DE102009044822A1 - Computer-controlled metal-cutting machine's tool e.g. drill, testing device for detecting tool cracks before or after machining process, has mechanical switches arranged with different distances behind pushbutton in adjusting direction - Google Patents

Abstract

The device (10) has a pushbutton (12) adjustably supported in a housing, where a device having signal generators is assigned to the pushbutton. The signal generators emit an error signal in an axial direction of a tool in case of errors in the tool. The signal generators consist of two switches that are arranged with different distances behind the pushbutton in an adjusting direction. The switches are formed as mechanical switches (22, 24), where the pushbutton includes an operating controller (18) that acts on the switches.

Description

The present invention relates to a device for detecting tool breaks in processing machines with a clamped in the machine tool before or after a machining operation.

State of the art

Modern computer-controlled machine tools are used for the fully automatic, machining of workpieces. In this case, a multiplicity of machining operations are carried out according to a predetermined program sequence using different, consecutive tools. These tools must be checked for integrity and functionality before each use. This is associated with a staff effort and is often neglected. However, monitoring is necessary in order to detect possible sources of error at an early stage and to avoid damage. Furthermore, because of the often jarring motions, tools may partially or completely slip out of the chuck. Tools regularly wear during processing, become worn or even break. If this happens and the tool is nevertheless used in an automated process, it can lead to considerable damage to the workpiece and / or also to subsequently used tools that are used in one of the subsequent subsequent processing steps.

Further, since multiple machining operations on the same or consecutive workpieces in an automatic machining operation are often performed with one and the same tool, it must be ensured that each of these tools is in a functional state.

• – Werkzeugbrüchen
• – fehlendem Werkzeug, wenn sich ein solches vollständig aus dem Futter gelöst hat
• – Verschleiß von Werkzeug

und zwar insbesondere bei Bohrern, Fräsern oder anderen spanabhebende Werkzeugen.An important role is played by capturing

• - Tool breaks
• - Missing tool, if such has completely detached from the feed
• - Wear of tools

in particular with drills, milling cutters or other cutting tools.

Due to the above mentioned facts, various systems have been developed for the fracture control of drills and other tools, especially for universal drilling and milling equipment, with which each of the different tools can be measured before or after each machining operation. The respectively determined measured values are compared electronically either in the numerical control device of the machine tool or in a separate device, and with larger deviations an error message is issued. Thus, these devices are often designed as surveying systems. For example, a tool touch system from Heidenhain is known, which works with an optical switch as a sensor, although highly accurate, but it is elaborately constructed and expensive to manufacture and purchase. On the other hand, the present invention is less for surveying than exclusively for fracture detection.

It is also known to use electro-optical systems for tool breakage monitoring, but with the serious disadvantage that shavings and the cooling and lubricating liquids often lead to disruptions of the control system.

From the DE 36 27 796 a device for state and breakage monitoring of rotating tools with a structure-borne sound sensor element is known, however, such sensors for noise are extremely error prone and not practical.

In the DE 85 19 094 A mechanical breakage detection with a scanning sensor and with an electronic device for evaluating the measured values recorded by the sensor is described. However, the device described here has the disadvantage that it is too large and complex and completely unsuitable for use in confined spaces.

task

Object of the present invention is to provide a tool breakage detection available that avoids the error rate of the known prior art devices, yet works very accurately with a mechanical sensor and can be produced inexpensively.

The solution of this problem arises from the features of claim 1. Further features and advantages of the invention will become apparent from the dependent claims and from the following description of an embodiment which is illustrated in the drawing. Show it:

1 a side view of the device

2 a sectional view of the device

3 a schematic sectional view of the device

The 1 shows a side view of the device 10 for testing tools in processing machines with one in a housing vertically displaceable mounted button 12 , The button 12 consists of a Tastteller 14 and one with this over a stamp shaft 16 connected actuator 18 , The button 12 is associated with a device with a signal generator. The signal generator consists of two in the direction of the push button 12 at different distances behind the button 12 arranged switches 22 respectively. 24 , Preferably, mechanical or magnetic switches come into consideration. In the 1 are these in an exemplary embodiment as mechanical switches (S1) 22 and (S2) 24 shown. The vertically movable button 12 is over the Tastteller 14 operated and moved in the direction of signal generator, via a return spring 20 he is brought back to the starting position.

A tool is checked before or after each machining operation. For this, the tool is on the Tastteller 14 pressed and moved the button 12 down against the signal generator. If the tool is in perfect condition, the button will be activated 12 over a distance a _{is to} move and activates the switch S1. The distance covered a _is in this case the predetermined distance a _soll with a perfect tool.

