NC machining system

Abstract

We provide an NC machining system that can be used in both high temperatures during the summer and low temperatures during the winter. [Solution] An NC machining system comprising an NC machine tool, a machining control means, a dimension measuring sensor, and a temperature sensor, wherein the system processes a workpiece based on a machining command value provided by the machining control means, the dimension measuring sensor measures the actual dimensions of the machined workpiece, the temperature sensor measures the ambient temperature of the dimension measuring environment, the actual dimensions of the workpiece measured by the dimension measuring sensor are converted to dimensions at a standard reference temperature using the ambient temperature of the dimension measuring environment measured by the temperature sensor, and a correction value for the machining command value is calculated based on the difference between this and the target dimensions of the workpiece, the machining control means receives the corrected machining command value based on this correction value, and the system is configured to have a wide operating temperature range.

Description

Technical Field

[0001] The present invention relates to an NC machining system centered on an NC machine tool that machines a workpiece based on a machining command value.

Background Art

[0002] Conventionally, an NC machine tool is known that obtains a correction amount according to the thermal displacement amount of machine parts caused by heat generation of a spindle or a ball screw, a change in cutting water temperature, etc., and performs thermal displacement correction by axial movement according to this correction amount (for example, Patent Document 1). The NC machine tool described in Patent Document 1 is configured to be able to correct a machining dimension error of a workpiece by effectively estimating the cutting edge displacement amount of a tool caused by thermal displacement.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the NC machine tool described in Patent Document 1 only corrects the machining dimensional error of the workpiece by estimating the cutting edge displacement. In other words, it did not actually verify the machining dimensional error of the workpiece. On the other hand, inspection work is also performed to measure the actual dimensions of the workpiece and correct the dimensional error, but the correction is reflected at the earliest in the next batch, and it is common to measure workpieces that were machined the previous day the next day. In other words, the feedback is not done in real time, which has resulted in a problem of producing many defective products. Regarding this, it seems that attempts have been made to measure the dimensions of the workpiece on the manufacturing line and provide real-time correction feedback, but in order to suppress the effects of thermal expansion of machine tool parts and the workpiece itself, strict temperature control is required, for example, by maintaining the room temperature at ±0.5℃ of the set temperature.

[0005] Incidentally, in recent years, due to the declining birthrate and resulting decrease in the number of students, many school facilities are being closed every year, and there is a desire to utilize existing closed school facilities. Under these circumstances, it is ideal for factory production lines to be installed in the longest possible straight line, and using school buildings and gymnasiums as production lines is a good fit for utilizing closed school facilities.

[0006] However, buildings such as school buildings and gymnasiums do not always have adequate air conditioning. As a result, in summer and winter, the working environment often falls far outside the temperature range intended for the production line. Therefore, even when abandoned school facilities are used as factories, they are usually used to produce goods that do not require such strict temperature control, and production lines using NC machine tools that require precise processing are not well suited to the utilization of abandoned school facilities. Incidentally, the NC machine tool described in Patent Document 1 seems to take into account changes in ambient temperature, but it does not take into account processing in high temperatures in summer or low temperatures in winter. On the other hand, factories equipped with air conditioning can produce goods that require strict temperature control, but the challenge remains that temperature control in summer and winter is expensive.

[0007] The present invention aims to address these problems and provides an NC machining system that can correct dimensional errors in workpiece machining, while also having a wide operating temperature range, allowing it to be used in high temperatures in summer and low temperatures in winter. [Means for solving the problem]

[0008] To achieve this objective, the technical means according to the present invention is an NC machining system comprising at least the following configuration.

