Structural principle and maintenance of the hottes

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Structural principle and maintenance of automatic tool change device

form of tool change device

automatic tool change device is an important actuator of machining center. Its forms are diverse, and the following are common at present

1. tool change of rotary tool rest

the rotary tool rest used by CNC machine tools is the simplest automatic tool change device, with square tool rest and hexagonal tool rest, that is, four, six or more tools are installed on it

the rotary tool rest must have good strength and stiffness to bear the cutting force of rough machining: at the same time, it is necessary to ensure the repeated positioning accuracy of the rotary tool rest in each rotation

Figure 1 shows the hexagonal turret of CNC lathe, which is applicable to the processing of disc parts. When machining shaft parts, square rotary tool rest can be used. Since the bottom mounting dimensions of the two are the same, it is very convenient to replace the tool holder

Figure 1 hexagonal turret of CNC lathe

1 - piston 2 - turret body 3, 7 - gear 4 - ring gear 5 - loose gear

6 - piston 8 - rack 9 - fixed bolt 10, 11 - push rod 12 - contact

all actions of the turret are controlled by the hydraulic system through the electromagnetic reversing valve and sequence valve. Its actions are divided into four steps:

(1) when the turret is lifted, when the CNC device sends the tool change command, The pressure oil enters the lower chamber of the compression hydraulic cylinder from hole a, the piston 1 rises, and the tool rest body 2 rises, so that the movable bolt 10 for positioning is separated from the fixed bolt 9. At the same time, the end gear clutch at the lower end of the piston rod is combined with the loose gear 5

(2) turret transposition when the turret is lifted, the pressure oil enters the left chamber of the transposition hydraulic cylinder from hole C, the piston 6 moves to the right, and the rack 8 is driven to move through the connecting plate, so that the loose gear 5 rotates counterclockwise. Rotate the tool holder by 60 through the end tooth clutch. The stroke of the piston should be equal to 1/6 of the circumference of the gear 5 graduation circle and controlled by the limit switch

(3) after the tool holder pressing tool holder is rotated, the pressure oil enters the upper chamber of the pressing hydraulic cylinder from hole B, and the piston 1 moves the tool holder body 2 down. The chassis of gear 3 is accurately installed with six cylindrical fixed pins 9 with wedges, and the movable pins 10 are used to eliminate the gap between the locating pins and holes to achieve reverse positioning. When the tool rest body 2 is lowered, the positioning movable bolt 10 is clamped with another fixed bolt 9, while the gear 3 contacts the conical surface of the ring gear 4, and the tool rest is positioned and clamped in a new position. At this time, the end gear clutch is disengaged from the loose gear 5

(4) after the positioning hydraulic cylinder is reset and the tool holder is pressed, the pressure oil enters the right chamber of the positioning hydraulic cylinder from hole D, and the piston 6 drives the rack to reset. Because the end tooth clutch has been disengaged at this time, the rack drives the gear 3 to rotate over the shaft

if the positioning and clamping actions are normal, the push rod 11 contacts the corresponding contact 12 and sends a signal to indicate that the tool change process has ended, and the cutting can continue

in addition to the hydraulic cylinder rotation and positioning pin positioning, the rotary tool rest can also use the motor to drive the clutch for positioning, as well as other rotation and positioning mechanisms

2. change the spindle head and change the tool

in CNC machine tools with rotating tools, changing the spindle head is a simple tool change method. There are usually two kinds of spindle heads, horizontal and vertical, and the spindle head is often replaced by the rotation of the turret to realize automatic tool change. Each spindle head of the turret is pre installed with rotating tools required for each process. When the tool change command is issued, each spindle head turns to the machining position in turn, and turns on the spindle movement, so that the corresponding spindle drives the tool to rotate, while other quality problems are also highlighted. The spindle in the non machining position is disconnected from the main movement

