CN101629929B - System for measuring capacitive powder flow for laser refabrication - Google Patents
System for measuring capacitive powder flow for laser refabrication Download PDFInfo
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- CN101629929B CN101629929B CN 200910101275 CN200910101275A CN101629929B CN 101629929 B CN101629929 B CN 101629929B CN 200910101275 CN200910101275 CN 200910101275 CN 200910101275 A CN200910101275 A CN 200910101275A CN 101629929 B CN101629929 B CN 101629929B
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- 239000000843 powder Substances 0.000 title claims abstract description 90
- 238000001514 detection method Methods 0.000 claims abstract description 18
- 238000007600 charging Methods 0.000 claims abstract description 10
- 238000005259 measurement Methods 0.000 claims abstract description 10
- 239000002184 metal Substances 0.000 claims description 9
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 238000005516 engineering process Methods 0.000 claims description 2
- 238000007599 discharging Methods 0.000 abstract description 7
- 238000000034 method Methods 0.000 description 10
- 239000003990 capacitor Substances 0.000 description 7
- 230000035945 sensitivity Effects 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 238000009826 distribution Methods 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 238000005253 cladding Methods 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 238000004372 laser cladding Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000010309 melting process Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
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Abstract
本发明公开了一种激光再制造用电容式粉末流量测量系统，包括送粉器，送粉器通过电机控制送粉量，送粉器连接输送管，所述输送管包括一检测段，该检测段外面设置螺旋表面极板电容传感器，螺旋表面极板电容传感器连接充放电式测量电路，该测量电路与电机的控制器连接。本技术方案采用了螺旋表面极板电容传感器来检测粉末流量的变化，采用充放电式测量电路拾取信号并连接送粉器的流量控制装置，从而实现对送粉流量的闭环控制。
The invention discloses a capacitive powder flow measurement system for laser remanufacturing, which includes a powder feeder, the powder feeder controls the powder feeding amount through a motor, and the powder feeder is connected to a delivery pipe, and the delivery pipe includes a detection section. A spiral surface plate capacitive sensor is arranged outside the section, and the spiral surface plate capacitive sensor is connected to a charging and discharging measuring circuit, and the measuring circuit is connected to a controller of the motor. This technical solution uses a spiral surface plate capacitive sensor to detect changes in powder flow, uses a charge-discharge measurement circuit to pick up the signal and connects to the flow control device of the powder feeder, thereby realizing closed-loop control of the powder flow.
Description
Technical field
The invention belongs to the flow detection technical field, particularly relate to a kind of laser and make again with condenser type powder mass flow detection system.
Background technology
At present, laser is made as a kind of novel material processing method again and is widely used in the every field that industry is made.The basis that laser is made again is laser melting coating, and the quality of cladding layer in the laser cladding process (such as surfaceness etc.) depend on to a great extent whether the powder feeding process is stable, in addition, the accurate control of powder feeding rate also is the basis of making gradient material component.React whether stablize of powder feeding rate so detect the flow of powder in powder feeding pipe by pick-up unit, to the closed-loop control that realizes powder and and then raising surface cladding quality significant.From domestic document, stability and the homogeneity of carrying in order to improve powder, domestic scholars have mainly been done the work of following four aspects:
(1) controls stability, the uniformity coefficient of powder feeding or realize other functions by the structure of research powder feeder and feeding head;
(2) the counter technological parameter of asking powder feeding of performance by the technological parameter in the research powder feeding process such as powder mass flow or research cladding layer;
(3) by the impact of numerical simulation study powder stream on laser cladding process;
(4) reach requirement to powder feeding by changing control method and control strategy.
It is to be noted especially that wherein domestic research on the powder pick-up unit also is blank, want to realize the Real-Time Monitoring to the powder feeding rate, and then realize the closed-loop control to the powder feeding flow.The powder mass flow pick-up unit is absolutely necessary.
Summary of the invention
In order to solve above-mentioned technical matters, the purpose of this invention is to provide a kind of laser makes and uses the powder mass flow measuring system, it detects powder mass flow online by capacitive transducer, learns the feed status of powder, and then realizes the closed-loop control to the powder feeding flow.
