JPH0253954B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a mounting apparatus for mounting electronic components on a printed circuit board.
The present invention relates to a mounting device in which the unit is mounted on a table along a straight line and is moved in the direction of the straight line to sequentially supply components to a component mounting device.

Background Art A type of device for mounting electronic components onto a printed circuit board includes (a) a board support device that positions and supports the printed circuit board, and (b) a holding mechanism for electronic components to mount the electronic components on the printed circuit board. a parts mounting device,
(c) A parts supply table with a plurality of component supply units mounted on the table, each holding a large number of parts of one type and with each component supply unit arranged in a straight line, and (d) The parts supply table. a table guiding device that movably guides the table in a direction parallel to the straight line; and (e) alternatively positioning each component supply section of the plurality of component supply units to a supply position for supplying components to the component mounting device. Some devices include a table moving device that moves a component supply table to perform unit selection.

The number of component supply units corresponding to the type or number of electronic components to be mounted on the printed circuit board is mounted on a component supply table, and the movement of the component supply table causes the component supply section of each unit to mount the electronic components on the printed circuit board. The electronic components are sequentially positioned at the supply position and supply the electronic components to the component mounting device.

Problems to be Solved by the Invention Normally, the types or numbers of electronic components mounted on a single printed circuit board are not so many, but there are cases where there are many, and the component supply table is designed to Or, because they are made with the greatest number of tables in mind, they are large, require a table moving device with a large driving force, and have a large inertia, resulting in poor responsiveness, difficulty in high-speed operation, and reduced work efficiency. There was a problem that it was bad. In addition, there is also the problem that the vibrations that occur when the component supply table starts or stops moving are large, which can change the direction of electronic components or tilt them, making it easy for the component placement device to incorrectly hold electronic components. Ta.

Means for Solving the Problems In order to solve the above problems, the present invention includes two component supply tables, a first supply table and a second supply table, and a table guide device that is connected to the first supply table and the second supply table. A second supply table is guided to a common work area for supplying parts to the component mounting device, and a first supply table evacuation area and a second supply table evacuation area respectively provided on both sides of the work area. In addition, the table moving device is configured to move one of the first supply table and the second supply table to the work area while keeping one of the first supply table and the second supply table in the retracted position to select the component supply unit. It is something.

Effect By using two component supply tables, the size of the table can be changed to accommodate all the necessary component supply units on one table when the types or number of electronic components to be mounted on a printed circuit board are not very large. In addition, if the types or number of electronic components to be mounted on the printed circuit board are the largest, it is possible to increase the number of electronic components to be mounted by making the table large enough to mount all the necessary component supply units by using two tables. If one table is sufficient to supply parts, move only one table, or if there are a large number of electronic parts and two tables are required, move both tables alternately or simultaneously. Parts can be supplied.

Effects of the Invention Therefore, the component supply table can be made smaller than the conventional one, which was made assuming the maximum number or type of electronic components to be installed, and therefore has good responsiveness and high speed. In addition to improving work efficiency, the electronic components are less likely to change orientation or tilt because the vibrations that occur when starting and stopping the movement are small. The effect of reducing the number of electronic component suction mistakes made by the component mounting device can be obtained.

In particular, if there are only a few types or numbers of electronic components to be mounted on a single printed circuit board and all the necessary component supply units can be mounted on one table, it is recommended to mount the same types of electronic components on both tables. By doing so, if a table in operation runs out of electronic components, that table can be moved to the evacuation area, while the other table can be moved to the work area, and electronic components can be supplied from that table. Since the component supply unit can be replaced in between, there is no need to stop the operation of the apparatus for replacing the component supply unit, and the operating rate of the mounting apparatus can be improved.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on the drawings.

FIG. 2 is a diagram showing the appearance of a mounting apparatus that is an embodiment of the present invention. This mounting device has main body frame 1
0, a board carry-in device 12, a board carry-out device 14, a board support device 16, a component mounting device 18, a component supply device 20, and the like.