Figure 2 shows the horizontal eight shaft turret head. There are eight main shafts 7 with exactly the same structure distributed radially on the turret head, and the rotation movement of the main shaft is input by the gear 12. When the NC device sends the tool change command, first disengage the moving gear 3 from the gear 12 through the hydraulic fork, and at the same time, apply pressure oil to the upper chamber of the central hydraulic cylinder 14. Since the piston rod and piston 15 are fixed on the base, the central hydraulic cylinder 14 is lifted with the turret turret body 18 supported by two thrust bearings 17 and 16, and the clutches 2 and 1 are disengaged. Then the pressure oil enters the indexing hydraulic cylinder, pushes the piston rack, and then rotates the big gear 4 with the turret tool rest body 18 by 45 through the intermediate gear, turning the spindle of the next process to the working position. After the transposition, the pressure oil enters the lower chamber of the central hydraulic cylinder 14 to lower the turret head and re engage the clutches 2 and 1, realizing accurate positioning. Under the action of pressure oil, the turret head is compressed, and the indexing hydraulic cylinder returns to its original position. Finally, move the gear 3 through the hydraulic shift fork to mesh it with the newly replaced main shaft gear 12. In order to improve the assembly process of the spindle structure, the whole spindle part is installed in the sleeve 5. As long as the screw 10 is removed, the whole part can be extracted. The front bearing 9 of the main shaft adopts a tapered double row cylindrical roller bearing. When adjusting, first remove the lower cover 6, and then tighten the nut 8 to make the inner ring move axially, so as to eliminate the radial clearance of the bearing

Figure 2 horizontal eight axis turret head

1, 2 - clutch 3, 4, 12 - gear 5 - sleeve 6 one end cover 7 - main shaft 8 - nut

9, 16, 17 - bearing 10 - screw 1L - push rod 13 - control rod 14 - hydraulic cylinder 15 - piston 18 - turret tool rest body

in order to facilitate the removal of the tool in the taper hole of the main shaft, each main shaft has a control rod 13. As long as you press the control rod, you can push the rod 11 through the inclined plane to eject the tool

in an automatic system,

the rotation, positioning and pressing mode of the turret spindle head is very similar to the rat toothed disc indexing workbench, but the structure is more complex because many rotating spindle components are distributed on the turret

due to the limitation of space position, the structure of the spindle components cannot be designed very solid, which affects the stiffness of the spindle system. In order to ensure the rigidity of the main shaft, the number of main shafts must be limited, otherwise the structural size will be greatly increased under the leadership of the provincial leading group for major project construction of new and old kinetic energy conversion

The main advantage of the turret spindle head tool change mode is that it eliminates a series of complex operations such as automatic unclamping, tool unloading, tool loading, clamping and tool handling. Thus, the reliability of tool change is improved and the tool change time is significantly shortened. However, due to the above structural reasons, the turret spindle head is usually only used for machine tools with few processes and low accuracy requirements, such as CNC drilling machines

3. automatic tool change system with tool magazine

automatic tool change system with tool magazine is composed of tool magazine and tool exchange mechanism. First, install all the tools needed in the machining process on the standard tool handle respectively, and put them into the tool magazine in a certain way after pre adjusting the size outside the machine. When changing the tool, first select the tool in the tool magazine, and take out the tool from the tool magazine and the spindle by the tool exchange device. After exchanging the tool, install the new tool into the spindle and put the old tool back into the tool magazine. The tool magazine for storing tools has a large capacity. It can be installed either on the side or above the headstock, or as a separate part outside the machine tool, and the tools are transported by the handling device

compared with the spindle head of the turret, since there is only one spindle in the spindle box of the NC machine tool with the automatic tool change device with the tool magazine, the design of the spindle part may fully enhance its stiffness, so it can meet the requirements of precision machining. In addition, the tool magazine can store a large number of tools, so it can carry out multi process processing of complex parts, accounting for about 35% of the domestic market segment, which significantly improves the adaptability and processing efficiency of the machine tool. Therefore, the automatic tool change device with tool magazine is especially suitable for CNC drilling machines, CNC milling machines and CNC boring machines. (end)

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