[0009] An NC machining system comprising an NC machine tool, a machining control means, a dimension measuring sensor, and a temperature sensor, wherein the NC machine tool processes a workpiece based on machining command values ​​provided by the machining control means, the dimension measuring sensor measures the actual dimensions of the processed workpiece, the temperature sensor measures the ambient temperature of the dimension measuring environment, and the actual dimensions of the workpiece measured by the dimension measuring sensor are compared with the ambient temperature of the dimension measuring environment measured by the temperature sensor. and the coefficient of thermal expansion stored for each metal material The system is characterized in that, after converting the dimensions to those at a standard reference temperature, a correction value for the machining command value is calculated based on the difference between the workpiece's dimensions and the target dimensions, and the machining control means receives the modified machining command value based on this correction value, thereby widening the operating temperature range of the system. [Effects of the Invention]

[0010] Having these characteristics, the present invention provides the following effects. This NC machining system can compensate for dimensional errors in workpiece machining, and its wide operating temperature range allows it to be used in both high-temperature and low-temperature environments. Furthermore, it is possible to provide an NC machining system suitable for unattended operation. In addition, it is possible to minimize the occurrence of defective products. [Brief explanation of the drawing]

[0011] [Figure 1] This is a system configuration diagram of an NC machining system according to an embodiment of the present invention. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. The following drawings are for illustrative purposes only, and in order to make them easier to understand, some components that are not necessary for the explanation may be intentionally omitted.

[0013] (System configuration) Figure 1 is a system configuration diagram of an NC machining system according to an embodiment of the present invention. The NC machining system 100 according to an embodiment of the present invention generally consists of an NC machine tool 1, a machining control means 2, a dimensional measurement sensor 3, a temperature sensor 4, a data acquisition device 5, and a data server 6, and performs automatic collection of machining data by the NC machine tool 1, automatic correction of machining control parameters, and visualization of unmanned equipment. Specifically, by visualizing manufacturing data (number of units manufactured) and operating status, it is possible to avoid situations where abnormal stoppages of unmanned lines go unnoticed, thereby improving product quality and productivity. Communication between each element of the system is preferably performed by a high-speed, real-time industrial network such as EtherCAT (registered trademark), but communication may also be performed by ordinary Ethernet.

[0014] NC machine tool 1 is a machining tool that performs cutting while numerically controlling (NC: Numerical Control) the movement of the machine tool. For example, it has a stage and a spindle, and a drive mechanism that moves the spindle relative to it in three dimensions. The stage, on which the workpiece is placed and held by chucking, is movable in the X-axis and Y-axis directions of the XYZ coordinate system, and the spindle is configured to be movable in the height direction (Z-axis direction). This allows for machining of the workpiece, such as turning, milling, and grinding. The target workpieces are cylindrical materials into which holes or screw shapes are machined, or flat plate-shaped materials are cut, but may also involve many machining processes, such as when a flange is provided inside.

[0015] Although the machining control means 2 is shown as a separate block diagram from the NC machine tool 1 in Figure 1, it is actually an auxiliary control means of the NC machine tool 1 that controls the NC machine tool 1 based on machining command values ​​that quantify the depth and amount of tool movement. The machining command values ​​are detailed control parameters related to the tool and material, such as how many rpm to rotate the tool, how fast (in m / s) to move it in which direction and how, and how and to which direction to tilt the material to be machined by how many mm. The machining command values ​​are manually entered by a skilled worker based on the machining drawing, or they are automatically entered by linking with a CAD system and inheriting CAD data. Furthermore, in this embodiment, it is assumed that the machining command values ​​corrected based on correction values ​​calculated by the data acquisition device 5 are also input to the machining control means 2.

[0016] The dimension measurement sensor 3 is located in the manufacturing line downstream of the NC machine tool 1 and measures the actual dimensions of the workpiece that has been processed by the NC machine tool 1. The dimension measurement sensor 3 is an optical measurement sensor that measures dimensions as the workpiece passes between the light-emitting and light-receiving parts, enabling in-line measurement without stopping the manufacturing line. Furthermore, because it is an optical sensor, the measuring instrument itself is not affected by temperature changes, unlike measuring gauges.

[0017] The temperature sensor 4 measures the temperature around where the dimension measurement sensor 3 is located and is used for the automatic correction of the machining control parameters described later. Previously, the temperature of the manufacturing line was kept constant by running an air conditioner at all times. In addition, although the values ​​of the temperature sensor were monitored in order to monitor the temperature of the manufacturing line and keep it constant, the idea of ​​using the temperature information for the control of the NC machine tool 1 had not been considered.

