REPUBLIC OF TURKEYYILDIZ TECHNICAL UNIVERSITY

DEPARTMANT OF MECHANICAL ENGINEERING

WATER JET AND ABRASIVE WATER JET MACHINING PROCESSES

MURAT ATAK

MAY 2016, ISTANBUL

CONTENTS

Nontraditional machining process Water jet machining Applications of water jet machining Abrasive waterjet machining Applications of abrasive water jet machining Water jet vs Lasers /Milling/Punch Press Cost of Water jet Cutting Future of Water jet Machining

Nontraditional Machining Process

Non-traditional manufacturing processes is defined as a group of processes that remove excess material by various techniques involving mechanical, thermal, electrical or chemical energy or combinations of these energies but do not use a sharp cutting tools as it needs to be used for traditional manufacturing processes.

Extremely hard and brittle materials are difficult to machine by traditional machining processes such as turning, drilling, shaping and milling. Non traditional machining processes, also called advanced manufacturing processes, are employed where traditional machining processes are not feasible, satisfactory or economical due to special reasons as outlined below.

Very hard fragile materials difficult to clamp for traditional machining

When the workpiece is too flexible or slender

When the shape of the part is too complex Several types of non-traditional machining processes have been developed to meet extra required machining conditions. When these processes are employed properly, they offer many advantages over non-traditional machining processes. The common non-traditional machining processes are described in this section

WATER JET MACHINING

Usage of water jets in manufacturing processes, has been known for many decades. A wide range of

engineering materials can be cut by water jets with satisfactory results. Enhanced reliability and efficiency of

the technique, have yielded the technology greater interest for manufacturing applications.

Water jet cutting can reduce the costs and speed up the processes by eliminating or reducing expensive

secondary machining process. Since no heat is applied on the materials, cut edges are clean with minimal burr.

Problems such as cracked edge defects, crystalisation, hardening, reduced wealdability and machinability are

reduced in this process.

WJM has the following advantages:

The process requires a limited volume of water (100–200 L/h).

The tool (nozzle) does not wear and therefore does not need sharpening.

It is ideal for cutting asbestos, glass fiber insulation, beryllium, and fi ber-reinforced plastics(FRP), because the process provides a dustless atmosphere. For this reason, the process isnot hazardous and is environmentally safe. The process provides clean and sharp cuts that are free from burrs.

WJM has the following disadvantages: WJM is unsafe in operation if safety precautions are not strictly followed. The process is characterized by high production cost due to The high capital cost of the machine The need for highly qualified operators WJM is not adaptable to mass production because of the high maintenance requirement.

Schematic illustration of WJM system

Process capabilities of water jet machining

APPLICATIONS OF WATER JET MACHINING

 

WJM is used on metals, paper, cloth, leather, rubber, plastics, food, and ceramics.

ABRASIVE WATER JET MACHINING PROCESS

AWJM is a hybrid process (HP) since it is an integration of AJM and WJM processes. The addition of abrasives to the water jet increases the range of materials which can be cut with a water jet drastically and maximizes the MRR of this HP.

AWJM process is capable of machining both soft and hard materials at very high speeds as compared with those realized by WJM. It cuts 10–50 times faster than WJM process. Moreover, the cuts performed by AWJM have better edge and surface qualities.

 

Advantages of abrasive water jet machining technology;

There is no thermic effect on the material, and there are no changes in its structure Minimum influence of jet power on the material, and there are no micro-cracks

There are no chemical effects on the material

It is possible to cut layered materials with very complex characteristics of individual layers and composites

Quality finish; Materials cut by the abrasivejets have a smooth, satin-like finish, similar to a fine sandblasted finish.

Disadvantages of abrasive waterjet machining technology:

In the process of high-speed cutting of linear angles, water jet may cause indents in the material

Materials affected by corrosion must be protected from corrosion after cutting

 

 

APPLICATIONS OF ABRASIVE WATER JET MACHINING

 Abrasive waterjet has the ability to cut almost all materials and thickness. Most uses are for cutting of specialty materials such as stainless steel and aluminium.Its flexibility makes it useful for all applications.

The AWJ machining operations consist of cutting, multi-axis machining, milling, turning, drilling, polishing, etc.

 

Awjm milling Awjm turning

COMPARISON BETWEEN WATER JET MACHINING AND OTHER PROCESSES

WATER JETS VS LASERS Abrasive waterjets can machine many materials that lasers cannot.( Reflective materials in particular, such as

Aluminum and Copper)

Uniformity of material is not very important to a waterjet

Maintenance on the abrasive jet nozzle is simpler than that of alaser,though probably just as frequent.

After water jet cutting After laser cutting

WATER JETS VS MILLING

Waterjets can also machine almost any material, including brittle materials, pre-hardened materials, and

otherwise difficult materials such as Titanium, Hastalloy, Inconel, SS 304, and hardened tool steel.

WATER JETS VS PUNCH PRESS

Waterjets have a lower cost-per-piece for short runs than a die press, because of the expense (and time)

involved in creating the dies and punches. Creating the drawing for a part on a waterjet machine is all

that's needed to begin machining the part, where with a punch press, the drawing is usually only the first

step to creating the die.

COST OF WATER JET CUTTING

The cost to operate a waterjet is a common question, as people struggle to understand the

difference between running a typical plasma cutting machine and a waterjet cutter. There are

different consumables, different power requirements, cost of water, and most importantly, the cost

of abrasive.

To dig into this question a little deeper, looked at six different waterjet system configurations,

including:

60,000 PSI / 50 HP pump60,000 PSI / 100 HP pump60,000 PSI / 100 HP pump running two cutting heads90,000 PSI / 60 HP pump90,000 PSI / 125 HP pump90,000 PSI / 125 HP pump running two cutting heads 

Water Jet Cost Per Hour

For each of these, figured the cost of power, wear parts, water, and abrasive, on a cost-per-hour basis, as shown in the chart below.

Water jet cost percante

FUTURE OF WATER JET MACHINING

 In the next half-dozen years later, we can expect to see the following changes:

More manufacturers

More machines in different shops More engineers who understand water jets Easier maintenance Faster and more accurate machines Cheaper better mixing tubes

In the future, people will look back at the early 21st century as the beginning of the most exciting period in the waterjet industry. If future advances in waterjet technology rival those of the past few years, waterjet usage will experience tremendous growth. 

 

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