adhesion properties of the surfaces of the carbide plate processed by ultra high speed grinding

Investigation of the adhesion properties of the surfaces of the carbide plate processed by ultra high speed grinding

Experimental investigation on the efficiency of the wrap around nozzle as coolant delivering system for ultra high speed grinding

In recent years, attention has been given to develop efficient and optimised cooling systems for grinding to reduce the process cost and to limit the health hazards of operators. In ultra-high speed grinding this issue is particularly complex because the thick air barrier rotating with the grinding wheel prevents the fluid from reaching the grinding zone. In this paper, results of experiments conducted to characterise the application of the wrap around nozzle (WRN) to the ultra high speed plunge surface grinding are presented. Experiments were conducted in a peripheral wheel speed ranging from 50 to 380 m/s and the effects of the nozzle position. This efficiency was compared to a cooling system composed of double air scrapper and a conventional jet type system. Experiments showed that the WRN has higher and much stable cooling efficiency in the ultra-high-speed range of the grinding wheel.

Experimental investigation on the efficiency of the wrap around nozzle as coolant delivering system for ultra high speed grinding

Experimental investigation on the efficiency of the wrap around nozzle as coolant delivering system for ultra high speed grinding

Surface Quality after High-Speed Grinding

In producing machine parts from the hard materials used today in the military–industrial complex, attainment of the required precision is difficult and sometimes unfeasible unless finishing operations are employed. In general, finishing operations are expensive and slow and they require highly skilled workers and specialized equipment. That considerably increases the production costs. Finishing operations can only be eliminated if the cutters used in the prior machining processes ensure satisfactory surface quality. However, that is not always the case, on account of bluntness of the tool. In the present work, attention focuses on the precision that may be attained in machining key components made of hard materials when using high-quality hard-alloy cutters produced by ultrahigh-speed grinding.

Research on the high quality replacement carbide plates operability with Al-Si-N hardening coating

Quality requirements for the manufacturing parts made of hard-to-machine materials with cutting tools are quite high. At the same time, modern carbide cutting tools are not always able to maintain working capacity throughout the entire mechanical operation, providing these requirements. The article considers test results of replaceable carbide plates during finish processing of a heat resistant alloy. Carbide plates were sharpened with ultra high speed grinding, and then hardened with Al-Si-N coating, which made it possible to obtain tool blade sharpness ρ = 3...5 μm and to achieve resistance several times higher compared to a similar tool.

New Development of Supersonic Surface Grinding Machine Tool with a Linear-Motor-Driven Table System

Ultra-high speed grinding (UHSG) is a significant and promising machining technology in grinding hard-to-cut materials. To find out the aerodynamics of the grinding wheel body when the airflow field has subsonic, transonic, and supersonic speed characteristics and clarify the corresponding influence on the grinding mechanism, the study is conducted to develop a supersonic grinding machine tool that is capable of being operated at extreme wheel speed up to 450 m/s and meanwhile accompanying with high grinding capability. In accordance with the main design objectives, a high performance grinding motorized spindle with maximum rotational speed 36000r/min and maximum power 28kW is developed. The linear motor feed driven system is also exploited to satisfy the requirement of maximum reciprocating speed up to 2m/s. Following plenty of specific design and performance analysis works, a prototype of supersonic grinding machine tool is finally developed. In the end, this paper also puts forward a number of further studies and prospective for the research activities on basis of the developed grinder.

Effects of Grinding Time on Rheological, Textural and Physical Properties of Natural Peanut Butter Stored at Different Temperatures

AbstractThe effects of ultrahigh speed grinding process duration of 2–4 min and its storage temperature on rheological, textural and physical properties of natural peanut butter produced from peanuts of Virginia and Spanish varieties were investigated. Both types of peanut butter samples exhibited food suspension with multimodal particle size distribution, fitted adequately to the Casson model and demonstrated nonNewtonian shear‐thinning behavior with apparent yield stress. The storage (G′) and loss (G′′) modulus decreased as a function of grinding time and temperature. Grinding time and storage temperature gave significant effects on all the responses (P < 0.05) while peanut variety only has impact on the particle size distribution. Identical trends were observed for the natural peanut butter from both Virginia and Spanish peanut varieties.Practical ApplicationsProcessing and storage temperature are among factors influencing texture of food suspension such as butter and spreads. Our research investigated the effect of grinding time and storage temperature on rheological, textural and physical properties of natural peanut butter in the effort of producing optimum quality in terms of finest texture. The relationship between particle size distribution and textural properties is useful in the development of natural peanut butter with this study focusing on grinding effects as its processing and stability in terms of storage temperature.

