A real-time detection method for laser cutting shielding gas pressure

Abstract

The present invention discloses a real-time detection method for shielding gas pressure of laser cutting. Firstly, the output current and the shielding gas pressure data of the inlet are collected, the laser cutting event is captured and the steady-state value of the shielding gas pressure in each laser cutting event is calculated; then, the shielding gas pressure is detected after filtering the gas source replacement situation, and an alarm is issued for insufficient shielding gas pressure; in addition, by receiving a plurality of laser cutting events for joint detection, occasional alarms are filtered; finally, when a new gas source replacement is detected, the comparative detection is repeated; the method provided by the present invention filters the gas source replacement and occasional false alarm situations, and can further improve the detection accuracy of insufficient shielding gas pressure.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent welding and cutting, and in particular relates to a real-time detection method for the pressure of laser cutting shielding gas. Background Art

[0002] In the laser cutting process, the pressure of the shielding gas has a crucial impact on the cutting quality. The main function of the shielding gas is to blow away the molten material during the cutting process, cool the processed object, and prevent oxidation of the cutting surface. When the shielding gas pressure is insufficient, it may cause problems such as incomplete cutting, slag residue, burrs, etc., thus affecting the cutting quality and efficiency.

[0003] The prior art lacks effective detection for insufficient shielding gas pressure, and the shielding gas pressure fluctuation caused by the replacement of the gas source cannot be accurately identified, so it is impossible to effectively monitor and alarm for abnormal insufficient shielding gas pressure. Summary of the invention

[0004] Purpose of the invention: In view of the problems existing in the above-mentioned background technology, the present invention provides a real-time detection method for the pressure of laser cutting protective gas, which judges the steady-state value of gas pressure based on the laser cutting event, takes the fluctuation of the steady-state value of gas pressure between different laser cutting events as the basis for judgment, and provides a specific comparative judgment method. In addition, a corresponding filtering method is provided for gas source replacement and occasional abnormal alarm situations.

[0005] Technical solution: A real-time detection method for laser cutting shielding gas pressure, comprising the following steps:

[0006] Step S1, collecting the output current and the shielding gas pressure data at the inlet in the laser cutting process in real time, capturing the laser cutting event based on the time series of the output current, and calculating the steady-state value of the shielding gas pressure in each laser cutting event; setting a sliding window openpressure_shoulder_list for storing the steady-state value of the shielding gas pressure, and receiving the steady-state value of the shielding gas pressure in sequence;

[0007] Step S2, setting a front switch new_gas_fluctuation_check for detecting the replacement of the gas source, and filtering the replacement of the gas source;

[0008] Step S3, performing a shielding gas pressure detection on the filtered openpressure_shoulder_list, and giving an alarm for insufficient shielding gas pressure; setting a switch alarm_switch for controlling the alarm and a list constantly_list for recording the continuity of alarm events, receiving a plurality of laser cutting events for joint detection, and filtering occasional alarms;

[0009] Step S4: When it is detected that the gas source is replaced, the front switch new_gas_fluctuation_check is reset and steps S1 to S3 are repeated to perform a new round of protective gas pressure detection.

[0010] Furthermore, the specific method of capturing the laser cutting event in step S1 includes:

[0011] The first current point greater than the preset threshold th1 is taken as the starting point of the laser cutting event, and the last current point greater than th1 is taken as the ending point of the laser cutting event. The current sequence from the starting point to the ending point constitutes a complete laser cutting event.

[0012] Calculate the steady-state value of air pressure corresponding to each laser cutting event and store it in openpressure_shoulder_list; set the window length of openpressure_shoulder_list to 3.

[0013] Furthermore, in step S2, when the number of steady-state air pressure values ​​in openpressure_shoulder_list is 3, the air source replacement situation is filtered; specifically, when the air source is replaced, new_gas_fluctuation_check is set to true, and the protective gas pressure detection is no longer performed at this time, and the captured laser cutting events are counted. When the count reaches a preset threshold value n, new_gas_fluctuation_check is set to false, and n is reset to 1, and the protective gas pressure detection continues.

