Group Aggregate Unit for Boring Gearbox Housings
Abstract Generated abstract
This paper describes the development of a group aggregate unit for boring seating holes in gearbox housings at the Krasnoyarsk Sibtyazhmash plant, where diverse gearbox types and limited production volumes made dedicated special machines economically impractical. The authors analyze standardized center distances across several gearbox housings and use this grouping to design one six-spindle aggregate installation capable of machining four principal gearbox types with only replaceable or slightly adjustable locating fixtures. The proposed unit adapts a 1D65 machine with an aggregate gearbox, guided boring bars, hydraulic lifting and clamping devices, and quick-change locating elements. The design is reported to meet the plant’s annual production program in two-shift operation while reducing changeover time between gearbox types to approximately 2 to 3 minutes.
Full Text
GROUP AGGREGATE MACHINE FOR BORING GEARBOX HOUSINGS
V. D. VARLAKOV, I. I. RYABOVOL
(Presented by the scientific seminar of the Department of Mechanical Engineering Technology, Machine Tools, and Metal Cutting)
Questions of increasing labor productivity in machine-building production are always connected with improvement of the technological process for manufacturing parts. Improvement of the technological process may proceed through the use of special and specialized equipment, the application of more complex high-speed fixtures, special types of tools, and more precise methods for obtaining blanks. Thus, in most cases, in order to implement new, more productive processes, it is necessary to improve the means by which they are carried out, i.e., to face the need for additional capital expenditures.
One of the principal requirements imposed on any technological process is its economy, i.e., carrying out machining at minimum cost. This requirement is fairly easily met under conditions of a substantial production program—large-series and mass production. However, when the production program is small, and the products are structurally complex and have considerable dimensions, the question of applying means of mechanization and automation of the technological process becomes very difficult. The means of mechanization required for operation under these conditions turn out to be bulky and expensive, while the volume of production is small. As a result, it is very often necessary to abandon devices that mechanize and automate the technological process and to organize machining with considerable expenditures of highly skilled labor, i.e., under conditions of relatively low labor productivity.
The most expedient way out of this difficult situation may be the organization of group machining of parts, the basic principles of which were formulated by Mitrofanov.
The Krasnoyarsk plant “Sibtyazhmash,” which produces gearboxes of a very wide range of types, decided to proceed along the path of creating aggregate machines for boring seating holes in gearbox housings. One such machine has been created and is operating. However, it proved to be very lightly loaded and accelerates the machining process for only one type of gearbox (R-06). The creation of special aggregate machines for the entire
of the range of gearboxes produced by the plant is practically impossible and economically inexpedient.
An analysis of the center distances of gearbox housings showed that certain standardized series are in effect in them. This made it possible for us to consider the question of creating group aggregate installations for machining several gearbox housings.
Thus, at first we intended to create two aggregate installations for machining: one for the housings of the KTs-750 and KTs-500 gearboxes, with center distances of 200, 300, 450 mm; the second for the housings of the VK-950 and VK-750 gearboxes, with center distances of 200, 250, 300, 400 mm.
The boring operation in this case was to be carried out as follows:
Table 1
| Gearbox type | Center distances in mm | Center distances in mm | Center distances in mm | Center distances in mm |
|---|---|---|---|---|
| 1st installation | 200 | 300 | 450 | |
| KTs-500 | 200 | 300 | — | |
| KTs-750 | — | 300 | 450 | |
| 2nd installation | 200 | 250 | 300 | 400 |
| VK-750 | 200 | 250 | 300 | — |
| VK-950 | — | 250 | 300 | 400 |
An analysis of the center-to-center distances of the second installation shows that, if the center-to-center distance of 400 mm is divided in half, i.e., if one additional spindle is installed, then we obtain all the center-to-center distances of interest to us for the 4 types of housings. In this case the group aggregate installation will have the necessary center-to-center distances, and machining can be carried out on it in the following combinations:
Table 2
| Gearbox type | Center distances in mm | Center distances in mm | Center distances in mm | Center distances in mm | Center distances in mm |
|---|---|---|---|---|---|
| Group aggregate installation | 200 | 200 | 300 | 250 | 200 |
| KTs-500 | — | 200 | 300 | — | — |
| KTs-750 | — | — | 300 | 450 | |
| VK-750 | — | — | 300 | 250 | 200 |
| VK-950 | 400 | 300 | 250 | — |
The indicated 4 types of gearboxes are the principal ones in the plant’s program. A calculation showed that this installation will fully ensure fulfillment of the plant’s annual program with two-shift operation.
To machine 4 types of gearbox housings on this aggregate installation, it is necessary to equip it only with replaceable locating fixtures.
In solving this question we also proceeded along the path of using group tooling. Instead of 4 locating fixtures, two were designed, with only very slight adjustments.
In the first fixture the housings of the VK-950 and KTs-750 gearboxes are machined; in the second, VK-750 and KTs-500.
Labels in the figure:
- Gearbox (1)
- Machine spindle
- (2)
- Boring bar (5)
- Rear support
- Setup fixture (3)
- (4)
- \(S\)
Fig. 1. Group aggregate installation for boring gearbox housings.
The transition from machining one gearbox to machining another is carried out by switching the clamping and lifting mechanisms of the gearboxes by means of special hydraulic panels, and by installing and removing one locating pin and one support. The designs of the replaceable pins and supports are quick-detachable. Thus, resetting the fixture from one gearbox to another takes a minimum amount of time (2–3 minutes).
Structurally, the aggregate unit consists of a six-spindle gearbox 1 (Fig. 1), mounted on the ways of the bed of the 1D65 machine and receiving the required spindle motion through a hinged coupling 2 from the spindle of the 1D65 machine. The setting fixtures 3 are placed on a special table 4 with a permanent column for guiding the boring bars 5. The base of the table is formed by the transverse slides of the machine carriage. Thus, the required rotational speeds of the spindles of the aggregate gearbox and the feeds required for operation are obtained, respectively, by switching the speed and feed gearboxes of the machine.
The fixtures are equipped with hydraulic lifting devices. The gearbox is raised after it has been installed in the fixture and seated on the locating pins, in order to introduce the boring bars into the holes to be bored. At the moment when the boring bars are introduced into the holes, they are stopped in a position in which the cutters are at the upper point. After the boring bars have been introduced, the gearbox is lowered onto the locating pads and clamped.
Control of raising, lowering, clamping, and unclamping is performed with a single handle of the hydraulic panel.
The design of the hydraulic panel is such that the lifting and clamping mechanisms are automatically interlocked.
The aggregate unit described has been accepted for introduction at the Krasnoyarsk Sibtyazhmash plant.