Advanced manufacturing technology project.pptx

Abrasive water jet machine

1. JLD ENGINEERING AND MANAGEMENT COLLEGE Name – Manotosh Samanta Topic name – Abrasive water jet machine Subject – Advanced manufacturing technology Subject code – PC-ME701 University roll – 34700722022 Semester – 7th

2. Table of contents Introduction. Basic principle. Components. Advantages. Process variables. Mechanics of metal removing. MRR. Application and Limitation. Conclusion.

3. INTRODUCTION Abrasive Jet Machining (AJM) is one of the mechanical energy based modern machining processes where material is removed by controlled micro-cutting action caused by the impact of a concentrated high-velocity (100 – 300m/s) jet of abrasive grits accelerated by dehumidified pressurized gas (10 – 15bar). A nozzle directs the abrasive jet in a controlled way onto the work surface. When this high-velocity abrasive jet is made to impinge the work surface in a particular direction from a suitable stand-off distance (SOD), it erodes material primarily by micro-cutting and sometime assisted by brittle fracture. In Abrasive Jet Machining (AJM), usually air is directly taken from atmosphere, cleaned it and compressed it to a high pressure with the help of compressor. Loose abrasive particles having predefined average size are mixed with this pressurized gas in certain proportion (mixing ratio) and the mixture is then allowed to strike the work surface in the form of jet at a particular incident angle at very high velocity. A nozzle converts the hydraulic energy (pressure) of the jet-abrasive mixture into kinetic energy (velocity). After cutting action, grits leave the machining zone, which are then collected and disposed safely (usually, abrasive grits cannot be reused as grits lose sharpness after first impact).

4. Principle of Operation The principle of AWJ machining involves using a high-velocity stream of water mixed with abrasive particles to erode material from a workpiece. The high-pressure pump forces water through a nozzle, creating a high-speed jet. Abrasive particles are introduced into the jet, and their kinetic energy is used to cut through materials. This process is particularly effective for materials that are difficult to cut with traditional methods, such as ceramics, composites, and thick metals.

5. Components The construction of Abrasive Water Jet Machining (AWJM) centres around a high-pressure system and precision components. It begins with a powerful water pump that generates pressures exceeding 40,000 psi, which is directed to a mixing chamber where abrasive particles are added to create a slurry. Fig. – Abrasive water jet machine

6. The various parts of Abrasive Water Jet Machining are: Reservoir The reservoir serves as the fundamental component for storing water, ensuring a consistent supply to all other parts of the system for proper operation. Hydraulic Pump In the AWJM setup, the hydraulic pump assumes a crucial role as it facilitates the transfer of fluid from one location to another. It acts as an intermediary, drawing water from the reservoir and conveying it to the hydraulic intensifier. Hydraulic Intensifier Positioned after the hydraulic pump, the hydraulic intensifier is responsible for elevating the water's pressure to the required level for effective operation. Accumulator The accumulator functions as a temporary water storage unit, providing water to the system in instances of pressure drops or when high-pressure water is needed.

7. Control Valves The pressure control valve within the system plays a dual role, regulating both water  pressure  and its direction. A flow regulator valve is also incorporated to control the flow of water into the system. Flow Regulator As its name suggests, the flow regulator governs the water flow originating from the control valve, directing it toward the nozzle. Abrasive Tank Abrasive particles are pivotal in the AWJM process, especially for cutting hard materials. Commonly used abrasives include  aluminium oxides , sand, garnet, and glass particles, among others. Mixing Chamber In contrast to traditional water jet machining, AWJM employs a mixture comprising 70% water and 30% abrasive particles blended in the mixing chamber. Nozzle The nozzle's primary role is to convert high-pressure water into kinetic energy (K.E), which is intensified as the nozzle area decreases. This high  kinetic energy  of water, combined with abrasive particles, is directed onto the work piece's surface, rapidly achieving the desired shape and size. Drain System The drain system's primary function is to collect water discharged from the work region and return it to the reservoir through the pump and filter, ensuring a continuous water supply for the process.

