GB2262061A

GB2262061A - Double spindle type lathe

Info

Publication number: GB2262061A
Application number: GB9217234A
Authority: GB
Inventors: Kenjiro Mori
Original assignee: OKUMA HOWA KIKAI KABUSHIKI KAI; OKUMA HOWA KIKAI KK
Current assignee: OKUMA HOWA KIKAI KABUSHIKI KAI; OKUMA HOWA KIKAI KK
Priority date: 1991-12-05
Filing date: 1992-08-13
Publication date: 1993-06-09
Also published as: DE4227552A1; GB9217234D0; ITMI922031A0; IT1256353B; ITMI922031A1; JPH05154701A

Abstract

In a double spindle type NC lathe, between a first spindle 4 for a first machining step and a second spindle 5 for a second machining step is interposed a third tool carriage 7 which can operate simultaneously with a first 3 or a second 6 tool carriage for the first or the second machining step. The third tool carriage operates with either the first or second tool carriage which requires a longer machining period, to participate in either the first or second machining step and hence minimise overall machining time. <IMAGE>

Description

1 " ---. j -) 1 DOUBLE SPINDLE TYPE LATHE The present invention relates

generally to a double 5 spindle type lathe and, more particularly, to a double spindle type lathe of the type in which a third tool carriage is interposed between first and second spindle heads so that a shorter machining cycle can be obtained.

In order to combine various cutting machines such as numerically controlled (NC) lathes, various types of combined cutting machines have been developed recently.

In an example of double-spindle, four-axes lathes which can accomplish two machining steps by a single machine tool, a lathe comprises a first machining step section and a second machining step section which are disposed symmetrical with respect to a center partition.

In the first machining step section is installed a slide which can slide on a bed in both the X-axis and the Z-axis directions by means o X-axis and Z-axis feed screws which extend at right angles with each other. A first tool carriage having an indexable turret is mounted on the slider and tool holders are attached an the turret. Cutting tools are attached to the tool holders and a workpiece held by a chuck at one end of a f irst spindle of a first spindle head is machined by a plurality of such cutting tools.

On the opposite side of the first machining step section with respect to the center partition is disposed the second machining step section which is substantially similar in construction to the first machining step section which includes a second spindle head having a second spindle, and a second tool carriage. The spindles and the tool carriages of the f irst and second machining step sections operate completely independently of each other.

In the case of the ordinary machining cycle, upon completion of machining the workpiece in the 2 machining step section, the machined workpiece held by the chuck of the first spindle is transferred to a chuck of the second spindle in the second machining step section. The distance in the horizontal direction 5 between the first and second spindles is of an order of 40-50 cm and the transfer of the workpiece can be accomplished by one step by an automatic loading mechanism or by an operator. Therefore, two machining steps can be accomplished quickly by only a single 10 machine tool.

However, in general, the net machining time periods for machining the workpiece in the first and second machining step sections are different so that the first or second machining step period longer than the second or first machining step period becomes a critical element to determine the machining cycle period. That is, first or second machining step sections has a noncutting period which is not good for the overall production efficiency.

Furthermore, when unreasonable tooling and machining conditions are employed in order to minimize the difference between the first and second machining step periods, an unreasonable machining must - be carried out, thus resulting in a degradation in machining accuracy.

In view of the above, the object of the present invention is to solve the various technical problems encountered in the prior art and to provide a double spindle type lathe which can minimize the difference between the first and second machining step periods so that the noncutting period can be reduced to a minimum and, therefore, the overall machining cycle period can be shortened, whereby higher production efficiency can be attained.

According to the present invention, there is provided a double spindle type lathe comprising: a first machining step section including a first spindle head with a first spindle having a first chuck for holding a 3 workpiece, and a first tool carriage having cutting too! means thereon; a second machining step section including a second spindle head with a second spindle having a second chuck for holding a workpiece, and a second tool carriage having cutting tool means thereon; and a third tool carriage having cutting tool means and interposed between said first and second machining step sections, said third tool carriage being movable so as to cause the cutting tool means thereof to approach and cut the workpiece held by either said first or second chuck while the workpiece is being cut by the cutting tool means of either said first or second tool carriage.

