By combining the end-face grooving cutter with the bridge boring cutter body, a special tool for end-face grooving is designed and manufactured to replace the end milling cutter, and the end-face grooves of large structural parts are processed by boring instead of milling on the CNC double-sided boring and milling machining center.
After the process optimization, the end face groove processing time is greatly reduced, which provides an efficient processing method for processing the end face grooves of large structural parts on the boring and milling machining center.
01 Introduction
In the large structural components of engineering machinery (refer to Figure 1), it is common to find end face grooves within the box. For instance, the end face groove depicted in the “Ⅰ enlarged” view in the G-G section of Figure 1 has specific dimensions: an inner diameter of 350mm, an outer diameter of 365mm, a groove width of 7.5mm, and a groove depth of 4.6mm.
Given the crucial role of the end face groove in sealing and other mechanical functions, it is essential to achieve high processing and positional accuracy [1]. Therefore, post-weld processing of the structural components is necessary to ensure that the end face groove meets the size requirements outlined in the drawing.
The end-face groove of a rotating workpiece is typically processed using a lathe with an end-face groove cutter. This method is efficient for most cases.
However, for large structural parts with complex shapes, it is not feasible to use a lathe. In such cases, a boring and milling machining center is used to process the end face groove.
The processing technology for the workpiece in Figure 1 has been optimized and improved by using boring instead of milling, resulting in significantly improved end-face groove processing efficiency.
02 Optimize the front face groove processing technology
The material of the structural part depicted in Figure 1 is SCSiMn2H. The end face groove processing equipment used is a CNC double-sided boring and milling machining center with Siemens 840D sl operating system. The tool being utilized is a φ6mm end mill, and the cooling method employed is oil mist cooling.
End face groove processing technique: The process involves using a φ6mm integral end mill for spiral interpolation milling (refer to Figure 2). Initially, rough milling is performed to achieve a groove depth of 2mm, followed by reaching a groove depth of 4mm, leaving 0.6mm for fine milling of the groove. The rough milling program is detailed in Table 1. Fine milling can be accomplished by adjusting the cutting parameters and spiral interpolation coordinate values in the program. The cutting parameters for rough milling and fine CNC milling precision are outlined in Table 2.
Figure 2 End milling with spiral interpolation to cut the end face groove
Table 2 Cutting parameters for face slot milling
Based on the processing technology and procedures, a φ6mm end mill is utilized to mill a face slot with a width of 7.5mm. It takes 6 turns of spiral interpolation for rough milling and 3 turns for fine milling. Rough milling with the large slot diameter takes approximately 19 minutes per turn, while fine milling takes about 14 minutes per turn. The total time for both rough and fine milling is approximately 156 minutes. The efficiency of spiral interpolation slot milling is low, indicating a need for process optimization and improvement.
03 Optimize the end-face groove processing technology
The process for end-face groove processing on a lathe involves the workpiece rotating while the end-face groove cutter performs axial feeding. Once the specified groove depth is reached, radial feeding widens the end-face groove.
For end-face groove processing on a boring and milling machining center, a special tool can be designed by combining the end-face groove cutter and the bridge boring cutter body. In this case, the workpiece remains stationary while the special tool rotates and performs axial feeding to complete the end-face groove processing. This method is referred to as boring groove processing.
Figure 3 End face grooving cutter
Figure 4 Schematic diagram of the machining principle of end face groove on lathe
The precision of mechanical parts processed by machine-clamped blades in CNC boring and milling machining centers can generally reach IT7 and IT6 levels. Additionally, the new grooving blades have a special back angle structure and are sharp, which reduces cutting resistance and vibration. The chips generated during processing can quickly fly away from the machined products surface, resulting in higher surface quality.
The surface quality of the milling inner hole groove can be controlled by adjusting different cutting parameters such as feed speed and speed. The end face groove precision processed by the machining center using a special groove cutter can meet the drawing precision requirements.
3.1 Design of a special tool for face groove processing
The design in Figure 5 illustrates a special tool for processing face grooves, similar to a bridge boring tool. The tool comprises a bridge boring tool body, a slider, and a non-standard tool holder. The non-standard tool holder consists of a tool holder, a tool holder, and a grooving blade.
The bridge boring tool body and the slider are standard tool accessories, and only the non-standard tool holder, as shown in Figure 6, needs to be designed. Choose a suitable grooving blade model, mount the grooving blade on the face groove tool holder, attach the non-standard tool holder to the slider, and adjust the diameter of the face groove tool by moving the slider.
Figure 5 Structure of special tool for end face groove processing
3.2 Machining the end face groove using a special tool
The specialized tool for machining the end face groove is depicted in Figure 7. Use the tool setting instrument to adjust the tool to the appropriate groove diameter by moving the slider. Record the tool length and enter the tool diameter and length into the corresponding table on the machine panel. After testing the workpiece and ensuring the measurements are accurate, use the boring process according to the machining program in Table 3 (refer to Figure 8).
The CNC program controls the groove depth, and the rough machining of the end face groove can be completed in one boring. Following rough machining, measure the groove size and fine-mill the groove by adjusting the cutting and fixed cycle parameters. The cutting parameters for the end face groove boring machining are detailed in Table 4. The end face groove machining time is approximately 2 minutes.
Figure 7 Special tool for end face groove processing
Table 3 End face groove boring process
Figure 8 End face groove boring
Table 4 Cutting parameters for end face slot boring
3.3 Implementation effect after process optimization
After optimizing the CNC manufacturing process, the boring processing verification of the end face groove of 5 workpieces was carried out continuously. The inspection of the workpieces showed that the end face groove processing accuracy met the design requirements, and the inspection pass rate was 100%.
The measurement data is shown in Table 5. After a long period of batch processing and quality verification of 20 box end face grooves, it was confirmed that the end face groove accuracy processed by this method meets the drawing requirements.
The special processing tool for end face grooves is used to replace the integral end mill in order to improve tool rigidity and significantly reduce cutting time. After process optimization, the time required for end face groove processing is reduced by 98.7% compared to before optimization, leading to greatly improved processing efficiency.
The grooving blade of this tool can be replaced when worn out. It has a lower cost and longer service life compared to the integral end mill. Practical experience has shown that the method for processing end-face grooves can be widely promoted and adopted.
04 END
The end-face groove cutting tool and the bridge boring cutter body are combined to design and manufacture a special tool for end-face groove processing. Large structural parts’ end-face grooves are processed by boring on the CNC boring and milling machining center.
This method is innovative and cost-effective, with an adjustable tool diameter, high versatility in end-face groove processing, and excellent processing performance. After extensive production practice, this end-face groove processing technology has proven to be valuable and can serve as a reference for similar structural parts’ end face grooves processing on boring and milling machining centers.
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Post time: Sep-25-2024