The present invention relates in general to a system and method for controlling a production machine. More particularly the present invention relates to measuring working and environmental parameters of a cyclic production machine, setting up a production machine and controlling its operation.
The exact ratio between components used as input in a chemical process is of crucial importance in the determination of the final properties of the product. Therefore appropriate adjustments are normally applied to the incoming flow of materials consumed at the production process. Common gravimetric dosing and feeding devices provide for accurate dosing and blending ratios of raw materials composing a chemical product. An exemplary gravimetric dosing device (GDD) is disclosed in U.S. Pat. No. 6,688,493. The disclosed GDD consists of a controller, a weighing unit and a feeder. The controller is operative in activating the feeder for dispensing material into the production machine, weighing the dispensed material by means of the weighing unit, calculating weights of dosed portions of dispensed material out of the feeder, and for controlling the size of a dispensed dose, and or the feeding times and rates in which material is fed into the production machine.
A typical BS for feeding materials into production machines is shown in
Blending of scrap with virgin raw materials is often implemented in the production process. The blending ratios of scrap with virgin raw material normally impact the level of fluidity of the mix through different stages within a production machine. Such changes in the fluidity of materials may effect some properties of the products. Properly adjusting and fine-tuning the setup parameters of, and uptake of raw materials by, the production machine when utilizing scrap may significantly contribute in lowering the cost of production.
Accommodating the configuration parameters of a production machine to the blending ratios of raw materials while carrying out such chemical process is of an equivalent importance as the proper adjustment of the flow of materials consumed. A cycle of cyclic production machines, such as injection molding machines or blow molding machines of the plastic industry, includes distinct steps in which molten material is first pressurized into a mold; a step of product curing; a step in which the mold is opened for releasing the cured product, and a step in which the mold is closed and gets ready for an identical cycle to be repeated all over again.
Such production machines normally comprise various sensors for measuring working parameters at different stages of the production process and/or at different locations within the production machine. Normally at least some of such parameters are displayed to the operator, by his choice. The parameters are typically displayed across a local monitor linked to the controller of the production machine. The operator may wish to adjust some of the configuration parameters of the production machine in cases in which he or she detects deviations from a characteristic profile associated with any of such working parameters. Normally such adjustments of the configuration parameters of the production machine as well as the configuration parameters of the BS require detailed understanding and intimate knowledge of the production machine and the production process. Normally such know how is unique and is available only to a few experts. Therefore a control system that will assist any staff member in adjusting such setup parameters of a BS and/or a cyclic production machine is called for.
The control system (CS) according to the present invention includes a multiplicity of controllers, some of which may respectively serve as the controllers of dispensing and/or dosing devices, such as gravitational dosing devices (GDDs) and volumetric dosing devices, all of which are linked to a control processor. Each such dispensing and dosing device feeds a production machine with one type of raw material at specified doses, at specified points in time during specified time interval and/or at a specified rates.
One or more controllers are coupled to a cyclic production machine (CPM), which may be for example an injection molding or a blow-molding machine in the plastic industry. An operator supervises the production through a user interface of the control processor.
At least one of the controllers coupled to a CPM receives signals from a sensor associated with the CPM for measuring a working parameter. Signals of the sensors provide indications as to the working parameters of the CPM. These signals are periodically sampled by the respective controller. As the working parameters of the GDDs are changeable and are therefore individually sampled by each GDD. Gathered working parameters of the CPM and working parameters of the dispensing and/or dosing devices are time tagged, and temporarily stored in the respective controllers coupled to the CPM.
The working parameters are associated according to the invention with characteristic profiles such as time profile of a pressure measured at a specific location within a CPM. Some of the working parameters are statistically analyzed on the fly, statistical attributes known in the art as statistics, for example mean, standard deviation, minimum and maximum are computed for a number of samples acquired along a specified time interval to be referred to hereinafter as statistics.
