阅读说明：本技术 一种fdm打印过程应力检测方法 (Stress detection method in FDM printing process ) 是由 侯和平 岳阳 刘健 刘善慧 雷晓飞 于 2021-07-13 设计创作，主要内容包括：本发明提供一种FDM打印过程应力检测方法,包括如下步骤：步骤一、制作待成型Solidworks零件模型,选定待测区域,于待测区域留有空槽以放置传感器；步骤二、当FDM打印机打印至空槽位置所在层处暂停打印过程；步骤三、在模型中调整待测区域空槽的方位,进而调整应变片方向得以测量X、Y、45°等方向应力；步骤四、通过桥盒与应变仪连接,将应变仪连接采集卡,采集卡将应变仪传输的电压信号存储至计算机,准备采集；步骤五、应变仪开始记录应变片输出的电压；FDM打印机继续打印零件；步骤六、根据零件实际打印、冷却时间,测量30min内的零点漂移,采用信号处理的方法,去除零漂；本发明解决其他应变检测方法无法检测FDM制件内部应力、价格昂贵的问题。(The invention provides a method for detecting the stress in an FDM printing process, which comprises the following steps: firstly, manufacturing a Solidworks part model to be molded, selecting a region to be tested, and reserving a hollow groove in the region to be tested for placing a sensor; step two, when the FDM printer prints to the layer where the empty slot position is located, pausing the printing process; thirdly, adjusting the position of the empty groove of the area to be measured in the model, and further adjusting the direction of the strain gauge to measure stress in directions of X, Y, 45 degrees and the like; step four, connecting the strain gauge with an acquisition card through a bridge box, and storing a voltage signal transmitted by the strain gauge into a computer by the acquisition card to prepare for acquisition; fifthly, the strain gauge starts to record the voltage output by the strain gauge; the FDM printer continues to print the parts; measuring zero drift within 30min according to actual printing and cooling time of the part, and removing the zero drift by adopting a signal processing method; the invention solves the problems that other strain detection methods cannot detect the internal stress of the FDM workpiece and are expensive.)

1. An FDM printing process stress detection method is characterized by comprising the following steps:

firstly, manufacturing a Solidworks part model to be formed as a part (1), selecting a region to be measured, and reserving a hollow groove in the region to be measured for placing a sensor; the size of the empty groove is the same as that of the strain gauge, wherein the type of the strain gauge is BA-120-3AA, and the strain gauge is packagedComprises the following steps: working strain gage R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄；

Loading the part (1) by using an FDM printer, setting printing parameters, starting printing, and pausing the printing process when the FDM printer prints to the layer where the position (2) is located;

step three, polishing the bottom of the strain gauge, using 502 glue to polish the working strain gauge R₁Sticking and fixing the strain gauge to a to-be-measured area at the empty groove, adjusting the direction of the empty groove of the to-be-measured area in the model, and further adjusting the direction of the strain gauge to measure stress in directions of X, Y and 45 degrees;

step four, arranging a working strain gauge R₁And compensation strain gauge R₂Compensating strain gage R₃Compensating strain gage R₄Forming a full bridge, connecting the full bridge with the strain gauge through a bridge box, connecting the strain gauge with an acquisition card, and storing a voltage signal transmitted by the strain gauge into a computer by the acquisition card for acquisition;

step five, compensating strain gauges R₂、R₃、R₄The temperature of the programmable heating platform (3) is set to be 25 ℃; leveling a strain gauge, setting the sampling frequency of an acquisition card to be 500Hz, and starting to record the voltage output by the strain gauge; the FDM printer continues to print the part (1); recording strain gauge voltage V_εF (i), wherein i is the number of collected samples;

step six, zero drift is generated in the strain gauge in the process of measuring stress for a long time, the zero drift can influence the accuracy of the measured stress, the zero drift within 30min is measured according to the actual printing and cooling time of the part (1) by using the same conditions as the actual measurement, and the zero drift is removed by adopting a signal processing method;

seventhly, in the FDM printing process, the temperature of the region to be tested is changed strongly, and the strain gauge can show different resistances at different temperatures, so that the temperature characteristic of the strain gauge needs to be researched; therefore, the voltage change of the strain gauge under the same temperature change in the FDM process is measured by using the same conditions as the actual measurement, and the temperature drift is removed by adopting a signal processing method according to the temperature drift characteristics of the strain gauge;

step eight, strain and stress calculation;

(1) the stress calculation method comprises making the stress measurement voltage after removing zero drift and temperature drift be V_L；

