Method for the reliable detection of vibrations of the drill body of a drill during the drilling process

Abstract

Method for the reliable detection of vibrations of the drill body of a drill during the drilling process, wherein coolant bores are provided in the drill body through which a coolant lubricant is supplied under pressure via a coolant lubricant system to cool the drill during the drilling process, characterized in that the pressure and / or the flow rate in the coolant lubricant system is detected immediately upstream of the drill with one or more sensors and the measured values ​​of the sensor(s) are evaluated in an evaluation unit in order to reliably detect vibrations referred to as chatter via pressure fluctuations and / or flow rate fluctuations.

Description

[0001] The invention relates to a method for the reliable detection of the drill behavior, the drill body and the drill bit during the drilling process.

[0002] From EP 1 748 859 B1 a drill is known which has coolant bores incorporated into the drill body for cooling the drill.

[0003] From DE19942440A1, another drill bit with internal coolant channels is known, in which the cutting tip is shaped in such a way as to prevent chatter during the drilling process as far as possible. Chatter refers to disruptive vibrations of the drill bit during the drilling process, which particularly negatively affect the quality of a hole.

[0004] From DE102010026947B3, a method is known in which chatter is reduced by changing the feed rate or the rotational speed of the drilling tool. The chatter is detected by a sensor on the drilling machine.

[0005] Document DE 10 2007 053 644 B4 discloses a method for process monitoring during drilling operations, particularly deep drilling, in which the feed rate of the drilling tool is controlled depending on the flow rate of the coolant. If the flow rate falls below a reference value, indicating a chip buildup, the feed rate is reduced to prevent tool breakage.

[0006] Document DE 10 2009 031 166 A1 discloses a forming machining tool, for example a boring bar, which is equipped with several integrated devices for process monitoring. These include optical monitoring by means of a camera, acoustic monitoring by means of a microphone, and monitoring of oscillations and vibrations via sensors in order to control the machining process directly at the machining point.

[0007] Document DE 202 05 861 U1 discloses a drilling device with a multi-edged drilling tool that has at least two supply channels for coolant / lubricant. To prevent blockages caused by chips, the channels are equipped with independent coolant / lubricant supply devices, such as separate pumps or a flow divider. This makes it possible to selectively increase the pressure in one channel to clear the blockage.

[0008] The object of the invention is to provide a method and a device that enables reliable detection of rattling and that makes it possible to initiate appropriate countermeasures when rattling is detected.

[0009] This problem is solved by the features specified in claim 1.

[0010] Advantageous further developments are specified in the dependent claims.

[0011] The main idea of ​​the invention is to reliably detect the chattering by measuring the pressure and / or flow rate in the coolant lubricant supply system.

[0012] Advantageously, the pressure and / or flow rate of the coolant lubricant is measured directly in front of the drill.

[0013] The invention is explained in more detail below with reference to an embodiment shown in the drawing.

[0014] They show: Fig. 1 drill bit during the cutting process.

[0015] The drill bit features internal coolant passages that extend to the cutting edge, where the coolant lubricant emerges. Besides cooling the cutting edges, the coolant lubricant also serves to remove chips from the borehole.

[0016] The function of the invention is explained in more detail below.

[0017] High cutting forces are generated at the drill bit cutting edges, which create a torque on the drill bit.

[0018] Due to the geometric shape of the drill bit, it lengthens with increasing torque, caused by the cutting forces.

[0019] This continues until the chip breaks again, thereby reducing the torque and shortening the drill bit until the next chip thickness increase. This effect causes the familiar "chatter" of a drill bit, which is essential for the quality of the drilled hole.

[0020] This “rattling” causes a pressure and flow fluctuation in the coolant supply system, which is optimally measured according to the invention.

[0021] The closer the measuring point is to the cutting edge, the more accurate the measurement using pressure and / or flow sensors becomes.

[0022] Using process records of the "good" state or other existing empirical data, the following can be achieved by comparing them with the current measured values: In the simplest case, this can prevent drill bit breakage by stopping the feed rate when a limit value is exceeded. Drill bit wear limit detection, also prediction

[0023] Voids, cracks, and inhomogeneous areas in the workpiece / material can be detected by a drop in back pressure or a change in the coolant's pressure oscillation profile. This allows for optimization of the drilling process through direct feedback of the drilling situation. Feed rate / speed optimization through detection / prevention of "chatter"

[0024] Early detection of resonances and / or machine or workpiece vibrations allows for real-time adjustment of speed or feed rate to largely avoid such damaging operating ranges. AI or simple window definition can determine relevant parameters for future drilling operations. Optimization of coolant quantity / pressure or fault detection (through target / actual deviation and control).

[0025] This can also affect the cutting performance, the service life of the cutting edge, and the safety distance to a drill bit breakage. Cutting and tool life extension; overheating or damage to the workpiece or drill bit can be effectively prevented.

[0026] The idea according to the invention can be used with many other cutting edges which have the coolant supply under pressure directly at (in) the cutting edge (chip former).

[0027] Drilling and cutting processes are often monitored and optimized using force and vibration measurements. This works reasonably well with large drill bits held in small and medium-sized spindles.

[0028] In general, this arrangement offers significant advantages when the ratio of drill / cutting tool to clamping / spindle / machine is large.

[0029] Advantageously, the pressure sensor is positioned in close proximity to the drill bit. The pressure sensor (0-100 bar, dynamic range 10-90% in 2 ms) is integrated into the drill bit holder and monitored via an induction coupler during operation.

[0030] As an alternative mounting location for the pressure sensor, the rotary union for machine tools can be used. This slightly reduces the dynamics with very small tools / drills because the measurement takes place further away from the cutting edge. The internal coolant supply through the electric spindle requires a high-quality rotary union. The most important parameters for selecting the correct rotary union include: - the medium to be conveyed (i.e., coolant, minimum quantity lubrication, air, cutting oil), - machine speed, - pressure and temperature, - connection to the machine: threaded rotor, plug-in rotor with housing-supported design, or bearingless seal assembly, - filtration of the medium.

[0031] In addition to these parameters, the available space for mounting the rotary union must also be considered. Rotary unions with rolling bearings have the advantage of being easy to install on the spindle.

Claims

[1] Method for the reliable detection of vibrations of the drill body of a drill during the drilling process, wherein coolant bores are provided in the drill body through which a coolant lubricant is supplied under pressure via a coolant lubricant system for cooling the drill during the drilling process, characterized by , that the pressure and / or flow rate in the coolant lubricant system immediately before the drill is detected by one or more sensor(s) and the measured values ​​of the sensor(s) are evaluated in an evaluation unit in order to reliably detect vibrations referred to as chatter via pressure fluctuations and / or flow fluctuations. [2] Method according to claim 1, characterized by that the pressure sensor is located in the drill holder. [3] Method according to claim 1, characterized by that the pressure sensor is arranged in a rotary feedthrough provided on the machine tool. [4] Method according to claim 1, characterized by , that the sensor(s) readings are continuously recorded during the drilling process and compared with stored readings from drilling processes classified as error-free.

Images