[0014] Furthermore, the specific method of performing protective gas pressure detection on the filtered openpressure_shoulder_list in step S3 includes: recording them as P1, P2 and P3 in sequence, and performing the following comparison and judgment respectively:

[0015] (1) When the difference between P1 and P2 is greater than or equal to the preset threshold th2 and the difference between P2 and P3 is greater than or equal to the preset threshold th3, if alarm_switch is true, an alarm is issued; otherwise, alarm_switch is true and an alarm is issued;

[0016] (2) When the difference between P1 and P3 is greater than th3 and the difference between any two sets of steady-state pressure values ​​among P1, P2, and P3 is greater than the preset threshold th4, if alarm_switch is false, constantly_list records 1; if alarm_switch is true, an alarm is issued;

[0017] (3) When the difference between P1 and P2 is greater than or equal to the preset threshold th5 and the difference between P2 and P3 is greater than or equal to the preset threshold th5, if alarm_switch is false, constantly_list records 1; if alarm_switch is true, an alarm is triggered.

[0018] When P1, P2, and P3 do not meet the judgment conditions (1)-(3), openpressure_shoulder_list removes P1 and receives the new steady-state pressure value, and repeats the comparison judgment; if the number of values ​​in constantly_list is greater than 0 at this time, 0 is added to constantly_list as a placeholder;

[0019] When the number of values ​​in constantly_list is equal to three, the following judgment is made: if there are 2 consecutive 1s in constantly_list or there are 2 1s in 3 consecutive positions, alarm_switch is set to true and constantly_list is cleared.

[0020] Furthermore, when the difference between the newly received steady-state pressure value and the previous steady-state pressure value is greater than the preset threshold th6, it means that a new round of gas source replacement has started. At this time, new_gas_fluctuation_check is set to true and alarm_switch is set to false.

[0021] Compared with the prior art solutions, the technical solution adopted by the present invention has the following beneficial effects:

[0022] (1) The real-time detection method of the laser cutting protective gas pressure provided by the present invention captures the laser cutting events in real time, and compares and judges the steady-state value of the gas pressure in each event, finds out the fluctuations therein and analyzes whether there is insufficient pressure, and can give the judgment result of insufficient gas pressure in real time.

[0023] (2) The present invention proposes a special filtering method for the situation where the protective gas pressure is unstable due to the replacement of the gas source. When the replacement of the gas source is detected, the alarm will no longer be issued until the gas pressure is stabilized and the detection will continue, thereby reducing the possibility of misjudgment and making the judgment of abnormality more accurate.

[0024] (3) The present invention sets up an auxiliary detection mechanism for occasional alarms. The alarm is only issued when the number of insufficient air pressure detections reaches a preset requirement, which effectively improves the robustness of the detection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the real-time detection method of laser cutting shielding gas pressure provided by the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a real-time detection method for the pressure of laser cutting shielding gas. Aiming at the problem that the workpiece cutting fails to meet the standard due to insufficient shielding gas pressure during laser cutting, a method for real-time detection of insufficient shielding gas pressure is designed. By capturing laser cutting events and comparing the steady-state gas pressure values ​​of different cutting events, an alarm method for insufficient gas pressure is provided. At the same time, the instantaneous unstable gas pressure and occasional alarm events caused by changing the gas source are filtered, and a more accurate method for detecting insufficient gas pressure is provided.

[0027] The present invention will be further explained below in conjunction with the accompanying drawings.