According to the present invention, during a longer one of the machining periods in the first and second machining step sections, the third tool carriage participates in the machining operation so that the workpiece is machined simultaneously by using two too! carriages whereby the difference between the first and second machining step periods can be decreased to a minimum. As a result, the overall machining cycle can be shortened and the machining efficiency can be remarkably improved.

The present invention will become more apparent from the following description of a preferred embodiment thereof taken in conjunction with the accompanying drawings.

FIG. 1 is a perspective view of a preferred embodiment of a double spindle type lathe in accordance with the present invention; FIG. 2 is a fragmentary front elevation thereof; FIG. 3 is a plan view thereof; FIG. 4 is a partial view, on an enlarged scale, illustrating a simultaneous machining operation by cutting tools of a first tool carriage and a third tool carriage; and 4 FIGS. SA and 5B are views similar to FIG. 4, but illustrate simultaneous machining operations by the first tool carriage and a third tool carriage and by a second tool carriage and the third tool carriage, respectively.

Referring now to the drawings, a preferred embodiment of a double spindle lathe in accordance with the present invention will be described in detail.

FIG. 1 illustrates a perspective view of the double spindle lathe 1 in accordance with the present invention. The lathe 1 may be a numerically controlled (NC) lathe. The lathe 1 comprises a first machining s'k--eD section 2A on the- left side as viewed and a second machining step section 2B on the right side.

As also shown in FIG. 2, which is a front elevation of the lathe 1, the first machining step section 2A comprises a first tool carriage 3 and a first spindle head 4 while the second machining step section 2B comprises a second spindle head 5 and a second tool carriage 6. As shown in FIG. 3 which is a plan view, with parts broken away, of the lathe 1, the first spindle head 4 has a f irst spindle 4a with a f irst chuck 20, while the second spindle head 5 has a second spindle Sa with a second chuck 22. A third tool carriage 7 is interposed between the f irst and second machining step sections 2A and 2B. The third tool carriage 7 is slidable in the direction B-C shown in FIG. 2 so that it can participate in either one of the machining steps in the sections 2A and 2B. All of the above-mentioned components are so mounted on a bed 8 that their axes are substantially at the same height.

The components stated above will be described below in more detail. The first tool carriage 3 has a turret 3a revolvable about a horizontal axis and consists of, for example, eight stations at which tools 16 such as turning, facing, drilling and other machining tools are securely mounted through respective holders on the 11 respective faces of the stations. In order to avoid interference among the mounted tools, the working diameter of the tool carriage 3 is determined greater than a predetermined value and the height position of the tool carriage 3 is determined to avoid interference with the bed 8.

As indicated in FIG. 2 which is a plan view, with some parts removed, of the double spindle lathe shown in FIG. 1, the f irst tool carriage 3 is mounted on a slide 10 which is slidable in an X-axis direction. The slide 10 in turn is mounted on a saddle 9, which is slidable in a Z-axis direction. Therefore, the first tool carriage 3 is slidable in both the Xand Z-axis directions.

Sliding guide surfaces of the saddle 9 and the slide 10 are provided with square guides 11 (See FIG. 2) so that the saddle 9 and the slide 10 are guided by the square guides 11 when they are caused to slide in a predetermined direction to a predetermined position by the rotation of two feed screws 12 and 13 which extend in orthogonal relationship with respect to each other. The feed screws 12 and 13 are drivingly coupled IL-0 servomotors 14 and 15, respectively, whose directions and speeds of rotation are determined in response to command signals from a control unit (not shown) so that the slide 10 can be moved to and located at a predetermined position. Therefore, a cutting tool 16 securely mounted at a station on the turret 3a of the tool carriage 3 can be moved in the Xand/or Z-directions to machine a workpiece, which is securely clamped by the first chuck 20 at one end of the f irst- spindle 4a and is rotated by the force- of rotation transmitted from a f irst spindle motor (not shown) through a known power transmission gear train (not shown).

