Types of Chemical Processing

Milling

Chemical milling is to protect the parts of the workpiece surface that need not be processed with a corrosion-resistant coating, and then immerse the workpiece in a chemical solution of the appropriate composition.

The exposed workpiece processing surface reacts with the chemical solution and the material is continuously dissolved and removed.

The speed at which the workpiece material dissolves is generally 0.02 to 0.03 mm/min.

After reaching a predetermined depth for a certain period of time, the workpiece is taken out to obtain the desired shape.

The process of chemical milling includes: surface pretreatment of the workpiece, application of protective glue, curing, engraving, etching, cleaning and deprotection.

The protective glue is generally made of neoprene or butyl rubber;

Shape incision generally uses a knife to cut the protective layer along the contour of the plate and peel it off.

Chemical milling is suitable for machining shallow concavities and grooves on the surface of thin sheet, thin-walled parts, such as the aircraft’s integral reinforced panels, honeycomb panels, skins and wing leading edge panels.

Chemical milling can also be used to reduce the thickness of local dimensions of forgings, castings and extrusions, as well as etching patterns, etc., with a depth of less than 13 mm.

The advantages of chemical milling are simple process and equipment, easy operation and low investment.

The disadvantage is that the processing accuracy is not high, generally ±0.05~±0.15 mm;

Moreover, dissolution occurs in the side direction under the protective layer, and an arc shape is formed between the bottom surface and the side surface of the processing, and it is difficult to process sharp corners or deep grooves;

Chemical milling is not suitable for processing loose castings and welded surfaces.

With the development of digital control technology, some applications of chemical milling have been replaced by digitally controlled milling.

Engraving

Chemical engraving is mainly used to make signs and plates;

Lithography is mainly used to manufacture transistors, integrated circuits or large scale integrated circuits;

Photolithography is mainly used to produce various printing plates.

Pickling

Pickling is mainly used to remove scale or rust on metal surfaces;

Chemical polishing is mainly used to improve the surface finish of metal parts or articles;

Chemical deburring is mainly used to remove fine burrs of brittle parts of small sheets.

Photochemical processing

Photochemical processing is a combination of photocopying and chemical etching.

A chemical processing method in which complicated concave-convex pattern or complicated-shaped sheet member is processed on the surface of the workpiece.

It includes photolithography, photolithography, chemical die cutting (or chemical blanking), and chemical engraving.

The processing principle is to first apply a layer of photosensitive glue on both surfaces of the sheet-shaped workpiece;

Then two photographic negative films with the desired processing pattern are correspondingly placed on the photosensitive adhesive on both surfaces of the workpiece for exposure and development.

The photosensitive adhesive becomes a corrosion-resistant substance after being irradiated with light, and forms a corresponding processing pattern on the surface of the workpiece;

Then immerse (or spray) the workpiece into the chemical etching solution.

Since the corrosion-resistant coating protects the underlying metal from corrosion, the desired processing pattern or shape can be obtained.

Photochemical processing is widely used.

Among them, chemical die cutting is mainly used for the processing of various complicated and finely shaped sheets (typically 0.025 to 0.5 mm in thickness), especially for sheet parts which are difficult to mechanically punch.

This method can be used to manufacture TV picture tube baffles (5000 holes per square centimeter surface), leaf springs, precision filters, micro-motor rotors and stators, fluidic components, liquid crystal display panels, clock pinions, printed circuits, strain gauges and samples.

Surface treatment

Chemical surface treatments include pickling, chemical polishing, and chemical deburring.

There is no need to apply a protective layer on the surface of the workpiece, as long as the workpiece is immersed in a chemical solution to dissolve and dissolve.