The present invention relates to a method and an apparatus for the finish-machining of the bearing diameters, particularly the main bearing diameters and of the adjoining cheek side surfaces on crankshafts and similar workpieces in a single chucking. In order that this machining can be carried out rapidly and nevertheless with a high quality of production, the following method steps are carried out, one after the other: milling of the cheek side surfaces to nominal size up to the bearing diameter; turning of the bearing diameter down to a small oversize; turning-broaching of the bearing diameters to nominal size in order to obtain a good quality surface, and possibly turning/turning-broaching of recesses, clearance cuts and undercuts in the region of the bearings.

BACKGROUND OF THE INVENTION 
The present invention relates to the machining of the bearing diameter, 
particularly the main-bearing diameters, as well as of the adjoining 
cheek-side surfaces on crankshafts and similar workpieces. 
In the case of these workpieces, it is desired not only, in particular, to 
obtain the highest possible precision upon production both of the 
roundness and of the desired diameter, especially of bearing diameters 
but, in addition, to obtain a manufacture which is as cost-favorable as 
possible, as is true in the case of all mass-produced workpieces. In order 
to achieve these goals, which frequently diverge in their effects, the 
machining method which seemed optimal was in the past already selected, 
namely cutting, milling or grinding. In addition, it is also clear that 
frequent rechucking of the workpiece during the machining leads, due to 
slight differences upon the rechucking, to inaccuracies in manufacture or 
at least to an increase in the time required for the next machining steps, 
so that complete machining in a single chucking is desirable. 
In addition to the machining methods indicated above, so-called 
turning-broaching is also already known from German Application P 35 23 
274; in it a disk-shaped broaching tool which has cutting edges on its 
circumference rotates slowly during the machining with respect to the 
rapidly rotating workpiece and machines the circumferential surface 
thereof. In this connection, the infeed movement can be effected in the 
manner that the individual cutting edges have an increasing distance from 
the center point of the turning-broaching tool on the circumferential 
surface of said tool. The infeed movement can, however, also be effected 
in the manner that all cutting edges are at the same distance from the 
center of the tool and the infeed movement is effected by a radial 
movement of the entire tool towards the workpiece. By this so-called 
turning-broaching, greater precision than with normal turning can be 
obtained upon the production of the bearing diameters. To be sure, the 
number of cutting edges of the turning-broaching tool is limited by the 
circumference of the tool, so that only limited radial oversizes of the 
workpiece can be removed. 
Therefore, a combination of turning and turning-broaching, carried out on a 
single machine tool, has gained acceptance recently for the 
finish-machining of crankshafts. In this connection, both cutting edges 
used for the plunge-cut turning and cutting edges used for the 
turning-broaching are present on the tool, which is swingable around an 
axis parallel to the longitudinal axis of the workpiece. In the simplest 
case, a plunging-turning edge which has the width of the entire bearing 
diameter to be machined is present on this tool as well as a 
turning-broaching cutting edge which also has the full width of the 
bearing diameter to be produced. With the plunging turning tool--which in 
practice, is normally narrower than the length of the bearing diameter in 
order to avoid chattering--the bearing diameter is, first of all, cut down 
from the original high oversize to a very small oversize on the order of 
about 1/10 mm. The tool is then withdrawn from the workpiece and, while 
maintaining a high speed of rotation of the workpiece on the order of 
about 1000 rpm, the turning-broaching cutting edge of the swingable tool 
is swung in an arcuate path into the bearing diameter to be produced, the 
swinging movement being of such a speed that the turning-broaching cutting 
edge remains in engagement for more than one and generally for about two 
revolutions of the workpiece. With this turning-broaching machining, the 
bearing diameter of the crankshaft is completely machined to such an 
extent that pre-grinding can be dispensed with so that only 
finish-grinding is effected. 
The machining of the side surfaces of the cheeks, which is effected by 
surfacing with a lathe tool, is effected before said machining. 
In addition, recesses or even undercuts, etc., which are, for instance, 
required in the cheek side surfaces in the vicinity of the bearing 
diameter, must be produced by plunge feeding or turning-broaching, etc. 
The tools for this are also integrated in the swingable tool. 
Although a faster advance of the machining, particularly upon the 
plunge-cutting, can be obtained by means of traditional turning than upon 
a turning-broaching which provides a good surface--particularly upon the 
removal of large amounts of material--milling is usually even faster but, 
to be sure, it results in a substantially poorer surface than 
turning-broaching or normal turning. 