CFRP grinding wheels for high speed and ultra-high speed grinding: A review of current technologies and research strategies

This paper primarily reviews the general condition of research on and applications of high speed and ultra-high speed grinding technology. Both technical requirements for grinding wheels used for high speed and ultra-high speed grinding, and existing problems with the current processes are pointed out. Specific to these problems, the discussion regarding high-performance lightweight grinding wheels with a carbon fiber reinforced plastic (CFRP) substrate focuses on three aspects, i.e., design and manufacture, experimental grinding research, and practical industrial applications. Based on the summary of existing research and the application status of the CFRP grinding wheel, existing deficiencies are qualitatively discussed. Focusing on the development of a lightweight CFRP grinding wheel for high speed and ultra-high speed grinding at the end of the paper, some key technical problems with CFRP substrate grinding wheels, such as controlled performance, controlled shape, and the grinding mechanism, are identified, along with further research strategies to resolve them.

Structural design of a carbon fiber-reinforced polymer wheel for ultra-high speed grinding

Ultra-high speed grinding (UHSG) is receiving considerable attention owing to its ability to achieve high machining accuracy and productivity. The materials and design of the grinding wheels play a significant role in this technology. Wheels with steel bodies are currently widely used, but have deficiencies such as a large mass loading imposing on the spindle, along with high power consumption, large stress and deformation, and limited practical grinding wheel speed. Wheel bodies made of carbon fiber-reinforced polymer (CFRP) show promise for use in UHSG because of the low density and high specific strength of this material. The main aim of this paper is to carry out a structural design of a CFRP grinding wheel for UHSG. Comparisons of stress and deformation, dynamic characteristics, thermal deformation, and power consumption between steel and CFRP wheel bodies reveal the superior performance characteristics of CFRP. The design of the laminate structure of the CFRP is then optimized, considering various laminate processes. The abrasive layers are designed with regard to the number and thickness of segments. Finally, a CFRP wheel for UHSG is developed based on the design proposal.

Development of a novel supersonic grinding machine tool

Ultra-high speed grinding (UHSG) is a significant and promising machining technology for grinding hard-to-cut materials. To study the aerodynamics of the grinding wheel body when the airflow field has subsonic, transonic, and supersonic speed characteristics and to clarify the corresponding influence on the grinding mechanism, this study is carried out to develop a supersonic grinding machine tool capable of high-speed operations at wheel speeds up to 450 m/s while also maintaining high grinding capability. In accordance with main design objectives, a high-performance grinding motorized spindle with a maximum rotational speed of 36,000 r/min and a maximum power of 28 kW is developed. A linear motor feed-driven system is also exploited to satisfy the requirement of maximum reciprocating speed up to 2 m/s. In particular, carbon fiber-reinforced plastic (CFRP) grinding wheel with ceramic-bond cubic boron nitride (CBN) abrasives is manufactured for the UHSG process. Furthermore, some analyses on the developed whole grinding machine tool are also conducted to verify and further improve the performance. Finally, following specific design and performance analysis, a prototype of supersonic grinding machine tool is finally developed.

Particle Size Distribution of Natural Peanut Butter and Its Dynamic Rheological Properties

This study compared the dynamic rheological properties of natural peanut butter with commercial peanut butter at 25°C. The natural peanut butter was produced using ultra-high speed grinding (˜20,000 rpm) at different grinding times (2–5 min) from peanuts of China and India. Multimodal particle size distribution was observed for all the samples. The linear viscoelastic region obtained from stress sweep test of the peanut butter produced at 2–3 min fell within the linear viscoelastic region of commercial peanut butter of 0.1–11 Pa. Longer grinding time (3.5–5 min) produced a shorter and lower linear viscoelastic region of 0.03–3 Pa. The storage modulus, G′ is an increasing function of particle size distribution. All peanut butter samples exhibited elastic properties.

Development of an ultra-high speed grinding motorised spindle

This paper describes the development of an ultra-high speed grinding motorised spindle specially designed for a project aiming to implement research on mechanism and process of the ultra-high speed grinding of hard-to-cut materials at a maximum wheel speed of 450 m/s. At such high speeds, the loss power caused by air resistance should be primarily focused on as it could even exceed the real cutting power. In this study, a theoretical analysis of loss power was firstly carried out to optimise and determine the spindle rotational speed and wheel diameter. Furthermore, based on the designed motorised spindle, further work was concentrated on estimating the dynamic performance of motorised spindle such as its natural properties and balancing characteristics with finite element method. As well, theses physical properties were experimentally measured for the developed spindle. The results showed that work on the development of the motorised spindle was valid and reliable.

