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Noise abatement in aviation ranks second in importance after flight safety. 140 dB sound intensity (airplane taking off) it can cause concussion in humans, and at 160 dB, ruptures of the eardrum are possible. To reduce noise in an aircraft, sound-absorbing structures with numerous holes in the material are used. In aircraft engine building, a robot is involved in shaping these holes, which processes them with a drilling tool. During the production process, the drill may accidentally fall into the rigid inner hidden partition of the filler and break. A scientist at Perm Polytechnic University has developed a way to regulate the robot's feed using a sensitive sensor. It increases the reliability of the drill by 2 times.

The development was carried out within the framework of the strategic academic leadership program "Priority 2030". Patent No. 2806359 was issued for the research.

The sound absorption product is a multilayer structure, between the inner and outer layers of which there is a filler in the form of honeycombs with rigid partitions. The inner layer is perforated, that is, there are small round holes on its surface, arranged in a certain order. The noise in the form of waves, passing through the holes, enters the cellular cells and then dissipates.

Now the manufacture of such a structure is automated. If you need to drill 2000 holes or more with a diameter of 2 mm to absorb noise, it is irrational to manually perform such a task by monotonous drilling, therefore, a robot is used for this in real production. This way the work is done faster and better.

The perforation process itself is quite simple at first glance. A special program is written for the robot, following which it perforates the holes in order. But since a sound-absorbing product most often has a structure with rigid partitions inside, drilling small holes (up to 3 mm) is difficult to automate without a sensitive sensor on the cutting tool. At the same time, it is easy to get a defect in the product and break the drill, and its frequent replacement slows down production and is economically unprofitable.

A scientist at Perm Polytechnic University has developed a control method in which such an important indicator as axial force, the force acting on the tool during drilling, is constantly monitored using a strain gauge sensor.

– We preload a preset amount of load on the tool into the robot's memory. We move the drill bit to the location of the first hole, and the robot begins to rotate it until it touches the surface. A strain gauge mounted on the tool continuously measures the actual value of the axial force that occurs during perforation and compares it with the initially set value. If the load on the drill bit increases sharply by 50% or more, the sensor detects the detection of an obstacle and reduces the speed of the tool by 2 times. The robot drills the hole to a predetermined depth and proceeds to the next one," explains Alexander Dudarev, Associate Professor of the Department of Innovative Engineering Technologies at PNRPU.

Reducing the feed rate of the tool is necessary to reduce the axial force so that the tool remains intact. Therefore, when perforating the material, it is important to constantly monitor this indicator. Now this has become possible thanks to the development of a PNRPU scientist. The strain gauge detects a load surge during drilling and transmits a signal to the robot to reduce the feed rate, thereby preventing tool breakage.

The researcher has already tested a method for perforating holes of a sound-absorbing structure and notes that the quality of the holes obtained meets all technical requirements. The drills do not break when they hit the partition, their service life is significantly increased. Durability increases by 1.5-2 times.

The development of the Perm Polytechnic University scientist improves the quality of drilling holes in a product with rigid partitions, prevents tool defects and breakage. Thanks to this method of controlling the robot, the manufacture of sound-absorbing structures for aviation will be more reliable and efficient.

PHOTO: Alexander Dudarev next to the robot. Source: PNRPU Press Service

Source of information and photo: PNRPU press service Information taken from the portal "Scientific Russia" (https://scientificrussia.ru /)