[0018] The data collection device 5 collects the dimensional data of the workpiece measured by the dimension measurement sensor 3 and the temperature data measured by the temperature sensor 4, and calculates a correction value for the machining command value based on the dimensional data. In addition, the data collection device 5 also collects the actual production quantity of the workpieces obtained by counting the workpieces that have passed through the dimension measurement sensor 3, collects the operating status of the NC machine tool system 100, and collects information when an abnormality occurs. In addition, when an abnormality occurs, an alarm is created and an email is sent to the customer, etc. The collected information is managed by being stored in various storage devices or transferred to the data server 6, etc. The data collection device 5 has a function of generating emails.

[0019] The data server 6 acquires data from the data collection device 5 and accumulates the production performance data and temperature data so that they can be utilized. Specifically, the data server 6 has a function of accumulating the dimensional data acquired by the data collection device 5, and is configured to be able to search, extract, and display the accumulated dimensional data. In addition, the data server 6 has a function of accumulating the temperature data acquired by the data collection device 5, and is configured to be able to search, extract, and display the accumulated temperature data, so that trend monitoring can be performed thereby.

[0020] A monitoring screen is displayed on the display connected to the data server 6. The monitoring screen is configured to transition between the top screen and the individual screen. The top screen is configured so that the operation status monitoring screen and the temperature monitoring screen can be mutually exclusively selected. On the operation status monitoring screen, the operation status of the factory can be viewed, and on the temperature monitoring screen, the temperature monitoring status of the entire factory can be viewed.

[0021] The individual screen is composed of a factory list screen, a manufacturing screen, an alarm monitor screen, an operation history screen, a temperature trend, a dimension trend, a correction value control screen, etc.

[0022] On the factory list screen, the operating status of the factory can be checked. On the manufacturing screen, operations and settings for counting each processing machine (NC machine tool 1) can be performed. The alarm monitor screen displays a list of the alarms that have occurred. The operation history screen displays the operation history. The temperature trend shows the temperature trend of the factory. The dimension trend displays the dimension trend of the factory. On the correction value control screen, automatic correction settings can be made for each machine number.

[0023] The correction value control screen is composed of a screen related to the main axis 1 and a screen related to the sub-axis 2 for each machine number, and correction values for the main axis 1 and the sub-axis 2 of the NC machine tool 1 can be set.

[0024] Settings related to the linear expansion rate, change upper limit setting, alarm setting, and machine tool stop setting can be made, and switching between manual mode and automatic mode is possible. In automatic mode, in addition to automatically correcting the processing command value according to the measured temperature when manufacturing 3 products, alarm determination and machine tool stop determination are executed. This will be described later. In manual mode, editing of the machine tool correction value, writing of the correction value, and reading of the correction value are performed manually. In writing the correction value, the machine tool correction value is reflected in the processing control means 2 of the NC machine tool 1, and in reading the correction value, the correction value of the processing control means 2 is reflected on the reading screen. When reading, the final reading date and time are updated.

[0025] (Regarding the automatic correction process) The NC machining system 100 according to an embodiment of the present invention is configured to measure the actual dimensions of the machined workpiece and calculate a correction value for the machining command value based on the difference between the actual dimensions and the target dimensions of the workpiece. However, since the metal material of the workpiece expands when heated and contracts when cooled, a temperature difference of 10°C can easily cause the dimensions to fall outside the range if the dimensional tolerances are set too tightly. Therefore, the NC machining system 100 according to an embodiment of the present invention is configured to calculate a correction value (temperature correction value) for the machining command value based on the difference between the target dimensions of the workpiece and the dimensional measurement environment temperature measured by a temperature sensor, after converting the dimensions to those at a standard reference temperature. The temperature correction value is calculated by the following (Equation 1). (Equation 1) Temperature correction value = linear expansion coefficient (20°C) × 10 ―6 ×(20℃-temperature)×L(mm) Here, L is the product dimension. The coefficient of linear expansion is 17.3 for bronze, for example, but it varies depending on the metal material, so a unique coefficient of linear expansion is stored for each metal material. Thus, assuming that the reference value is the dimension measured at an ambient temperature of 20°C, a temperature correction value is used to convert the dimension measured at the current ambient temperature to the dimension measured at 20°C. For example, if the dimension measured at an ambient temperature of 23.5°C is 12.3 mm, then when measured at an ambient temperature of 20°C it would be equivalent to 12.299 mm. If the target dimension is 12.5 mm, then 0.201 will be calculated as the correction value, so 0.201 is added to the processing command value up to that point.