Grinding characteristics of Asian originated peanuts (Arachishypogaea L.) and specific energy consumption during ultra-high speed grinding for natural peanut butter production

Roasted peanuts of China and India origin were ground in a commercial ultra-high speed grinder operated at 20,000rpm for 2.0–5.0min for natural peanut butter production. Grinding characteristics of both peanuts were evaluated in terms of specific energy consumption, Esc with respect to its grinding time and mean particle size. The Esc increased with grinding time with China peanuts having higher Esc than India peanuts. The specific energy consumption modeled to the size reduction ratio of China and India peanuts was predicted more accurately using a linear and exponential model respectively compared to the classical models by Bond, Rittinger and Kick. From the comparison of Bond’s working index, Wi, the ultra-high speed grinder is said to be more energy efficient than other comminutors in terms of its capability to produce finer particle size in shorter time than the rest.

Investigate on distribution and scatter of surface residual stress in ultra-high speed grinding

The purpose of this study is to investigate the residual stress induced by ultra-high-speed grinding of difficult-to-machine materials considering the thermomechanical coupling effect that is generated due to the friction between diamond tool and workpiece’s surface. A three-dimensional finite element method taking the rotational motion of tool into account is proposed. The simulation consists of three operations including loading, unloading, and cooling. The influences of different grinding conditions (grinding speed and grinding depth) on the residual stress field are analyzed. Results show that the main grinding force comes from normal rather than tangential direction due to the tool’s negative rake angle and their ratio is in the range of 1.2 to 1.7. The residual stress state on the finished surface is either tensile or compressive depending on various grinding condition; even both states may exist simultaneously. Further study shows that the ultra-high speed grinding can obtain lower surface residual tensile stress comparing with the high-speed grinding. Besides, a larger grinding depth is not advantage for obtaining a better machined quality in subsurface layer as the tensile maximum principal stress is also larger. Finally, the effects of different grinding conditions on residual stress scatters are analyzed utilizing mathematical statistic method. Results show that both smaller grinding depth and higher grinding speed are beneficial to achieve a better consistency of residual stress.

Development and Application on Ultrahigh Speed Grinding Processing Technology

Ultrahigh speed grinding technology is an advanced processing technology, which chould improve grinding efficiency, reduce surface roughness and improve processing quality. This paper introduces the origin of ultrahigh speed grinding processing technology, the development situation of ultrahigh speed grinding, summarizes its advantages comparing with the common grinding, analyzes the application on efficiency deep grinding, ultrahigh speed precision grinding, grinding hard materials grinding, grinding green and so on. And then it expounds the development trend of the ultrahigh speed grinding.

Investigations of the "Speed Effect" on Critical Thickness of Chip Formation and Grinding Force in High Speed and Ultra-high Speed Grinding of Superalloy

Investigations of the "Speed Effect" on Critical Thickness of Chip Formation and Grinding Force in High Speed and Ultra-high Speed Grinding of Superalloy

Thermal Characteristics Analysis of Liquid Hybrid Bearing on Ultra-High Speed Grinding

The carrying of Liquid hybrid bearing for ultra-high speed grinding is complex. The oil film temperature distribution in different input state is obtained through CFD analysis by FLUENT. On this basis, the temperature characteristics laws of the oil film with the input parameters change were obtained. Analysis shows that the relationships of oil film temperature with spindle speed and eccentricity are directly proportional and super linear, the relationship of oil film temperature with oil supply pressure is inverse ratio and the relationship with oil supply temperature is approximation directly proportional to the linear. Finally the significant of the various input parameters are analyzed through the orthogonal test. The results show that the effect of spindle speed is most significantly.

Thermal-Mechanical Analysis of Hybrid Spindle System Based on FEM

The deformation of the spindle system is the main factor affecting the accuracy of ultra-high speed grinding. To calculate the deformation of ultra-high-speed grinding spindle system is required to consider not only the formation of structural deformation, but also the thermal deformation. Using the simulation method, oil temperature and grinding force are calculated in this paper. Based on these two factors, the thermal-mechanical deformation of the hybrid spindle system is analyzed and calculated with the method of FEM. the This article uses simulation methods, analysis and calculation of the oil film temperature rise and the grinding force caused by deformation of the liquid and hydrostatic spindle system factors. The methods presented in this paper can be used in digital design of various kinds of spindle systems, in order to improve the accuracy of the spindle system design.