Optimization for Morphology of Grinding Layer on Textured Laser Cladding Grinding Tool

In order to improving the grinding performance of laser cladding textured grinding tool (LCTGT) under high speed grinding process, the topography shape (height, width and height/width ratio) of laser cladding grinding layers on LCTGT were designed with RSM (response surface method) through optimizing laser cladding processing parameters and laser cladding layers structure parameters that based on Archimedes helix coefficients. The LCTGTs were produced with optimized laser cladding parameters and structural parameters for laser cladding grinding layers. The results showed that laser cladding parameters of 397W of laser power, 3.56 mm/s of the laser scanning speed and 0.91 r/min of powder feeding rate and structure parameters of laser cladding layers of 6-10-10 can meet requirement.

of traditional ceramic bond grinding wheel is deeply dressed by using diamond pen, which makes the engineered surface form and puts forward a grinding strategy to get structured workpiece. Through controlling the grinding strategy with the grits wheel, the forming of concave surface of workpiece can be controlled [16]. As the cooling fluid cannot directly reach the grinding zone due to the effect of air barrier during grinding process, Jarosław Sieniawski et al. proposed that a coolant filling method by adding cooling fluid directly to the grinding wheel hub. The coolant can be ejected from surface of excircle of grinding wheel with centrifugal force. In this case, the amount of coolant used is reduced by 10 times, and the quality of workpiece surface is improved compared with that of traditional grinding wheel grinding GrV12 steel under the same processing parameters [17]. C. Walter et al. pointed out that using ultra-short pulse picosecond laser to dress and produce structured grinding wheel can overcome the size and kinematic constraints that occurs from dressing tools. The flexibly structured surface of grinding wheel can be sintered by ultra-short picosecond laser beam with microns high geometric accuracy. Comparing with the traditional SiC grinding wheel, the grinding force of SiC grinding wheel with structured surface sintered by ultra-short pulse picosecond laser is reduced by 54%, and the surface finish of the workpiece is greatly improved [18]. The mixed diamond and metal powders (Cu-Sn-Ti) in a certain proportion (5.4%, 13.5%, 7.5% and 25%) were fused to a medium carbon steel substrate by continuous lasers and pulse lasers to produce grinding tools, which proposed by Iravani et al.. The effects of scanning speed and laser power on cladding layer, porosity, micro crack, graphitization of diamond, chemical composition of powder and diamond powder and distribution of diamond particles are discussed. The reaction layer between powder and diamond is detected and analyzed. By comparing continuous laser processing with pulse laser processing, pulse laser has lower carbonization layer and finer TiC layer at the same laser power and scanning speed. It provides a technical basis for the fabrication of laser cladding structural grinding wheel [19]. In order to solve the problem that traditional machining methods and micro-machining tools are difficult to obtain enough precision micro-grooves of injection molds, a rotating EDM corrosion machining method was proposed for micro-grinding tools, and a high-precision matrix micro-CBN grinding tool was obtained to process multi-matrix micro-grooves of NAK80 steel discussed by Shun-Tong Chen et al.. In this way, cost is saved and ideal precision surface topography of NAK80 steel with multi-matrix microgrooves are obtained [20]. Designed pores size and shape uniformly distributed on AISI10Mg metal bond diamond grinding wheel was fabricated by Tian with using laser selective sintering technology. The purpose of making this kind of structured grinding wheel is to overcome the disadvantages of traditional metal bond grinding wheel, such as poor chip tolerance, poor self-sharpening, poor dressing ability, and easy to burn for workpieces when grinding [21].
However, designing and optimizing for the topography of textured grinding layers which in favor of high speed grinding on LCTGT has not been reported yet. In this case, in order to getting LCTGT for high speed grinding process with high precision of ground workpieces, the laser cladding parameters were optimized by RSM and multi-objective optimization method to modify cross-section of morphology of laser cladding grinding layers on LCTGT. And also, the parameters for macro structure of laser cladding grinding layers with Archimedes helix shape were selected through analyzing abrasive trajectories on grinding layers and air flow and pressure field on non-grinding zone. Then, with the optimized laser cladding parameters and structural parameters of laser cladding grinding layers, LCTGTs were fabricated.