SUMMARY OF THE INVENTION 
Starting from this, the object of the invention is to provide a method, as 
well as an apparatus for the carrying out thereof, by means of which cheek 
side surfaces as well as bearing diameters on crankshafts can be produced 
rapidly and nevertheless with a high quality of production. 
Only slight demands are made on the quality of the machining of the side 
surfaces of the cheeks. At the same time, not only must the largest radial 
advance of machining be carried out there but, at the same time, the 
largest amount of material to be removed is also present there. 
In this connection, first of all the cheek side surface adjoining the 
bearing diameter, or even both adjoining cheek side surfaces depending on 
the stability of the workpiece, are machined simultaneously by, for 
instance, a disk-shaped outer miller which works slowly from the outer 
edge of the cheeks towards the bearing diameter. Depending on the 
dimensioning of the milling tool and of the cheek to be machined, the 
workpiece is, in this connection, stationary, at least at the start, and 
will possibly slowly turn further upon reaching the desired radial depth 
of infeed so as to obtain advance of the machining in the direction of 
rotation of the crankshaft along the cheek side surface. For this, 
naturally, a so-called C-axle drive, where the rotational position of the 
drive of the workpiece can be controlled, is necessary. 
If such a drive is not present, but, instead of this, as shown in the 
embodiment, the Y-axis is developed for the milling unit, it is then 
sufficient to align the cheek directly on the milling unit and allow the 
latter to work forward towards the bearing diameter. In this way, after 
the desired depth of milling has been reached, further material on the 
cheek side wall which is to be removed remains alongside the disk miller. 
In order to reduce it, the milling unit is now moved on both sides in Y 
direction. In this way, the remaining amounts, to be sure, are not 
completely eliminated but are sufficiently small not to impair the 
function of the workpiece. 
Nor is this disturbing for the machining of the bearing diameters, since 
the side surfaces of the cheeks are in any event arranged still further 
back with respect to the outer limitations of the bearing diameters in the 
lengthwise direction. In view of this, the machining sequence can also be 
so selected that first of all, the bearing diameter is machined by turning 
and turning-broaching before the cheek side surfaces are machined by 
milling. 
After completion of this machining step, the milling tool is withdrawn from 
the workpiece and the known combined turning/turning-broaching tool is 
placed in action, the bearing diameter itself being finish-machined by it 
in known manner and any recesses, etc. in the cheek side surfaces, etc. 
which are still required are produced. 
During this machining the workpiece, of course, remains firmly chucked, it 
being dependent primarily on the stability of the workpiece whether this 
chucking is effected on both sides by rotation-driveable chucks, or on one 
side only by a center point. 
In order to be able to finish-machine a crankshaft in this way without 
rechucking, both the milling unit and the combined 
turning/turning-broaching unit must be moveable in each case independently 
at least in X direction without interfering with each other. If several 
bearing places on a crankshaft are to be machined one after the other, the 
possibility of movement of these machining units also in Z direction is 
furthermore necessary. 
The arrangement of the two machining units diametrically opposite each 
other with respect to the workpiece is advantageous, the X direction being 
furthermore selected vertical in order, in this way, to assure, on the one 
hand, a good dropping off of the chips and, on the other hand, a good 
possibility of observing the progress of the machining. 
The vertical displaceability of the two machining units above and below the 
workpiece can be realized with different designs of the bed which differ 
with respect to the arrangement of the guide planes for the displacement 
in the Z direction of the carriages on which the machining units are 
mounted. 
For this purpose, there is advantageously employed a machine bed which 
consists, in known manner, of a bed lower part of, for instance, polymer 
concrete and a metal bed upper part, two separate guide planes arranged at 
an angle to each other being provided on the bed upper part for the 
guiding of individual components in Z direction. A bed slide on which in 
each case one machining unit is mounted, can be guided in each of the two 
guide planes. 
The bed upper part, in this connection, has a shape such as known from 
German Application P 39 21 649: the two guide planes are arranged at a 
right angle to each other, the first guide plane, the upper one, 
descending forward towards the operator from the rear region of the lathe 
and the second guide plane extending downward and rearward from the front 
edge of the first guide plane, thereby forming an overhang. Furthermore, 
except for the uppermost guide surface of the second guide plane, all 
guide surfaces are so steep or even overhanging that no metal chips can 
deposit thereon. The guide surfaces of the first guide plane all lie above 
the lathe center. In this connection, the individual guides have, in part, 
a plurality of guide surfaces one of which in each case is always parallel 
to the corresponding guide plane to which the corresponding guide belongs. 