If, on the other hand, the tool has been broken off, not firmly clamped or possibly no longer present, then the actual distance traveled _{is a} smaller than the predetermined distance a _{should be} for a perfect tool, so that the switch 22 (S1) is not activated.

If the tool is too long or not properly clamped, the displacement is a _{is of} the probe 12 greater than the given distance a _{should be} at a faultless tool, so that both the switch ( 22 ) S1 as well as the switch ( 24 ) S2 are activated to output an error signal (a _is > a _soll ). For this purpose, the second switch (S2) has a greater distance (a) from the actuator 18 when the first switch (S1) such that upon displacement of the stylus _is a> a _to - as mentioned - both the first switch (S1) and the second switch (S2) are activated for delivering an error signal.

The 2 shows a sectional drawing in the arrangement of buttons 12 , Return spring 22 as well as switches S1 and S2 can be seen.

• • Bohrer intakt, a_ist = a_soll; Folge: Schalter S1 wird aktiviert => Signal: ok
• • Bohrer abgebrochen oder aus dem Futter gelöst, a_ist < a_soll; Folge: Schalter S1 wird nicht aktiviert => Signal: Fehler
• • Bohrer zu lang (nicht richtig eingespannt), a_ist > a_soll; Folge: Schalter S1 + S2 werden aktiviert => Signal: Fehler

In 3 The following operating states are shown using the example of a drill:

• • Drill intact, a _is = a _soll ; Result: Switch S1 is activated => signal: ok
• • Drill broken off or loosened from the chuck, a _is <a _should ; Result: Switch S1 is not activated => Signal: Error
• • Drill too long (improperly clamped), a _is > a _should ; Result: Switches S1 + S2 are activated => Signal: Error

The tool is released only in the case of the activation of the switch S1, in the case of an error message (switch 1 and switch 2 are activated or no switch is activated), a technician with an acoustic and / or visual signal can be made aware of the faulty tool , In an automated process, the replacement of the tool can continue independently.

Instead of mechanical switches and electromagnetic switches can be used. Disadvantage of the commercial mechanical switch is that they can hardly be protected from moisture and therefore can corrode, they continue to wear and eventually fall out. Practical tests have shown that electromagnetic switches cast in synthetic resin can be well protected against moisture and even rendered watertight and therefore can be used well in the device according to the invention. Furthermore, electromagnetic switches are relatively wear-free.

Furthermore, an electro-pneumatic actuation element, not shown in the figure, which can be mounted, for example, on an on / off switch, also shown in the drawing, or another release switch of the machine tool by means of a clamping connection, can be connected to the breakage detection device and actuate this release switch. If there is no error message from the breakage detection device, the electro-pneumatic actuator releases the tool and the tool can be moved to the next position. In this way, older models can be easily and inexpensively retrofitted with the invention break detection.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3627796 [0007]
• DE 8519094 [0008]

Claims (8)

Device for testing tools in processing machines with a button displaceably mounted in a housing ( 12 ), which is associated with a device with signal transmitters that emit an error signal in case of errors of the tool in the axial direction, characterized in that the signal transmitter consists of two in the direction of displacement at different distances (a) behind the button ( 12 ) arranged switches ( 22 . 24 ) consist. Apparatus according to claim 1, characterized in that the first switch (S1) upon displacement of the button ( 12 ) (Over an adjustable distance a _soll) corresponding to a proper tool the switch (after covering the distance a _is) is activated, such that the first switch (S1) generates no error signal (a = _{a soll),} while it _is at a <a _{should give} an error signal. Apparatus according to claim 2, characterized in that the second switch (S2) a greater distance (a) from the button ( 12 ) as the first switch (S1) has such that when moving the button ( 12 ) (a _is > a _soll ), both the first switch (S1) and the second switch (S2) are activated to emit an error signal. Device according to one of the preceding claims, characterized in that the switches (S1, S2) are mechanical switches. Device according to one of claims 1 to 3, characterized in that the switches (S1, S2) are electromagnetic switches. Device according to one of the preceding claims, characterized in that the button ( 12 ) from a touchable by the tool probe plate ( 14 ) and one hereby over a stamp shank ( 16 ), acting on the switch actuators ( 18 ) consists. Device according to one of the preceding claims, characterized in that the button ( 12 ) is vertically displaceable. Device according to one of the preceding claims, characterized in that it releases the next processing operation via an electropneumatic actuating element which is connected to it and which is subsequently mountable on a release switch on a machine tool, with actuation of the release switch.

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