The board support device 16 is similar to the printed circuit board positioning device disclosed in Japanese Patent Application No. 1988-8808 filed by the applicant, and the details are not necessary for understanding the present invention. Therefore, only the main parts will be explained here based on FIGS. 3 and 4. The substrate support device 16 includes an X table (not shown) movable in the X-axis direction parallel to the substrate transport direction, and a Y table 24 provided on the X table and movable in a direction perpendicular to the X-axis direction.
and a table plate 26 mounted on the Y table 24 so as to be immovable relative to both the X and Y tables and movable in the vertical direction. Two guide bars 30 and 32 are attached to the table plate 26, which are parallel to the board conveyance direction, and are designed to support the printed circuit board. The guide bar 30 is connected to the table plate 26
However, the guide bar 32 is supported by a pair of sliders 34 that are attached to the table plate 26 so as to be movable in the Y-axis direction.
By moving the top in the Y-axis direction, the guide bar 32 approaches and separates from the guide bar 30, making it possible to support a plurality of types of printed circuit boards of different sizes.

Further, among the ends of the Y table 24 in the X-axis direction, a main positioning member 36 and a sub-positioning member 38 are attached to the end on the guide bar 30 side, which engages with the printed circuit board to accurately position it. There is. The main positioning member 36 is provided in a fixed position, whereas the sub-positioning member 38 is attached to a guide rail 39 provided on the Y table 24 so as to be movable in the X-axis direction. The sub-positioning member 38 is always prevented from moving relative to the guide rod 39 by a clamp mechanism (not shown), but when the action of the clamp mechanism is released by the clamp release member, the sub-positioning member 3
By moving the table plate 26 in the X-axis direction in a state where the table plate 8 is immovably positioned, the relative position in the X-axis direction with respect to the table plate 26 can be changed. Various types of printed circuit boards can be positioned.

A substrate carrying-in device 12 and a substrate carrying-out device 14 are arranged on both sides of the table plate 26 as described above, and a pair of conveyor belts 40,
The printed circuit board placed on 42 is carried in and out while being guided by guide plates 44 and 46. One conveyor belt 42 and guide plate 4 of these carrying-in device 12 and carrying-out device 14
6, a plurality of feed screws 52 connected via a chain 48 and a sprocket 50 connect to the handle 5.
4, it is brought close to and separated from the other conveyor belt 40 and guide plate 44, so that it is possible to convey a plurality of types of printed circuit boards of different sizes.

Furthermore, an engaging member 56 is provided at the end of the guide plate 46 on the table plate 26 side. This engaging member 56 is connected to the table plate 26.
When the slider 34 is in the raised position, the slider 34 engages with the formed engagement groove 58, and the handle 54
As the conveyor belt 42 and guide plate 46 move due to the operation, the slide 34 is moved in the Y-axis direction, and the guide bar 32 moves toward the guide bar 30.
It is now possible to approach and move away from the enemy.

Then, the printed circuit board transported by the board loading device 12 is transferred to the table plate 26 in the raised position. Next, the table plate 26 is moved to the lowered position, so that
It is moved in the X-axis direction and the Y-axis direction without interfering with the carrying-in device 12 and the carrying-out device 14,
The portion of the printed circuit board on which the electronic components are mounted is sequentially positioned under the suction tube of the component mounting device 18, which will be described later.After the mounting of the electronic components is completed, the printed circuit board is moved to the raised position and the printed circuit board is unloaded. It is transferred to the device 14 and taken out.

Furthermore, the component mounting device 18 is similar to the electronic component mounting device described in the specification of Japanese Patent Application No. 1988-8811 filed by the applicant of the present application, and herein, FIGS. Only the main parts will be explained based on FIG. This component mounting device 18 includes a rotating shaft 60 that is rotatably held around an axis perpendicular to the main body frame 10 . This rotating shaft 60 is designed to be rotated intermittently by 30 degrees, and has an intermittent rotating disk 6 fixed to its lower end.
2, twelve suction heads 70 are attached at equal angular intervals via rods 64, shaft members 66, and arms 68, and are used for receiving electronic components from the component supply device 20, mounting electronic components on printed circuit boards, etc. are now being carried out in parallel. As shown in FIG. 6, these suction heads 70 include an outer cylinder 72 that is held movably in the vertical direction by an arm 68, and
It has an inner cylinder 74 fitted into the outer cylinder 72, and is biased upward by a spring 76 disposed between the outer cylinder 72 and the arm 68, so that the sixth
Although it is kept in the state shown in the figure, it is moved downward by a push-down device (not shown) when receiving and installing electronic components. Transparent plates 80 and 82 made of glass or synthetic resin are fixed to both ends of the inner cylinder 74, and the lower transparent plate 82 has an airtight space 84 formed between the two transparent plates 80 and 82. A hollow suction tube 86 is press-fitted so as to communicate with the tube. The space 84 includes the inner cylinder 74,
It is connected to a vacuum device (not shown) through passages formed in the outer cylinder 72, arm 68, shaft member 66, and rod 64, and when a switching valve is operated, the adsorption tube 86 is connected to the vacuum device and the atmosphere. The electronic parts are selectively communicated with each other to attract and attach electronic parts.