Then, V_L＝V_ε-Y_l-V₂；

In the above formula V_εFor the strain gauge voltage during printing, Y_lIs a zero drift voltage, V₂Is a temperature drift voltage;

the strain ε is:

stress, F ═ E ∈; wherein E is the elastic modulus of the printed material;

(2) compiling strain and stress calculation software; the denoising part is used for removing noise by adopting a Gaussian denoising method, a median filtering method, a mean filtering method, a wavelet denoising method and an EMD model decomposition method aiming at the temperature stress data characteristics measured in the FDM printing process; the stress calculation part comprises zero drift filtration, temperature, strain and stress calculation; and the functions of a brush, data scaling and a clock are added to facilitate the processing of the detailed part of the data.

2. An FDM printing process stress detection method according to claim 1 in which said step of removing null shift in step six is:

(1) hardware connection, strain gage R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄Form a full-bridge connection, and a polishing work strain gauge R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄Bottom, sticking and fixing 4 strain gauges on a programmable heating platform (3), setting the temperature of the heating platform to be 25 ℃, and collecting a working strain gauge R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄Zero drift;

(2) data pre-processingThe strain gauge drift is divided into two types, one is horizontal zero drift, and the other is slope zero drift; in the strain sampling process, the total strain sampling duration is T, the number of samples is N, and the acquired signal is y₁-y_n，As sample mean:

wherein i is 1,2, …, N

σ_yAs sample variance:

when in useThe time is the drift of the horizontal zero point,the time is the slope zero drift;

(2.1) removing the horizontal zero drift, and making the voltage signal after removing the zero drift be Y_i；

The zero drift voltage is then:

Y_i＝y(i)-Y_l；

(2.2) removing slope zero drift:

whereinIs the first average value point, and the second average value point,is a second mean value point; n is the number of samples; t is the total sampling time length;

wherein

Wherein

The slope of the sample data

The zero drift voltage is then: y is_l＝(k*t)

Removing signal Y after slope zero point drift_i：

Y_i＝y(i)-Y_lWhere i is 1,2, …, N.

3. An FDM printing process stress detection method according to claim 1 in which said seventh step of removing temperature drift is:

(1) the temperature of the printing process is tested, the FDM printer loads a second part (5), an empty slot is formed in the position of a region to be tested, the temperature measuring position of the temperature measuring region is the same as the measuring position of strain detection, and the size of the empty slot is the same as that of the temperature sensor PT 100;

printing the second part (5) in a slicing mode, and pausing the printing process when the FDM printer prints to the layer where the position (2) is located; sticking and fixing a temperature sensor PT100 in the empty slot by using glue, wherein the model of the temperature sensor PT100 is; connecting a temperature sensor to a temperature transmitter, wherein the type of the temperature transmitter is ASC605-V2.0, and recording the voltage change of the temperature sensor in the printing process of the FDM printer by using an acquisition card;

(2) calculating the temperature of the area to be measured in the printing process; temperature transmitter records voltage change of temperature sensor as V₁；

V₁F (i), wherein i is 1,2, …, N.

The temperature change of the test point during printing is T₁；

T₁＝20*V₁；

(3) Determining temperature drift, adopting full-bridge connection in strain gauge bridge circuit connection mode, and measuring the temperature change T of FDM printing process₁Inputting the temperature of the programmable heating platform (3) and determining the temperature of the programmable heating platform (4) to be constant at 25 ℃; strain gage R₁The compensation strain gauge R2, the compensation strain gauge R3 and the compensation strain gauge R4 are connected with a full-bridge circuit access bridge through a bridge box and a strain gauge, the strain gauge is connected with an acquisition card, and the acquisition card records R₁Temperature change T of working strain gauge in FDM printing process₁Under the environment, the voltage changes of the compensation strain gauge R2, the compensation strain gauge R3 and the compensation strain gauge R4 are at the environment temperature of 25 ℃; recording temperature drift voltage V of strain gauge₂(ii) f (i); where i is 1,2, …, N.

Technical Field

The invention relates to the technical field of stress detection, in particular to a stress detection method in an FDM printing process.