Grinding angle analyzing for LCTGT
Laser cladding processing parameters have great influence on mechanical properties and physiochemical properties of laser cladding layer. Meanwhile, the geometric shapes of laser cladding layers are determined by laser cladding process parameters. And chip space for chip flow and heat dissipation capability during grinding process are affected by geometric shapes of laser cladding grinding layers on LCTGTs [22]. The qualities of geometric shape of laser cladding grinding layer refer to width, height, height-width ratio, dilution between laser cladding layer and substrate, bonding capability between laser cladding layer and grit, cutting edges integrity of CBN grits, which the surface qualities of machined workpiece are impacted. The cross section of geometric shape for laser cladding layer is shown in Fig. 1. From Fig. 2(a), it can be seen that the processing can be compared to milling process because of the high cutting depth, when the height is high while, the width is short and laser cladding layer edge angle θ is close to 90°. However, layers cracking phenomenon is taken place as the height of laser cladding layer is high and width of laser cladding layer is short, which lead to high stress between substrate and layer during high depth grinding process, shown in Fig. 3.
On the other side, there will be no layer fracture when laser cladding grinding layer has a large height and width under heavy load grinding process of LCTGT. And also, the grinding performance of LCTGTs can be maintained with grinding time increasing whether in the surface grinding or free surface grinding process. But, when laser cladding grinding layer is short enough for LCTGT, shown in Fig. 2 (b), (d), collision between substrate and workpiece cannot be avoided, and process safety factors cannot be guaranteed. The worst type of laser cladding layer is shown in Fig. 2 (d), the height and width are both short, in this case, the grinding quality, grinding life span and safety factors all cannot be guaranteed. In this case, the ideal condition of geometric morphology for laser cladding grinding layer is shown in Fig. 2 (C).

Response surface method theory
In 1951, Box and Wilson proposed response surface method (RSM) which has been widely used in various fields [23]. Response surface method theory has been commonly recognized as an important method in experimental design method. The theory can be shown: An exception of a function = ( ) is related to experimental variables 1 ， 2 ，⋯， , can be expressed by function (1): In function (1), 1 ， 2 ， ⋯ ， are system parameters, ϵ is error and k is number of variables.

Experimental results analyzing
The purposes of optimizing B4C/CBN/CuSnTI laser cladding process parameters (including laser power, laser scanning speed, and powder feeding rate) are to get propitiate grinding layer morphology (including height, width and height-width ratio) for LCTGTs, enhance grinding capability and efficiency of LCTGTs during grinding. Two steps are contained in the experiments, first is to find fitting relationship between heights, widths and height-width ratio of laser cladding grinding layer and laser cladding process parameters, and then, find a group of optimized laser cladding process parameters for LCTGTs producing.
Laser cladding process parameters experiments are designed by response surface method with central composite design (CCD) algorithm. The modern experimental designing software, Designexpert 8, as supplementary for experimental data designing and analyzing. In order to fitting accurate functions related between laser cladding layer morphology and laser cladding parameters based on experimental results, two-order fitting function is adopted, shown in function (3).  Table 1.
The tracks of laser beam scanning are 20 single lines with 6mm long and 5mm pitches away from each other in this experiment. The laser cladding process orders is in accordance with table 2 and laser cladding process is carried out in turn. After laser cladding, each single track was cut in to 3 equal parts along the direction of cross section of laser cladding layers. Each cross section was ground by SiC abrasive papers and diamond polishing agent to reach mirror-like finish. After mirror-like finish processing, each cross section of laser cladding layers was measured by LSCM to require the dimension data. Table 2 shows average results of each dimension parameters including height, width and height-width ratio average measurement results.