[0028] like Figure 1 As shown, the present invention provides a method for real-time detection of laser cutting shielding gas pressure, comprising the following steps:

[0029] Step S1, real-time acquisition of output current and inlet shielding gas pressure data during laser cutting, capturing laser cutting events based on the timing sequence of output current, and calculating the steady-state value of shielding gas pressure in each laser cutting event. Specifically,

[0030] The first current point greater than the preset threshold th1 is taken as the starting point of the laser cutting event, and the last current point greater than th1 is taken as the ending point of the laser cutting event. The current sequence from the starting point to the ending point constitutes a complete laser cutting event. Each laser cutting event corresponds to a number of shielding gas pressure data in time sequence. The steady-state value of air pressure corresponding to each laser cutting event is calculated based on the shielding gas pressure data, and a sliding window openpressure_shoulder_list for storing the steady-state value of shielding gas pressure is set to receive the above-mentioned steady-state values ​​of air pressure in sequence. In this embodiment, the window length of the sliding window is 3. When 3 steady-state values ​​of air pressure are stored in openpressure_shoulder_list, proceed to the next step of judgment. In this embodiment, th1 is 0.6A.

[0031] Step S2, set the front switch new_gas_fluctuation_check for detecting the replacement of the gas source, and filter the gas source replacement. When the shielding gas source is replaced manually, the shielding gas pressure will be temporarily unstable, which belongs to the normal fluctuation range, so it needs to be filtered. Set new_gas_fluctuation_check to true, then no longer perform shielding gas pressure detection, and count the captured laser cutting events. When the count reaches the preset threshold n, set new_gas_fluctuation_check to false, and reset n to 1, and continue to detect the shielding gas pressure.

[0032] Step S3: After filtering the gas source replacement, the protective gas pressure is detected based on the protective gas pressure steady-state value received by openpressure_shoulder_list. Specifically,

[0033] Set the switch alarm_switch for controlling the alarm and the list constantly_list for recording the continuity of alarm events. When the steady-state value of the air pressure in the openpressure_shoulder_list window is equal to 3, it is recorded as P1, P2 and P3 in sequence, and the following comparisons are performed respectively:

[0034] (1) When the difference between P1 and P2 is greater than or equal to the preset threshold th2 and the difference between P2 and P3 is greater than or equal to the preset threshold th3, if alarm_switch is true, an alarm is issued; otherwise, alarm_switch is true and an insufficient air pressure alarm is given.

[0035] In this embodiment, th2 is 0.1 bar and th3 is 0.15 bar.

[0036] (2) When the difference between P1 and P3 is greater than th3 and the difference between any two sets of steady-state pressure values ​​among P1, P2, and P3 is greater than the preset threshold th4, if alarm_switch is false, constantly_list records 1; if alarm_switch is true, an insufficient pressure alarm is triggered;

[0037] In this embodiment, th4 is set to 0.02.

[0038] (3) When the difference between P1 and P2 is greater than or equal to the preset threshold th5 and the difference between P2 and P3 is greater than or equal to the preset threshold th5, if alarm_switch is false, constantly_list records 1; if alarm_switch is true, an alarm is triggered.

[0039] In this embodiment, th5 is set to 0.03.

[0040] When P1, P2, and P3 do not meet the judgment conditions (1)-(3), openpressure_shoulder_list removes P1 and receives the new steady-state pressure value, and repeats the comparison judgment; if the number of values ​​in constantly_list is greater than 0 at this time, 0 is added to constantly_list as a placeholder;

[0041] When the number of values ​​in constantly_list is equal to three, the following judgment is made: if there are 2 consecutive 1s in constantly_list or there are 2 1s in 3 consecutive positions, alarm_switch is set to true and constantly_list is cleared.

[0042] Step S4: When the difference between the newly received steady-state gas pressure value and the previous steady-state gas pressure value is greater than the preset threshold value th6, it means that a new round of gas source replacement has begun. At this time, new_gas_fluctuation_check is set to true, alarm_switch is set to false, and steps S1 to S3 are repeated to determine whether the protective gas pressure is insufficient. In this embodiment, th6 is 0.5 bar.