[0026] For NC machine tool 1, after applying tool position correction, it takes time for the results to be reflected in the measurement values ​​on the inspection machine. Therefore, automatic correction needs to take into account the machining timing of the next product on NC machine tool 1. This correction is performed once every three products are manufactured. However, the correction value is calculated once every product is manufactured, and the correction value is displayed on the screen each time so that the operator can confirm that the correction has been applied correctly.

[0027] Data server 6 stores various information for automatic correction. For example, it stores information about part numbers, the coefficient of thermal expansion for each material (metal), alarm setting machine correction settings for activating alarms, and machine stop setting machine correction settings for emergency stopping of NC machine tool 1. With this configuration, a correction value suitable for automatic correction is calculated for each metal, and if the calculated correction value exceeds the alarm setting machine correction setting or machine stop setting machine correction setting, an alarm can be activated or NC machine tool 1 can be emergency stopped. If a predetermined threshold is exceeded, a malfunction will occur in the tool, etc., which cannot be handled by automatic correction and requires maintenance, so measures are taken to address this. In addition, when an alarm is activated, an automatic email is sent to the customer, which is convenient.

[0028] (Regarding the track record of automatic correction processing) The NC machining system 100 according to an embodiment of the present invention is installed in a gymnasium of a closed school, using the existing facilities. This allows for lower initial investment costs. However, because it utilizes the existing gymnasium facilities, it does not have air conditioning or similar equipment. The NC machining system 100 has been operated throughout the year, and it has been recorded that it was used in environments with temperatures of 41.2°C in the summer and 11.3°C in the winter. Nevertheless, even in such high and low temperature environments, it has been confirmed that the system was able to machine workpieces that fit within dimensional tolerances without exceeding the alarm setting machine correction setting value or the machine stop setting machine correction setting value, through automatic correction based on dimensional and temperature measurements.

[0029] This result is revolutionary compared to previous manufacturing lines. This is because, in previous manufacturing lines equipped with processing machines that did not have temperature compensation, air conditioners were kept running constantly to maintain a constant temperature year-round. As a result, a large amount of capital was required for the initial investment in factory equipment. On the other hand, some existing factories do not have sufficient sealing and it is difficult to maintain a constant room temperature, so temperature compensation for processing machines is performed manually. Specifically, the processed workpiece is brought to a standard temperature, measured, and the dimensional difference is determined, or the dimensional difference is determined using a block gauge, the resulting dimensional difference is estimated to be due to the effect of temperature change, and the processing command value is updated by dividing by that amount. In any case, since the measurement has to be performed separately from the manufacturing line, the necessary correction is not performed in real time. As a result, there was a risk that products that fell outside the dimensional tolerances would be produced, resulting in a large number of defective products. The NC machining system 100 according to the embodiment of the present invention applies corrections in real time, and more precisely, the correction value is reflected every three units manufactured. As long as the dimensional tolerance is within the limits, the product will not be considered defective, making it possible to reduce the occurrence of defective products to as close to zero as possible.

[0030] Furthermore, an alarm is triggered if the machine's compensation setting value is exceeded. In addition to the effects of temperature changes, maintenance may be necessary to ensure that machining within dimensional tolerances is performed due to tool wear or damage, etc. In such cases, an alarm is triggered, and an email is sent to the customer, allowing for a quick response.

[0031] Furthermore, if the machine stop setting or machine correction setting value is exceeded, the NC machine tool 1 will be stopped in an emergency, and an email will be sent to the customer in this case as well. When a former school facility is used as a factory, the number of managers is small, and especially at night, it is not uncommon for the facility to operate completely unmanned. In such cases, in conventional facilities, the fact that the production line has stopped would be recognized the next day, and recovery work would then begin. However, in this embodiment, information that the production line has stopped is sent by email, making it possible to minimize downtime. Thus, according to this embodiment, an NC machine system that enables unmanned or near-unmanned operation can be provided, which greatly contributes to work style reform. In addition, the degree of specialized knowledge required of managers can be reduced. For this reason, there is no need to select managers on an individual basis, and it also contributes to measures against depopulation by employing residents of sparsely populated areas.