Exemplary working parameters of the CPM are: count of machine cycles, product units produced within a specified time interval, lengths of time intervals corresponding to various segments of CPM's cycles, distances along which certain parts of the CPM periodically move, rotational speed of certain members of a CPM, temperature and or pressure values at specific locations within the CPM, power consumption of a CPM, flow rates and capacities of coolant liquids and or pressurized gases fed to a CPM, specific features and or dimensions of product units.
Characteristic profiles and statistics stored in the control processor, as well as histories of a working parameter are presented to the operator by his choice. The operator is able to compare between currently acquired characteristic profiles and statistics with stored characteristic profiles and or standards and associated tolerances. Tuning of the setup parameters of a CPM and or of respective GDD or a blending system coupled to a CPM is carried out according to the invention to bring at least one measured characteristic profile and or statistics to conform with a pre-stored characteristic profile and or statistics.
A control system of the invention is incorporable with any CPM in which the blending ratios of raw materials influence the level of homogeneity of the mixed components of raw material and the flow features of such mix along various stages of processing within the CPM. The system of the invention promotes the control over the production process of such chemical products.
In accordance with the present invention a control system for cyclic production machines (CPMs) is provided. Controlling CPMs according to the method of the present invention is accomplished by adjusting configuration parameters of a CPM to conform with a standard or a pre-stored configuration parameters associated with a desired set of blending ratios of raw materials to be consumed along the production process.
Reference is first made to
For better understanding the CS of the invention an exemplary system configuration to which injection-molding machines such as of the plastic industry are incorporated is hereby described with reference to
The current configuration parameters of each GDD respectively feeding a CPM with one type of raw material, or scrap, and/or the BS as well as their stored history, namely data including values of the configuration parameters stored at points in time in which at least one such parameter is modified, doses of materials respectively inputted into the CPM at various machine' cycles, and/or an associated statistics of these doses and/or rates, are also regarded as working parameters of the CPM. Therefore link 66 provides for uploading data from the BS or the other GDDs respectively feeding this CPM related to these working parameters into controller 62. Such data is further incorporated with the data related to GDD 64 stored in controller 62, to be further transferred to control processor 61.
CPMs in which sensors some of which are similar to some of the aforementioned sensors are incorporated linked to the integral CPMs' controller or controllers each of which its signals are periodically measured and gathered by such integral controller or controllers are common. Reference is now made to
Deriving Working Parameters from Sensor Data
Parameters whose values are indicative to the features of the production process and/or features of a product are regarded as the working parameters of the production machine. Such parameters include according to the present invention parameters related to internal members of a CPM, features of a product unit as well as to environmental conditions, such as ambient temperature. Signals of sensors are used to derive working parameters of the CPM. Sensor signals are periodically acquired, working parameters are derived from them, time tagged and stored in the corresponding controller. Such sensors are normally integrated into the CPM at various locations providing for meaningful data. Such are the aforementioned sensors of the exemplary CS described in example 1 above.
Similarly sensors typically employed for measuring features or dimensions of product units produced by the CPM, as well as sensors for measuring energy and or power consumption of the CPM can be implemented according to the method of the present invention as well. Such sensors may be in contact with the CPM or they may be remote. An example of a remote sensor is an infrared thermometer employed for measuring a temperature of specific member of the CPM or the respective temperatures of product units. Control signals generated by the timing unit of a CPM are regarded according to the invention as a timing sensor. In accordance with some embodiments of the present invention, an operator manually measures features of a product unit such as its color or its weight and feeds the measurements results to the control processor. Such manual measurements when are directly inputted into the control processor by means of a user station, or indirectly inputted to a controller and further transferred to the control processor, are also regarded according to the present invention as being accomplished by the controllers of the CS.
Description of a System According to a Preferred Embodiment of the Present Invention
A CS according to a preferred embodiment of the present invention consists of one or more sets of controllers respectively coupled to one or more CPMs. Each set includes a multiplicity of controllers. Each controller of a set is respectively linked to the timing unit of the respective CPM. One or more controllers of a set are further linked to an additional sensor associated with the respective CPM, which is different from the timing unit. Optionally a controller of a set also serves as a controller of a dispensing and/or dosing device feeding the respective CPM with one type of material. Such a dispensing and/or dosing device can be either a GDD or a volumetric dosing device. In such a case such controller (of a GDD or a volumetric dosing device) need not be according to the invention further linked to a sensor, which is different from the timing unit of the respective CPM.