As shown in FIG. 1, the component supply device 20 includes a first supply table 90 and a second supply table 92.
It is equipped with The first supply table 90 and the second supply table 92 are plate-shaped, and a front positioning pin 94 and a rear positioning pin 96 are provided along the longitudinal direction on both sides of the upper surface in the width direction.
A plurality of pins 94,
A toggle clamp mechanism (not shown) is fixed to the groove 97 formed between the grooves 96.
The tables 90 and 92 have a plurality of component supply units 98 as shown in FIG.
The parts supply section is positioned in a straight line by a toggle clamp mechanism. Normally, the types or number of electronic components to be mounted on a printed circuit board are not very large, and each table 90, 92 can hold the types or number of components necessary for mounting electronic components on such a normal printed circuit board. Supply unit 9
It is formed in a size that can carry 8.

The parts supply unit 98 is the same as the device described in the specification of Japanese Patent Application No. 59-278167 filed by the applicant of the present application, and only the main parts are shown in FIG. 7 and briefly explained here. . In each component supply unit 98, one type of electronic component 100 is engaged with tape-shaped electronic components 104 (see FIG. 8) housed at equal intervals on a carrier tape 102, and with a feed hole 106 formed in the carrier tape 102. A feeding device 10 that feeds the carrier tape 102 one pitch at a time (a distance equal to the housing interval of electronic components)
8, and a winding device 1 that winds up the cover film 110 bonded to the upper surface of the carrier tape 102.
12.

The tape-shaped electronic component 104 is wound around a reel (not shown) disposed at the rear of the component supply unit 98, and its tip end is connected to the feeding device 10.
It is fitted into the guide groove 116 formed on the flat block 114 of No. 8, and the guide groove 1
The cover member 118 that covers the opening of the cover film 11 prevents the electronic components from floating up from the guide groove 116 or flying out.
0 is the slot 12 formed in the cover member 118
0, and is appropriately wound up by a take-up reel 122.

The feeding device 108 includes a slider 124 accommodated in the block 114 so as to be able to move forward (in the direction indicated by arrow A in the drawing) and backward, and a feeding member that is engaged with the slider 124 so as to be rotatable around a horizontal axis. 126, and a positioning member 1 movable in the vertical direction
28, and a lever 130 which is rotatably mounted about a horizontal axis and is engaged at both ends with the feed member 126 and the positioning member 128, respectively. The carrier tape 102 is moved when the return lever 134 is rotated in the direction indicated by arrow B in the figure by a cam device (not shown) with the feed pin 132 formed on the feed member 126 engaged with the feed hole 106. , as the slider 124 is moved forward, the electronic component 100 is sent one pitch along with the cover member 118 and the cover film 110 is wound up, so that the frontmost one is located directly below the suction tube 86. It is said that From this state, the adsorption tube 86
is started to suck air and is lowered to come into contact with the cover member 118, and then the driven portion 136 of the feed member 126 is pushed down in the direction shown by arrow C by a cam device (not shown), thereby causing the feed to begin. The member 126 is rotated, the feed pin 132 is removed from the feed hole 106, and the lever 130 is rotated to remove the positioning member 12.
8 is raised, and a positioning pin 138 formed at its upper end is engaged with the feed hole 106.
With the carrier tape 102 positioned in this manner, the slider 124 is moved back,
At the same time that the cover member 118 is retreated, the suction tube 86 is further lowered to suction the electronic component 100, and the part of the component supply unit 98 that faces the suction tube 86 as described above is the component supply section. will be achieved.

