TO COMPLY WITH THE DISTATES OF TIME
Manufacture of gas turbine engines for aviation and industrial purposes requires constant improvement of production process and introduction of new equipment. This determines in many ways not only product cost and labor-output ratio, but the corporate culture as a whole.
PMZ specialists are fully aware of necessity to replace obsolete and worn-out equipment with modern and highly productive ones. Acquisition of numerical control machine tools of new generation and upgrading existing machine tools by using modern numerical control racks makes equipment not only easy-to-use, but attractive for young workers, and permits the use of different systems for measuring base dimensions of the part and tool extension of the machine, enhances quality and reliability of machining, reduces time for tooling change and the costs for instrumentation upkeep. PMZ 2009-2010 Investment Program envisages acquisition of a large variety of new production equipment.
With this article we are beginning a series of articles on some advanced production methods and equipment already introduced in production.
DMITRY OKONESHNIKOV
Chief Process Engineer, PMZ
Machining of the Gas Turbine Engine Shafts
In order to enhance machining quality for all types of gas turbine engine shafts and reduce production costs, PMZ acquired a Ì65 Millturn milldrive turning center by Austrian WFL MILLTURN TECHNOLOGIES GmbH & Co.KG. This center permits to perform, in one shaft installation, the following operations:
- lathe machining and milling of inner and outer surfaces;
- drilling, hole enlarging, reaming and boring at any angle;
- milling and slotting of outer and inner recesses and tooth;
- measurements of machined surface and corrections to the NC program if necessary.
Ì65 Millturn is equipped with a 72-tool change matrix with Capto C8 fastening which permits storage of all the necessary tools and measuring probes and does not require additional resetting of the machine when changing from one piece for another.
Use of a special CNC boring bar of Cogsdill and damped boring bars of Sandvik and Botek permits resolving the machining of the inner profiled surfaces of components. High-speed machining with abundant cooling and the use of high-quality carbide tooling (fast-change plates, reamers) enhance quality of machined surfaces, reciprocal angular location of grooves, bores, and recesses, variations in wall thicknesses within 0.1 mm on the length of up to 1500 mm, and reduce production cycles of components.
In studying technical characteristics of the machining center and developing shaft manufacturing methods and control software, PMZ specialists created a post-processor based on Unigraphics operating system which permitted to implement the machining techniques and assimilate production of all the range of gas turbine engine shafts.
 Ì65 Millturn mill-drive turning center at PMZ |  RAWX 16x8500x320 horizontal broaching machine |
 Ì65 Millturn mill-drive turning center control panel PMZ |  Manufacturing program setup on RAWX 16x8500x320 horizontal broaching machine |
Making «Fir Tree» Slots on Turbine Disks
A new RAWX 16x8500x320 horizontal broaching machine made by Hoffman Raumtechnik GmbH, Germany, was put in operation at PMZ. Acquisition of this machine tool became a final step in turbine disk slot broaching reequipment program. A CNC optical projection device for slot form control, flat surface grinder, and profile surface grinder with CNC of ELB SCHLIFF and ARTUR KLINK for slot profiling and grinding have already been put in operation.
This set of machines permits performance of the hi-tech process of «fir tree» slots making on turbine disks with high quality tools without manual finishing of slots and to ensure advanced control over dimensions and parameters without human participation.
RAWX 16x8500x320 will replace outdated equipment, reduce costs related to tooling manufacture and upkeep. Its use will enhance endurance of expensive slots, and reduce consumption of expensive material for making samples.
Pipe Bending
Earlier bending of 12...42 mm pipes was made on CNC pipe bending machines (TGSP-24U and TGSP-40À models made by Savelovsky Machine Building Plant in 1981). Bending control and pipe geometry control was performed by IPK-1 measuring and programming unit. In the last years the bending machines' failures became more frequent, bending quality and precision became lower. Besides, Aviadvigatel's specialists began to make drawings with the help of Unigraphics system with 3-D pipeline models. This required a more advanced pipe bending equipment adaptable to Unigraphics.
PMZ reviewed proposals from a number of Italian, French, Swiss, and Chinese manufacturers, as well as from Savelovsky Machine Building Plant.
 Silfax SE932 pipe bending machine. PMZ |  Developing an element of distribution pipeline. PMZ |
The pipe bending machine is equipped with servo drives and provides high speed, positional accuracy, repeating accuracy, and good manufacturing quality. The drive is positioned directly under the bending head, which reduces the number of transfer members in the machine's chain and notably enhances precision of the product. The machine's software permits to do the following:
- Load a 3-D model created in Unigraphics and convert it into pipe bending control software, the data being put in via polar coordinates and cartesian coordinates integrated into the bending program.
- Calculate the length of a rough workpiece, demonstrate a 3-D pipe model.
- Perform real-time bending simulation using a model of the bending head in any moment of the bending process; when errors occur in the control software (e.g., impact with the machine's parts), the software gives a warning.
- Perform automatically, together with the measuring unit, calculations of the pipe's spring-back and correct the control software.
When making a new batch of pipes, one or two corrections to the software are enough to have correct pipe geometry.
Separate movement of the front and the hind clamps before the final bending permits to notably reduce allowance and material consumption.
Use of processing capabilities of the bending machine and the measuring unit allow obtaining economic benefit from reduction of material consumption, reduction of labor content, and production of high-precision quality parts.