To achieve the above object, the present invention has adopted following technical scheme:
A kind of system for measuring capacitive powder flow for laser refabrication, comprise powder feeder, powder feeder is by the Electric Machine Control powder sending quantity, the powder feeder connecting conveying pipe, described delivery pipe comprises a detection segment, this detection segment outside arranges the helical surface plates capacitance sensor, and the helical surface plates capacitance sensor connects the charging/discharging type metering circuit, and this metering circuit is connected with the controller of motor.
As preferably, the pipeline center of the detection segment of above-mentioned delivery pipe is provided with shunt.The detection segment inwall of above-mentioned delivery pipe is provided with diversion trench.Above-mentioned diversion trench be shaped as zigzag, wavy or V-shaped groove, width is at least more than 3 times of diameier that described powder feeder is carried.
As preferably, above-mentioned metering circuit is the charging/discharging type testing circuit based on CMOS technique.
The powder that above-mentioned powder feeder is carried is 2Cr13 or H13 metal powder.
Above-mentioned helical surface plates capacitance sensor is 180 ° of helical surface plates capacitance sensors.
The present invention is owing to adopted above technical scheme, adopted the helical surface plates capacitance sensor to detect the variation of powder mass flow, adopt charging/discharging type metering circuit pickoff signals and connect the volume control device of powder feeder, thereby realize the closed-loop control to the powder feeding flow.And, carry out testing experiment with 2Cr13 and H13 metal powder as pumped (conveying) medium, the result shows and obtains well to detect effect in the situation take the H13 powder as pumped (conveying) medium, when powder mass flow changes greater than 1g/min, have preferably resolution, thereby this system accuracy satisfies the accuracy requirement that laser is made melting and coating process more fully.
Description of drawings
Fig. 1 is syndeton synoptic diagram of the present invention;
Fig. 2 is the structural representation of capacitive transducer;
Fig. 3 is measuring principle figure of the present invention;
Fig. 4 is the top cross-sectional view of shunt;
Fig. 5 is metering circuit figure of the present invention;
Fig. 6 is powder mass flow of the present invention-dutycycle curve map.
Embodiment
Below in conjunction with accompanying drawing the specific embodiment of the present invention is made a detailed explanation.
Embodiment 1:
A kind of system for measuring capacitive powder flow for laser refabrication as shown in Figure 1, comprise powder feeder 7, powder feeder 7 is provided with hopper 6, powder feeder 7 is by motor 5 control powder sending quantities, powder feeder 7 connects feeding head (not drawing on the figure) below by delivery pipe 1, be provided with capacitive transducer 2 at delivery pipe 1, capacitive transducer 2 connection detection circuit 3, testing circuit 3 is connected with the controller 4 of motor 5.
The capacitance measurement principle is: when the two-phase fluid with differing dielectric constant by between pole plate during formed checkout area, because the variation of solid concentration can cause the change of fluid effective dielectric constant, thereby the electric capacity output valve of sensor is changed thereupon, so the size of capacitance namely can be used as measuring of two-phase flow solid concentration.Yet following two problems can not be ignored in actual applications: one, and the diphasic flow process is very complicated, solid phase skewness in the checkout area, variations in flow patterns is fast; Its two, the capacitive transducer checkout area belongs to " soft ", and the non-uniformity problem of its intrinsic sensitivity profile is arranged, and makes measurement result not only relevant with solid concentration, and distributed mutually and the impact of variations in flow patterns very large, measuring error is larger.