Empirical equation for height of laser cladding layer
ANOVA method is adopted to analyzing dimension measurement for cross section of laser cladding layer. The analyzing results are shown in table 3. The F value of the model is 97. 16 and P value less than 0.0001, which indicates that the fitting equation is significant and the fitting degree is high. In this case, it can be seen that laser power (A), laser scanning speed (B) and feeding powder rate (C), interaction parts of AB, AC and BC, secondorder parts of A 2 and C 2 are all significant factors of height of laser cladding layer. The second-order of B 2 has the least effect on the height of laser cladding layer, while feeding powder rate (C) is the most effect.
An R-squared is mainly used to explore the fitting effect between the established empirical model  Fig. 4(b), which is used to compare the influence of curve changes of various laser processing parameters passing through the center point of the design domain on the height of the cladding grinding layer. It can be seen that the height of the cladding grinding layer increases with the increase of the powder feeding rate, and there is a positive correlation between the layer height and the powder feeding rate. This is because when the powder feeding rate is increased, the amount of powder per unit time in the laser cladding process will be increases, so the amount of powder in the cladding area will increase. In this case, more powder absorb energy in the cladding area base pool interacting with each other, and then form a higher cladding layer. It can also be seen that when the laser power increases, the cladding grinding height will be increased, and there is a positive correlation. This is because energy increase per unit time leading to melting powder increasing.  Figure 5 shows that interactive effect between laser power and scanning speed on the height of laser cladding layer when feeding rate is constant at 0 point. When the laser scanning speed is fixed and the laser power is increased, the height of the cladding grinding layer can be increased. However, when the laser scanning speed is increased under the action of high laser power, the change of the cladding grinding layer is not great. Fig. 5(b) shows the contour diagram of the influence of the grinding layer height on the interaction between laser power and powder feeding rate when the laser scanning speed is at the level of 0. These two parameters are positively correlated to the laser cladding grinding layer, so the maximum height of the cladding grinding layer can be achieved by increasing the laser power and powder feeding rate together. When the laser power and powder feeding rate are reduced simultaneously, the height of the cladding grinding layer will be reduced to the minimum.

Empirical equation for width of laser cladding layer
It can be seen that table 4 that the F value of the fitting model is very high (84.85) and P value is very small (< 0.0001). The adequate precision is 28.925 which the fitting degree is much greater than 4, and the R-squared is 0.9871, which is very close to 1. All the above data show that the experimental measured values fit well with the empirical fitting model. It can also be seen from the table 4 that the laser power, scanning speed the two-factor interaction AB, AC, BC and the second-order interaction of A 2 , B 2 and C 2 are all significantly correlated. According to the analysis of F value, the width of grinding layer is most affected by laser power and least affected by powder feeding rate.
It can be seen from Fig. 6(a) that the validity of the prediction model for the grinding layer width of cladding can be calculated from the images made by formula (5) and experimental measurement data.
It can be seen from table 4 that laser power has the greatest influence on width of laser cladding layer. phenomenon may be that when the laser power increases, the metal substrate receives more laser power, which leads to a wider molten pool width of the metal substrate. Therefore, a wider molten pool can receive more cladding B4C/CBN/CuSnTi powder to accumulate in the molten pool, and finally leads to a wider layer width. However, the increase of laser scanning speed and powder feeding rate will decrease the width of the cladding grinding layer, and the laser scanning speed and powder feeding rate are negatively correlated with the width of the cladding grinding layer, shown in Fig. 6(b). The reason of negative relation between width of laser cladding layer and scanning speed is that when the laser scanning speed increases, the average power of the laser will decrease, so that the substrate will receive less heat, resulting in the narrow width of molten pool, which leads to the less powder in the molten pool, and eventually narrow width of laser cladding layers are formed. The reason of feeding powder rate increasing leading to width laser cladding layer decreased is that the laser energy reaching to the substrate was reduced by flying high density powder from powder nozzles to the substrate. In this case, the height of the laser cladding layer will be increased, while the width of the grinding layer becomes narrower. However, when the laser power is the maximum and the laser scanning speed is the minimum, the width of the cladding layer can reach the maximum. Fig. 7(b) shows contour diagram for laser cladding layer width changing, which is interactively influenced by laser power and feeding powder rate. Fig. 7(b) is similar to Fig. 7(a), when the laser power is the maximum and the rotary speed is the minimum, the width of the cladding grinding layer can reach the maximum. However, the difference between Fig. 7(a) and (b) is that when the laser power is fixed and the powder feeding rate increases or decreases, the change rate of the laser cladding layer width will be larger than that of the laser scanning speed changing. This phenomenon can also be illustrated by the F value of laser scanning speed and the F value of powder feeding rate in table 4.

