Patent Application
20080021589
In the following, the present invention will be explained in detail with the help of a preferred embodiment and with reference to the accompanying drawings.
An exchange of information between the machine tool and the transfer device can be realized by executing a sequence by means of a sequential interface. As such an interface, for example a profibus or a RS232/RS422 interface can be used, operating according to a certain protocol. Using a sequential interface has the advantage that a simple reliable connection may be realized and that there is no dependency on the number of positions for the loading of parts. However, thereby, it is required to adapt the software of the machine tool; this can be done often only by the manufacturer of the machine tool. Particularly in the case of machine tools that are already in practical use, an adaptation of the machine software is not readily possible or even not at all possible.
Moreover, there is the possibility to create logical bit patterns appearing at the digital outputs, which can be used by the transfer device for calculating a position. The creation of bit patterns, thereby, can be done by an operator by means of simple programming using an ISO code. However, it can happen that not enough digital outputs are available in already present machine tools, and sometimes it is not possible to add more digital outputs to a present machine tool. The number of the required digital outputs depends on the size of a storage area of the transfer device in which transmitted signals can be stored.
In the following, as an example, a simple embodiment of a communicating exchange of information between the machine tool and the transfer device is described which follows the teaching of the present invention.
As can be seen in
Further, the particular information or data streams a and b between the interfaces 4 and 14 and the digital inputs/outputs 5 and 15, respectively, can be seen.
The information stream a runs unidirectionally from the printer interface 4 of the machine tool 1 to the interface 14 of the transfer device 11. It contains an instruction, being a printer instruction due to the fact that it originates from the printer interface 4, which requires that a piece, for example a work piece or a tool, of the machine tool has to be exchanged. This information, i.e., the exchange instruction a for the activation of the transfer device 11, is received via the interface 14 of the transfer device 11 by the control unit 13 of the transfer device 11 and causes the control unit 13 of the transfer device 11 to activate a protocol for performing different operation steps, as will be explained in more detail with reference to
The information stream b runs in both directions between the digital inputs/outputs 5 of the machine tool 1 and the digital inputs/outputs 15 of the transfer device 11. It contains signals for the synchronization of the machine tool 1 with the transfer device 11, as will also be explained in more detail with reference to
First, in a step S1, a system with a machine tool 1 and a transfer device 11 is activated. Thereby, an operator loads a special macro, normally an ISO code, into the control unit 3 of the machine tool 1. The result is that the control unit 13 can initiate, for example after the machining of a work piece has been finished, that the printer interface 4 can transmit a “print request”, i.e., the information a requesting the exchange of a work piece; the “print request” and information a, respectively, is transferred to the interface 14 of the transfer device 11. It is understood that the transmission of a “print request” a can take place also prior to machining a work piece in order to load a work piece to be machined into the machine tool 1. Moreover, a “print request” a can be created for loading or exchanging a tool.
Moreover, during step S1, connections are established between the machine tool 1 and the transfer device 11, particularly between the interfaces 4 and 14 as well as between the digital inputs/outputs 5 and 15. At the side of the transfer device 11, this is shown by a step S2, also showing a waiting state of the transfer device 11. At the side of the transfer device 11, in a step S3, it is checked whether or not the system has been established. Moreover, in this step S3, according to a later described second embodiment, it can be checked whether or not the machine tool 1 is in a state of readiness for an exchange of a work piece and/or a tool. If the result if the check is NO, a reset to the wait state in step S2 is performed. Otherwise, if the result of the check is YES, the program sequence at the side of the transfer device 11 proceeds to a step S6.
