DE10019669C2 - Process and machine tool for machining workpieces - Google Patents

Description

The invention relates to a method for processing Workpieces, on the two slides, at least of which one carries a tool or workpiece, along two intersecting traversing axes moved relative to each other to make relative movements between a tool and to produce a workpiece. In addition, the Invention a corresponding machine tool.

Known machine tools have a stand a horizontal work spindle by means of a support is vertically movable. Extends in front of the stand Bed on which a workpiece table with horizontal Clamping surface and vertical axis of rotation is guided parallel to the work spindle. With a cubic Each of the four sides will face one in the workpiece Tool spindle picked up and turned This works by making the workpiece table relatively moved to the stand. On the other hand, it is common knowledge to guide the stand parallel to the spindle and the  Arrange the workpiece table in a fixed position. In both cases the top surface remains unprocessed.

For processing both the side surfaces and the A milling machining center is known for the top surface the workpiece table is not just about a vertical axis rotatable, but also about a 45 degree inclined axis is pivotable, so that with a horizontal clamping surface of the Workpiece table all sides and with vertical Clamping surface, the top surface can be brought in front of the tool is. It is also known that instead of the workpiece table Working spindle about a 45 degree inclined swivel axis store the tool in a horizontal or vertical position Panning position.

All of the above machine tools are independent on the number of editable pages, common that the possible delivery speed along the horizontal Tool axis z and the perpendicular axis y relative is low. In addition, the chip disposal prepares Difficulties while the asymmetrical Machine structure represents a large total effort.

In a known milling process (DE 31 01 781 A1) are tool slides and workpiece slides in the Coordinate axes of the machine coordinate system simultaneously moves in opposite directions, so that in these axes resultant feed rates that  are twice as high as the travel speeds of the Carriage. The corresponding machine tools each have Coordinate axis a movable along this axis Tool slide and one that can be moved in the same axis Workpiece slide on what the opposite Arrangement of two complete machine tools corresponds. The increase in speed and power goes on here A great effort.

The invention is based on the object generic method and a generic Machine tool to create the high Combine feed speeds with little effort. According to the invention, this object is achieved through the features of Claims 1 and 7 solved.

Advantageous training result from the subclaims.

In the process of machining workpieces two sledges, at least one of which is a tool or carries a workpiece along two intersecting ones Traversing axes moved relative to each other Relative movements between a tool and one To produce the workpiece. This is done according to the invention in that the relative movements along one both Moving axes intersecting the first coordinate axis of a Cartesian diagonal to the traversing axes Coordinate system through simultaneous co-movement  Move both sledges and one along both Traversing axes intersecting the second coordinate axis of this Coordinate system through simultaneous opposite Movement of both carriages are generated using the tool with its tool reference axis, for example a longitudinal and / or axis of rotation, and / or the workpiece with its Reference axis, for example one perpendicular to the Workpiece surface standing axis, parallel or is aligned perpendicular to these coordinate axes. The two sledges can be a cross slide system form that a tool or one placed thereon workpiece arranged on it with respect to a spatially fixed arranged workpiece or a spatially arranged Tool moves. But it is also possible to get one Tool-carrying slide and a workpiece moving carriage to move relative to each other. The Traversing axes are symmetrical to the coordinate axes arranged. They are preferably mutually orthogonal and to the mutually orthogonal coordinate axes rotated against each other by 45 degrees. Both sledges will be especially moved at the same speed.

The corresponding machine tool has two slides, at least one of which is a tool or a workpiece carries, and two intersecting traversing axes, lengthways of which the slides are movable relative to one another in order to  Relative movements between a tool and one To produce the workpiece. According to the tool its tool reference axis, for example a longitudinal and / or axis of rotation, and / or the workpiece with its Workpiece reference axis, for example one perpendicular to Workpiece clamping surface axis in which the Traversing axes spanned plane aligned or can be adjusted so that the slide moves at the same time Relative movements between tool and workpiece orthogonal or parallel to the tool and / or Workpiece reference axis are possible. The cuts aligned tool and / or workpiece reference axis both Traversing axes. The particularly parallel to each other extending reference axes of the tool and the Work piece with orthogonal to each other Travel axes angle of 45 degrees. Relative movements between tool and workpiece are along the first Coordinate axis by moving in the same direction and along the second coordinate axis by moving the two slides can be generated. The traversing axes are among the Coordinate axes arranged symmetrically, orthogonal traversing axes and orthogonal to each other coordinate axes running to each other the sled turned against each other by 45 degrees can be moved just as quickly.  