Empirical equation for height-width ratio of laser cladding layer
It can be seen from ANOVA analysis of height and weight ratio of laser cladding layer in table 5. F values of all parameters are very high and P values are very small. The F values of powder feeding rate is the greatest, which is 730.61. The F value for the influence of interaction between laser power and powder feeding rate on the H/W ratio is ranked after that of powder feeding rate, and the value is 688.72.
This indicates that the laser cladding processing parameters (whether single factor, interaction factor or second-order factor) are significantly correlated with the aspect ratio of the laser cladding layer. In addition, the value of the R-squared is 0.9961, which is close to 1. The value of the predicted R-squared is 0.9745, which is close to the value of the adjusted R-squared (0.9926), and the value of the Adequate precision is 65.418, which is far greater than the value of 4. All these data indicate that the experimental observation data of the aspect ratio of the cladding grinding layer fit well with the empirical model.  which leads to less powder aggregation and melting, resulting in the height of the cladding grinding layer decreasing more rapidly than the width of the cladding grinding layer. Therefore, with the increase of laser scanning speed, the H/W ratio of the cladding grinding layer decreases. When the speed of feeding rate increases, more B4C/CBN/CuSnTi powders are blown into the molten pool per unit time.
As a large number of powders weaken the irradiation effect of laser energy, the powders will be melt more in width direction of melt pool on substrate than that of accumulating in height direction. As the result, the H/W ratio decreases gradually.

Laser cladding processing parameters calculating
According to the formula [24] (7), the laser cladding process parameters of laser power, laser scanning speed and feeding rate can be optimized at the same time. The formula can satisfy all the parameters in the research range, and the ultimate goal needs to satisfy the maximum laser cladding layer height, maximum laser cladding layer width, and minimum laser cladding layer H/W ratio.
N is the response number, represents the importance of correlated response and is specific response coefficient.

Archimedes helix theory
The polar coordinate formula of Archimedes helix is： = + Where a and b are the factors, θ is the independent variable, r is the dependent variable, and figure   10 shows the Archimedes helix in the polar coordinate system when the coefficient a is 0.

