The document provides a comprehensive overview of the chemical machining process, detailing its principles, steps, preparation, and the roles of maskants and etchants. It highlights key advantages such as minimal effect on material properties and low tooling costs, as well as disadvantages like limited dimensional accuracy and safety concerns related to etchants. Additionally, the applications of chemical machining in industries such as electronics and aerospace are discussed.

1. Chemical Machining
J. Hemwani, GPC, Betul (M.P.) 460001 1

2. CHM -- Principle
 The Chemical Machining process is the controlled
chemical dissolution of the machined work piece material
by contact with a strong acidic or alkaline chemical reagent
(Etchant).
 The part of the work piece whose material is to be
removed, is brought into the contact of etchant.
 Special coatings called maskants protect areas from
which the metal is not to be removed.
J. Hemwani, GPC, Betul (M.P.) 460001 2

3. CHM -- Steps
The Chemical Machining has following steps
 1 Preparing : Cleaning the work piece
 2 Masking : Application of chemically resistant material
(if selective etching is desired)
 3 Etching : Dip or spray exposure to the etchant.
 4 De-masking : Removing Mask and clean work piece.
 5 Finishing : Inspection and post processing.
J. Hemwani, GPC, Betul (M.P.) 460001 3

4. CHM -- Process
PREPARATION
 The cleaning is done to remove the oil, grease, dust, rust
or any substance from the surface of material.
 The most widely used cleaning process is chemical
method due to less damages occurred comparing to
mechanical one.
 Ultrasonic cleaning machine is applied with using special
cleaning solution and heating is beneficial during the
cleaning process.
J. Hemwani, GPC, Betul (M.P.) 460001 4

5. CHM -- Process
MASKING
 The selected masking material should be readily
strippable mask, which is chemically impregnable
(impenetrable) and adherent enough to stand chemical
abrasion during etching.
 Work piece is guided by templates to expose the areas
that receive chemical machining process. The selection of
mask depends on the size of the work piece material, the
number of parts to be produced, and the desired detail
geometry.
J. Hemwani, GPC, Betul (M.P.) 460001 5

6. CHM -- Process
ETCHING
 Etching is carried out by immersing the work piece
material is into selected etchant and the uncovered areas
thus machined.
 This Etching process is generally carried out in elevated
temperatures which are depended on the etched material.
 Then the etched work piece is rinsed to clean etchant
from machined surface.
J. Hemwani, GPC, Betul (M.P.) 460001 6

7. CHM -- Process
DEMASKING And FINISHING
 Final step is to remove masking material from etched part.
 The inspections of the dimension.
 Surface quality are completed before packaging the
finished part.
J. Hemwani, GPC, Betul (M.P.) 460001 7

8. CHM -- Advantages
 No effect on work piece materials properties such as
hardness etc because of no stresses in process.
 Less time consuming because of simultaneous material
removal operation.
 Requirement of less skilled worker.
 Low tooling cost and low equipment cost.
 The good surface quality and no burr formation.
 Using decorative part production Low scrap rates (3%).
J. Hemwani, GPC, Betul (M.P.) 460001 8

9. CHM -- Disadvantages
 Difficult to get sharp corner in CHM.
 Difficult to chemically machine thick material (limit is
depended on work piece material, but the thickness should
be around maximum 10 mm).
 In CHM scribing (final cleaning) accuracy is very limited,
causes less dimensional accuracy.
 Etchants of CHM are very dangerous for workers.
 Etchant disposals of CHM are very expensive..
J. Hemwani, GPC, Betul (M.P.) 460001 9

10. CHM -- Applications
 Manufacuring of printed circuit board (PCB).
 Aerospace industry to remove shallow layers of material
from large aircraft components, missile skin panels, and
extruded parts for airframes.
 Etching is used widely to manufacture integrated circuits
and Micro electro-mechanical systems.
 The semiconductor industry commonly uses plasma
etching, in addition to the standard, liquid-based
techniques.
J. Hemwani, GPC, Betul (M.P.) 460001 10

11. J. Hemwani, GPC, Betul (M.P.) 460001 11
MASKANTS
 Masking material which is called maskant is used to protect workpiece
surface from chemical etchant. Polymer or rubber based materials are
generally used for masking procedure.
 The selected maskant material should have following properties:
• Tough enough to withstand handling.
• Well adhering to the work piece surface.
• Easy scribing.
• Inert to the chemical reagent used.
• Able to withstand the heat used during chemical machining.
• Easy and inexpensive removal after chemical machining etching.
 Multiple maskant coatings are used to provide a higher etchant
resistance.
 Long exposure time is needed when thicker and rougher dip or spray
coatings are used.
 Various maskant application methods can be used such as dip, brush,
spray, and electro coating as well as adhesive tapes

12. J. Hemwani, GPC, Betul (M.P.) 460001 12
ETCHANTS
 Etchants are the most influential factor in the chemical machining of any
material. Various etchant are available due to workpiece material. The best
possible etchant should have properties as follow :
1. High etch rate. 2. Good surface finish. 3. Minimum undercut.
4. Compatibility with commonly used Maskants. 5. High dissolved-
material capacity. 6. Economic regeneration. 7. Easy control of process.
8. Personal safety maintenance.
 Ferric chloride (FeCl3) is the most widely used etchant in chemical
machining. It is mainly used for etching iron-based alloys as well as
copper and its alloys, aluminum, etc.
 Cupric chloride (CuCl2) is generally applied for copper and copper
based alloys in electronics industry because various regeneration systems
are available for the waste etchant.
 Alkaline etchants are introduced to the fabrication of electronic
components such as printed circuit board.

13. Thank You
J. Hemwani, GPC, Betul (M.P.) 460001 13