Background

The fused deposition modeling technology is abbreviated as FDM technology, FDM is widely applied by the advantages of wide modeling materials, low cost, low equipment operation and maintenance cost and the like, but most of materials used in the fused deposition modeling technology are polymer organic synthetic plastics, so that the final modeling part has dimensional shrinkage, warping deformation and the like to influence the modeling precision. The distribution gradient of the temperature field in the forming process can cause the thermal stress and deformation in the part, further cause the change of the outline dimension of the part and seriously affect the forming precision of the part. The low molding quality of the parts seriously limits the popularization and application of the fused deposition rapid molding technology in the market. So that the application field is mainly focused on research and development of test models and functional prototype manufacture in the test link. Therefore, the research on the distribution of the temperature field and the stress field in the FDM forming process has great significance for disclosing the dimensional shrinkage rule and mechanism of the workpiece and popularizing and applying the FDM technology.

Resistance strain gage measurement is the most traditional method for measuring strain and is widely used. The measuring principle is that the strain gauge is pasted at a deformation position, when the structure is strained, the resistance value of the strain gauge is changed, and a signal of resistance change is converted into a signal of voltage or current through the strain gauge, so that the strain value of the structure can be obtained. The strain gauge measuring method has the advantages of high precision, small size and the like. The strain gauge can be embedded into the test piece, mechanical parameters are converted into electrical parameters according to the relation that the resistivity of the resistance wire changes along with the deformation of the resistance wire, and then the electrical parameters are converted into the strain value of the test piece, so that the distributed point strain of the test piece can be measured, and the possibility is provided for researching the internal stress change of the FDM. And the strain gauge measuring equipment is cheap and is convenient to be used in the measurement of the stress of the FDM test piece in a large quantity.

The invention aims to develop a test system for a temperature field and a stress field in an FDM forming process. A method for testing stress in an FDM forming process is provided.

Disclosure of Invention

The invention aims to provide a method for measuring the internal dynamic stress of an FDM workpiece in an FDM forming process, and solves the problems that other strain detection methods cannot detect the internal stress of the FDM workpiece and are expensive.

The invention discloses a method for detecting the stress in an FDM printing process, which comprises the following steps of:

firstly, manufacturing a Solidworks part model to be formed into a part 1, selecting a region to be measured, and reserving a hollow groove in the region to be measured for placing a sensor; the size of the empty slot is the same as that of the strain gauge, wherein the strain gauge is BA-120-3AA, and the strain gauge comprises: working strain gage R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄；

Loading the part 1 by using an FDM printer, setting printing parameters, starting printing, and pausing the printing process when the FDM printer prints to the layer at the position 2;

step three, polishing the bottom of the strain gauge, using 502 glue to polish the working strain gauge R₁Sticking and fixing the strain gauge to a to-be-measured area at the empty groove, adjusting the direction of the empty groove of the to-be-measured area in the model, and further adjusting the direction of the strain gauge to measure stress in directions of X, Y, 45 degrees and the like;

step four, arranging a working strain gauge R₁And compensation strain gauge R₂Compensating strain gage R₃Compensating strain gage R₄Forming a full bridge, connecting the full bridge with a strain gauge through a bridge box, connecting the strain gauge with an acquisition card, and storing a voltage signal transmitted by the strain gauge into a computer by the acquisition card for acquisition;

step five, compensating strain gauges R₂、R₃、R₄Fixing the heating device on a programmable heating platform 3, and setting the temperature of the programmable heating platform 3 to be 25 ℃; leveling a strain gauge, setting the sampling frequency of an acquisition card to be 500Hz, and starting to record the voltage output by the strain gauge; the FDM printer continues to print the parts; recording strain gauge voltage V_εF (i), wherein i is the number of collected samples;

step six, zero drift is generated in the strain gauge in the process of measuring stress for a long time, the zero drift can influence the accuracy of stress measurement, the zero drift within 30min is measured according to the actual printing and cooling time of the part by using the same conditions as the actual measurement, and the zero drift is removed by adopting a signal processing method;

seventhly, in the FDM printing process, the temperature of the region to be tested is changed strongly, and the strain gauge can show different resistances at different temperatures, so that the temperature characteristic of the strain gauge needs to be researched; therefore, the voltage change of the strain gauge under the same temperature change in the FDM process is measured by using the same conditions as the actual measurement, and the temperature drift is removed by adopting a signal processing method according to the temperature drift characteristics of the strain gauge;

step eight, strain and stress calculation;

(1) the stress calculation method comprises making the stress measurement voltage after removing zero drift and temperature drift be V_L；

Then, V_L＝V_ε-Y_l-V₂；

In the above formula V_εFor the strain gauge voltage during printing, Y_lIs a zero drift voltage, V₂Is a temperature drift voltage;

the strain ε is:

stress, F ═ E ∈; wherein E is the elastic modulus of the printed material;

(2) compiling strain and stress calculation software; the denoising part is used for removing noise by adopting a Gaussian denoising method, a median filtering method, a mean filtering method, a wavelet denoising method and an EMD model decomposition method aiming at the temperature stress data characteristics measured in the FDM printing process; the stress calculation part comprises zero drift filtration, temperature, strain and stress calculation; and the functions of a brush, data scaling and a clock are added to facilitate the processing of the detailed part of the data.

