As a key component of turbomachinery, integrated impellers are widely used in aerospace and other fields, and their processing technology has always been an important issue in turbine manufacturing. From the geometry and process of the integrated impeller, it can be seen that the machining of the integral impeller elbow has more constraint conditions in the planning of the machining trajectory. The space between adjacent blades is smaller, and the collision interference is easy to occur during processing, and automatic generation is not possible. It is difficult to interfere with the machining trajectory. Therefore, not only the trajectory of the surface of the blade must be guaranteed in the process of machining the impeller, but also the requirement of geometric accuracy must be met. Due to the limitation of the thickness of the blade, the trajectory planning must be paid attention to in the actual processing to ensure the quality of the force.

The DELCAM company's PowerMILL software has been applied in the five-axis machining of the aerospace industry for many years. Its technology and services are mature. With its powerful and easy-to-operate features, it is widely used in aerospace, automobiles, and ships. Internal combustion engines, household appliances, light industrial products and other industries.

The advantages of five-axis machining

The main advantage of five-axis machining is that it requires only one set-up and positioning to complete all machining of complex parts and saves a lot of machining time. When PowerMILL positions five-axis machining, the spindle is fixed in a series of directions for machining. In addition, PowerMILL also provides continuous five-axis machining capabilities that allow the use of multiple machining strategies and a full range of cutting tools to create a continuous five-axis tool path on complex surfaces, solids, and triangular models, with all toolpath sections being cut through Check and machine tool simulation to ensure the safety of personnel and equipment.

Fig. 1 Golf-seed knife advance and retreat

Five-axis machining is an important embodiment of high-tech processing. With the rapid development of software technology, machine tool technology, and cutting tool technology, with the rapid decline in equipment prices, five-axis technology has gradually entered the company. PowcrMILI's new automatic collision avoidance function makes automatic five-axis programming a reality. With this function, PowerMILL can automatically adjust the tool axis according to the collision gap set by the programmer, and automatically avoid the tool axis at the position where the three axes cannot be processed. The three-axis machining position is automatically restored when the three axes do not collide. This ensures that the tool can be machined with as short a tool as possible, which not only increases the rigidity of the machining but also increases the machining range.

PowerMILL Application in Impeller Processing

At present, there has been great progress in the manufacture of impellers at home and abroad. The majority of impeller manufacturers in China have a certain gap with foreign countries in terms of complex impeller manufacturing technology. This article uses PowerMILL7.0 to explain the force II trajectory planning for the impeller. The basic process flow is based on the geometric characteristics and application requirements of the impeller. The specific content includes:

1 Prepare blanks

The material is a forged aluminum piece, which is turned into a basic shape of a revolving body and can reduce the time required for numerical control machining.

2 tools

From the roughing to the final finishing, different specifications of ball nose or taper ball nose knives are adopted. In this example, R6, R3 ball nose knives and R2 full taper taper ball milling cutters are used.

3 processing arrangements

(1) Clamping: Using the mandrel clamping position, it can also be considered in the blank on the key slot for auxiliary positioning, and to produce a special fixture for the positioning of the mandrel;

(2) Finding: Find the table or use the edge finder.

Figure 2 Five-axis automatic avoidance programming

4 roughing runner section

(1) Use the 3+2 positioning five-axis machining to minimize the number of linkage axes and improve the processing stability. In addition to the three-dimensional region, please remove the strategy, the remaining allowance for rough machining is 0.5 mm, the undercut is 3 mm, the spindle speed is 8OO Or/min, and the feed speed is 1200 mm/min. The use of racetrack processing, smoothing margin, undercut spiral way, give full play to high-speed processing efficiency.

(2) In the narrower part of the flow channel, the 3+2 positioning five-axis machining is adopted, and the five-uranium linkage processing may also be considered. The advantage is that it can leave a more uniform allowance for subsequent processing. The disadvantage is that the cutting is linked. It is better to position the five axis stability.

5 roughing blades

Select the blade to be roughed. PowerMILL will automatically determine the direction of the cutter axis and automatically avoid the interference of the blades next to it.

6 Conduct reasonable artificial aging

It can do stress aging treatment, which can change the chemical composition of the workpiece surface, give or improve the performance of the workpiece to improve the inherent quality of the workpiece.

7 secondary roughing

Part of the semi-finished runner, using five-axis linkage processing, leaving a margin of O.2mm, leaving a more uniform margin for finishing, to ensure the stability of the follow-up machining, in this process, the use of surface projection strategy.

8 semi-finished blades

Using SWARF processing method, the tool axis is automatically judged, leaving O.15mm margin, leaving a more uniform margin for finishing, to ensure the stability of the follow-up machining.

9 Finishing Runners

With surface projection, pay attention to the latitude and longitude distribution of the surface and the projection quality of the surface, which will directly affect the quality of the tool path and the surface quality of the machining.

Figure 3 Five-axis collision simulation

10 Finishing blades

The SWARF machining method can be used for blade finishing, and curved surface projection can also be used. In this example, because the blade is formed by a ruled surface, the SWARF machining method is more convenient.

After completing all the procedures, you can do a machine simulation first to check whether the prepared program has overcuts and collisions, and to prevent all possible accidents from occurring before machining, in order to ensure the safety of personnel and equipment, and then For NC program output.

Difficulty analysis and solution

1 Making thin-walled parts

Due to the thinness of the mouthpiece, the method of layer-by-layer cutting is used as much as possible in semi-finishing and finishing. Even the position of the blade tip can be processed to ensure that the blade has sufficient strength during processing, and then the blade is processed. If there is enough space between two adjacent blades, you can consider leaving a step-like allowance during processing, such as dividing the blades into 3 sections, leaving the O.5mm margin in the upper section, leaving 1mm margin in the middle section, and 1.5 in the lower section. The mm margin ensures that the bottom of the blade will always have enough strength to support seven parts, although this will greatly increase the programming complexity and programming time, but it can improve the quality of the processing.

2 Root processing safety issues

PowerMILL uses a curved tool axis control method to ensure that the tool path follows the root of the blade when the root is in the root. It can provide over-cutting inspection of parts, collision check of tool holders, machine tool simulation and collision check function to ensure the safety of the machining process.

The development trend of numerical control processing

With the continuous development of CNC machining technology, five-axis and high-speed machining will become the mainstream. Nowadays, more and more manufacturers use five-axis machine tools to process products. This aspect can improve processing efficiency and shorten production time. On the other hand, it can improve the processing quality of blades and reduce the workload of fitters. Whether the high-speed five-axis machine tool can play the benefits it deserves and the choice of CAM software is very important, PowerMILL is undoubtedly a more professional product in many CAM processing softwares that can be selected in the field of five-axis and high-speed mirror cutting.

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