In this chapter, we will select the corresponding machining tools for each machining element of a typical part in Figure 7-1. The workpiece is made of 45 steel quenched and tempered, and the machining allowance on one side on the shape is
3mm, the use of machine tools for vertical four-axis linkage machining center, rigidity is sufficient. The production scale is medium volume production.
Determine the milling cutter type
The maximum size of the workpiece plane milling is 150mmx250mm, in the method of greater than or equal to the diameter of the second gear of the milled plane (see Fig. 1-30 and related text), the first gear is 160mm, the second gear is 200mm, so the selected milling cutter diameter is 200mm. From the illustration of the tool sample on the selection of face milling cutters (see Fig. 7-2), there are a total of nine cutters in the preliminary range: F2010, F2260, F4033, F2265, F2146, F4045, F4047, F2250 and F4050. Fig. 7-3 shows a partial list of the nine types of milling cutters that are recommended for machining steel, cast iron, and non-ferrous metals. Among these four types of milling cutters, the F4033 is the first recommended for machining steel, while the actual options are F4033 (45° entering angle), F2265 (60° entering angle) and F2010 (about 15° ~ 90° entering angle). Since the F2010 is a modular milling cutter (see Figure 2-89), many angles can be selected in practice.
According to the method of selecting the entering angle described above, the 45° entering angle is relatively balanced in terms of cutting force distribution, and the F4033 with a 45° entering angle is selected here.
Why not choose the F2010, which also has a 45° entering angle? The following is a flowchart for deciding whether or not to choose a modular tool, as shown in Figure 7-4. On a medium-sized scale, it is better to use non-modular tools for face milling on a single machine. For this reason, the F4033 milling cutter with a diameter of 200 mm was chosen.
The selection cutter head is shown in Figure 7-3, and the F4033 cutter with a diameter of 200mm is shown in Figure 7-5.
There are three types of F4033 milling cutters with a diameter of 200mm in Figure 7-5, and the difference is in the number of teeth, which are 10, 18 and 26 teeth, which are coarse, medium and close (see Figure 2-22 and related descriptions for the related concepts of coarse, medium and close teeth). Considering that the medium tooth milling cutter takes into account the metal removal rate and cutting stability, the medium tooth milling cutter is selected, that is, the milling cutter disc is: F4033. B60.200.Z18.06
Select the blade
Next, let's choose the blades mounted on this cutterhead. Figure 7-5 In the rightmost column is the condition that must be met for the mating blade: SN. X 1205
Select the appropriate insert from the information of the inserts that are matched to the F4033 milling cutter (see Figure 7-6). The steps for selecting the inserts are as follows: Step 1: Find the material to be machined from the table of materials in Figure 7-7.
The material group code P2 for 45 steel (corresponding Germany grade C45) in the table of materials is shown in Figure 7-8, please keep in mind this group.
Step 2: Select the processing conditions. According to the given condition of "rigid sufficient", see blue frame; This processing does not require a long overhang, and the processing conditions can be determined by a short overhang, as shown in the red box, and the symbol at the intersection of the two is "heart" (see Figure 7-9), which will also be used later. Step 3: Select a processing method, as shown in Figure 7-10. This step has been completed earlier, and the tool is determined to be F4033. B60.200.Z18.06. Step 4: Select the insert grade and geometry (see Figure 7-11). At the same time, it is necessary to pay attention to the processing conditions (step 2) and the material to be processed.
