1 the introduction
Hole machining technology is an important link in metal cutting, precision deep hole machining is the most important.
Traditional heavy machinery is gradually replaced by hydraulic machinery, and the process of this replacement largely depends on the processing technology of the key parts of hydraulic parts, the processing accuracy of hydraulic valve hole directly affects the performance, life and use of the product.
Therefore, to intensify the exploration of novel valve hole processing methods, and has been used in the production of some methods analysis, research, do consciously and accurately popularize the application, so as to make valve hole processing more rationalization.
The valve hole and the valve body precision match, the clearance between 0.005 ~ 0.015mm, the valve working pressure up to 21 ~ 35MPa, the valve hole diameter D1 is generally in the range of<10 ~ <41mm, the valve body length between 70 ~ 300mm, the length to diameter ratio of the maximum 11∶1, the valve hole size accuracy H6 ~ H7, cylinder requirements 0.003 ~ 0.00 5mm, surface roughness Ra0.2.
The dimensional accuracy, geometric accuracy and surface roughness of valve holes are the main factors affecting the quality of products. How to ensure the requirements of product precision and grasp reasonable processing means is very necessary.
2. Hydraulic valve hole processing scheme.
Reasonable process plan is based on the production program, precision requirements, blank condition, workpiece material, aspect ratio, equipment conditions, tool manufacturing capacity and supply conditions and other related factors to develop. At present, the domestic hydraulic valve hole processing has the following several schemes :A. drilling - reaming - boring - reaming - push - research B. Drilling - reaming - boring - hinge - research C. Drilling - boring - boring - hinge - research (honing) D. Expanding - boring - boring - hinge - research (honing) E. Drilling -- Rigid boring and reaming -- Research (honing) F. Drilling -- Rigid boring and reaming -- Diamond reaming G. Expanding -- Rigid boring and reaming -- Diamond reaming H. Drilling -- reaming -- reaming -- honing -- diamond reaming I. Drilling -- reaming -- boring -- reaming -- rigid boring and reaming -- diamond reaming J. Boring - Boring - Reaming - Diamond Reaming
For different specifications of the valve hole processing, before determining the program, first of all to comprehensive analysis of the influence factors, and then adopt a more reasonable process route.
The usual process schemes are D, G and J. The above three schemes all have their own processing characteristics and application scope. The following is an analysis of their use.
2.1 Boring -- Boring -- Hinge -- Research (vertical honing)
This processing scheme is applicable to a wide range of traditional use of processing routes, especially suitable for larger specifications of blank, valve hole is greater than<30mm valve body processing using this processing scheme.
Boring and boring and reaming are usually completed at one time in ordinary hexagon lathe or machining center. The reaming removal allowance is large. The use of double-edged drilling and reaming plays the role of finding straight valve holes.
Through the above process, the size precision of the hole can reach more than 0.02mm, the geometric precision can reach 0.003 ~ 0.005mm, and the surface finish can reach RA0.8 ~ 0.4, which lays a good foundation for the final honing, and the precision of the hole after honing can completely meet the product requirements.
2.2 Expanding -- Rigid boring and reaming -- Rigid boring and reaming -- Diamond reaming
The above technology belongs to mature technology. After reaming, the valve hole is semi-finished by rigid boring and reaming technology, and then honed with diamond reamer.
Its basic characteristics are suitable for the hole with large ratio of length to diameter, especially for the processing of the multi-way valve hole of the chip type, good stability, and the rigid boring reamer before and after the guide to ensure the straightness of the workpiece requirements, coupled with the internal cooling chip discharge, greatly improved the processing conditions, to ensure the surface finish requirements.
After boring and reaming, the surface roughness is RA1.6 ~ 0.8, the geometric accuracy is higher than 0.005, and the workpiece size can reach the precision of 6 grades. Diamond hinge is a new technology, but has been widely used in our factory, it as the final machining process played a very good control effect on dimensional accuracy, requirements for equipment is very low (because it belongs to float processing), but higher requirements on the working procedure, and the rigid boring hinge have this ability, so they are used to make processing and economical and practical.