Parts supply unit 98 configured as described above
first and second supply tables 90 supporting the
92 is movably supported by a guide rail 150 arranged parallel to the printed circuit board conveyance direction. The tables 90 and 92 are guided by a guide rail 150 so that the component supply parts of the plurality of component supply units 98 move along a straight line located above the table, and are fixed to the lower surface thereof as shown in FIG. The nut 151 has a feed screw 152,
154 are screwed together. Feed screw 152, 15
4 are each attached to the guide rail 150 so as to be immovable in the axial direction and rotatable, and
The tables 90 and 92 are rotated by dedicated drive motors 156 and 158, so that the tables 90 and 92 can be moved independently. Guide rail 15
At a position adjacent to the longitudinal center of 0, a first
As shown by circles in the figure, a supply position 160 for supplying electronic components to the suction tube 86 is set, and when electronic components are mounted, the component supply sections of each component supply unit 98 supply the components in sequence by moving the tables 90 and 92. It is positioned at position 160. Based on this supply position 160, the table 9
The maximum range in which the parts supply units 90 and 92 move, that is, those located at both ends of the component supply units 98 mounted on the tables 90 and 92 are at the supply position 160, respectively.
The range of movement during positioning is a common work area for both tables 90 and 92, and when supplying parts, the tables 90 and 92 are moved in turn in the work area to supply electronic components, and one table While in the work area, the other table is retracted onto a portion of the guide rail 150 adjacent to the portion forming the work area so as not to interfere with the table being worked on. The tables 90 and 92 are retracted to positions on opposite sides of the work area, and these positions are dedicated evacuation areas for the tables 90 and 92, respectively. The evacuation area is long enough to move between.

The electronic component mounting apparatus configured as described above is
It is controlled by a control device shown in FIG. In the figure, 170 is a CPU (Central Processing Unit), and to this CPU 170, information such as an operation start switch, a component mounting mode switch, completion of replacement of the component supply unit 98, and the type of printed circuit board to which electronic components are to be mounted is input. An operating device 172 equipped with various operating sections, such as an input device for use, is connected.
The CPU 170 also includes a ROM (read only memory) 174 and a RAM (random access memory).
176 is connected. In ROM174,
Starting with the program for the three component mounting modes that can be executed by this mounting device, parts are selected according to the type of electronic component to be mounted on the printed circuit board, the mounting position, the mounting order, the moving order of the printed circuit board, and the mounting order of the electronic components. Programs and the like for moving the tables 90 and 92 so as to supply electronic components to the mounting device 18 are stored.

The CPU 170 further includes a first supply table movement motor drive circuit 178, a second supply table movement motor drive circuit 180, a substrate loading device driving circuit 182, a substrate loading device driving circuit 184, a substrate support device driving circuit 186, and component mounting. Device drive circuit 18
8 are connected to each other, and each motor 1
53, motor 158, board loading device 12, board supporting device 14, board unloading device 16, component mounting device 1
8 is connected, and the interface 190
A tape end detection sensor 192 detects when an electronic component owned by the component supply unit 98 is used up, and a display device 194 displays to the operator that the size of the printed circuit board to be mounted has changed.
(See Figure 2) are connected.

The three component mounting modes that can be executed by this electronic component mounting apparatus can be selected by the operator by operating a mode changeover switch (not shown), but normally the mode shown in the flowchart of FIG. Mounting of electronic components is performed in one mode. This mode is used when there are not many types or numbers of electronic components to be mounted on one printed circuit board, and all the necessary component supply units 98 can be mounted on either table 90 or 92. . Furthermore, in Figure 10,
The operations described within the solid line frame are due to the mounting equipment, and the operations described within the double-dashed line frame are due to the manual operation of the operator.
The same applies to figures.

In this mode, before starting work,
Input the type of printed circuit board on which the electronic component is to be mounted, and select the component supply units 98 necessary for mounting the electronic component in the tables 90 and 9 in a predetermined order.
2. This mounting order may be in the order in which the electronic components are mounted on the printed circuit board or in a different order, but in any case, it is predetermined. , 92 within the work area is set and stored in the ROM 174. The tables 90 and 92 are both evacuated to the evacuation area before the start of operation, and when the mounting device is activated after the component supply unit 98 has been loaded, the first supply table 90 is moved to the work area. , the component supply unit 98 is sequentially positioned at the supply position 160 to supply electronic components to the component mounting device 18, and the component mounting device 18 receives the electronic components and mounts them at predetermined positions on the printed circuit board.

