Chemical Machining Process

International Research Journal of Innovations in Engineering and Technology (IRJIET)

ISSN (online): 2581-3048

Volume 3, Issue 11, pp 37-39, November - 2019

Chemical Machining Process - An Overview

Anurag Raj,

Anirudh V,

Dr T S Nanjundeswaraswamy

1,2

Student, Department of Mechanical Engineering, JSS Academy of Technical Education, Bangalore-560060, India

Associate Professor, Department of Mechanical Engineering, JSS Academy of Technical Education, Bangalore-560060, India

Abstract - Chemical machining (CHM) is the material

removal process for the production of desired shapes

through selective or overall of material by controlled

chemical attack with acids or alkalis. This is one of the

oldest nontraditional machining processes and also has

some drawbacks .The main issues face by chemical

machining process is the reduced material removal rate

when compared to other nontraditional machining

techniques. Accuracy of machine should also paid

attention. Apart of this, since we are using chemical

etchant for the process, it also has some environmental

issues. The machining quality of chemical machining is

comparatively less. So it is necessary to think of an idea to

improve the quality. So in this paper we discussed below

about working principle, need, procedure, application of

chemical machining process.

Keywords: Chemical Machining, Types, Needs, Maskant,

Etchant, Process Parameters, Non Traditional Machining.

I. INTRODUCTION

Chemical machining is well known as nontraditional

machining process and is controlled by chemical dissolution

of the machines work piece material by contact with a strong

chemicals reagent. It is also known as a chemical etching

.mostly all the material from metal to ceramics can be

chemically machined. Chemical machining process is

employed where metal removal is difficult. Chemical

machining is a controlled dissolution of the work material by

means of contact with a strong acidic or alkaline chemical

reagent. The major characteristics of chemical machining are

material removal rate, accuracy and surface finish.

The main challenges for this process are the same as is

characteristics. Material removal rate is dependent on the

selected etchant. Accuracy of the process may be affected by

the under cutting behavior in simple contouring.

II. WORKING PRINCIPLE OF CHEMICAL

MACHINING

The working principle of chemical machining is based on

chemical etching .the part of the work piece metal where

material is to be removed is brought into contact with a strong

corrosive chemical called etchant. The etchant react with the

workpiece in the material to be cut and causes the solid

material to be removed. Thus the metal is removed by the

chemical attack of the etchant.

The portion of the work material where material is not to

be removed is protected from chemical attack by means

special coating called as maskants. So by this chemical

machining process from all metal to ceramic substance can be

machined with chemical machining process. This process of

chemical reaction between the material of the work piece and

some chemical reagent use to produce a reaction between then

so that it can be removed easily .thus the surface of the

workpiece is etched away, exposing the lower layers, and the

process is continued until the desired amount of material is

removed.

Figure 1(a): Brief illustration of the chemical machining process, Figure 1(b): Stages of producing a profiled cavity by the help of

machine called agitator

International Research Journal of Innovations in Engineering and Technology (IRJIET)

ISSN (online): 2581-3048

Volume 3, Issue 11, pp 37-39, November - 2019

Need For Chemical Machining

Hard and difficult to shape metals cannot be easily

machined by conventional machining methods .further, thin

work parts with complex configuration or delicate parts fail to

withstand the forces of cutting tool. Although some

nontraditional process can be used in such conditions, they are

not economical due to high capital and tooling costs involved.

These disadvantages are overcome with the use of chemical

machining process.

Types of Chemical Machining Process

There are two type of chemical machining:

 Chemical blanking method

 Chemical milling or contour machining method

III. PROCEDURE FOR CHEMICAL MACHINING

Workpiece pre cleaning process: The surface of workpiece

metal is cleaned thoroughly, degreased and pickled by acid or

alkalis. Pre cleaning is the most important method to remove

oil, grease, dirt, rust, or any foreign substance from the work

surface to produce a good adhesion of masking material.

Masking and scribing mask: Masking involves covering the

portion of the workpiece metal where material is not to be

removed by the chemical action .masking with adhesive types

or paints is a common practice although rubber (elastomers)

and plastics are also used. Since it is difficult to apply maskant

on small surface, the maskant is initially applied on a large

surface

Etching: The unmasked surface of the workpiece is machined

chemically with selected etchant. Etching is carried out by

immersing the work material in a tank of agitated etchant. The

process is carried out at high temperature depending on the

etched material. Temperature control and agitation during

chemical machining. Erosion of the work material takes place

from the exposed surface. The work piece is converted into

metallic salt, which is then dissolved and carried away in the

etchant solution.