Because the rigid boring and reaming equipment belongs to the special machine, the rough and fine boring and reaming process can not be completed at one time, and the inner hole cutting groove can not be completed in this equipment, and the rotary diameter is limited, which restricts its application, and the processing of porous valve body and large size valve is not suitable for using this process route.
2.3 Boring -- Boring -- Reaming -- Diamond Reaming
The traditional process route, through the technological innovation of some processes, used for advanced equipment, has played a very good role indeed, no matter the processing quality, or processing efficiency has reached a higher level. In the processing process of the machining center, the fine boring process with shock proof fine tuning boring tool bar boring, processing length to diameter ratio of close to 10 holes, cylindricity can be controlled within 0.005mm. In the process of processing the valve body on the CNC lathe,
First, the boring reamer technology for ordinary reamer, rigid and flexible combination, not only improve the quality of the product, but also extend the service life of the cutter;
The second use of trapezoidal reamer instead of ordinary reamer, from the cutting force aspect to find a way, also played a role in stabilizing the straightness, by a better effect.
Design and use of several typical cutting tools
3.1 Rigid boring reamer
Figure 2 rigid boring cutter is the characteristic of the reamer is: boring ream and squeezed together, cutlery front end more than 45 ° Angle of cutting edges, as most cutting allowance of boring tasks, 3 ° Angle and coarse hinge things that the cylindrical part of calibration, carbide plays a role of guidance, supporting and extrusion guide block, coolant flow from inside the tool to the rake face, good cooling effect . Rigid boring reamer is suitable for hole processing of cast iron. The tool has good wear resistance and long service life.
3.1.1 Guide bar length selection: according to the valve hole length selection,
Generally, when processing hydraulic valve holes, the guide block length should be at least more than three oil channel steps, so as to play a good guiding role.
3.1.2 Selection of the number and distribution of guide blocks:
Rough boring and reaming, cutting task heavy extrusion component is small, so the guide block with two, and a guide block is on the cutting edge, plays a good guiding role; In fine boring and reaming, the cutting component is small, the extrusion task is heavy, and three guide blocks are set, and the distribution is basically uniform.
3.2 Step reamer
The cutting part of the reamer is ground into three ring segments, each segment is 3 ~ 4mm long. The diameter of the first ring segment is 0.15mm smaller than that of the second ring segment. The diameter of the second ring segment is 0.15mm smaller than that of the third ring segment. Compared with the ordinary reamer, the ordinary reamer is cut once and the chip is thin and wide, while the ladder reamer is completed in several times and the chip is thick and narrow, so the cutting force is significantly reduced, the cutting is light, the cutting deformation is small and the surface finish is improved.
Step reamer has the following advantages:
Simple manufacturing; The annular segment plays a better guiding role in the cutting process and improves the stability. There is no variable cutting force on the axis of the reamer to ensure that the reamer can move correctly along the axis; Suitable for large allowance of hinge; It can straighten the partial bottom hole.
3.3 Diamond reamer
Using nickel or resin as binder, diamond particles are plated on the cutter body and polished. Diamond reamer is a kind of multi - edge particle cutting. During the hinging process, the chips are hidden between the diamond particles and are flushed out by coolant and spun at high speed. As the final process of hydraulic valve hole, the geometric accuracy can be improved to 0.002mm, the surface roughness can reach Ra0.2, and the processing diameter of the hole is consistent, so as to achieve the best match with the valve core. It has been widely used in valve hole processing.
Prospects of valve hole processing technology
With the continuous development of technology, the hydraulic parts precision demand is higher and higher, foreign body with valve core are often used interchangeably, completely and not as a unit assembly, so that the body of the machining accuracy raised several levels, in this case, the coarse fine two honing, honing technology and the original floating into rigid, honing machine guide, this is not only a process of innovation, with It is also a new development of digital control equipment. In addition, as the final processing process of hole, ultrasonic honing is more and more widely favored by people. It is not only convenient to operate, but also has high processing accuracy. It is a hole processing method worthy of promotion.