Furthermore, the second guide plane has a guide which has two guide 
surfaces each of which is parallel to one of the two guide planes. This 
guidance lies in the vicinity of the point of intersection of the two 
theoretical guide planes. From said Application, there can also be noted 
in detail the advantages of this bed design, namely, stated roughly, an 
unimpeded dropping off of the chips, which however, need not be obtained 
by the disadvantage of machining units which protrude horizontally from 
the bed and of the turning moments which result thereby already from the 
force of gravity. Due to this form of bed, an additional possibility of 
movement in Y direction can also be provided, which, to be sure, is not 
absolutely necessary just for the machining described of a crankshaft but 
makes possible the manufacture of additional details on the workpiece. 
Other features and advantages of the present invention will become apparent 
from the following description of the invention which refers to the 
accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
On the end of the bed 1 which can be noted on the right-hand side of FIG. 1 
there is the division into the bed lower part 11, consisting usually of 
concrete and having an approximately triangular cross section, and the 
metal bed upper part 10 seated thereon which is of approximately 
rectangular cross section. This bed upper part 10 with its rectangular 
cross section is, however, set obliquely so that its upper surface is 
inclined obliquely forward and therefore towards the operator of the 
machine tool. 
One of the two machining units of the machine tool is guided on this upper 
surface of the bed upper part 10. For this purpose, a bed carriage 3 can 
move on the upper surface of the upper part of the bed in the longitudinal 
direction of the machine and therefore in Z direction. On this bed 
carriage 3, an upper support 4 is moveable transverse to the Z direction 
towards and away from the operator, whereby the Y axis of the machine tool 
is also realized. 
The X axis of the machine tool is realized by a cross slide 5 which is 
moveable in vertical direction on the upper support 4. The milling unit 6 
which bears the externally toothed disk mill 14 and drives it is fastened 
on this cross slide 5. This disk mill 14 is shown as a simple disk in FIG. 
1, and only a few teeth of the disk mill 14 are shown symbolically in FIG. 
2 also. 
The machine tool furthermore also comprises the headstock 12 as well as the 
tailstock 2 for the attachment and drive of the crankshaft as well as 
another machining unit, both of them however being guided on the 
overhanging front surface of the bed upper part 10. Since in the second 
machining unit only the X axis but not the Y axis is realized, the cross 
slide 15 is fastened directly vertically on the bed carriage 13. 
As shown in FIG. 2, neither the lower machining unit nor the headstock 12 
has contact with the oblique front surface of the bed lower part 11, which 
serves, inter alia, for the removal of the chips falling thereon into the 
chip conveyor 8 which is present in front of the bed 1 and is shown 
diagrammatically in the form of a trough. 
In FIG. 2, in addition to the groups explained in connection with FIG. 1, 
the individual guides and guide surfaces are shown on which the relative 
displacement of the individual components with respect to each other takes 
place: On the top of the bed upper part 10, the bed carriage 3 which bears 
the milling unit is guided in Z direction by means of two guides 20, 24. 
Each of these guides consists of a plurality of guide surfaces, the guide 
surfaces 21 and 23 of the guide 20 as well as the guide surface 26 of the 
guide 24 lying in the direction of the guide plane 101 and therefore 
obliquely forward towards the operator. In addition, each of the two 
guides 20 and 24 has a guide surface 22 and 25 respectively, which 
surfaces extend transverse to the direction of the other guide surfaces. 
In this way the guide surfaces 22 and 23 of the guide 20 form an upward 
extending ridge-shaped prism which is supplemented to form a U-shaped 
guide by additional guide surfaces 21 which adjoin the guide surface 22 
and are parallel to the guide surface 23. For the mounting and removal of 
the bed carriage 3, there is therefore necessary a ledge 38 which is 
removable from the bed carriage 3, engages behind said U-shaped guide 20 
and rests against the guide surface 21. 
In the case of the guide 24, the guide surfaces, in contradistinction to 
those of the guide 20, are not in each case at a right angle to each 
other; rather the two guide surfaces 25 and 26 are at an acute angle to 
each other and thus form practically half a dovetail guide. The part of 
the bed carriage 3 which engages in this guide 24 is also developed 
removably as a V-ledge 27. 
The drive of the bed carriage is effected via the drive spindle 7 shown in 
FIG. 2. 
Furthermore, it can be noted in FIG. 2 in connection with this upper tool 
unit that, despite the inclined guide plane 101 along which the bed 
carriage 3 is displaced on the bed upper part 10, the upper carriage 4 
which is displaceable transversely to the length of the machine is 
displaced along a horizontally lying guide 18. On this upper carriage 4, 
in its turn, the cross carriage 5 is moveable vertically in the direction 
to and away from the center of rotation 40 of the workpiece. 