Damasking: When etching is completed the mask is removed

either through mechanical or chemical means. any etchant on

the work material is also removed by cold water to clean. A

deoxidizing bath may also be required in order to remove the

oxide coating or films left on the surface of the work material.

Process Characteristics of Chemical Machining

 Metal removal rate

 Accuracy

 Surface finish

Maskants

Masking material is known as Maskant which is used to

protect workpiece surface from chemical etchant. In another

words maskants protect the portion of workpiece metal where

material is not to be removed by chemical action of the

etchant. Polymer or rubber based materials are generally used

as a maskant material. Various maskant application methods

can be used such as dip, brush, spray, roller, and electro

coating as well as adhesive tapes.

The type of maskant to be selected for machining is based

on the following factors

 Be inert to the chemical reagent used

 Chemical resistance required

 Be tough enough to withstand handling

 Adhere well to the work piece

 Allow itself to be scribed easily

 Be removed easily after etching

 Be inexpensive after etching

 Be able to withstand the heat generation by etching

 Availability and low cost

TABLE 1

Masking material for various work material

Work material

Maskant

Aluminium & Alloys

Polymer, butyl rubber &

neoprene

Copper & alloys

Polymer

Iron based alloys

Polymer, poly vinyl chloride,

polyetilien butyl rubber

Nickel

Neoprene

Magnesium

Polymer

Titanium

Polymer

Etchants

Etchants are acid or alkaline solutions maintained within a

controlled range of chemical composition and temperature.

The workpiece material to be removed is sprayed or immersed

in a suitable etchant .various etchant are available for

machining different material as listed in table 2. The type of

etchant to be selected for machining is based on following

factor:

International Research Journal of Innovations in Engineering and Technology (IRJIET)

ISSN (online): 2581-3048

Volume 3, Issue 11, pp 37-39, November - 2019

 Type of workpiece metal that is being etched

 Rate of metal removal

 Surface finish required

 Type of maskant used

 Depth of etch required

 Ability to regenerate the etchant solutions

 Un harmful Or non toxic to human operator

 Availability at low cost

TABLE 2

Etchant characteristics

Work

material

Etchant

Etchant temperature

Aluminum &

alloys

Ferric

Chloride

Copper &

alloys

Cupric

Chloride

Steel

Ferric

Chloride

Nickel

Ferric

Chloride

Magnesium

Nitric acid

Titanium

Hydrogen

fluoride

Glass

Hydrogen

fluoride

IV. CONCLUSIONS

Material removal rate, accuracy, surface finish and

environmental issues are the major challenges what chemical

machining face. Rate of removal of material is depended on

the type of etchant we are using for machining process.

Etchant which remove metal in a faster manner will have

many side effects including surface finish, higher heating etc.

So the etchant should be selected in such a way that it should

balance among all these problems. Undercutting is the issue

which reduces the accuracy of machining. Hydrogen

embrittlement also causes alterations. The surface produced by

CHM process is otherwise stress free and show no thermal

effects. Chemical machining greatly affects the environment

since it make use of chemical etchants. To improve the

material removal rate of chemical machining is to combine

both laser machining and chemical machining.

REFERENCES

[1] Benedict, G. (2017). Nontraditional manufacturing

processes. Routledge.

[2] Çakir, O., Yardimeden, A., & Ozben, T. (2007).

Chemical machining. Archives of Materials Science

and Engineering, 28(8), 499-502.

[3] Langworthy, M. (1994). Chemical Milling By

Nontraditional machining process. Machining ASM

Handbook.

[4] Tehrani, A. F., & Imanian, E. (2004). A new etchant

for the chemical machining of St304. Journal of

materials processing technology, 149(1-3), 404-408.

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Citation of this Article:

Anurag Raj, Anirudh V, Dr T S Nanjundeswaraswamy, “Chemical Machining Process - An Overview” Published in

International Research Journal of Innovations in Engineering and Technology (IRJIET), Volume 3, Issue 11, pp 37-39,

November 2019.