According to a first training, the two slides form a cross slide system, with which one arranged on it Tool or workpiece with respect to a fixed Workpiece or tool is movable. By the two Slide along the traversing axes with the same Velocities v are traversed between moving tool and fixed workpiece or between moving workpiece and stationary tool along the Coordinate axes x and z resulting speeds in the amount of vx = vz = v.√2, with these two sledges compared to the prior art instead of an axial direction two axis directions x and z can be generated, which is the Machine expenditure significantly reduced. The cut Tool axes are the traversing axes, preferably under 45 degree angles. That is in front of the bed Workpiece that is on an immovable workpiece table is recorded, the clamping surface parallel to Traversing plane of the tool runs. The workpiece table can be rotated about a normal axis of rotation. The Tool is in one on the cross slide system arranged tool holder arranged. Are preferred at least two arranged on a common bed Cross slide systems provided, in particular on are guided tours. The tool axes  two cross slide systems are orthogonal to each other.

According to a second training, an as Tool slide trained slide and an as Workpiece slide trained slide relative movable to each other. By the tool slide and the Workpiece slides along the travel axes with the same Velocities v are traversed between moving tool and moving workpiece along the Coordinate axes y1 and z1 resulting speeds in the amount of vy1 = vz1 = v.√2, even with this training with two sleds not just one, but two Coordinate axes are operated. The tool slide carries a tool holder for holding a tool, the workpiece slide a workpiece table for holding of a workpiece.

One especially for five-sided editing The machine tool provided has a first orientation the tool holder and the workpiece table in which the mutually orthogonal coordinate axes of the Machine coordinate system compared to each other orthogonal travel axes are rotated by 45 degrees and Relative movements between tool and workpiece along the first coordinate axis by moving the Tool holder and the workpiece table away from each other  or towards each other and along the second coordinate axis by moving the Tool holder and the workpiece table can be generated. In addition, a second alignment of the Tool holder and the workpiece table can be provided, in which the traversing axes are parallel to the coordinate axes run and relative movements along the coordinate axes by moving the workpiece holder or the Work table can be generated. In the first orientation can be four with a rotating workpiece table Process workpiece sides, with the same Travel speeds v along the workpiece axes y1 and z1 resulting velocities of vy1 = vz1 = v.√2 surrender. In contrast, in the second alignment with lower speeds vy2 = vz2 = v the fifth Workpiece side are processed. To realize the x The axis is the tool holder and / or the workpiece table can be moved in this direction with the speed Vx = v. In the first orientation, the tool axis intersect the Tool holder and the clamping plane of the workpiece table the respective travel axis at angles of 45 degrees. In In the second orientation, the tool axis of the Tool holder and the clamping plane of the workpiece table parallel to the respective traversing axis. Assign the Traversing axes inclinations of 45 degrees, there is a  symmetrical machine structure, on the one hand represents little overall effort and a good one Chip disposal guaranteed and on the other hand vertical and horizontal machines united without problematic stands get along. Here is the Tool slide guided on inclined first guides, while the tool holder is a first pivot axis is pivotable between a first Position in which the tool axis runs horizontally, and a second position, in which the tool axis is parallel to the first tours. The is accordingly Workpiece slide guided on inclined second guides, while the workpiece table is a guide orthogonal second pivot axis is pivotable between a first Position in which the clamping surface runs horizontally, and a second position in which the clamping surface runs parallel to the second tours. The Workpiece table can be an orthogonal to the clamping surface The axis of rotation can be rotated. The first and second tours are one in the opposite inclined planes Cross-section V-shaped bed arranged, preferably over a chip conveyor, which is in the direction of the third coordinate of the machine coordinate system extends.  

Both training courses have in common that Tool holder and / or the workpiece table in this third coordinate are movable.