Of the plurality of component supply units 98,
If any electronic component is missing, this is detected by the tape end detection sensor 192. This detection is performed, for example, when the suction tube 86 fails to suction the electronic component twice in a row.
92 emits a signal, and the CPU 170 moves the first supply table 90 to the evacuation area based on this detection signal, while moving the second supply table 92 to the work area, The second supply table 92 is caused to supply electronic components. The worker is notified that an electronic component is missing by lighting an indicator lamp provided on the main body frame 10, and the worker replaces the component supply unit 98 in which the electronic component is missing with a new one. The end of the process is input to the CPU 170. When any electronic component in the component supply unit 98 mounted on the second supply table 92 runs out, the CPU 170 uses the sensor 192
The second supply table 92 is moved to the evacuation area based on the signal. At this time, the first supply table 90
If the replacement of the component supply unit 98 has not yet been completed, the first supply table 90 will be moved upon receiving the input to complete the replacement. Normally, the process is finished before the parts run out, and the CPU 170 can immediately move the first supply table 90 to the work area in exchange with the second supply table 92, and the mounting of electronic components can be carried out without stopping. It will be held continuously.

Even after the above-mentioned electronic components have been mounted on a predetermined number of printed circuit boards, if electronic components are to be mounted on a different type of printed circuit board, the order shown in the flowchart in Figure 11 will be used. The table is automatically exchanged according to the table. The mode involving this automatic setup change is the second mounting mode. At this time, for example, the first supply table 90 is in the work area and is in operation, and the supply of electronic components by the first supply table 90 completes the mounting of electronic components onto a predetermined number of printed circuit boards. If the operator is tired, the operator switches the mode changeover switch to the automatic setup changeover mode, and inputs data representing the type of printed circuit board to be mounted next from the operating device 172. Also, replace the component supply unit 98 of the second supply table 92 that has been evacuated to the evacuation area with one that is equipped with the electronic components for the printed circuit board to be mounted next, and when the replacement is completed, enter the completion of set. do. Next, when the type of printed circuit board to be mounted changes, the type or number of electronic components to be mounted and/or the size of the printed circuit board change, but in either case, it is necessary to switch to automatic setup change mode. For example, even if the automatic setup change is completed after a predetermined number of printed circuit boards have been mounted, the second supply table 92 in the evacuation area will not move until the above-mentioned set completion is input. There is.

If the next printed circuit board to be mounted is of the same size but differs only in the type or number of electronic components to be mounted, it is only necessary to change the table, and when the set number of boards have been mounted, the If the completion of setting the component supply unit 98 to the second supply table 92 has already been input, the table will be replaced immediately after the automatic setup change to change the electronic component mounting program is performed, and the next print will be started. Electronic components will be mounted on the board.

In addition, if the next printed circuit board to be mounted is of a different size, the operator is notified of this on the display device 194 based on the input of the type of printed circuit board, and the set number of sheets is After the installation is completed, in addition to changing the program, automatic setup change is performed, including adjusting the dynamic position of the sub-positioning member 38 in the substrate support device 16. Display device 1
After receiving the notification from 94, the operator operates the handle 54 to move the substrate loading device 1 after this automatic setup change.
2 and the conveyor belt 4 of the substrate unloading device 14
0 and 42, the width between the guide plates 44 and 46, and the width between the guide bars 32 and 30, and after completing the adjustment, enter the completion of adjustment. If the setting of the component supply unit 98 on the second supply table 92 has already been completed before this adjustment is completed, the table is replaced after the above setup is completed, and electronic components are mounted. . Also,
If the setting of the component supply unit 98 is not completed, the table will be replaced after waiting for the input of the completion of the setting, and the electronic components will be mounted.

Another mode that can be executed by the present mounting apparatus is that the types or number of electronic components to be mounted on the printed circuit board are large, and only one of the first supply table 90 and the second supply table 92 can handle the required parts. This is a mounting mode when all the supply units 98 cannot be mounted and are mounted separately on both tables 90 and 92. In this case, both tables 90 and 92 are considered as one table and are alternately moved to the work area so as to supply electronic components in the order in which they are mounted on the printed circuit board, and the component supply unit is divided into parts in the order in which they are mounted. If it is mounted on tables 90 and 92, 1
The tables 90 and 92 only need to be replaced once when mounting electronic components onto a single printed circuit board.