After the step S1 having finished at the side of the machine tool 1, the system is ready so that the machine tool 1 can be loaded by the transfer device 11, and at the side of the machine tool 1, the sequence proceeds to a step S4. In this step S4, a sub-program requesting an exchange is started by the control unit 3 of the machine tool 1, if such exchange is required at the side of the machine tool 1; such requirement is determined by the control unit 3 of the machine tool 1. Upon starting the above mentioned sub-program, the main program transfers for example the following parameters to the sub-program: The location identification of the work piece or tool in the magazine, a positioning identification, i.e., the information where the work piece or tool has to be placed, and possibly a description of the transfer movement to be performed by the transfer device. The sub-program having been started, the sequence at the side of the machine tool 1 continues to a step S5 in which the serial or parallel printer interface 4 sends a “print request”, as previously mentioned, to the serial or parallel interface 14 of the transfer device 11. Thereafter, the sequence at the side of the machine tool 1 continues to a step S9 in which the control unit is waiting for an acknowledgment of the exchange of a work piece or tool requested by sending out the “print request”.
Simultaneously, it is checked at the side of the transfer device 11 in a step S6 whether or not a “print request” has been received by the interface 14, and whether or not this “print request” is valid. The validity of the “print request” can be checked, for example, by transmitting the information in the “print request” together with a check sum. If the answer is NO in step S6, the sequence at the side of the transfer device 11 is reset to the waiting state in step S2. If, however, the answer in step S6 is YES, the sequence at the side of the transfer device 11 continues to a step S7, in which an exchange of the work piece or the tool is performed which has been initiated by the “print request” on the basis of the parameters transferred to the sub-program in step S3.
After the step S7, the sequence at the side of the transfer device 11 continues to a step S8 in which it is acknowledged that a work piece and/or a tool has been exchanged in the machine tool 1. Such acknowledgement is realized by means of sending a signal from a digital output 15 of the transfer device 11 to a digital input 5 of the machine tool 1 since the printer interface 4 of the machine tool 1 can transmit signals only in a direction from the machine tool 1 to the transfer device 11.
At the side of the transfer device 11, the sequence after step S8 returns to the waiting state in step S2, while at the side of the machine tool 1, a check is performed in step S9 whether or not an exchange of a work piece and/or tool has been acknowledged by the transfer device 11. If the answer is NO, the sequence at the side of the machine tool 1 returns, according to a first embodiment to be described later, to step S4 in which a “print request” is sent out, or, according to a second embodiment, the sequence is stopped to wait until the answer is YES. If the answer is YES, the sequence at the side of the machine tool 1 continues to a step S10 in which the machining program to be performed by the machine tool 1 is started; this means that the sub-program is left and the main program is resumed.
The first and second embodiments, which have been addressed above, relate to the case in which the machine tool 1 is not ready for an exchange of the work piece and/or tool. In this case, which is relevant for the reliable operation of the system, it is required that an exchange compellingly cannot take place; the result is that the “print request” and an exchange request, respectively, has to be canceled. This can be accomplished in one of two possible ways:
In a first embodiment, the “print request” can be cyclically repeated; according to the description herein above, this is the case if the answer in step S9, in which an acknowledgment of an exchange of a work piece and/or a tool is awaited, is NO.
In a second embodiment, for example after the sub-program in step S4 has been called, a signal can be sent to a digital output 5 of the machine tool 1 which indicates the readiness for an exchange. That signal, appearing at a digital input 15 of the transfer device 11, is recognized by the control unit 13 of the transfer device 11, as has been previously described in connection with step S3; this signal is temporarily stored or buffered by the control unit 13. In this case, only the receipt of an acknowledgement of the exchange of a work piece and/or tool has to be awaited in step S8; a repeated execution of step S6 is avoided. However, the signal for indicating the readiness for an exchange at the digital output 5 of the machine tool 1 has to be reset after an acknowledgment has been received that a work piece and/or a tool has been exchanged in step S8 (YES).
The sequence has been described above for a single exchange of a work piece and/or tool. According to the system of the invention, such an exchange can be performed, by simply initiating the sub-program, whenever a work piece has been finally machined by means of a machining program; thus, the main program (the machining program) and the sub-program are executed alternately.
According to the invention, it is easily possible to upgrade a machine tool with a transfer device and to coordinate them without the need to significantly modify the machine tool. It is only required to load a macro in order to enable the machine tool to transfer “exchange requests” to the transfer device to activate the latter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01157/06 | Jul 2006 | CH | national |
