Heavy-plate materials waterjet cutting effectiveness improvement

Аuthors

Tamarkin M. A.^1*, Verchenko A. V.^2**, Kishko A. A.^1***

1. Don State Technical University, DSTU, 1, Gagarin square, Rostov-on-Don, 344003, Russia
2. Rostvertol Helicopters, 5, Novatorov st., Rostov-on-Don, 344038, Russia

*e-mail: tehn_rostov@mail.ru
**e-mail: alex290292@mail.ru
***e-mail: aleksandr_kishko@mail.ru

Abstract

A voluminous assortment of parts, characterized by higher requirements to accuracy and reliability, is used while aircraft manufacturing. They are fabricated fr om various materials, such as steel, aluminum, plastics and composites. Special attention is payed to developing new methods of the parts manufacturing and improvement of conventional technologies.

The majority of the parts is produced by pattern cutting of various materials of 0.5 to 200 mm thickness, followed by their machining or without it. It is interlinked with the development of CNC metalworking Machinery Park, where forged pieces or form workpieces are used in increasing frequency. The main question consists in productivity and quality of cutting blanks. There is a great variety of pattern cutting methods, distinguished by productivity and principles, with peculiar advantages and disadvantages. The authors consider the hydro-abrasive cutting, which is the newest and prospective metal cutting methods.

Hydro-abrasive cutting is the most up-to-date and efficient method for obtaining either blanks or parts from plate aviation materials. The cutting process is carried out by the thin water jet with abrasive grains mixture, emitted at high (supersonic) speed under high pressure up to 6000 bar. Garnet sand with 7.5-8 hardness is used as an abrasive material. The process represents erosion destruction under impact of working jet, wh ere the abrasive cuts the chips microlayers, while water takes them away from the cutting zone. The main advantages of hydro-abrasive cutting are high productivity ensured for high cutting speed (steel up to 300 mm), the absence of residual strains at the cut edge, the possibility of cutting practically any metal and non-metal as well as the ability of cutting figured profile and irregular shape parts.

Nowadays the process of hydro-abrasive cutting is poorly studied. Theoretical dependencies accounting for all technological parameters effects for the cut ruggedness and corrugation determination, and dependencies reflecting the value of cutting jet lagging.

The quality of hydro-abrasive cutting depends on the feed rate, the thickness and type of cutting material. It was found, that feed increase reduces the quality of cutting, increases ruggedness, and the area of smooth

cutting reduces, while the corrugation and obliquity of the cut increases. Deffects caused by jet lag cutting, such as formation of a burr on the sharp outer corners, forming holes in the inner corners, overcut and undercut at the beginning of the cut are also found.

The goal of this study was to explore the effect hydro-abrasive cutting modes, namely the feed effect on the cut roughness.

After a row of experiments the samples made of three different materials with 30 mm thickness, namely, steel 30HGSA, aluminum D16, multi-layer polymer composite such as titanium-fiberglass were obtained.

When cutting the feed was changed stepwise from 5 mm/min to 120 mm/min for a sample of steel, to 200 mm/min for samples of D16, and to 160 mm/min for a sample of the composite. The ruggedness of these samples was measured at the specific areas of the cutting section.

Analysis of ruggedness dynamics allowed suggest a mathematical model of cutting surface ruggedness profile forming. The ruggedness is formed by free abrasives, which remove repeatedly the micro-chip layers. The mathematical model is proved by experimental data, as indicated by a graph of the cutting ruggedness dependence from the cutting head feed.

The experimental data and theoretical curves allow predict the cut quality of the hydro-abrasive cutting. Based on this data, the possibility arises to select the most optimal hydro-abrasive cutting mode cutting, or a certain type of defects elimination. The cutting rate optimization is possible by slowing down the feed in areas of defects formation, or ruggedness unevenness.

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Keywords:

hydro-abrasive cutting, metal erosion destruction, garnet abrasive (sand), abrasive particles with water mixture, abrasive grit, aviation materials, composites, jet cutting head feed, cutting jet pressure, jet cutting lag, cut surface roughness and waviness, material micro-fracturing, microchip, waterjet nozzle installation

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