All the controllers are respectively linked to a control processor. A personal computer (desktop or laptop) may implement the control processor wherein the links to the controllers are implemented by means of a suitable computer communication network as known. Data is periodically and automatically uploaded, or occasionally and manually uploaded by an operator demand, into the control processor. Current and/or historical measured data related to each CPM and its corresponding GDDs and/or volumetric dosing devices, and/or BSes is occasionally displayed by an operator demand across a screen of a user station or a terminal linked to the operator interface, either incorporated into, or linked to, the control processor. The operator may compare such data to other data stored in the control processor. The operator may further correlate a piece of displayed data with other data stored in the control processor. He or she may decide to modify the settings or the configuration parameters of a CPM and/or its corresponding GDDs, volumetric dosing devices and/or BS accordingly, as is further described infra.
Any cyclic CPM for producing chemical products in which the blending ratios of raw materials utilized influence the level of homogeneity of the mixed components of raw material and the flow features of such mix along various stages of processing within the CPM is incorporable with a CS of the invention.
Measured Working Parameters
The values of working parameters of a CPM and the time profiles of such parameters are indicative as to the level of deviations of the product units produced from their specifications. Following is an exemplary list of working parameters to be measured and acquired by a controller according to the present invention: (i) CPM cycles count and the number of produced product units within a time interval; (ii) time intervals corresponding to complete and/or partial cycles of a CPM; (iii) temperature and/or pressure values, measured at different points within the CPM; (iv) distances along which some members of the CPM cyclically, or periodically move; (v) rotational speeds of certain members of a CPM; (vi) specific features of product units measured periodically and/or synchronously with the CPM's cycles, such features measured are associated with dimensions or lengths such as a width of a segment of product unit, or distances between specific points of a product unit, or with weights and/or color of product units or segments of product units; (vii) energy and or power consumption of a CPM, rates of flow and capacities of coolant liquids, and or pressurized gases into a CPM, (viii) quantities of raw materials fed to the CPM by each GDD and/or a BS, (ix) setup or configuration parameters of each GDD, BS and the volumetric dosing devices when are accessible through their integral controller, and or (x) any combination thereof.
The working parameters of the GDDs, volumetric dosing devices and/or BSes and of the CPMs, which are collectively referred herein as the working parameters of a CPM, are amendable and their values impact the production process. Some of the above mentioned working parameters are successively measured according to the method of the present invention at a respective predefined rate along a segment of, or the entire, cycle of the CPM. Such are for example the parameters referred to in categories (iii), (iv), and (vii) described above. Such working parameters are referred hereinafter as parameters measured along the machine cycle. Working parameters of the other categories are sampled according to the present invention in-between machine cycles. All the measured working parameters are timely recorded in the respective controllers. All acquired data are time tagged and are respectively stored within each controller.
All, or a portion, of such time tagged data periodically, or occasionally, such as by an operator demand, is uploaded to the control processor for further processing as is further described infra.
Characteristic Profiles and Statistic
Profiles of working parameters whose functional shapes are indicative to the level of homogeneity of features of currently produced product units are referred to hereinafter as characteristic profiles. Reference is now made to
A plot of the measured distance along which the screw feeder of the CPM moves while delivering material into the mold along an injection cycle versus time can be similarly plotted. Differentiating such a time distance profile in time and correlating distances with time values results in another characteristic profile, which is the speed distance profile 120 as is shown in
Combining both aforementioned characteristic profiles and employing the same coordinates transformation of time to distance results in a typical characteristic pressure distance profile 130 corresponding to the same injecting cycle as is shown in
Optionally, the measured values of the working parameters are further statistically analyzed on the fly as seen by reference to
In
Changes of the characteristic profiles in time are statistically analyzed in order to assess the level of deviations from their typical values and functional shapes. The integral of pressure along distance, whose value equals the area below the pressure-distance profile shown in
Another example is associated with the weights of product units computed by employing the measured quantities of raw materials dispensed by some or all the GDDs feeding the same CPM and their respective blending ratios. Such a computation is carried out at each machine cycle in a discrete production process such as of the injection molding, or along consecutive specified time intervals such as in a continuous process as of the extrusion machines in the plastic industry. These computed weights are statistically analyzed along a specified time interval and the resulting average, maximal and minimal computed values and or the computed standard deviation present characteristic statistics associated with the weight of a product unit. Correlating the computed products weights with the values of the backpressure exerted by the material contained within a mold, or with the distance along which the screw feeding the mold moves, may improve the accuracy of the computed weights.