The invention is illustrated below with two Exemplary embodiments explained in more detail. In the associated schematic drawings show:

Fig. 1 is a front view of a milling center for five-face machining with horizontally oriented work spindle and horizontally oriented workpiece table in the relative operating y1max, z1max,

Fig. 2 y1min in the relative operating point Z1max,

Figure 3 y1max. In the relative operating point z1min,

Fig. 4 y1min in the relative operating point z1min,

Fig. 5, the milling center with work spindle inclined at 45 degrees and 45 degrees inclined workpiece table in the relative operating y2max, z2max,

Fig y2min. 6 in the relative operating point z2max,

Figure 7 y2max. In the relative operating point z2min,

Fig y2min. 8 in the relative operating point z2min,

Fig. 9 is a plan view of a milling machining center with two operating spindles illustrating the tool movement in the x direction, and

Fig. 10 illustrating the tool movements in the z direction.

The milling machining center according to the Figs. 1 to 8 comprises a symmetrical bed 2 with an upwardly open V-shaped profile 4 on whose mutually orthogonal guide planes 6, 8, 45 degrees are respectively inclined guides 10, 12 carry, following the inclinations.

On the inclined guides 10 of the one bed half 14 , a carriage 16 is guided between the upper and lower ends thereof along the travel axis A1. This carries a carriage 18 which is displaceable on guides 20 parallel to the guide plane 6 and perpendicular to the guides 10 along the coordinate axis x. A spindle head 24 , in which a milling spindle 28 rotates about a spindle axis 26, is mounted on the slide 18 about an x-parallel pivot axis 22 .

The inclined guides 12 of the opposite second bed half 30 guide a slide 32 between their upper and lower ends along the travel axis A2, on which a rotary or partial table 36 with an axis of rotation 40 orthogonal to the workpiece clamping surface 38 is mounted about an x-parallel pivot axis 34 . A tool WZ1 is inserted into the milling spindle 28 , and a cubic workpiece WS1 is clamped on the workpiece clamping surface 38 .

The mutually inclined guide planes 6 , 8 open out via an x-parallel chip conveyor 42 .

The mode of action is as follows:  

In a first orientation according to FIGS. 1 to 4, the spindle head 24 together with the spindle axis 26 is just as horizontal as the rotary table 36 including the workpiece clamping surface 38 . The second coordinate axis y1 of the machine coordinate system runs vertically and the third coordinate axis 21 horizontally, ie the coordinate axes y1 and 21 are rotated by 45 degrees with respect to the travel axes A1 and A2. In the starting position according to FIG. 1, the slide 16 is located at the upper end of the guide level 6 and the slide 32 is in the middle of the guide level 8 . This corresponds to a relative working point y1max, z1max.

If the slides 16 and 32 are moved in opposite directions along the travel axes A1 and A2 with vA1 = vA2, ie the slide 16 from top to bottom and the slide 32 from bottom to top, only the mutual distance between the work spindle changes 28 and rotary table 36 in the y1 direction and their absolute z1 positions, while the mutual distance in the z1 direction is retained. At the relative working point z1max, y1min ( FIG. 2), the carriage 32 is in its upper position, while the carriage 16 has reached its middle position.

If, on the other hand, the slides 16 and 32 are moved in the same speed from the positions shown in FIG. 1, ie, both slides 16 and 32 from top to bottom, only the mutual distance in the z1 direction and the absolute y1 positions change while the mutual distance in the y1 direction is retained. FIG. 3 shows the relative working point z1min, y1max, in which the slide 16 is at its middle height and the slide 32 at the lower end.

In order to get to the relative working point z1min, y1min ( FIG. 4), the two slides 16 and 32 are moved in opposite directions from the positions according to FIG. 3, ie the slide 16 from top to bottom and the slide 32 from below upwards, whereby the mutual distances in the y1 direction and the absolute z1 positions change, but not the mutual distance in the z1 direction.

In all of these cases, the direction arises from that Coordinate axis in which there is a mutual distance changes, a rate of change that is √2 times the Carriage speed is.

If one wanted to get out of the positions according to FIG. 2 into the positions according to FIG. 3, one would have to hold the slide 16 and only move the slide 32 from top to bottom, so that both the mutual distances z1, y1 move in both directions the absolute positions also changed. A corresponding procedure would have to be followed if one wanted to get from the positions according to FIG. 1 into the positions according to FIG .

It would also be possible to generate simultaneous changes in distance in both directions z1, y1 with different speeds of the slides 16 and 32 . If one were to turn each of the sides of the workpiece WS1 in the direction of the work spindle 28 by means of a rotary table 36 and the slide 18 was also moved in the x direction, four workpiece sides could be machined completely in this way.

