METHOD FOR DIVIDING THE WORKING-CYCLE OF A MACHINE-TOOL

Abstract: System for automatic condition monitoring of machine-tools in operation. The workingcycle is divided into phases, where different reference values may be valid for the parameters that are monitored, e.g. the current consumption of motors. When a new phase is to be initiated this is stated by the operator. Furthermore, there is a possibility to get impulses for phase changing from generators positioned on the machine-tool or the control system. Unambiguousness regarding where in the working-cycle a change of reference values (phase change) occurs is obtained in that the monitoring systems add pulses from pulse generators coupled to the feeding axes of the machine-tool. The monitoring is synchronized with the working-cycle in that the starting pulse of the detail programme is fed to the monitoring system. By deviations from the valid reference values, obtained from recording, ALARM or STOP signals are obtained in dependence of the type of deviation.

Description: Method for dividing the working-cycle of a machine-tool Background In monitoring systems the allowed reference values are compared with the actual values. In machine-tools it is difficult to predetermine the allowed reference values in view of the great natural variations generally existing i.e. hardness and working allowance in the work pieces. Therefore, recording technique is beginning to be marketed for numerically controlled machines, where new reference values automatically are inserted by means of different computer calculations. Disadvantage of these systems is that the computer cannot decide if a variation is normal (i.e. due to variation of working allowance) or abnormal (breakdown). On the other hand, if a skil¬ led operator may decide when new periods or phases should be valid, greater consideration can be paid to normal variations. Description The invention relates to a system for automatic condition monitoring of machine-tools during operation. The system is based on a micro-computer with adaptation to sensors/generators for both analogous and binary quantities, placed on the machine-tool. Existing systems work according to the principle that actual parameters of operation are compared to reference values, predeter¬ mined or obtained by recording technique. The reference value is frequently a limit value which may not be exceeded. When recording technique is used the reference value is obtained in that the re¬ corded value is increased by a certain percentage. The division of the working-cycle, i.e. for change of reference values, is made in blocks or by using M-codes in the detail programme. A condition for this is use of NC- achines and the later method means that al¬ ready when drafting the detail programmes it must be decided when a new limit value is to be valid. The novelty of the present system is that reference values are recorded during phases, the length of which are determined by switches in the equipment and/or the operator, i.e. division of the working cycle is made completely independent of block limits and the like. Such a method makes it possible to use the system also on ot h er than NC-machines.. The division is ' made by a push button actuated by the operator and/or said switch, and unambiguousness regarding where in the working-cycle change of reference value is taking place is obtained by simple pulse ge¬ nerators, coupled to the feed movements. Reference values for analogous parameters are calcula¬ ted and are stored in the form of maximum and minimum values during recording. • When changing tools and work pieces the time for the change can be automatically measured and compared to reference values. There are also inputs for generators in two levels, AL¬ ARM and STOP. The inputs of the monitoring system are divided in functional groups, i.e. analogous time sequency, binary alarm and binary stop. The monitoring is synchronized with the working-cycle in that the starting pulse of the detailed programme is fed to the monitoring system. When the reference values are exceeded an ALARM or STOP signal is obtained from the system in dependence of the type of deviation. Error print outs are made on a printer. The monitoring system is contained in a box having space for the micro- computer with adaptation card, generators on the machine-tool, medium for storing reference values for the de¬ tail in question, panel with ALARM and STOP signals (control lamps) and printer. The system includes inputs for thte generators, grouped according to the above description. There, are also inputs for signals from the pulse generators, coupled to the feed movements and start and stop signals from the control cabinet cf the ma¬ chine-tool. The recording of reference values is made as follows: When the machining of a detail is started the monitoring system gets a start pulse and starts to collect measuring values and to count pulses from the pulse generators to the feeding mo¬ vements. When the operator determines that a phase with diffe¬ rent reference values is to be started he pushes a push button switch. When the button is pushed the system calculates maximum P and minimum reference values for each analogous parameter in that to the highest value of the interval is added a. value, the amount of which depends on the difference between the highest and lowest recorded value, and in the same manner a corresponding amount is subtracted from the lowest value. These reference va¬ lues are stored together with the added pulses from the feeding movement pulse generators and reference values for the binary ALARM and STOP generators on a memory medium, e.g. floppydisc. The same co'urse of events is initiated when said switch is actuated. An example of the operation of the monitoring system is schematically shown in fig. 1. The figure shows how the system after start 1 senses switches2 to determine if it is a question of recording of reference values. If this is the case a start signal from the control system of the machine-tool is awaited, where upon collection and treatment of measuring values is star- ted. At the same time the phase division button of the operator is sensed, which shows if a new phase with new reference values is to be started. If not the collection and treatment of easu- ring values is continued. If a new phase is to be started the total amount of counted pulses from the pulse generators on the 7 feeding axes is registered, and reference values are calculated for the analogous parameters, where upon reference values and o pulse number for identification on the phase are stored on a suitable memory medium, e.g. Floppy Disc. After storing of valu¬ es for the latest phase an investigation is made if the machining g is completed . If not collection and treatment of measuring values iι_q ior the new phase is started, and the cycle y is repeated. If the machining is finished the recording is terminated. - When the switch for recording/operation instead shows that there is no question of recording but of operation with monitoring the start signal from the control system of the ma¬ chine-tool is awaited, where upon reference values for the first phase are collected from said memory medium . There upon collec- 105 tion of measuring values and comparision with the present re- *1 __• Λ C "7 fεrence values , is started, whereby differences ' give STOP 108 and ALARM 109 . If the machine has not been stopped 108 an - URE 110 investigation is made if a phase limit ^ as- been reached, said test being made by means of .the ulse " number from said pulse generator and the pulse number registered at the record ing. If a new phase is to be initiated new reference values lOii 104-110 are inserted and the cycle is repeated. If the phase limit is not reached it is investigated if the machining is 1 1 )E * _ A A ( finished . If not the cycle ° is repeated, i.e. measur¬ ing values are collected and compared with the valid reference values. If the machining is finished the monitoring is finished. Olvϊ

Claims: Patent claims 1. The invention relates to a method for dividing the working cycle of a machine-tool. The method is intended to be applied to machine-tools with coupled monitoring systems, based on recording technique, where actual values of parameters are compared to recorded reference values. The working-cycle is divided in phases, and the limit between different phases is marked during the rec-ording of re¬ ference values, and the division in phases is characterized in that a switch is actuated physically when a new phase is to be initiated. 2. The positions relative to the working-cycle of the marked phase limits mentioned in claim 1 is determined by an accumulated number of pulses, registered at the recording, when the switch mentioned in claim 1 is actuated. The pulses are obtained from pulse generators coupled to the feeding axes of the machine-tool. A number of pulses unambiguously determining the positions of the phase limits is obtained by collection and treatment of pul¬ ses from all feeding axes of the machine-tool. The treatment of the collected pulses is characterized in that the pulses from all pulse generators are added.

Inventors: HJELM S, HOLMLOEV H, SJOELINDER B
Applicants: HJELM S, HOLMLOEV H, SJOELINDER B
Application year: 1980
Main classification: G05B19
IPC codes: G05B19