Standard Profiles and Statistics
Each set of blending ratios of materials normally employed for producing a chemical product is associated with a corresponding set of appropriate ranges of values of working parameters of the CPM selected to produce a specific product. The level of conformance of the product's units with their specifications may vary with varying the configuration parameters within these ranges. There are, however, sets of configuration parameters in which the level of deviations from the specified features of a product is permissible. Typically there is a set of configuration parameters in which such level of deviations is minimal for a desired set of blending ratios. The characteristic profiles corresponding to such configuration parameters for each set of blending ratios are regarded according to the present invention as standard profiles.
Some of the features of a characteristic profile are indicative to the level of homogeneity of the product's units. Such as is for example the average distance presented by horizontal line 142 in
Standard profiles and statistics are stored in a database in the control processor according to the invention and are employed as is further described infra.
Control Limits
The current values of some characteristic statistics serve according to the invention as control limits. Control limits are automatically displayed to the operator over the operator station. Such are for example lines 144, 146 and 148 of
Adjusting Configuration Parameters of a CPM
The operator can select characteristic profiles and statistics of working parameters from a set of profiles and statistics stored in the control processor. The operator may compare actual characteristic profiles and statistics to pre-stored and/or standard profiles and statistics corresponding to the same CPM, product, blending ratios and a list of raw materials specified by types of materials and optionally by manufacturers. He or she may correlate between characteristic profiles or statistics associated with different working parameters and/or stored at different points in time. Based on such analysis, the operator may evaluate whether by modifying the current configuration parameters of a CPM a match between currently measured profiles with the standard profiles and or statistics is improvable. The operator is optionally assisted by procedures stored in the control processor for such evaluation. Optionally recommendations for further comparisons between other currently measured profiles and statistics and their corresponding standard or pre-stored profiles and statistics that are suitable for the specific product and or materials utilized are presented to the operator by his choice.
The operator is assisted by stored procedures for adjusting some or all of the configuration parameters such that the actual characteristic profiles and/or statistics will better conform with the pre-stored or standard respective items. When the introduction of new configuration parameters is accomplished the operator rechecks the matching between current profiles and statistics of the newly set working parameters with the stored and or standard profiles and statistics. He/she then may improve the setting in a case that the actual profiles deviate from the stored ones by more than is typically advised as is specified in the setting procedure.
Uses of a CS of the Invention
A CS of the invention provides for matching configuration parameters of CPMs and or their GDDs and/or BSes with desired blending ratios of materials composing a chemical product. The utilization of scrap or recycled materials can be promoted by adjusting the configuration parameters of a CPM and/or dispensing and dosing devices to enlarged concentrations of scrap in its input materials. The controllability of the production process is promoted since real time data related to quantities of raw materials utilized, product units produced, and production machines are gathered and stored. Portions of components of raw material consumed can be measured by means of the CS. These quantities combined with computed portions of materials that are not weighed during the production process are optionally documented in the database. Product units are counted and time tagged. Data related to the production process of batches of product units is accessible providing for a detailed quality control process. Time tagged data related to power and energy consumption, capacities of coolant liquids and pressurized gasses are optionally gathered and individually documented for each CPM. Shut down, idle and production times are computable employing individually measured working parameters for each CPM. Such documented data may provide for further analysis and planning of the production process.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IL07/00683 | 6/6/2007 | WO | 00 | 12/8/2008 |
Number | Date | Country | |
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60804100 | Jun 2006 | US |