Traditional capacitor sensor structure adopts straight pole plate mostly, the inhomogeneity raising of its checkout area depends primarily on the increase of pipe thickness, the distance of checkout area in also namely increasing battery lead plate and managing, reduce the edge effect (on the tube section direction) of pole plate, but this structure is unsuitable for using on the industrial pipeline.In order to make solid concentration measure the impact that is subjected to less flow pattern, the present invention adopts 180 ° of helical surface plates capacitance sensors.This is a kind of novel sensor construction, as shown in Figure 2, is made of 4 pole plates: source plates 21, and Detection electrode 23, the protection pole plate 22 on symmetrical both sides (open-angle is 30 degree), they reverse 180 ° along duct orientation simultaneously.Checkout area has occured to reverse, and great changes have occured the distribution character of its sensitivity, has relatively uniformly sensitivity profile, and it is 6mm that present embodiment is selected internal diameter, and external diameter is 10mm, and length is that the rubber tube of 90mm is as the experiment detection segment; Capacitance sensor electrodes (pole plate) is selected the Copper Foil of 0.03mm, and electrode is close on the outer wall of rubber tube, and electrode is twining the silica gel sheet outward as insulation course, and insulation course is outward as screen layer by metal shell.But, above-mentioned helical surface plates capacitance sensor has also only been considered the structure and distribution of pipe wall electrode, consider the non-uniformity problem of the interior diphasic flow of pipe and capacitive transducer checkout area sensitivity profile, in order further to reduce measuring error, the applicant improves the pipeline inner structure in the capacitance sensor electrodes and optimizes, such as Fig. 2, Fig. 3 and shown in Figure 4, shunt 11 has been arranged in the pipeline center that the delivery pipe detection segment of capacitor plate is set outside, has increased a plurality of diversion trenchs 12 at delivery pipe detection segment 13 inwalls simultaneously.Present embodiment, shunt are arranged in above-mentioned rubber tube center, form concentric circles with pole plate, have reduced like this unevenness of checkout area; The rubber tube inwall is established diversion trench, and Dual-Phrase Distribution of Gas olid can reduce turbulent flow, thereby reduce the impact on sensor along diversion trench by sensor, has improved sensitivity, and in order to guarantee the water conservancy diversion effect, the diversion trench width is at least more than 3 times of diameier.Dual-Phrase Distribution of Gas olid is by capacitive transducer the time, and owing to reducing of cross section, Dual-Phrase Distribution of Gas olid speed is accelerated, and the setting of diversion trench has also prevented the generation of plugging.
Because it is minimum that laser is made the electric capacitance change that causes owing to the variation of powder in conduit in the powder feeding process again, carry out little capacitance detecting, testing circuit must possess following characteristics: resolution wants high, and sensitivity will be stablized; Extremely low drift (comprise temperature is floated and time drift); Insensitive to distributed capacitance; Operating frequency range and universal circuit device are well compatible; Electric field disturbs insensitive to external world; For the differential capacitive sensor of reality, circuit signal output is
Funtcional relationship; Circuit complexity is low, is easy to integrated.
The metering circuit that the present invention adopts is based on the charging/discharging type testing circuit of CMOS technique.Present embodiment adopts a COMS binary width modulation type picking up signal special IC---BH5001, its inner theory structure as shown in Figure 5, C1 and C2 are two variable capacitances of external differential capacitance sensor.Principle of work is as follows: when establishing the direct supply connection (for example VDD=6V), the Q end is high level, the Q end is low level, then signaling control unit makes and discharges and recharges network 1 to capacitor C 1 charging, the upper voltage of C1 edges up, in case reach circuit control level value, signal processing unit makes the Q end become immediately low level, and the Q end is high level; At this moment, the voltage on the capacitor C 1 is discharged to rapidly zero through discharging and recharging network 1, and the synchronous signal control module makes and discharges and recharges network 2 to capacitor C 2 chargings, the upper voltage of C2 edges up, in case reach circuit control level value, signal processing unit makes the Q end be high level again, and the Q end is low level; So begin again the C1 charging C2 discharge in next cycle ... so go round and begin again, respectively produce the rectangle square wave that a string its width is subjected to C1 and the control of C2 capacitance change at the output terminal (being Q and Q) of circuit.When detected physical quantity made capacitor C 1＞C2, the difference of the average voltage of two output terminals was:
Wherein,
U
1Be V
DD, and U
2The control level value that then sets for the signal controlling processing unit, T
1And T
2Be respectively the Q end cycle length shared with Q end high level, R is that charging resistor (in discharging and recharging network) is generally got 51k Ω～1M Ω.Formula 2 and formula 3 substitution formulas 1 are got:
During the present embodiment experiment, C1 is fixed capacity (20pF), and C2 is Detection capacitance (being above-mentioned helical surface plates capacitance sensor); The output of signal and the preservation of data are finished by the TDS2012B digital storage oscilloscope; Powder feeder 7 adopts the roller type powder feeders, also can be the dust feeders such as spiral, scraper-type that adopt electric machine speed regulation; Buncher 5 adopts stepper motor, also can adopt AC servo motor; Controller 4 is the controllers that use microcomputer development.