The third tool carriage 7 is located substantially 35 at the center of the bed 8 and mounted on a slide 21 which is moved by an X-axis feed screw not shown to t-he left and right as viewed in FIG. 3 between the first 6 spindle head 4 and the second spindle head 5. The X-axis feed screw for the slide 21 is rotated by a servomotor not shown. The slide 21 is slidably mounted on a saddle 24 which is movable in the Z-axis direction. The tool carriage 7 is preferably smaller in diameter than the first tool carriage 3 and slides in the X-axis and Z-axis directions to machine the workpiece securely held by the chuck 20 of the first spindle 4 or by the chuck 22 of the second spindle 5, with a cutting tool 17 mounted on a third turret 7a of the tool carriage 7. The tool carriage 7 can be also moved by a predetermined distance in the Z-axis direction upon energization of a servomotor 23 which rotates a Z-axis feed screw.

Because of the provision of the third tool carriage 3 in the manner described above, when the first and second machining steps are determined, the third tool carriage 7 can be determined to participate in the machining in either the first or second machining step. Thus, the length of period of a complete machining cycle can be shortened as described hereinafter.

The second spindle head 5 and the second tool carriage 6 are similar in construction to the first spindle head 4 and the first tool carriage 3 and are mounted in symmetrical relationship with respect to the intermediate third tool carriage 7. The second tool carriage 6 has a Z- axis servomotor 30, a Z-axis feed screw 31, an X-axis servomotor 32, an X- axis feed screw 33, a slide 34 and a saddle 35. The second tool carriage 6 has a turret 6a on which a series of tools 18 are securely mounted. In the second machining step section 2B, the second tool carriage 6 is moved to the lef t (in the X-axis direction) as viewed in FIG. 1 and machines the workpiece securely held by the second chuck 22 of the second spindle head 5.

The mode of operation of the double spindle lathe will now be described. The first tool carriage 3 mounted on the slide 10 is moved in the X-axis direction as 7 indicated by an arrow A when the servomotor 14 is energized. Then, the cutting tool mounted on the tool carriage 3 approaches the workpiece securely held by and rotating with the chuck 20 of the first spindle head 4 and machines the workpiece. The movement in the Z-axis direction of the first tool carriage 3 is effected by the rotation of the feed screw 13 drivingly coupled to 'the servomotor 15.

When the third tool carriage 7 is to be used together with t-he first tool carriage 3 in the first machining step section 2A, the tool carriage 7 is moved in the X-axis direction as indicated by an arrow B by the servomotor (not shown) to approach the workpiece securely clamped by the chuck 20 of the first spIndle head 4 so that both the cutting tools mounted on the first and third turrets 3a and 7a of the tool carriages 3 and 7 concurrently machine the workpiece.

As described before, the second tool carriage 6 is located in symmetrical relationship with the first tool carriage 3 and is substantially similar in construction to the tool carriage 3. A desired operation of the second tool carriage 6 can be accomplished by controlling the feed screw 31 drivingly coupled to the servomotor 30 and the feed screw 33 drivingly coupled to the servomotor 32.

When the third tool carriage 7 is to be used in the second machining step section 2B, the tool carriage 7 is moved in the X-axis direction as indicated by an arrow C by the servomotor (not shown) so that one of cutting tools 17 mounted on the tool carriage 7 approaches the workpiece clamped by the chuck 22 of the second spindle head 5 and, together with one of the cutting tools 18 mounted on the second tool carriage 6, machines the workpiece.

In these operations, the tool carriages 3, 6 and 7 can be moved independently of each other. Therefore, a comparison is made between the machining step periods in 8 the first and second machining step sections 2A and 2B to determine which machining step is longer. After the determination, the third tool carriage 7 is moved toward either the first or second machining step section which requires a longer machining period to participate in the longer machining step. As a result, the difference between the first and second machining step periods can be decreased.