As is clear from the above description, in the mounting apparatus of this embodiment, each table 90, 92 has enough space to mount the component supply unit 98 when there are not many types or numbers of electronic components to be mounted on the printed circuit board. Compared to the case where a table is formed based on the assumption that there are many types or numbers of electronic components, the table is smaller, so it has better operational response and can be moved at high speed.
In addition to improving work efficiency, there is less vibration when starting and stopping movement, and electronic components are less likely to tilt or change their posture.
The effect of reducing the number of electronic component suction errors by the component mounting device 18 can be obtained.

In addition, in the first and second mounting modes, while one supply table is in the work area and supplies parts, the component supply unit 98 of the other supply table in the evacuation area is replaced in parallel. Therefore, when an electronic component is lost, it does not take much time to change the setup, and the operating rate of the mounting apparatus can be improved.

In addition, in the above embodiment, the feed screw 15
2,154 are dedicated drive motors 156,
158, but it is also possible to switch the rotation transmission of the drive motor by a clutch so that both feed screws 152 and 154 are rotated by one drive motor. .

In addition, the table guide device and table moving device include a guide rail 150 and a feed screw 15, respectively.
2, 154 and drive motors 156, 158, various configurations can be adopted, and the component supply unit is not limited to that of the above embodiment.

Although not illustrated in detail, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a component supply device of a mounting apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view showing the appearance of the entire mounting apparatus. FIG. 3 is a perspective view showing the substrate supporting device of the mounting apparatus, and FIG. 4 is a plan view showing the substrate supporting device, the substrate carrying-in device, and the substrate carrying-out device. FIG. 5 is a front sectional view showing the main parts of the component mounting device of the mounting apparatus, and FIG. 6 is a front sectional view showing the suction head of the component mounting device taken out. FIG. 7 is a front view showing the main parts of the component supply unit mounted on the table of the component supply device, and FIG. 8 is a plan view showing a part of the taped electronic components included in the unit. FIG. 9 is a block diagram showing a control circuit for controlling the mounting apparatus. FIGS. 10 and 11 are flowcharts respectively showing electronic component mounting modes that can be executed by the mounting apparatus. 10: Main body frame, 12: Board loading device, 1
4: Board unloading device, 16: Board supporting device, 18:
component mounting device, 20: component supply device, 26: table plate, 70: suction head, 86: suction tube, 90: first supply table, 92: second supply table, 98: component supply unit, 100: electronic component, 108: Feeding device, 112: Winding device, 1
50: Guide rail, 152, 154: Feed screw, 156, 158: Drive motor, 160: Supply position, 170: CPU (central processing unit), 174:
ROM (read only memory), 176: RAM (random access memory).

Claims (1)

[Scope of Claims] 1. A board support device that positions and supports a printed circuit board, a component mounting device that is equipped with an electronic component holding mechanism and that mounts electronic components on the printed circuit board, and a large number of components of one type each. a component supply table on which a plurality of component supply units are mounted on a table with each component supply section aligned along a straight line; and a component supply table that is movably guided in a direction parallel to the straight line. a table guide device; and a table moving device that moves the component supply table to select a unit that selectively positions each component supply section of the plurality of component supply units to a supply position for supplying components to the component mounting device. An electronic component mounting apparatus comprising: two component supply tables, a first supply table and a second supply table, the table guiding device and the first supply table and the second supply table, respectively, and A common work area for supplying parts to the table, and a first supply table evacuation area and a second supply table evacuation area respectively provided on both sides of the work area, and the table moving device The unit selection is performed by moving one of the first supply table and the second supply table to the work area while keeping one of the first supply table and the second supply table in the retracted position. Electronic component mounting equipment equipped with a table. 2. The table guide device is provided with a common guide rail for the first supply table and the second supply table that extends across the work area and evacuation areas on both sides thereof, and the table moving device is The electronic component mounting apparatus according to claim 1, further comprising a feed screw and a feed screw drive motor provided exclusively for the first supply table and the second supply table, respectively.