Although this realizing of the Y axis is not necessary for the machining by 
a milling unit described, it must be assumed that this Y axis is 
nevertheless already present in many cases, namely when an existing lathe 
is re-equipped by replacing a tool unit with the milling unit. 
Vertical and horizontal course of X and Y axes facilitate not only the 
comprehending of the tool movements by the operator but also the 
programming of the machine, which is increasingly being left to the 
operator. 
Corresponding to the vertically placed X axis, the second machining unit, 
namely the combined turning/turning-broaching unit 44 lies precisely below 
the disk mill 14, as indicated by the line t. The bed carriage 13 which 
moves the turning/turning-broaching unit 44 in Z direction is guided in 
the guide plane 102, on top on the guide surface 33 and on bottom on the 
guide 34 which consists of the guide surface 36 which overhangs and is 
parallel to the guide plane 102 and of the guide surface 42 which adjoins 
it at a right angle, as well as of a guide surface 35 which adjoins it at 
the bottom at an acute angle and is held, for instance, by PEKU units 
against same. 
All guide surfaces of these guides are located behind the upper front edge 
of the bed upper part 10 which extends furthest forward and are thus 
protected from chips, tools and other objects dropping down from above. 
The drive spindles 7 and 17 serve for the Z-movement of the bed carriage. 
Furthermore, in FIG. 2 both the turning-plunge tool 45 and two 
turning-broaching cutters 46 are shown diagrammatically on the 
turning/turning-broaching unit 44. In the event that the bearing diameter 
to be machined is a large machining width, then, of course, in order to 
avoid chatter movements the plunge cutting can take place in several 
partial operating steps alongside of each other, either by repeated 
withdrawal and infeed of the turning/turning-broaching unit 44 or else by 
a plurality of plunge lathe tools 45 arranged spaced apart on this unit 
44, provided in each case for the machining of a partial region. 
Similarly, in the present case there are shown symbolically two 
turning-broaching cutters 46 which are at an increasing distance from the 
center point of the turning/turning-broaching unit 44 so that the infeed 
movement in this case is located in the increasing distance between the 
cutting edges and the center point. Of course, with correspondingly small 
oversize to be removed, these turning/turning-broaching cutters can be 
reduced to a single one or even, in the case of the presence of a 
plurality of turning-cutting broaches, they can be at the same distance 
from the center point of the turning/turning-broaching unit, in which case 
the infeed must be effected by an X movement of the tool holder unit 16. 
In this case, the infeed movement must be carried out when none of the 
turning-broaching cutters 46 is in engagement. For this, however, with a 
diameter of the turning/turning-broaching unit 44 of about 700 mm, a 
distance between cutters of 9.degree. is, for instance, sufficient. 
Theoretically, furthermore, for the carrying out of the turning plunge feed 
process, as well as of the turning-broaching process, one and the same 
cutting edge could be used. Since for both machining processes, however, 
geometrically slightly differently shaped cutting edges lead in each case 
to optimum machining results, the restriction to merely a single common 
cutting edge is dispensed with. The milling unit 6 in the present case is 
arranged above the turning center 40 and therefore the workpiece 29, since 
the turning/turning-broaching unit lying below it is less susceptible to, 
for instance, a jamming of the plunge cutting turning tool 47 with the 
workpiece 29 occurring due to chips falling down from above. With the 
reverse arrangement, on the other hand, chips could fall more easily into 
the spaces between the teeth of the disk mill 14 and lead there to an 
unsatisfactory result of the machining or to damage to the tool. Of 
course, further baffle plates, etc. can be arranged in front of the 
machine in order to conduct the chips falling down from the machine to the 
chip conveyor, but most of the small chips which easily fly about are 
produced upon the milling, in which connection it is possible, by 
selection of the direction of turning, to have these chips fly in the 
direction towards the machine and not of the operator, in which 
connection, of course, the entire machine is covered by a protective cover 
in order to protect the operator. 
Furthermore, the turning/turning-broaching unit may have still other plunge 
cutting tools such as necessary for the establishing of required recesses, 
etc. in the limit region between bearing diameter and cheek side surface. 
After this machining of the crankshaft, the pregrinding which is otherwise 
customary can be dispensed with, so that merely a finish grinding of the 
bearing diameter, and therefore the removal of a very small oversize, is 
still necessary. 
Although the present invention has been described in relation to particular 
embodiments thereof, many other variations and modifications and other 
uses will become apparent to those skilled in the art. It is preferred, 
therefore, that the present invention be limited not by the specific 
disclosure herein, but only by the appended claims.