According to the P2 group of the material to be processed in step 1, the symbol "heart" of step 2, the optional material in Figure 7-6 is WKP25, and the corresponding optional blade model (excluding material) is:
SNGX120512-F57SNMX120512-F57SNGX1205ANN-F57SNMXI205ANN-F57SNGX1205ANN-F67SNMXI205ANN-F67SNMXI20512-F67SNMXI20520-F57
In these models, the set on the left is G-level accuracy and the right group is M-class accuracy. G-level accuracy generally belongs to the grinding of the periphery of the blade, which has higher precision, but the general price is slightly higher: M-level accuracy is some of the peripheral direct sintering molding without grinding, and the accuracy is limited, but the price is relatively low. In addition to the occasions with relatively high precision requirements, the general milling with M-level precision will have a relatively high cost performance. Other blade accuracy level knowledge has been discussed in Figure 3-82 of Chapter 3 of "Full Diagram of CNC Turning Tool Selection", and you can check what you need to know. In this case, M-level accuracy is selected. Of the five insert models with M-class accuracy, three are inserts with rounded corners of 1.2mm and 2mm rounded, and the other two are inserts with wiper blades. Inserts with wiper blades produce a higher level of surface quality, but they need to be used at specific entering angles. The blade code standard (the international standard is IS05608:2012, and the current standard in China is GB/T 5343.1-2007) is shown in Figure 7-12. It replaces the two digits that originally represented the tip fillet with two letters, the first of which represents the applicable tool entering angle, e.g. in this case the milling cutter with a 45° entering angle selected, this symbol must be "A", and the second is the relief angle of the wiper edge (which should be the secondary cutting edge in principle). In order to obtain a good surface roughness grade (i.e., a small surface roughness value), choose an insert with a wiper edge, i.e. the code for the insert size part is 1205ANN In terms of cutting edge structure, both F57 and F67 have a rake angle of 16° (see Figure 2-65), and the rear structure is exactly the same, the difference between the two is the front edge structure (see Figure 2-77 and its introduction for details).
The difference between the two geometries is the sharpness of the cutting edge, the F67 is sharper than the F57, the cutting force is slightly smaller, and the tendency to vibrate is also slightly less; On the other hand, the F57 has a slightly stronger edge passivation, which makes it less likely to chip, and is more secure. But overall, the gap between the two is very small. Since the known condition is that the rigidity is sufficient, the geometry of the F57 was chosen.
At this point, the model of the blade has been selected, that is, the blade model is:
SNMXI205ANN-F57 WKP25 This insert has an M-level accuracy and is suitable for wiper edges with a 45° entering angle and a b-number of 1.5mm, with a rake angle of 16° and a medium degree of passivation.
Step 5: Select the cutting data (starting value). Select the cutting data according to Figure 7-13. There are guidelines like the one shown in Figure 7-14 in the sample. Among them, the relevant information of the F4033 milling cutter is enclosed, and the page number of the cutting parameters of the specific milling cutter is located in the red box (F119 in the figure is the page number of the figure on the sample).
Figure 7-15 shows a partial enlargement of the cutting data. On this figure, it can be seen that the quenched and tempered unalloy steel with a carbon content between 0.25% ~ 0.55% (45 steel with a carbon content of 0.45%), the cutting speed when using WKP25 material is 255m/min when the ratio of the cutting width a and the milling cutter diameter D is between 1/1 and 12 (in this example, a, 150mm, D. is 200mm, a./D is 0.75). Next, select the starting value of the feed per tooth. Figure 7-16 is a part of the selected feed page (due to the page relationship, we have truncated the processed materials such as stainless steel, cast iron, non-ferrous materials, difficult-to-machine materials, hard materials, etc., as well as other milling cutters such as F4080, F2146, and F2233).
According to the selected insert is SN.X1205ANN (the actual model is SNMX1205ANN), the initial feed per tooth for machining unalloyed steel is 0.25mm, and the correction factor is 1.0 when A/D. is 0.75, and the actual initial feed per tooth is determined to be 0.25mm/z.
For cooling, the tool does not have an internal cooling channel (see note below Fig. 7-5) and dry cutting is also recommended first in the cutting speed recommendations (see blue box in Fig. 7-15). At this point, the face milling cutter is selected, and the result is: milling cutterhead: F4033. B60.200.Z18.06 Milling cutter insert: SNMX120SANN-F57 WKP25 Starting cutting data:
Cutting speed: 255m/minCutting depth: 3mm (given conditions) Feed per tooth: 0.25mm/z Cooling: Dry cutting
It is recommended that the cut-in method is arc cut-in.