[0043] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A real-time detection method for laser cutting protective gas pressure, characterized in that: The following steps are involved: Step S1, collecting the output current and the shielding gas pressure data at the inlet in the laser cutting process in real time, capturing the laser cutting event based on the time series of the output current, and calculating the steady-state value of the shielding gas pressure in each laser cutting event; setting a sliding window openpressure_shoulder_list for storing the steady-state value of the shielding gas pressure, and receiving the steady-state value of the shielding gas pressure in sequence; The specific method for capturing the laser cutting event includes: The first current point greater than the preset threshold th1 is taken as the starting point of the laser cutting event, and the last current point greater than th1 is taken as the ending point of the laser cutting event. The current sequence from the starting point to the ending point constitutes a complete laser cutting event. Calculate the steady-state value of air pressure corresponding to each laser cutting event and store it in openpressure_shoulder_list; set the window length of openpressure_shoulder_list to 3; Step S2, setting a front switch new_gas_fluctuation_check for detecting the replacement of the gas source, and filtering the replacement of the gas source; Step S3, performing a shielding gas pressure detection on the filtered openpressure_shoulder_list, and giving an alarm for insufficient shielding gas pressure; setting a switch alarm_switch for controlling the alarm and a list constantly_list for recording the continuity of alarm events, receiving a plurality of laser cutting events for joint detection, and filtering occasional alarms; Step S4: When it is detected that the gas source is replaced, the front switch new_gas_fluctuation_check is reset and steps S1 to S3 are repeated to perform a new round of protective gas pressure detection.

2. A method for real-time detection of laser cutting shielding gas pressure according to claim 1, characterized in that: In the step S2, when the number of steady-state values ​​of air pressure in openpressure_shoulder_list is 3, the gas source replacement situation is filtered; specifically, when the gas source is replaced, new_gas_fluctuation_check is set to true, and the shielding gas pressure detection is no longer performed at this time, and the captured laser cutting events are counted. When the count reaches a preset threshold value n, new_gas_fluctuation_check is set to false, and n is reset to 1, and the shielding gas pressure detection continues.

3. The method for real-time detection of laser cutting shielding gas pressure according to claim 1, characterized in that: The specific method of performing shielding gas pressure detection on the filtered openpressure_shoulder_list in step S3 includes: recording them as P1, P2 and P3 in sequence, and performing the following comparison and judgment respectively: (1) When the difference between P1 and P2 is greater than or equal to the preset threshold th2 and the difference between P2 and P3 is greater than or equal to the preset threshold th3, if alarm_switch is true, an alarm is issued; otherwise, alarm_switch is true and an alarm is issued; (2) When the difference between P1 and P3 is greater than th3 and the difference between any two sets of steady-state pressure values ​​among P1, P2, and P3 is greater than the preset threshold th4, if alarm_switch is false, constantly_list records 1; if alarm_switch is true, an alarm is issued; (3) When the difference between P1 and P2 is greater than or equal to the preset threshold th5 and the difference between P2 and P3 is greater than or equal to the preset threshold th5, if alarm_switch is false, constantly_list records 1; if alarm_switch is true, an alarm is triggered; When P1, P2, and P3 do not meet the judgment conditions (1)-(3), openpressure_shoulder_list removes P1 and receives the new steady-state pressure value, and repeats the comparison judgment; if the number of values ​​in constantly_list is greater than 0 at this time, 0 is added to constantly_list as a placeholder; When the number of values ​​in constantly_list is equal to three, the following judgment is made: if there are 2 consecutive 1s in constantly_list or there are 2 1s in 3 consecutive positions, alarm_switch is set to true and constantly_list is cleared.

4. The method for real-time detection of laser cutting shielding gas pressure according to claim 1, characterized in that: When the difference between the newly received steady-state pressure value and the previous steady-state pressure value is greater than the preset threshold th6, it means that a new round of gas source replacement has started. At this time, new_gas_fluctuation_check is set to true and alarm_switch is set to false.

Images