Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23G—THREAD CUTTING; WORKING OF SCREWS, BOLT HEADS, OR NUTS, IN CONJUNCTION THEREWITH
  • B23G1/00—Thread cutting; Automatic machines specially designed therefor
  • B23G1/16—Thread cutting; Automatic machines specially designed therefor in holes of workpieces by taps
  • B23G1/18—Machines with one working spindle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
  • B23Q11/00—Accessories fitted to machine tools for keeping tools or parts of the machine in good working condition or for cooling work; Safety devices specially combined with or arranged in, or specially adapted for use in connection with, machine tools
  • B23Q11/04—Arrangements preventing overload of tools, e.g. restricting load
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
  • B23Q15/00—Automatic control or regulation of feed movement, cutting velocity or position of tool or work
  • B23Q15/007—Automatic control or regulation of feed movement, cutting velocity or position of tool or work while the tool acts upon the workpiece
  • B23Q15/12—Adaptive control, i.e. adjusting itself to have a performance which is optimum according to a preassigned criterion

Definitions

• the invention relates to a drive device according to the preamble of claim 1.
• Such a device is known from DE-PS 29 46 860.
• the multiphase stepper motor used in this device can be switched over when a certain torque is exceeded. This condition occurs e.g. when the tool reaches the bottom of a blind hole during thread cutting and the torque increases significantly.
• This drive device does not take into account the fact that considerable damage to the workpiece can be generated by the feed force of the tool, particularly when threading or grooving, but also when cutting sensitive materials.
• This feed force which can be caused when the feed speed is too high, but also due to the weight of all the assemblies acting on the tool, can cause material deformations that the threads created are no longer doctrinal.
• the invention is based, which
• the invention is based on the knowledge that with a rotating tool optimal results can be achieved if the tool is subjected to optimal torque.
• a reaction force arises during machining on the cutting edges, which is either in the feed direction or opposite to it.
• it is therefore crucial that the gate and the subsequent machining process are carried out with the correct contact pressure or support force that corresponds to the tool and the material.
• the torque-controlled feed device By using the torque-controlled feed device, all difficulties that can occur during a machining process can be detected and largely eliminated. With certain materials, optimum machining torques can be specified for optimal machining depending on the diameter, the required feed path, the lubricant used and the like. The actual torque determined in each case via the rotary drive, which is expediently designed as a stepper motor, can be compared with these known values.
• the Feed means are controlled so that, for example in a vertical configuration of a thread cutting machine, the tool is held in a floating state * type, which means that no undesirable forces or the opposite direction to occur in the feed direction.
• this type of control enables a series of processes to be recorded, which enable automatic processing and constant quality control. So it is e.g. It is possible to switch the driving stepper motor if there is an observed increase in torque and then start machining again. This can e.g. loosen a chip that was the cause of the torque increase and then cut it. Of course, this also applies to the return of the tool, in which the processes are reversed kinematically and the tensile force exerted on the tool must be dimensioned such that a certain frictional torque is not exceeded. Of course, due to the torque-controlled feed device, it is also possible to generate the gating force required at the start of a work process, since this requires an increased torque, the value of which is known. If this gating torque is not reached, but a higher torque is required, it can be concluded at the beginning of a machining process that the tool life has been exceeded.
• the optimal machining torque is not always constant over the entire machining process. For example, it is known that increased threading torques are required for thread cutting with a thread length exceeding twice the diameter. This is due, for example, to the greater friction and the greater distance over which chips have to be transported. It is also possible to identify any kind of error sources. If, for example, despite a corresponding control of the feed device over several workpieces, a gradual increase in torque is ascertained, this can be due to the wear of the tool. If the optimal torque cannot be achieved despite optimal conditions, this can be due to the fact that the hole predrilled for thread cutting is too small in diameter. However, the use of an unsuitable lubricant or the selection of an unsuitable cutting speed can also be determined in this way.
• the drive device can also be used if the optimal torque is not yet known. In this case, these values can be determined empirically. As soon as they are certain, the processing can be done automatically.
• the feed device may also be necessary to control the feed device as a function of the speed of the driving stepping motor.
• the target torque and the target speed can of course be within a tolerance range that can be changed over an entire machining process, for example depending on the machining depth.
• the torque controlled feed device can e.g. be designed in a thread cutting machine so that it consists of two slides guided in the feed direction, namely one with the directly driving the tool
• Stepper motor connected relative slide and a e.g. Absolute slide driven by a threaded spindle, which are connected by a tension and compression spring.
• the absolute slide of the feed device is controlled depending on the required torque on the tool and possibly depending on the required speed. However, it is also possible to control the feed device magnetically or by compressed air in the required manner.
• FIGS. 1 to 3 for example. It shows:
• Fig. 2 is a front view of a vertical threading machine
• FIG. 3 is a side view of the machine of FIG. 2.
• the block diagram shown in Fig. 1 relates e.g. to a threading machine in which a stepper motor 11 drives a tool 12 with which a workpiece 13 is to be machined. Between the tool 12 and the
• Workpiece 13 is a distance measuring device to in particular to determine the end of a processing operation.
• the stepper motor 11 is connected to a feed device which enables the tool 12 to be acted upon with the lowest possible feed force.
• the torque occurring on the tool 12 is detected by means of a torque sensor 15, which determines the current consumption of the motor 11.
• the torque sensor 15 is connected to an actual / setpoint torque comparator 16, the output signal of which is fed to a feed and motor control device 17 which controls the feed device 14 as a function of the required torque, but also the motor 11 when a changeover is required, for example if the required feed path is reached or if excessive torque occurs during machining.
• the feed and motor switchover 27 is also supplied with the output signal of the distance measuring device 18, so that it can be determined whether a machining process has ended and the switchover of the motor is therefore necessary.
• the torque comparator 16 receives the respectively required optimum torque from a setpoint torque memory 19.
• a sensor 22 determines the speed of the motor 11, which then compares in an actual / target value speed comparator 23 with a value called up from a target speed memory 24; and generates a comparison signal which is fed to a speed-dependent feed and motor control device 25 which acts on the feed device 14 and the motor 11.
• FIGS. 2 and 3 show the mechanical structure of a threading machine with a vertical arrangement and vertical axis of rotation and feed Z.
• the machine has a stepper motor 11 for direct drive of a tool 12 with which a workpiece 13 is to be machined.
• the motor 11 is connected to a feed device which consists of a relative slide 26 which is fixedly connected to the motor 11 and a driven absolute slide 27 which are connected by a tension and compression spring 28 and a damper 29 connected in parallel to this. Both slides are supported by means of guide bushes 34 on guide rods 33 which can be displaced parallel to the tool axis of rotation.
• the absolute slide 27 is connected to a spindle nut 30 which sits on a spindle 31 which is driven by a motor 32.
• two distance measuring devices 35 and 36 are provided, namely one between the two carriages 26 and 27 and one between the carriage 26 or 27 and a fixed reference point, e.g. a fixed scale. These two measuring devices provide not only the distance between the tool 12 and the workpiece 13, but also a signal dependent on the rotation of the spring 28, which is used to control the tool feed in connection with the motor 32 with the required feed force.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Automatic Control Of Machine Tools (AREA)
• Drilling And Boring (AREA)

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Cited By (4)

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Citations (2)

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• 1989
  • 1989-09-11 DE DE19893930306 patent/DE3930306A1/de active Granted
• 1990
  • 1990-09-11 WO PCT/DE1990/000695 patent/WO1991003349A1/de unknown

Patent Citations (2)

Non-Patent Citations (1)

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