Preferably, the step of removing the null shift in the step six is as follows:

(1) hardware connection, strain gage R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄Form a full-bridge connection, and a polishing work strain gauge R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄Bottom partSticking and fixing 4 strain gauges on a programmable heating platform 3, setting the temperature of the heating platform to be 25 ℃, and collecting a working strain gauge R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄Zero drift;

(2) data preprocessing, wherein the strain gauge drift is divided into two types, one type is horizontal zero drift, and the other type is slope zero drift; in the strain sampling process, the total strain sampling duration is T, the number of samples is N, and the acquired signal is y₁-y_n，As sample mean:

wherein i is 1,2, N

σ_yAs sample variance:

when in useThe time is the drift of the horizontal zero point,the time is the slope zero drift;

(2.1) removing the horizontal zero drift, and making the voltage signal after removing the zero drift be Y_i；

The zero drift voltage is then:

Y_i＝y(i)-Y_l；

(2.2) removing slope zero drift:

whereinIs the first average value point, and the second average value point,is a second mean value point; n is the number of samples; t is the total sampling time length;

wherein

Wherein

The slope of the sample data

The zero drift voltage is then: y is_l＝(k*t)

Removing signal Y after slope zero point drift_i：

Y_i＝y(i)-Y_lWherein i is 1,2, N.

Preferably, the step of removing the temperature drift in the step seven comprises the following steps:

(1) the temperature of the printing process is tested, the FDM printer loads the second part 5, an empty slot is formed in the position of a region to be tested, the temperature measuring position of the temperature measuring region is the same as the measuring position of strain detection, and the size of the empty slot is the same as that of the temperature sensor PT 100;

printing the second part 5 in a slicing mode, and pausing the printing process when the FDM printer prints to the layer where the position 2 is located; sticking and fixing a temperature sensor PT100 in the empty slot by using glue, wherein the model of the temperature sensor PT100 is; connecting a temperature sensor to a temperature transmitter, wherein the type of the temperature transmitter is ASC605-V2.0, and recording the voltage change of the temperature sensor in the printing process of the FDM printer by using an acquisition card;

(2) calculating the temperature of the area to be measured in the printing process; temperature transmitter records voltage change of temperature sensor as V₁；

V₁F (i), wherein i ═ 1,2, ·, N.

The temperature change of the test point during printing is T₁；

T₁＝20*V₁；

(3) Determining temperature drift, adopting full-bridge connection in strain gauge bridge circuit connection mode, and measuring the temperature change T of FDM printing process₁Inputting the temperature into the programmable heating platform 3, and determining the temperature of the programmable heating platform 4 to be constant at 25 ℃. Strain gage R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄The full-bridge circuit access electric bridge is connected with the strain gauge through the bridge box, the strain gauge is connected with the acquisition card, and R is recorded through the acquisition card₁Temperature change T of working strain gauge in FDM printing process₁Under the environment, compensate the strain gage R₂Compensating strain gage R₃Compensating strain gage R₄A voltage change at an ambient temperature of 25 ℃; recording temperature drift voltage V of strain gauge₂(ii) f (i); wherein i is 1,2, N. .

The invention has the beneficial effects that: the invention aims to provide a method for measuring the internal dynamic stress of an FDM workpiece in an FDM forming process, and solves the problems that other strain detection methods cannot detect the internal stress of the FDM workpiece and are expensive.

Drawings

In order to clearly illustrate the prior art solutions or embodiments of the present invention in the stress testing process, the drawings to be used will be briefly described below, and the drawings described below are only some embodiments of the present invention.

FIG. 1 is a stress detection method of an FDM part, which is disclosed by the invention;

FIG. 2 is a method for connecting a strain gage bridge according to the present invention;

FIG. 3 is a method of zero drift filtering in accordance with the present invention;

FIG. 4 is a method of temperature detection according to the present invention;

FIG. 5 is a temperature drift filtering method of the present invention;

FIG. 6 is a strain and stress calculation software of the present invention;

FIG. 7 shows a stress test example 1 according to the present invention;

fig. 8 shows a temperature detection example 2 of the present invention.