Airflow field and pressure field model for Archimedes helix grinding structure
As the width of laser cladding grinding layer is 1.1mm because of the dimension of laser beam, it is necessary to restrict the pitch between each two Archimedes spirals to be greater than 1.1mm in order to prevent overlapping among laser cladding layers. In this study, three model parameters of laser cladding grinding structure are defined, as the outer diameter R of grinding tool has been determined.
These three parameters are the inner circle diameter of grinding tool r which deciding the starting point for laser cladding grinding layers on grinding tool substrate, the shape coefficient β of Archimedes spiral, and the number of Archimedes spiral grinding layers on LCTGT substrate n. The model of Archimedes helix under different coefficients was established by SOLIDWORKS2015 software.
First, the range of shape coefficient β of Archimedes helix should be determined. The length of laser cladding layers are not changed much when β changes from 20 to 30. As longer laser cladding layer can perform better grinding effect, it is better for laser cladding layer to get the length as long as possible excluding mutual interference of two laser cladding layers. In this case, these three parameters need to be determined after comprehensive analysis of simulated grinding performance.
In this section, two parts of simulation analysis were conducted: first is the changes of velocity field and pressure field of non-grinding zone were simulated and analyzed by FLUENT software in various grinding speed with different structural coefficients of laser cladding grinding layers. The second is motion trajectory of laser cladding grinding layers were analyzed by SOLIDWORKS2018 motion module under different structural laser cladding grinding layers at different grinding speeds and feeding speeds.
According to the requirements of simulation, in this paper, five groups of structure of laser cladding grinding layers were selected. Figure 11 shows the structural parameters of these 5 groups of laser cladding grinding layers on the left corner. These structural parameters of each laser cladding layers are structural coefficient of laser cladding layer β -the number of laser cladding layers n -inner diameter of grinding tool r shown in table 6. The morphology of laser cladding layers are changed by changing Archimedes spiral coefficient β , number of laser cladding layers n and inner diameter of grinding tool r. These structural laser cladding layers mentioned above need to be analyzed by simulation under various grinding parameters (feeding speed and rotating speed) to choose a better structure for producing LCTGTs. The selected simulation grinding tool rotating parameters were shown in Table 7.    Figure 12 shows 3-5-6 structural laser cladding grinding layer under 2000 rpm, it can be seen that the distribution of air flow field and pressure field in the each non-grinding zone of the grinding tool is very uneven. The flow rate at the outlet reaches 3.9 × 10 4 m/s and the pressure exceeds 3 × 10 8 Pa.
From Fig. 13, it can be seen that there is a strong eddy in the non-grinding zone in the center of grinding tool, which is also not conducive to the grinding efficiency and safety in high grinding speed. In this case, as the air flow and pressure on one side of grinding tool are too high, which leads to the instability of grinding tool and bouncing off during grinding. The dynamic balance of grinding tool cannot be guaranteed, which is extremely unsafe in grinding process. Therefore, such structural parameters for grinding tools are not desirable. However, when rotating speed of LCTGT increases to 3000 rpm or above, as shown in figure 14(b), (c), (e) and (f), the distribution of air flow field in non -grinding zone of LCTGT appears uneven. Also, there are symmetrical high air flow velocity on both sides of non -grinding zone of LCTGT higher than that of other non -grinding region. When this phenomenon occurs, the grinding tool will get to the unstable state. In this state, the grinding tool cannot guarantee the dynamic balance of its own rotation.
Therefore, LCTGT with the 5-6-8 type structural laser cladding grinding layer cannot be guaranteed when the speed is equal or above 3000 rpm.  And also, it is difficult to see that there is serious eddy current at the inner center of LCTGT. The reason for this phenomenon may be that when the inner diameter is expanded to 10 mm, the internal space is improved, which alleviates the vortex phenomenon caused by the air collision caused by overcrowding when the air flow moves. In this way, the air flow inside the grinding tool is smoother and the grinding tool can rotate at a higher speed.

