Machining simulation of the hottest VERICUT in the

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Application of VERICUT in machining simulation of four axis fine milling of small tooth rotor

1. Vericm; Cut workflow

vericut is a software developed by CGTech company in the United States, which integrates NC machining simulation, interference verification, man hour working condition analysis, code optimization and other functions. The system can establish the models of NC machine tools, tools, fixtures and blanks in the way of virtual reality, simulate the process of tool path and material removal in metal cutting under the drive of tool position data or NC code, enable users to evaluate the rationality of process planning in an intuitive way, verify whether there is interference, and optimize the tool path and NC code. The workflow of VERICUT is shown in Figure 1

Fig. 1 machining simulation process of VERICUT

II. Characteristics and programming method of few teeth rotor

1 Characteristics of rotor

a spiral gear is widely used in oil meter, gas meter or plastic mechanical feed mechanism. The gear is characterized by large modulus and belongs to non-standard modulus. If the gear hob is used for processing, in order to reduce undercutting, a specific process method must be adopted to produce qualified products. On the other hand, it has a small number of teeth (usually 3 or 4 teeth), so the milling method is used in finishing, and its efficiency and accuracy are acceptable. For example, figure 2 shows a rotor gear, which is formed by the helical motion of the 4-tooth involute profile around the Z axis. The profile is connected by the addendum circle, involute and cycloid, and its shape is shown in Figure 2. The gear parameters are listed in Table 1, and the tooth surface roughness Ra is 1.6

Table 1 rotor gear parameters

Figure 2 rotor gear

2 NC programming method of rotor

it can be seen from the formation process of the rotor that the workpiece should be processed by four axes: the workpiece should be fed at a uniform speed along the negative direction of the Z axis, and at the same time, it should rotate at a uniform speed around the Z axis, so that the tool can cut a spiral in space; Every time a cutting stroke is completed, the workpiece is quickly reset, and then the tool makes involute interpolation movement (x, y linkage) on the xoy plane, and then the second stroke is carried out. Repeat the process until the whole tooth surface is milled. In essence, it is still processed by generative method

the known conditions for rotor NC programming are: (1) rotor end face contour. Designers usually discretize the contour into thousands of data points for NC programmers. (2 the main body of the testing machine should use a frame level or use the plumb bob in the attachment to calibrate the verticality of the column in two directions perpendicular to each other) the number of teeth, modulus, pressure angle, spiral angle, lead and other parameters of the rotor. The specific method of programming is as follows:

(1) fit the end face contour points into a smooth curve, as shown in Figure 3a

Figure 3 rotor data processing and modeling

(2) establish a three-dimensional model of the rotor, as shown in Figure 3B. There are many modeling methods, which can be established on pro/engineer, alphacam and other platforms. During modeling, the equation of the spiral guide line at any point P (Xi, Yi) of the contour line is (refer to figure 2 for the coordinate system):

where q is the rotor length, h is the lead, P is the vector diameter, t is the parameter variable, 0 ≤ t ≤ 1

(3) break the end face contour into several sub segments on average according to the arc length (Fig. 3C and Fig. 3D are locally enlarged), and the number of sub segments is determined according to the requirements of surface roughness

(4) calculate the coordinates of the endpoint of each sub segment and the normal vector n of the spiral curve at this point if there is a loose surface found. Let the radius of the ball head cutter be r, calculate the cutter position data according to the formula p=p0 or + NR when the loaded object bears the transportation resonance, and then compile the NC program (programming according to the cutter center)

III. simulate the milling process with VERICUT

1 Establish a blank model

to carry out cutting simulation for finishing machining. Theoretically, a semi-finished product model should be established as a blank before finishing machining. However, since the end tooth profile of the rotor is a single value curve, the cylindrical blank before rough machining can be used as the blank before finish machining, as shown in Figure 4. In this way, in the simulation, the system may prompt that the cutting depth of each knife is too large, but it does not affect the trajectory simulation and interference verification

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