[0032] In the embodiments described so far, the calculation of the correction value for the processing command value and the sending of the email were described as being performed by the data acquisition device 5. However, the calculation of the correction value for the processing command value and the sending of the email may be configured to be performed by the data server 6, or the processing may be divided between the data acquisition device 5 and the data server 6.

[0033] Although an NC machining system according to an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and any design changes, etc., that do not depart from the spirit of the present invention are also included. For example, while it was explained that the calculated correction value is reflected every three products manufactured, the design can be changed to reflect the correction every two or four products manufactured, depending on the operating speed of the production line. Furthermore, although it was explained in the embodiment that the temperature sensor is placed around the position of the dimension measurement sensor, the temperature measurement can be performed at any position on the manufacturing line, not at the processing position of the workpiece that becomes hot, but at the position of the workpiece after processing is completed. Furthermore, notifications of abnormalities, such as when an alarm is triggered or when NC machine tool 1 is stopped in an emergency, can be replaced with messages sent using online meeting tools or messaging apps on various social networking services, or, if linked to a dashboard for visualizing equipment status, messages sent using the notification function on that dashboard. In describing the embodiment, the calculation of the correction value for the machining command value was explained as being performed by the data acquisition device 5. With this configuration, a conventional type of NC machine tool 1 can be used. However, the machining control means 2 of the NC machine tool 1 may also be configured to perform the calculation of the correction value. In that sense, it is sufficient for any element of the NC machining system to perform the calculation of the correction value for the machining command value, and this is still within the scope of the present invention. Furthermore, the present invention can be implemented regardless of the material of the product, as long as there is a correlation between the dimensional change of the product and the temperature.

[0034] It should be correctly understood that the present invention represents a technological concept that sets it apart from conventional NC machining systems that maintain a constant temperature on the manufacturing line or NC machining systems that deal with temperature changes outside the manufacturing line. While attempts may exist to measure workpiece dimensions and provide feedback, it is generally assumed that the effects of temperature changes are absorbed by the feedback process when actual dimensions are measured and feedback is provided. Therefore, it should be correctly understood that literature that merely discloses NC machining systems that utilize feedback technology is teaching away from the present invention. [Explanation of Symbols]

[0035] 100 NC machining system 1 NC machine tool 2. Processing control means 3. Dimensional measurement sensor 4. Temperature Sensor 5 Data acquisition device 5 6. Data Server

Claims

1. An NC machining system comprising an NC machine tool, machining control means, a dimension measuring sensor, and a temperature sensor, The NC machine tool processes the workpiece based on the processing command values ​​provided by the processing control means. The aforementioned dimensional measuring sensor measures the actual dimensions of the machined workpiece. The aforementioned temperature sensor measures the ambient temperature of the dimensional measurement environment. The actual dimensions of the workpiece measured by the aforementioned dimension measuring sensor are converted to dimensions at a standard reference temperature using the ambient temperature for dimension measurement measured by the aforementioned temperature sensor and the coefficient of linear expansion stored for each metal material. A correction value for the machining command is then calculated based on the difference between these dimensions and the target dimensions of the workpiece. The aforementioned machining control means is input with a machining command value modified based on the correction value, thereby enabling the system to operate over a wide temperature range. An NC machining system characterized by the following.

2. The aforementioned correction value is calculated each time the workpiece is processed. The NC machining system according to feature 1.

3. The aforementioned machining command value is corrected once after machining multiple workpieces. The NC machining system according to feature 2.

4. The aforementioned "multiple items" are three. The NC machining system according to feature 3.

5. The correction value includes a stop threshold that is the upper limit for stopping the NC machine tool. If the correction value exceeds the stop threshold, the system will stop. The NC machining system according to feature 1.

6. If the system stops, it will output information to that effect. The NC machining system according to feature 5.

Images