In order to also be able to machine the fifth free side, the spindle head 24 is pivoted downward about the pivot axis 22 and the rotary table 36 about the pivot axis 34 by 45 degrees, so that the spindle axis 28 parallel to the guide plane 6 and the workpiece clamping surface 38 parallel to the guide plane 8 runs. The second coordinate axis y2 then runs parallel to the guide plane 8 , the third coordinate axis 22 parallel to the guide plane 6 . The speeds at which the distances between the work spindle and the workpiece table change along the coordinate axes correspond here to the speeds of the slide 16 or 18 , since only one slide 16 , 18 is involved per coordinate axis. Although shown on a machine tool with a V-shaped bed, the invention also includes solutions with a vertical and a horizontal bed half, provided the traversing axes arranged thereon are rotated relative to the coordinate axes of the machine coordinate system in such a way that simultaneous slide movements along the traversing axes to relative movements along the Lead coordinate axes.

Another embodiment is shown in FIG. 9. It shows the top view of a milling machining center with two spindle heads 44 and 46 , which are received on top slides 48 and 50 by cross slides 52 and 54 . Their lower slides 56 and 58 are guided on common longitudinal guides 60 which extend along a bed 62 and define a travel axis B1. They carry transverse guides 64 and 66 which guide the upper carriages 48 and 50 and define travel axes B2 and B3 which are parallel to one another. Work spindles 68 and 70 are supported in the spindle heads 44 and 46 , their horizontal spindle axes 72 and 74 being orthogonal to one another and defining the coordinate axes x and z which intersect the travel axes B1 to B3 at angles of 45 degrees. In front of the bed 62 is a partial table 76 with a square, horizontal workpiece clamping surface 78 , the parallel longitudinal edges 80 of which are aligned parallel to the spindle axis 72 and the parallel longitudinal edges 81 of which are aligned parallel to the spindle axis 74 . Tools 82 and 84 are accommodated in the work spindles 68 and 70 , and a workpiece WS2 on the indexing table with the axis of rotation D. The spindle heads 44 and 46 can be moved on the slides 48 and 50 along an axis y orthogonal to the axes x and z.

The mode of action is as follows:
If, for example, the slides 48 and 56 of the cross slide 52 are moved in opposite directions along the travel axes B1 and B2 with identical speeds vB1 = vB2 with respect to the dividing table 76 , ie the lower slide 56 from the center to the edge and the upper slide 48 from the rear to the front, the x positions of the tip of the tool 82 change while the z position is retained ( FIG. 9). The carriages 48 and 56 on the other hand moved at the same speed the same direction, that is, the sub-tray 56 from the center to the edge and the top slide 48 from front to back, to change the z position of the tip of the tool 82 while maintaining the x-position (Fig. 10). In both cases, speeds of the tip of the tool 82 result in the direction of the coordinate axes x and z, which correspond to √2 times the speeds of the slides 48 and 56 .

This results in the same way for the tool 84 , whose orientation facing both the tool 82 and the indexing table 76 contributes to the formation of a two-spindle milling machine which is as fast and compact as possible, and in which each of the two tools 82 and 84 with √2 times the slide speed is movable along the axes x and z in order to work simultaneously or in succession on one and the same or on different workpieces. Accordingly, one or two workpieces could also be moved with respect to a spatially fixed tool.

Claims (34)