8. Working of Abrasive Water Jet Machining The working of Abrasive water jet machining can be understood by going through the pointers given below: Water is sourced from the reservoir and distributed throughout the system, beginning with its journey from the reservoir to the drainage system. Initially, the water undergoes pressurisation in the hydraulic intensifier before being directed to the accumulator for temporary storage. Control valves within the system manage water pressure and control its directional flow. Subsequently, abrasive particles are introduced into the mixing chamber, forming a mixture with water in a ratio of 30% abrasive particles to 70% water. When these high-velocity abrasive particles impact hard work pieces, they can induce plastic deformation and fracture in the hard materials. Increasing the percentage of abrasives enhances material removal but diminishes the flow characteristics of the liquid mixture. Consequently, the optimal abrasive percentage typically falls within the range of 40% to 60%. This technology primarily finds its application in the intricate cutting of complex shapes in materials like granite and marble.

9. Abrasive Water Jet Machining Parameters Abrasive Water Jet Machining (AWJM) parameters are critical factors that influence the machining process's precision and efficiency. The parameters of the Abrasive Water Jet Machining process are as follows. Water flow rate Water Pressure Abrasive Flow rate Abrasive particle size Abrasive materials Nozzle diameter Traverse rate Stand-off distance Depth of cut Material properties.

10. Advantages and Limitations Advantages Versatility : Cuts a wide variety of materials. Precision : Capable of intricate and detailed cuts. No Heat-Affected Zone : Eliminates thermal distortion. Environmentally Friendly : Uses water and natural abrasives. Limitations Cost : High initial investment and operating costs. Abrasive Consumption : Continuous need for abrasive materials. Speed : Slower cutting speeds for certain materials compared to other methods.

11. Applications AWJ machining is used in numerous industries: Aerospace : Cutting of titanium, aluminium, and composites for aircraft components. Automotive : Precision cutting of parts and prototypes. Construction : Cutting of stone and glass for architectural purposes. Manufacturing : Metal cutting for various industrial applications.

12. MRR The Material Removal Rate (MRR) is a critical parameter in evaluating the efficiency of machining processes, including abrasive water jet (AWJ) cutting. MRR refers to the volume of material removed from a work piece per unit of time. In the context of AWJ machining, several factors influence the MRR: Factors Affecting MRR in AWJ Machining Water Pressure: Higher water pressure increases the kinetic energy of the abrasive particles, leading to a higher MRR.
Abrasive Flow Rate: Increasing the flow rate of abrasive particles generally enhances the cutting ability, thus increasing MRR, up to an optimal point beyond which additional abrasives may not contribute effectively due to interference effects.
Nozzle Diameter: A larger nozzle diameter can allow more abrasive particles to impact the material simultaneously, increasing MRR, but it may reduce precision.
Standoff Distance: The distance between the nozzle and the work piece affects the MRR. An optimal distance ensures maximum energy transfer to the material.
Cutting Speed: The speed at which the cutting head moves over the material affects MRR. Faster speeds can increase MRR but may reduce cut quality.

Material Properties: The hardness and toughness of the material being cut influence how easily material is removed. Softer materials generally allow higher MRR.

13. Calculating MRR However, ductile and brittle materials behave differently in indent formation, and thus size of indentation created by the impact of single abrasive grit is different for ductile and brittle materials. Under few assumptions, MRR for abrasive jet machining for different materials can be modeled analytically and can be expressed as provided below.

14. Process capability of abrasive jet machining Materials: Hard and brittle material preferred. Surface finish: Down to 0.10µm achievable. Tolerance: ±0.10mm. Feature size: Minimum limit 0.10mm. Corner radius: Minimum limit 0.2mm. MRR: 15mm 3 /min. Cut thickness: 2 – 6mm plates based on material.

15. Conclusion The MRR in AWJ machining is a crucial performance indicator that depends on multiple variables. Understanding and controlling these factors enable efficient machining operations, balancing productivity with quality.