Grinding trajectory analyzing for LCTGT model
There is a similar linear relationship between the number of abrasive particles and the length of the laser cladding grinding layer analyzed by statistical method, shown in figure 16. It can be seen that, when the length of the laser cladding layer is increased by 1mm, the number of abrasive particles will increase by 6. According to the formula of Archimedes spiral length in polar coordinates, the length of each grinding layer can be calculated as follows: In this function, 1 is the starting angle and 2 is the terminating angle. Through calculation, the number of abrasive of each type of structural laser cladding grinding layer can be obtained, shown in   In this paper, grinding trajectory of different types of structural laser cladding grinding layers are simulated by SOLIDWORKS2018 motion module. As the number of abrasive on single laser cladding grinding layer is large, the trajectory of a single abrasive on laser cladding grinding layer cannot be distinguished in high rotating and feeding speed of LCTGT. Therefore, in order to simplifying the observation of abrasive motion trajectory on various types of single laser cladding grinding layer, 10 abrasive on laser cladding grinding layer as 1 trajectory generation point in the motion simulation process. The moving parameters of simulated laser cladding grinding layers are shown in table 9, 4 groups of parameters were obtained by combining the rotating speed and feeding speed of LCTGT.  Figure 17 shows (a) grinding trajectory at 2000 rpm with a feeding speed of 10 mm/min, (b) 2000 rpm with a feeding speed of 30 mm/min, (c) 4000 rpm with a feeding speed of 10 mm/min and (d) 4000 rpm with a feeding speed of 30 mm/min of moving parameters for 3-5-6 type of laser cladding layer for LCTGT. It can be found that the shape of trajectory is affected by the rotating speed and feeding speed of laser cladding grinding layer for LCTGT. There are two more dense lines in the middle, which is the beginning of the cladding grinding layer from the center of the grinding tool. And the grinding trajectory in the process of running appeared condition of stratification. As can be seen from figure 17, when the feeding speed of LCTGT is 10 mm/min. The density of abrasive moving trajectory of LCTGT with rotating speed of 4000 rpm is higher than that of 2000 rpm. And also, when the feeding speed is 30 mm/min, the density of abrasive moving trajectory of LCTGT with rotating speed of 4000 rpm is higher than that of 2000 rpm.  Comparing figure 17 with figure 19, it can be found that the smaller coefficient β is, the more intensive density of the grinding trajectory is, and it is the main factor that affects the shape of the grinding trajectory. However, when the coefficient β is too small, there will be non-uniformity of grinding trajectory, and a large number of obviously different grinding density areas will appear in the grinding region of grinding tool. In this case, it is not conducive to guarantee the quality of the grinding workpiece.
This phenomenon will be gradually alleviated by the increase of coefficient β. When coefficient β is 6, the grinding density zone will become very narrow, while the grinding areas are uninform. Stratification of grinding trajectory can be reduced with better quality of workpiece under uniform surface roughness.

Fig. 19
Grinding tracks from single grinding layer under different process parameters using 6-10-10 structured grinding wheel According to the adjustment, selection, simulation and analysis for processing parameters of LCTGT mentioned above, when the coefficient β is 6, the number of laser cladding grinding layers is 10 and the inner diameter of LCTGT is 10mm, the distance between two laser cladding grinding layers is greater than 1.1 mm. In this case, the range of rotating speed of LCTGT is large and grinding condition is stable under high speed. Therefore, type of 6-10-10 of laser cladding grinding layer can be selected as the structural parameters for LCTGT grinding layers.
It is a key step to generate the laser cladding grinding layer trajectory file and import it into KUKA robot controller. In this paper, Solidworks 2018 is the three-dimensional model established software.
According to the shape and size of the grinding tools substrate end face, 6-10-10 type 3D model for textured laser cladding grinding structure is established. The model mentioned ahead is saved with IGS format.
After that, the IGS format of the 3D parts was imported into Robotart-2018 software. In the course of trajectory design, optimization, and output using Robotart-2018 software, the following steps are required: Firstly, select and load the robot model of KUKA16-2 and IPG laser head as 3d parts. Second, set up TCP points and measure parts. Third, design and optimize the trajectory of laser moving beam.
Fourth, detect and adjust the collision for KUKA 16-2 and IPG laser head during processing in the software with a simulation. Fifth, the laser head moving trajectory is derived and saved with identifiable program for KUKA 16-2 control system.
The designing and optimizing of the trajectory with software like Robotart-2018 greatly affect the quality of the laser cladding grinding layer, such as temperature gradient, thermal stress, surface tension, internal microstructure, porosity or crack appearance. Through reasonable design and optimization of the trajectory for laser cladding head, the quality of the laser cladding grinding layer can be improved, and the efficiency of the preparation can be improved. Figure 20 shows the designing environment in the Robotart-2018 software, and figure 20(a) shows the robot arm, laser head and workpiece in the simulation environment. In this environment, the previously generated workpiece IGS format files are imported into the Robotart-2018 software, and the movement track of laser head and mechanical arm is generated on the parts. After the trajectory being generated, it is necessary to optimize the trajectory of the laser head and the robotic arm: First is to fix the Z-axis of laser head to ensure that the laser head and arms cannot rotate arbitrarily during laser cladding. The second step is to determine the step length of the laser head and robotic arm movement.
When the moving step size decreases, the real laser cladding trajectory will have a higher fitness with the designed trajectory during laser cladding process. In other words, when the step size of each step decreases, the designed trajectory will be more accurate. The third step, choose the laser cladding starting point and end point. When selecting the starting point and ending point of the laser head, the position of the laser light on and off will also be considered. The operation of structure of LCTGTs is carried out by controlling laser on and off and cooperation with powder feeding from coaxial powder feeding outlets on laser head. The fourth step is to optimize laser cladding process trajectory. The purpose of trajectory optimization is to adjust the relevant position of the laser head. The laser head in this experiment needs to droop naturally and be perpendicular to the working plane. In this case, the safety of laser cladding can be ensured, and laser head can be fixed during laser cladding process while laser head moving. The arbitrary movement with swing action of laser head is inhibited during laser cladding process, then the accuracy of laser cladding layer can be improved. Finally, the designed and optimized trajectory of the laser cladding grinding layer is transformed into a machine language that can be recognized by KUKA 16-2 robot control system. The files are imported into KUKA robot control system, and the processing experiments are carried out by controlling the KUKA 16-2 robot. When the well-designed and optimized laser cladding orbit running files are imported to the KUKA robot, the processing experiment of laser cladding textured grinding wheel can be carried out. The powder is added into powder feeding barrel, the parameters of laser processing are set, and then laser cladding experiment can be carried out by KUKA robot controller. First, grinding tool substrate under the laser cladding head should be placed and the distance between the laser head should be adjusted.
The distance between the laser head and the grinding tool substrate is 15mm. Second, grinding structure of LCTGT is carried out by controlling Robot moving based on imported laser cladding track file. Third, the fabrication of LCTGT is completed, grinding structure on LCTGT substrate end face is shown in figure 21.