1. Method for machining workpieces, in which two slides ( 16 , 32 or 48 , 56 or 50 , 58 ), at least one of which carries a tool or workpiece, along two intersecting travel axes (A1, A2 or B1, B2 or B1, B3) are moved relative to one another in order to generate relative movements between a tool and a workpiece, characterized in that relative movements between the tool and workpiece along one of the two axes of travel (A1, A2 or B1, B2 or B1, B3) intersecting first coordinate axis (z1, z) of a Cartesian coordinate system running obliquely to the traversing axes by simultaneously moving in the same direction and along a second coordinate axis (y1, x) intersecting both traversing axes (A1, A2 or B1, B2 or B1, B3) of this coordinate system by simultaneous opposite movement of both slides ( 16 , 32 or 48 , 56 or 50 , 58 ) are generated, the tool with its tool reference axis, for example one Longitudinal and / or rotational axis, and / or the workpiece with its workpiece reference axis, for example an axis running perpendicular to the workpiece clamping surface, is aligned parallel or perpendicular to these coordinate axes. 2. The method according to claim 1, characterized in that the two slides ( 48 , 56 or 50 , 58 ) form a cross slide system ( 52 or 54 ), which is a tool arranged thereon ( 82 or 84 ) or a workpiece arranged thereon in relation to a fixed workpiece (WS2) or a fixed tool. 3. The method according to claim 1, characterized in that a carriage ( 16 ) carrying a tool (WZ1) and a carriage ( 32 ) carrying a workpiece (WS1) are moved relative to one another. 4. The method according to any one of claims 1 to 3, characterized characterized that the coordinate axes (y1, z1 or x, z) to mutually orthogonal traversing axes (A1, A2 or B1, B2 or B1, B3) are rotated by 45 degrees. 5. The method according to any one of claims 1 to 4, characterized in that the two slides ( 16 , 32 or 48 , 56 or 50 , 58 ) are moved at the same speed. 6. Machine tool with two slides ( 16 , 32 or 48 , 56 or 50 , 58 ), at least one of which carries a tool or workpiece, and two intersecting axes of travel (A1, A2 or B1, B2 or B1, B3) , along which the slides ( 16 , 32 or 48 , 56 or 50 , 58 ) can be moved relative to one another in order to generate relative movements between a tool and a workpiece, in particular for carrying out the method according to one of claims 1 to 6, thereby characterized in that the tool with its tool reference axis, for example a longitudinal and / or rotational axis, and / or the workpiece with its workpiece reference axis, for example an axis running perpendicular to the workpiece clamping surface ( 38 , 78 ), in which the axis of travel (A1, A2 or B1, B2 or B1, B3) are aligned or orientable in such a way that when the slide is moving at the same time, relative movements between the tool and the workpiece are orthogonal or parallel to the tool g and / or workpiece reference axis are possible. 7. Machine tool according to claim 6, characterized characterized that the aligned tool and / or Workpiece reference axis both travel axes (A1, A2 or B1, B2 or B1, B3) cuts. 8. Machine tool according to claim 6 or 7, characterized characterized that the tool reference axis and the Workpiece reference axis orthogonal or parallel to each other  run and with mutually orthogonal traversing axes Include 45 degree angles. 9. Machine tool according to one of claims 6 to 8, characterized in that the tool reference axis is the longitudinal and / or rotation axis of the tool and the workpiece reference axis is orthogonal to the workpiece clamping surface ( 38 , 78 ). 10. Machine tool according to one of claims 6 to 9, characterized in that the two slides ( 48 , 56 or 50 , 58 ) form a cross slide system ( 52 or 54 ) with which a tool ( 82 or 84 ) or a workpiece arranged thereon can be moved with respect to a stationary workpiece (WS2) or a stationary tool. 11. Machine tool according to claim 10, characterized in that the tool axis ( 72 or 74 ) intersects both travel axes (B1, B2 or B1, B3). 12. Machine tool according to claim 11, characterized in that the tool axis ( 72 or 74 ) intersects both travel axes (B1, B2 or B1, B3) at angles of 45 degrees. 13. Machine tool according to one of claims 10 to 12, characterized in that the workpiece (WS2) is arranged in front of or on a bed ( 62 ). 14. Machine tool according to one of claims 10 to 13, characterized in that the workpiece (WS2) is received on an immovable workpiece table ( 76 ), the workpiece clamping surface ( 78 ) of which runs parallel to the plane of travel of the tool ( 82 or 84 ). 15. Machine tool according to claim 14, characterized in that the workpiece table ( 76 ) can be rotated about a normal axis of rotation (D). 16. Machine tool according to one of claims 10 to 15, characterized in that the tool ( 82 or 84 ) is arranged in a tool holder ( 68 or 70 ) arranged on the cross slide system ( 52 or 54 ). 17. Machine tool according to one of claims 10 to 16, characterized in that at least two cross slide systems ( 52 , 54 ) are provided, each carrying a tool ( 82 , 84 ) to work in succession or simultaneously on a workpiece (WS2) . 18. Machine tool according to claim 17, characterized in that the cross slide systems ( 52 , 54 ) are arranged on a common bed ( 62 ). 19. Machine tool according to claim 17 or 18, characterized in that the cross slide systems ( 52 , 54 ) are guided on common guides ( 60 ). 20. Machine tool according to one of claims 17 to 19, characterized in that the tool axes ( 72 , 74 ) of two cross slide systems ( 52 , 54 ) run orthogonally to one another. 21. Machine tool according to one of claims 6 to 9, characterized in that a slide ( 16 ) designed as a tool slide and a slide ( 32 ) designed as a workpiece slide can be moved relative to one another. 22. Machine tool according to claim 21, characterized in that the tool slide ( 16 ) carries a tool holder ( 28 ) for holding a tool (WZ1) and the workpiece slide ( 32 ) carries a workpiece table ( 36 ) for holding a workpiece (WS1). 23. Machine tool according to claim 22, characterized by