Present embodiment experiment condition and process are as follows: conveying powder is 2Cr13 and H13 metal powder, about granularity 200 orders; Environment temperature is 20 ℃; Obstructed delivery air; The rubber tube that capacitor is set is installed in powder feeder lower hopper exit, and the powder collection position is below rubber tube; Motor speed of every adjustment, powder feeder all will move 3 minutes under the motor speed after the adjustment, to guarantee to reach a stable feed status; Adopt BS-224S type electronic balance to measure the quality of per minute conveying powder, measure and average for 5 times, be powder mass flow.
Experiment has chosen that the control motor speed is 20,40,60,80,100r/min is as test point, resulting dutycycle T
2/ T
1Be C
2/ C
1And the relation between the powder mass flow as shown in Figure 6, and as can be seen from the figure the increase powder mass flow along with motor speed increases dutycycle C
2/ C
1Also be linear increase thereupon.From Fig. 6, it can also be seen that under the identical motor speed when with the H13 metal powder during as pumped (conveying) medium the variation of dutycycle than the 2Cr13 metal powder during as pumped (conveying) medium more greatly, illustrate in the situation take the H13 metal powder as pumped (conveying) medium to obtain to detect preferably effect.This mainly is because the magnetic of H13 metal powder is better, has larger specific inductive capacity under identical powder mass flow.
Table 1 condenser type H13 powder concn measuring system resolution
| Motor speed (r/min) | 20 | 22 | 24 | 26 | 28 | 30 |
| Powder mass flow (g/min) | 11.1 | 12.3 | 13.1 | 13.9 | 14.5 | 15.2 |
| Dutycycle (C 2/C 1) | 0.70 | 0.71 | 0.71 | 0.72 | 0.72 | 0.73 |
Upper table is the resolution experimental result, has good resolution during greater than 1g/min at powder mass flow, the fully recombination laser accuracy requirement of making again melting and coating process.
Claims (5)
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US8767214B2 (en) * | 2011-10-06 | 2014-07-01 | Nordson Corporation | Powder flow detection |
| CN103542903B (en) * | 2012-07-12 | 2016-12-21 | 中国农业机械化科学研究院 | A kind of cotton picker cotton quality flow detector and method |
| CN104316441A (en) * | 2014-10-27 | 2015-01-28 | 江苏大学 | Device and method for detecting concentration distribution of powder in outlet section of screw conveying pipe |
| CN105571995B (en) * | 2015-12-18 | 2019-06-18 | 天津大学 | A kind of aircraft engine on-line oil wear particle imaging counting sensor and manufacturing method |
| CN105628570B (en) * | 2015-12-30 | 2019-10-11 | 东北大学 | Powder Phase Concentration Measuring Device |
| CN107083550A (en) * | 2017-02-21 | 2017-08-22 | 机械科学研究总院先进制造技术研究中心 | A kind of temperature, powder sending quantity can debug Intelligent Laser cladding head automatically |
| CN109932403A (en) * | 2017-12-19 | 2019-06-25 | 天津工业大学 | A capacitive sensor detection device for wide-width measured objects |
| CN114932238B (en) * | 2022-06-15 | 2024-03-26 | 昆明理工大学 | A multi-material additive manufacturing powder feeding device and powder feeding method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2332492Y (en) * | 1998-07-03 | 1999-08-11 | 李宗能 | Powder spray gun |
| CN1356608A (en) * | 2001-12-15 | 2002-07-03 | 华中科技大学 | Automatic controller for laser coating and powder feeding system |
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- 2009-07-27 CN CN 200910101275 patent/CN101629929B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2332492Y (en) * | 1998-07-03 | 1999-08-11 | 李宗能 | Powder spray gun |
| CN1356608A (en) * | 2001-12-15 | 2002-07-03 | 华中科技大学 | Automatic controller for laser coating and powder feeding system |
Non-Patent Citations (2)
| Title |
|---|
| 电容式传感器在高炉喷吹煤粉质量流量测量中的应用;金锋等;《钢铁》;19991031;第34卷(第10期);56-59 * |
| 金锋等.电容式传感器在高炉喷吹煤粉质量流量测量中的应用.《钢铁》.1999,第34卷(第10期),56-59. |
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