The manufacturing industry widely uses non-traditional machining processes for the purpose of manufacturing complex and accurate parts and components. Aerospace, automotive, and electronic industries are only some industries that widely use these non-traditional machining methods for the precision it showcases. Chemical machining is one such type of non-traditional machining process that is quite popular and well known. So here are the advantages and disadvantages of this method.
WHAT IS CHEMICAL MACHINING?
Chemical machining ( also called photochemical machining or photochemical milling) is a non-traditional machining process where there is the production of desired metal shapes by controlled chemical attack with strong acidic or alkaline chemical reagent. It removes metal from a machined workpiece material by immersing it into a chemical solution. All kinds of material like metals, ceramics, etc can be chemically machined and altered. This process is used in various ways that include industrial applications like screens and meshes, battery grids, microwave grids, semiconductor fabrication industries, and aerospace industries.
There are different types of chemical machining. Some types include chemical milling, chemical blanking, and chemical engraving. Firstly, chemical milling is a process used to produce shallow cavities by selective or complete removal of unwanted metal parts from large surface areas. Secondly, chemical blanking is a process where the material is removed from several areas with a chemical action. Finally, chemical engraving is a process where a design is engraved or incised onto a hard, flat surface by cutting grooves in it.
WHAT IS THE PROCESS?
It is the workpiece pre-cleaning process where the surface of the metal is cleaned, degreased, and pickled by acidic or alkaline chemical reagent. This is usually done to remove any oil, dust, grease, or other substances from the material surface.
Masking is the process where the pre-cleaned workpiece is coated with a masking material. It involves covering the portion of the workpiece that is not to be removed during the chemical machining process. For example, adhesives and paints are common masking materials.
Scribing of the mask
Scribing is where areas that will undergo the chemical machining process are exposed by templates. The particular mask is selected on the basis of properties for example, the size of the workpiece, parts to be produced, the required shape, etc.
Etching is an important step in the chemical machining process where the unmasked surface is machined chemically with an etchant to produce a particular component. Etchant is a type of acid or alkaline corrosive chemical maintained within a certain chemical composition and temperature.
Demasking is the final step where the masking material or maskant is removed from the part where etching took place. Rubber-based materials or some types of polymers are some types of materials used for masking.
ADVANTAGES OF CHEMICAL MACHINING
No Effect on Properties of Workpiece Materials
One of the advantages of chemical machining is that this process of machining does not have any effect on any of the properties of the material of a workpiece. In other words, the metal properties stay intact and without alterations. For instance, metal properties like hardness, adhesion, thermal conductivity, etc do not get altered.
In addition, it also does not produce any unwanted burrs. Burrs are raised edges of material that get attached to a workpiece after a machining process. This usually has to be removed with the help of a deburring tool. So, the added hassle of deburring gets eliminated with chemical machining.
No Introduction of Stress
Certain properties of the workpiece material change depending on thermal stresses developed and temperature history. Rapid heating and cooling deforms and transform a workpiece material. This is avoided by the process of chemical machining. There is no introduction of any stresses or residual stresses to the workpiece. Also, there are no additions to thermal effects through this process. Hence, there are no phase transformations or thermal plastic deformation in the workpiece with rapid heating and cooling.
Another important advantage of chemical machining is that it is cost-effective. This process requires minimal tools so there is a low expense on the tooling costs. In the few steps of the process, there are very few equipments used like the chemical reagent, maskants, and etchants. So, there is a low capital cost of equipments for the process of chemical machining. Since there is more precision with fewer types of equipment and tools, there are fewer workers required for the process. Therefore, the expense of skilled workers is also reduced. In other words, chemical machining as a process is not only highly effective but also economical in comparison to other non-traditional machining processes.
Several Unique Usages
Chemical machining can be applied in unique ways. Firstly, it is easily used on materials that are difficult to machine in comparison to other non-traditional processes. It is a simple process that needs no additional cleaning apart from the pre-cleaning done in the workpiece preparation. In addition, easy weight reduction, good surface quality, and low scrap rates are some additional advantages of chemical machining.
Another important consideration is that there is a growing need for chemical machining. Certain traditional machining methods are not as effective or as cost-effective as this process. It helps with machining certain metals that are hard and difficult to mold. Additionally, it is also a useful process when it comes to working with thin parts of metals with delicate or complex configurations. Therefore, chemical machining is an indispensable process of machining.
DISADVANTAGES OF CHEMICAL MACHINING
A serious drawback of chemical machining is that it has some serious environmental issues. During the process of chemical machining, several hazardous chemicals like etchants, residual chemical reagent, and cleaning solutions are disposed of. These chemicals cause acid corrosion of certain metals which damages the material. These chemicals end up polluting the soil and water. Similarly, corrosive gases can be a by-product of chemical machining from solid or liquid corrosive substances. When these gases combine or come in contact with water, they turn into an acid which causes serious environmental pollution.
Also, it is known to cause certain health issues like damage to the eyes, corrosive injuries or burns, and even lung cancer. And this depends on the kind of substance used for the chemical machining process.
Chemical machining is a better method of machining process in comparison to other non-traditional processes. But this process has certain limitations. It cannot be used on thick material for chemically machining them. It is very difficult to get sharp corners and has less dimensional accuracy. Moreover, the material removal rate of chemical machining is less in comparison to other non-traditional techniques. Also, there is limited scribing accuracy. In other words, this machining process has certain disadvantages that cannot be ignored.
A workpiece piece is sprayed or immersed in some type of etchant for the process of chemical machining. The kind of etchant that must be used for the machining process depends on various factors. For example, these include the type of workpiece material, depth, surface finish, type of maskant, cost, etc. One has to be very careful because etchants are hazardous. These are dangerous compositions that only skilled workers can handle. Disposal of etchants is a taxing process and also expensive. Additionally, etchants also cause environmental degradation. It can change the acidity or alkaline levels which adversely affects flor and fauna. Workers are advised to wear protective equipment before handling these harmful substances.
Though chemical machining helps in machining difficult and hard materials, the process is very slow. Because of this, this machining process is not used to produce large quantities of materials. Usually, this process is used to machine materials that are lesser than 2 millimeters in thickness. However, sometimes large quantities of small parts are made on a single plate to overcome this issue.
In conclusion, chemical machining is an important non-traditional process that should be undertaken with the utmost care and attention. So a combination of different non-traditional machining processes could yield better and quality results.
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