• 1. a first alignment of the tool holder ( 28 ) and the workpiece table ( 36 ), in which the mutually orthogonal coordinate axes (y1, z1) of the machine coordinate system are rotated by 45 degrees relative to the mutually orthogonal traversing axes (A1, A2) and relative movements between the tool ( WZ1) and workpiece (WS1) along the first coordinate axis (z1) by moving the tool holder ( 28 ) and the workpiece table ( 36 ) away from each other or towards each other and along the second coordinate axis (y1) by moving the tool holder ( 28 ) in the same direction at the same speed and the workpiece table ( 36 ) can be generated, and if necessary
  • - A second alignment of the tool holder ( 28 ) and the workpiece table ( 36 ), in which the coordinate axes (y2, 22) run parallel to the travel axes (A1, A2) and relative movements between the tool (WZ1) and workpiece (WS1) along the coordinate axes (y2, z2) can be generated by moving the workpiece holder ( 28 ) or the workpiece table ( 36 ).

24. Machine tool according to claim 23, characterized in that the tool axis ( 26 ) of the tool holder ( 28 ) in the first orientation intersects the travel axes (A1, A2) at angles of 45 degrees. 25. Machine tool according to claim 23 or 24, characterized in that the workpiece clamping surface ( 38 ) of the workpiece table ( 36 ) in the first orientation intersects the travel axes (A1, A2) at angles of 45 degrees. 26. Machine tool according to one of claims 23 to 25, characterized in that the tool axis ( 26 ) of the tool holder ( 28 ) in the second orientation runs parallel to its travel axis (A1). 27. Machine tool according to one of claims 23 to 26, characterized in that the workpiece clamping surface ( 38 ) of the workpiece table ( 36 ) in the second orientation runs parallel to its travel axis (A2). 28. Machine tool according to one of claims 21 to 27, characterized in that the traversing axes (A1, A2) each have an inclination of 45 degrees. 29. Machine tool according to one of claims 23 to 28, characterized in that the tool slide ( 16 ) is guided on inclined first guides ( 10 ) and the tool holder ( 28 ) is pivotable about a guide-orthogonal first pivot axis ( 22 ) between a first position , in which the tool axis ( 26 ) runs horizontally, and a second position in which the tool axis ( 26 ) runs parallel to the first guides ( 10 ). 30. Machine tool according to one of claims 23 to 29, characterized in that the workpiece carriage ( 32 ) is guided on inclined second guides ( 12 ) and the workpiece table ( 36 ) is pivotable about a second pivot axis ( 34 ) which is orthogonal to the guide between a first position , in which the workpiece clamping surface ( 38 ) runs horizontally, and a second position in which the workpiece clamping surface ( 38 ) runs parallel to the second guides ( 12 ). 31. Machine tool according to claim 30, characterized in that the workpiece table ( 36 ) is rotatable about an axis of rotation ( 40 ) orthogonal to the workpiece clamping surface ( 38 ). 32. Machine tool according to one of claims 29 to 31, characterized in that the first and second guides ( 10 , 12 ) are arranged on opposite inclined planes ( 6 , 8 ) of a cross-sectionally V-shaped bed ( 2 ). 33. Machine tool according to claim 32, characterized in that the inclined planes ( 6 , 8 ) open out via a chip conveyor ( 42 ) which extends in the direction of the third coordinate (x) of the machine coordinate system. 34. Machine tool according to one of claims 10 to 33, characterized in that the tool holder ( 28 or 68 or 70 ) and / or the workpiece table ( 36 or 76 ) are movable in the direction of the third coordinate (x or y) .