Using axial pulse vibration to improve the feed sp

2022-08-03
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Using axial pulse vibration to improve the feed speed of deep hole drill

in order to make the machining process reliable, it is necessary to produce short chips with the best chip shape for the deep hole drill (also known as gun drill) with a straight chip removal groove with internal coolant. This short chip can be reliably discharged from the chip holding groove of the tool. Especially when machining steel and long chip materials, this kind of tool can not use the highest feed speed because it often forms bad chips. Increasing the rotating speed can increase the feed speed, but it will increase the load of the tool, which will shorten the service life of the tool. In order to improve the durability of cutting tools, more and more coated deep hole drills are used. During machining, this kind of tool will produce chips with bad shape due to coating, which goes back to the original problem

in short: the machining efficiency of deep hole drills with straight chip removal grooves is limited by chip forming factors

through pulse vibration, we can make full use of the processing potential of deep hole drill. Therefore, we need to develop a reliable chip breaking device independent of tool geometry, so as to make full use of the potential processing efficiency of deep hole drill with straight chip removal groove, said Mr. Jurgen Deeg, director of the Laboratory of botek company (based in riederich). When the axial pulse vibrator is used and not used for deep hole drilling, the comparison of the generated chips (chip forming is related to materials) shows that the intended chip breaking purpose is achieved by using the axial pulse vibrator (Table 1)

figure 1 At present, the axial pulse vibrator manufactured by botek company can be used for deep hole drills with a maximum diameter of 4mm, while the large-size structure can be used for deep hole drills with a diameter of (4~12) mm

axial pulse vibrator (hereinafter referred to as pulse vibrator) is a device with low cost. It can be easily installed on the tool drive spindle, and can adapt to the service conditions of existing machine tools (such as 7:24 large taper, cylindrical handle, flange, etc.) according to the requirements of users. The pulse vibrator has two standard structures: the small-size structure is used for the deep hole drill with a maximum diameter of 4mm, while the large-size structure is used for the deep hole drill with a diameter of (4~12) mm (Fig. 1). The properties of these two standard structures are described in detail. Butyl rubber is mainly used in the tire industry as follows:

◆ small size structure:

tool diameter: max. 4mm; Maximum speed: 11000 r/min,

adjustable: the stroke can be adjusted by the user,

weight: 1.3 kg; Body diameter: 50mm; Length: 140mm

◆ large size structure:

tool diameter: 4mm~12mm; Maximum speed: 6000 r/min,

pre adjusted: stroke adjusted by the manufacturer,

weight: 4.4 kg; Body diameter: 70mm; Length: 160mm

if you need a device different from the two standard structures, you can ask the company. At present, a prototype is under development, and its structure size is much smaller than the standard structure

the reciprocating pulse motion of the tool promotes reliable chip breaking

when the processing equipment is running, the two kinds of pulse vibrators can make the deep hole drill realize the set reciprocating pulse motion in the drilling direction, so that the chip thickness increases and decreases from time to time. When the chip thickness is zero, the chip is forced to break. For the pulse vibration, a forming wheel is used to generate the mechanical pulse stroke, which is best adapted to the drilling process when the tool type, tool diameter, actual investment, product line expansion, new factories and other phenomena continue to occur: it is either pre adjusted by the manufacturer, or it can be adjusted on the vibrator for the small-size pulse vibrator

on the working principle of the pulse vibrator, Mr. Deeg explained that it is not percussive drilling here, but a set pulse vibration. The number of pulse strokes is always consistent with the spindle speed. In vibration, only the tool moves. During the process on the machine tool, the pulse movement is not measurable because the moving mass here is too small. Therefore, the adverse consequences such as the deviation of the spindle bearing to the machine tool are eliminated

reliable chip breaking in the process is helpful to improve the feed speed

pulse vibrator promotes reliable chip breaking in the process. Thus, when deep hole drilling is carried out for a tool with a straight chip removal groove, the machining capacity of the tool is improved and the production efficiency is improved. For example, the integral cemented carbide double-edged deep hole drill with a straight chip removal groove can also be applied to the processing of steel and materials producing growing chips without difficulty by using a pulse vibrator. A double-edged deep hole drill with a tool diameter of 6mm and a drilling depth of 45 x D mm. Under the condition of micro lubrication, the optimal feed speed VF can be as high as 1000 mm/min. If the pulse vibrator is not used, there is a typical chip forming problem due to the tool and workpiece materials. To achieve such a high feed speed, the process is not reliable

for single edge deep hole drilling with pulse vibration, it is also possible to significantly increase the feed speed. When the single edge deep hole drill (3mm in diameter) with integral cemented carbide structure is used to process steel (42CrMo4), the feed speed can reach VF = 400 mm/min without difficulty, and the process is quite reliable. For larger drill bit diameters, such as 8mm, when machining 16MnCr5 alloy steel, the feed speed can reach VF =800 mm/min. Here, the cooling and lubricating fluid commonly used in the single edge deep hole drilling process and its flow, pressure and temperature are also applicable to the single edge deep hole drilling with pulse vibration

Mr. Deeg emphasized: "compared with conventional deep hole drilling, we can significantly reduce the speed while increasing the feed speed during machining, reduce the cutting time and increase the favorable service conditions, and prolong the service life of the tool to varying degrees depending on the material of the workpiece."

in many tests, we have noticed that the high-efficiency deep hole drilling with pulse vibration can also obtain a good hole straightness as that of single edge deep hole drilling, explained Mr. Deeg, an expert. For the use of pulse vibrators, an accurate impact testing machine is used to confirm the corresponding relationship between the mass of the standard impact body and its impact energy; Deep hole drilling with at least 3 energy values in the energy section of the impact testing machine to be verified not only improves the process, but also has the general advantages of the single edge deep hole drilling process, such as good hole straightness, roundness and surface quality. High efficiency deep hole drilling with pulse vibrator can produce tiny burr similar to boring due to its special process parameters. This is just like the case of conventional deep hole drilling

for high-efficiency deep hole drilling with pulse vibration, the advantages can be obtained by using standard tools according to its frequency requirements. In order to achieve the highest machining efficiency, for example, the tool should be grinded to best adapt to the machining conditions

simple tool operation

compared with other tools used for efficient deep hole drilling, simple, fast and inexpensive tool edge regrinding is an important advantage of deep hole drilling with straight chip removal slots. Users only need to spend a very low cost even if they regrind the blade by themselves. It is also possible to give up the removal and recoating of tools, which results in significant cost and time savings, and reduces the number of tool turns

it can also be applied to machining centers

on all common deep hole drilling machines, the installation and operation of the pulse vibrator are effective, and there is no problem at all. For the machining center, it should be noted that the coolant of the high-pressure coolant centralized supply device can pass through the existing spindle. If people want to install an anti rotation device, it is necessary for the pulse vibrator to match the specific conditions of the machine tool. When applied to machining centers equipped with automatic tool change devices, taking into account the structural dimensions of pulse vibrators, it is recommended to use extraction tool change stations

botek's axial pulse vibrator improves the efficiency of deep hole drilling with a tool with a straight chip removal slot. Depending on the workpiece material and process parameters, the feed speed can be increased simply and at a low cost while maintaining the many advantages of the single edge deep hole drilling process with reliable process. (end)

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