CHEMICAL MACHINING(CHM)CHEMICAL MACHINING(CHM)

Presented by:Presented by:MANIKANDAN.KMANIKANDAN.K

PDM(1PDM(1stst year) year)

CONTENTSCONTENTS ObjectiveObjective IntroductionIntroduction HistoryHistory Steps in chemical Machining Steps in chemical Machining Schematic DiagramSchematic Diagram Advantages and Dis-advantagesAdvantages and Dis-advantages ApplicationsApplications Case StudiesCase Studies ConclusionConclusion ReferencesReferences

OBJECTIVEOBJECTIVE

To give some basic idea about the chemical machining, its To give some basic idea about the chemical machining, its history, various steps in machining ,application in history, various steps in machining ,application in Industries ,its advantage and disadvantage. Industries ,its advantage and disadvantage.

INTRODUCTIONINTRODUCTION Chemical milling or industrial etching is the subtractive

manufacturing process. The process essentially involves bathing the cutting areas in a

corrosive chemical known as an etchant which reacts with the material in the area to be cut

Inert substances known as maskants are used to etch specific areas of the material.

HISTORYHISTORY

Organic chemicals such as lactic acid and citric acid have been used to etch metals and create products as early as 400 BCE.

Armor etching, using strong mineral acids, was not developed until the fifteenth century

It became used to etch trajectory information plates for cannon and artillery operators

STEPS IN CHEMICAL MACHININGSTEPS IN CHEMICAL MACHINING

The Steps in chemical machining are as followsThe Steps in chemical machining are as follows::

Part preparation: cleaning.Part preparation: cleaning. Masking: application of chemically resistant materialMasking: application of chemically resistant material Scribing: Scribing: removal of maskant on the areas to be etched Etching: dip or spray exposure to etchantsEtching: dip or spray exposure to etchants Mask removal: stripping the maskant and cleaning the part.Mask removal: stripping the maskant and cleaning the part. Finishing: inspection and other processingFinishing: inspection and other processing

SCHEMATIC DIAGRAMSCHEMATIC DIAGRAM

Schematic of chemical machining process

CLEANINGCLEANING

Cleaning is the preparatory process of ensuring that the surface to be etched is free of contaminants which could negatively impact the quality of the finished part.

For most metals, this step can be performed by applying a solvent substance to the .surface to be etched.

The material may also be immersed in alkaline cleaners or specialized de-oxidizing solutions.

MASKINGMASKING

Masking is the process of applying the maskant material to the surface to ensure that only desired areas are etched.

Liquid maskants may be applied dip-masking flow coating Conductive Maskants is applied by electrostatic deposition

MASKANT SELECTIONMASKANT SELECTION

The maskant to be used is determined primarily by the chemical used to etch the material, and the material itself.

The maskant must adhere to the surface of the material, and it must be chemically inert.

. Most industrial chemical milling use maskants based upon neoprene elastomers or isobutylene-isoprene copolymers.

SCRIBING

Scribing is the removal of maskant on the areas to be etched This is often done by hand through the use of a scribing knife,

etching needle or similar tool Modern industrial applications may involve an operator

scribing with the aid of a template or use computer numerical control to automate the process

ETCHINGETCHING

Etching is the actual immersion of the part into the chemical bath, and the action of the chemical on the part to be milled.

The time spent immersed in the chemical bath determines the depth of the resulting etch

E=s/tE=s/t Where E is the rate of etching (usually abbreviated to etch

rate), s is the depth of the cut required, and t is the total immersion time

Etch rate varies based on a number of factors, including the concentration and composition of the etchant, the material to be etched, and temperature conditions

DEMASKINGDEMASKING

Demasking is the combined process of clearing the part of etchant and maskant Etchant is generally removed with a wash of clear, cold water A de-oxidizing bath may also be required in the common case that the etching process left a film of oxide on the surface of the material

MATERIALSMATERIALS

Aluminum Aluminum ChromiumChromium Copper (oxygen free, rolled…)Copper (oxygen free, rolled…) NickelNickel Steel (carbon, stainless…)Steel (carbon, stainless…) LeadLead ZincZinc

ADVANTAGESADVANTAGES Easy weight reduction No effect on work piece materials properties such as hardness Simultaneous material removal operation No burr formation No stress introduction to the work piece Low capital cost of equipment Easy and quick design changes Requirement of less skilled worker Low tooling costs The good surface quality Low scrap rates (3%)

DIS-ADVANTAGESDIS-ADVANTAGES

Difficult to get sharp corner Difficult to chemically machine thick material (limit is depended

on work piece material, but the thickness should be around maximum 10 mm)

Scribing accuracy is very limited, causes less dimensional accuracy

Etchants are very dangerous for workers Etchant disposals are very expensive

APPLICATIONSAPPLICATIONS

High Precision PartsHigh Precision Partsand Decorative Itemsand Decorative Items GasketsGaskets Washers Washers Sensors Sensors NameplatesNameplates Jewelry Jewelry Microprocessor ChipsMicroprocessor Chips

CASE STUDIESCASE STUDIES

Eyewear Developed by CM(chemical machining)Eyewear Developed by CM(chemical machining)

PROBLEM:PROBLEM:A client contacted us to manufacture an innovative A client contacted us to manufacture an innovative line of eyewear, with a sleek and complex design which required line of eyewear, with a sleek and complex design which required assembly without screws.assembly without screws.SOLUTION:SOLUTION:This particular request led us to develop a This particular request led us to develop a "sandwich" structured frame, which was only feasible to "sandwich" structured frame, which was only feasible to manufacture through our photochemical etching process.manufacture through our photochemical etching process.

CONCLUSIONCONCLUSION

Chemical machining is widely used to produce complex machine parts for various application as well as decorative parts.

The machining operation should be carried out carefully to produce a desired geometry.

REFERENCESREFERENCES

www.ieee.orgwww.ieee.org www.chemicalmachining.orgwww.chemicalmachining.org http://www.cm-italia.it/eng/case_studies.phphttp://www.cm-italia.it/eng/case_studies.php http://en.wikipedia.org/wiki/Chemical_millinghttp://en.wikipedia.org/wiki/Chemical_milling

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