Next referring to FIGS. 4 and 5, some examples of machining operation carried out by using the third tool carriage 7 will be described.

FIG. 4 illustrates an operation for cutting an outer surface of a workpiece W clamped by a hydraulic chuck 20 of the first spindle head 4 by simultaneously operating the first and third tool carriages 3 and 7.

In this case, the cylindrical workpiece W which is slightly greater in outer diameter than a portion to be machined is securely clamped by the hydraulic chuck 20 and the cylindrical surface of the workpiece W is cut by a cutting depth t with a cutting tool 40 mounted on the first tool carriage 3 and concurrently by a cutting depth t with a cutting tool 41 mounted on the third tool carriage 7. Therefore, as compared with the cutting operation only by the first tool carriage 3, when the two cutting tools are simultaneously used, the cutting period can be decreased by, for example, about 30% (from 81 sec. to 58 sec.) and the difference between the cutting period in the first machining step section 2A and the cutting period (51 sec.) in the second machining step section 2B can be decreased from 30 sec. to 7 sec. As a result, the machining cycle with this lathe 1 can be shortened to 58 sec. FIGS. 5A and 5B illustrate an example of a gear idler cutting operation-. 35 FIG. 5A illustrates a boring operation of a workpiece W clamped by a hydraulic chuck 20, by a cutting tool 42 mounted on the first tool carriage 3, as well as 9 a facing operation of the workpiece W by a cutting tool 43 mounted on the third tool carriage 7.

Since the machining operations are carried out simultaneously by the two cutting tools 42 and 43, the 5 cutting period can be shortened to, for example, 49 sec. as compared with the cutting period when only the cutting tool 42 on the first tool carriage 3 is used. In the succeeding machining step, the surface cutting of the workpiece W and the facing of the other end thereof can also be simultaneously carried out by concurrently using cutting tools 43 and 44 mounted on the second and third tool carriages 6 and 7 when the workpiece W is securely clamped by the hydraulic chuck 22. As a result, the difference in cutting period between the first and second machining step sections 2A and 2B can be shortened to only one second and the overall machining cycle can be decreased by, for example, about 15%.

In addition to the third tool carriage 7, a suitable attachment may be mounted on the slide 21.

For instance, when an automatic loader is mounted on the slider 21, the transfer of the workpiece from the first machining step section to the second machining step section can be automated and, in this case, the orientation of the workpiece can be suitably reversed. In addition, a tail stock for a long workpiece and a work rest may be mounted on the slide 21 so as to securely hold a workpiece in position.

Claims

CLAIMS:

1. A double spindle type lathe comprising:

a first machining step section including a first spindle head with a first spindle having a first chuck for holding a workpiece, and a first tool carriage having cutting tool means thereon; a second machining step section including a second spindle head with a second spindle having a second chuck for holding a workpiece, and a second tool carriage having cutting tool means thereon; and a third tool carriage having cutting tool means and interposed between said first and second machining step sections, said third tool carriage being movable so as to cause the cutting tool means thereof to approach and cut the workpiece held by either said first or second chuck while the workpiece is being cut by the cutting tool means of either said first or second tool carriage.

2. The double spindle type lathe according to claim 1, wherein said first and second spindle heads are disposed in parallel with said third tool carriage disposed in parallel between said two spindle heads and wherein said first and second tool carriages are disposed on the opposite sides of said third tool carriage with respect to the first and second spindle heads.

3. The double spindle type lathe according to claim 1, wherein said first and second tool carriages have first and second turrets for mounting the cutting tool means.

4. The double spindle type lathe according to claim 1, wherein said third tool carriage has a turret for mounting the cutting tool means.

5. The double spindle type lathe according to claim 2, wherein said third tool carriage has a slide movable toward and away from the first and second spindle heads and in a direction parallel to the first- and second spindle heads.

E A double spindle type lathe substantially as hereinbefore described and with reference to the accompanying drawings.