Detailed Description

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the various embodiments of the invention. It should be understood, however, that these physical details should not be construed as limiting the invention. That is, in some embodiments of the invention, such physical details are not necessary. In addition, some conventional structures and components are shown in simplified schematic form in the drawings.

In addition, the descriptions related to the first, the second, etc. in the present invention are only used for description purposes, do not particularly refer to an order or sequence, and do not limit the present invention, but only distinguish components or operations described in the same technical terms, and are not understood to indicate or imply relative importance or implicitly indicate the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

A stress detection method. Since the fused deposition modeling method has a complicated temperature change during the manufacturing process, a complicated change of internal stress is caused. The invention solves the problems of deformation, insufficient strength and the like of FDM manufactured parts, and therefore the invention develops a method for measuring internal stress in an FDM manufacturing process. The measuring structure is shown in figure 1.

(1) Manufacturing a Solidworks part model to be formed into a part 1, selecting a region to be measured, and reserving a hollow groove in the region to be measured for placing a strain sensor. The size of the empty groove is the same as that of the strain gauge.

(2) Loading the part 1 by using an FDM printer, setting printing materials, printing temperature, printing layer thickness, printing speed, printing path and starting printing. The printing process is suspended when the FDM printer prints to the layer at position 2.

(3) Grinding work strain gauge R₁At the bottom, 502 glue is used for bonding the working strain gauge R₁And sticking and fixing the film on the region to be detected at the empty groove. Standing for 5 minutes until the glue is solidified. The orientation of the empty groove of the region to be measured can be adjusted in the model, and further the direction of the strain gauge is adjusted to measure stress in directions of X, Y, 45 degrees and the like.

(4) Strain gage R₁And compensation strain gauge R₂，R₃，R₄Forming a full bridge, as in fig. 2. And the electric bridge is connected with the strain gauge through the bridge box, the strain gauge is connected with the acquisition card, and the acquisition card stores the voltage signal transmitted by the strain gauge into the computer. And opening the strain gauge and collecting the internal strain of the part.

(5) R is to be₂，R₃，R₄The compensation plate is fixed on the second programmable heating platform 4, and the temperature of the second programmable heating platform 4 is set to be 25 ℃. And leveling the strain gauge, setting the sampling frequency of the acquisition card to be 500Hz, and starting recording. The FDM printer continues printing. Recording strain gauge voltage V_εF (i), wherein i ═ 1,2, ·, N. And N is the number of collected samples.

2. And removing the null shift. The strain gauge generates zero drift in the process of measuring stress for a long time, and the zero drift influences the accuracy of the measured stress. Therefore, the present invention measures the zero point drift within a certain time by using the same conditions as those of the actual measurement, and the measurement structure thereof is as shown in fig. 3. And according to the characteristics of the zero drift, a signal processing method is adopted to remove the zero drift.

(1) And (4) connecting hardware. As shown in fig. 3, the working strain gage R₁Compensating strain gage R₂Compensating strain gage R₃Compensating strain gage R₄Forming full-bridge connection, polishing the bottom of the strain gauge,4 strain gauges are pasted and fixed on the programmable heating platform 3, and the temperature of the programmable heating platform 3 is set to be 25 ℃. The bridge is connected with the strain gauge through the bridge box, the strain gauge is connected with the acquisition card, and the acquisition card stores the zero drift voltage of the strain gauge into the computer.

(2) And (4) preprocessing data. The strain gauge drift is divided into two types, one is horizontal zero drift, and the other is slope zero drift. In the strain sampling process, the total strain sampling duration is T, the number of samples is N, and the acquired signal is y₁-y_n，As sample mean:

wherein i is 1,2, N

σ_yAs sample variance:

when in useThe time is the drift of the horizontal zero point,the time is the slope zero drift.

(3) Removing the horizontal zero drift, and making the signal after removing the zero drift be Y_i；

The zero drift voltage is then:

Y_i＝y(i)-Y_l；

(4) removing slope zero drift:

wherein the content of the first and second substances,

wherein

Wherein

The slope of the sample data

The zero drift voltage is then: y is_l＝(k*t)

Removing signal Y after slope zero point drift_i：

Y_i＝y(i)-Y_lWherein i ═ 1,2, ·, N;

3. and removing the temperature drift. In the FDM printing process, the region to be measured can have strong temperature change, and the strain gauge can show different resistances at different temperatures, so that the temperature characteristic of the strain gauge needs to be researched. Therefore, the present invention measures the voltage change of the strain gage under the same temperature change in the FDM process by using the same conditions as the actual measurement, and the measurement structure thereof is as shown in fig. 4. And according to the temperature drift characteristics of the strain gauge, a signal processing method is adopted to remove the temperature drift.

