Basic machining method of the hottest boring

2022-07-31
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Basic machining method of boring

1. What is the overhang boring method? What are its characteristics

answer: use the overhanging single boring tool bar to bore the coaxial holes with medium aperture and no through hole. This processing method is called overhanging boring method

the main features of overhang boring method are:

(1) the boring bar used for overhang boring is generally short, thick, rigid, and the cutting speed can be selected higher than the supporting boring bar, so the production efficiency is high

(2) it is convenient to clamp and adjust the tool on the overhanging boring bar, and it is also convenient to observe and measure during processing, which can save auxiliary time

(3) when the spindle feeding is used for cutting with the overhang boring method, because the boring bar is constantly overhang with the spindle feeding, the deflection of the tool bar system due to the change of self weight is also different. When machining long inner holes, the axis of the holes is easy to bend. Due to the continuous extension of the spindle cylinder body, the rigidity of the whole tool bar system is getting worse. During boring, the elastic deformation of the system gradually increases under the action of cutting force, which affects the boring accuracy of the hole and causes the cylindricity error of the machined hole

2. Try to describe the characteristics of overhang boring with workbench feeding. How does this boring method affect the accuracy of the machined hole

answer: when the worktable is used to feed the overhang boring; Since the overhang length of the spindle has been set before cutting, the bending deformation and elastic deformation caused by the dead weight of the tool bar system and the cutting force are relatively stable during the cutting process. Therefore, the axis bending and cylindricity errors of the machined hole are smaller than those of the spindle feed suspension boring. The main reason why this boring method affects the machining accuracy of other holes is the straightness error of the lathe bed and the guide rail of the workbench, as well as the fitting accuracy between them. If the bed guide rail has straightness error in the horizontal plane and vertical plane, it will cause straightness error of the axis of the machined hole and position error of the reference surface; If the fitting accuracy of the guide rail is poor, the roundness error of the machined hole will occur

3. What is the support boring method? What are its characteristics

answer: the support boring method is a cutting and processing method that uses the support boring bar mounted in the tailstock sleeve of the boring machine for boring

the characteristics of the support boring method are:

(1) compared with the overhang boring method, the rigidity of the boring bar is greatly enhanced

(2) suitable for machining coaxial hole system. It can be equipped with a variety of boring cutters with high precision, which can ensure the processing quality

(3) it is troublesome and time-consuming to clamp and adjust the boring cutter, and it is not easy to observe the processing conditions. The trial boring, measurement and other operations are not as intuitive and convenient as the overhang boring method

4. Try to describe the characteristics of boring method with boring bar feeding support. How does this boring method affect the accuracy of the machined hole

answer: boring with boring bar feeding support boring method. The extension length of the boring bar changes continuously with the spindle feeding, but the distance between the boring bar and the spindle at the two support points does not change. The distance between the two support points is shorter than that of the worktable feed support boring method. Therefore, the deflection deformation of the boring bar caused by the cutting force is smaller than the boring method of the feed support of the workbench, so it has good vibration resistance and can be processed with a wide knife. However, due to the boring bar feeding, the position of the boring cutter between the supports is changed, so the bending caused by the dead weight of the boring bar will affect the straightness error of the workpiece hole axis

5. Try to describe the characteristics of the boring method using the workbench feed support. How does this boring method affect the accuracy of the machined hole

answer: in this boring method, the distance between the two supports of the boring bar is very long, generally more than twice the hole length, because the workbench is used for feeding. The deflection deformation of the boring bar after being stressed is relatively large. When boring with this method, since the distance between the tool and the supports at both ends of the boring bar remains unchanged after the tool is adjusted, the aperture size is only uniformly reduced by a fixed value. The hole straightness error is mainly related to the straightness of the machine tool guide rail and the fitting accuracy between the machine tool guide rail and the guide rail of the hard worktable. The straightness error of the bored hole is small

6. Try to describe the main advantages and disadvantages of boring with a single head boring cutter. How to correctly select cutting parameters when boring with a single head boring cutter

answer: boring with single head boring cutter has the following main advantages and disadvantages:

(1) it has wide processing technology and can process holes that cannot be processed by reamer and reamer, such as through hole, step hole, cross hole, etc

(2) various deviations caused by drilling and reaming can be corrected. High machining precision, fine surface roughness, and can ensure the shape and position accuracy of the hole

(3) the use of cemented carbide inserts enables high-speed cutting and high production efficiency

(4) the main drawback is that there is too much time for tool adjustment and tool setting, which affects the improvement of production efficiency

when boring with a single head boring tool, the cutting depth and feed rate should not be too small. If they are too small, the tool head will be easily worn, so that the dimensional accuracy and surface roughness of the bored hole cannot meet the requirements

7. What basic technical requirements must be met before precision boring with floating boring cutter

answer: before precision boring with floating boring cutter, the boring must meet the following basic technical requirements:

(1) the straightness of the hole shall be good, and the surface roughness value shall be controlled within R α three point two μ M and it is required that there shall be no obvious tool feeding ripple on the hole wall

(2) the fine boring allowance shall not be too large and shall generally be controlled within 0.06~0.12mm

8. How to correctly select the cutting parameters to ensure the machining accuracy when the floating boring tool is used for fine boring

answer: the cutting depth during fine boring with floating boring cutter is generally 0.05~0.10mm; The feed rate is generally 0.3~0.7mm/r; Boring speed V can be converted into spindle speed per minute, generally 8~12r/min

9. Which positioning methods are commonly used when machining parts on boring machines? What are the characteristics of each

answer: when machining parts on the boring machine, the following four positioning methods are commonly used:

(1) marking, alignment and positioning, which is characterized by no special fixture and boring die; The production efficiency is low due to the addition of the scribing process; Low positioning accuracy

(2) positioning with positioning elements is simple and reliable; Complete set of process equipment is not required; Small positioning error; Low cost

(3) positioning by fixture is characterized by rapid workpiece positioning, reliable clamping and convenient processing. However, the manufacturing cycle of boring machine fixture is long and the cost is high

(4) use other forms of positioning, such as Jack and special cushion block, and use of process blocks on the workpiece for positioning. These methods have low positioning accuracy and low production efficiency

10. When machining hole system, what are the common methods to find the starting coordinate position of boring machine spindle? What are the characteristics of each

answer: when machining the hole system, the common methods for aligning the starting coordinate position of the boring machine spindle are:

(1) using the dial gauge measuring device to align and locate this method, you must first use the dial gauge centering device or positioning mandrel to determine the coordinates of the reference hole on the workpiece, and then determine the coordinate position of the spindle according to the coordinates of the reference hole. It is characterized by high precision and convenient operation

(2) alignment and positioning with inspection rod this method is characterized by low alignment and positioning accuracy and time-consuming alignment. However, this positioning method can directly find the coordinate position between the boring machine spindle and the starting hole

(3) this method can be used for boring the hole system of the separated box. The disadvantage is that the auxiliary time is long

(4) this method is characterized by simple template structure and no complex adjustment. However, the template is easy to deform, and when the workpiece needs to process several hole systems on different surfaces, several templates are required, and the alignment and positioning accuracy is also low. (end)

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