Fig. 21
Laser cladding textured grinding tool

Conclusions
(1) RSM method was used to analyze the relationship between the morphology of laser cladding layer (height, width and height/width ratio) and laser cladding process parameters (laser power, laser scanning speed and powder feeding rate), and the laser processing parameters were optimized by multi-objective. The height of laser cladding layer is mainly related to the powder feeding speed of grinding tool. The width of the laser cladding layer is mainly related to the laser power. The H/W ratio of laser cladding layer is mainly related to the power feeding rate. Through multi-objective optimization, the optimal laser processing parameters are 397W of laser power, 3.56 mm/s of the laser scanning speed and 0.91 r/min of powder feeding rate.
(2) The macro structural laser cladding grinding layers were optimized. When the rotating speed is 2000 rpm, the air flow and air pressure of the non-grinding area for structural type 3-5-6 of laser cladding layer appears instable. On the other side, the air flow and air pressure of the structural type 6-10-10 laser cladding grinding layer in non-grinding zone are stable under rotating speed of 4000 rpm. And also the coverage area of abrasive trajectory for structural type 6-10-10 laser cladding layer is more uniform and dense than of other structural type for LCTGT. In this case, structural type of 6-10-10 is suitable for LCTGT producing.
(3) LCTGT was fabricated in laboratory. The laser cladding process trajectory was designed and optimized by software. And with the cooperation of KUKA robot arm, LCTGT can be produced.

Acknowledge
This research was financially supported by The National Key Research and Development Program of China (No. 2020YFB2010500).

a. Funding
This research was financially supported by The National Key Research and Development Program of China (No. 2020YFB2010500).

b. Conflicts of interest
Not applicable.

c. Availability of data and material
The authors declare that the data and material supporting the findings of this work are available within the article

d. Code availability
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e. Ethics approval
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f. Consent to participate
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g. Consent for publication
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Changhe Li: research grinding and precession machining, high speed and ultra-high speed machining and digitalized manufacturing.
Tianbiao Yu: research grinding and precession machining, digital design and intelligent manufacturing, Additive manufacturing and 3D printing and green remanufacturing.