(1) And testing the temperature of the printing process. As shown in fig. 4, the FDM machine loads the second part 5, there is a hollow groove at the region to be measured, the shape of the part 1 is the same as that of the second part 5, only the size of the hollow groove in the region to be measured is different, the region to be measured is the same as the position to be measured of the strain detection in fig. 1, and the size of the hollow groove is the same as that of the temperature sensor PT 100.

And (4) printing the second part 5 by slicing, and pausing the printing process when the FDM printer prints to the layer at the position 2. Sticking and fixing a temperature sensor PT100 in the empty slot by using glue, wherein the model of the temperature sensor PT100 is; and connecting the temperature sensor to a temperature transmitter with the model of ASC605-V2.0, and recording the voltage change of the temperature sensor in the FDM printing process by using an acquisition card.

(2) And calculating the temperature of the area to be measured in the printing process. Recording the voltage change of the temperature sensor₁。

V₁F (i), wherein i ═ 1,2, ·, N.

The temperature change of the test point during printing is T₁；

T₁＝20*V₁；

(3) And (5) determining the temperature drift. As shown in FIG. 5, the strain gage bridge circuit connection mode adopts full-bridge connection, wherein R is₁Is a working piece and is stuck and fixed on the programmable heating platform 3. R₂，R₃，R₄And the second programmable heating platform 4 is fixed in a sticking way for a compensation sheet. Measuring the temperature change T of FDM printing process₁The temperature of the second programmable heating platform 4 is determined to be constant at 25 ℃ after being input into the programmable heating platform 3. Strain gage R₁The compensation strain gauge R2, the compensation strain gauge R3 and the compensation strain gauge R4 are connected with a full-bridge circuit access bridge through a bridge box and a strain gauge, the strain gauge is connected with an acquisition card, and the acquisition card records R₁Temperature change T of work piece in FDM printing process₁Under the environment, the working strain gauge R₁The compensation strain gauge R2, the compensation strain gauge R3 and the compensation strain gauge R4 are in voltage change under the environment of 25 ℃. Recording temperature drift voltage V of strain gauge₂F (i). Wherein i is 1,2, N.

And calculating strain and stress.

(1) A stress calculation method. The stress measurement voltage after removing zero drift and temperature drift is V_L；

Then, V_L＝V_ε-Y_l-V₂；

Then, the strain is increased,

stress, F ═ E ∈. Wherein E is the modulus of elasticity of the printing material

(2) The strain and stress calculation software is written as in fig. 6. The denoising part is used for removing noise by adopting methods such as Gaussian denoising, median filtering, mean filtering, wavelet denoising, EMD model decomposition and the like according to the temperature stress data characteristics measured in the FDM printing process. The stress calculation part comprises zero drift filtration, temperature, strain and stress calculation. And functions of a painting brush, data scaling, a clock and the like are added to facilitate processing of detailed parts of data.

Example 1: as shown in FIG. 7, the invention adopts a strain sensor with BA-120-3AA strain gauge type, a strain gauge with YF-3 type and an FDM machine with Ultimaker2 type⁺Setting a printing material to be PLA, printing temperature to be 210 ℃, printing layer thickness to be 0.6mm, printing speed to be 20mm/s, printing path to be a Chinese character 'hui', forming and manufacturing a cuboid part 1 with 30 x 5mm, and measuring stress of the cuboid part in the Y direction. The test position is 1.8mm of the height of the center position of the model.

Example 2: referring to FIG. 8, the present invention employs a PT100 temperature sensor model, an ASC605-V2.0 temperature transmitter model, and an Ultimaker2 FDM model⁺Setting the printing material to be PLA, printing temperature to be 210 ℃, printing layer thickness to be 0.6mm, printing speed to be 60mm/s, printing path to be in a shape of Chinese character 'hui', molding and manufacturing a cuboid second part 5 with 30X 5mm, and measuring the temperature at the stress measuring point. The test position is 1.8mm of the height of the center position of the model.

The above description is only an embodiment of the present invention, and is not intended to limit the present invention. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.