The workbench is the key core component of the cycloidal gear grinding machine, and its machining accuracy directly affects the overall accuracy of the machine tool . The previous period has been processed on the coordinate boring machine, but because the product is a small batch production, the cycle is short, the processing task on the coordinate trampoline is extremely heavy. In order to solve this problem, the author relies on many years of processing experience in the ordinary trampoline T611C. The machining of this workpiece was completed.
Workbench parts drawing
In this part of the workbench (see photo), there are three sets of holes required to be processed: 1 worm mounting hole, front end f92H7, rear end f (72 ± 0.01) mm, required to be parallel to the bottom surface 0.01mm, and the center distance of the worm wheel is (232 ± 0.02) mm. 2 drive shaft mounting hole, front end hole is f95H7, rear end hole is f (72±0.01)mm, requirement is 0.01mm parallel to the bottom surface, 0.01mm parallel to the center of the worm, 0.03mm position tolerance from the upper end surface of the worm wheel and the center of the worm wheel . 3 Motor drive shaft mounting hole f100H7, parallel to the axis of the 2 hole, required to be (108.75 ± 0.03) mm. The outer surfaces of the workpiece have been machined, the worm wheel hole has been machined to the size requirements, the end face has been scraped to the fourth level, the worm seat joint surface has been scraped to the fourth level, and the bottom surface has been scraped to the fourth level as the assembly reference and design basis. Each hole has a margin of about 5mm, and it is mainly required to process each hole and the end face of the hole to the technical requirements of the pattern.
There are many factors that affect the machining accuracy of the hole system in actual machining. Now, in the specific boring machine processing, several major problems affecting the processing quality of the hole system are analyzed.
(1) Influence of the deformation of the mast due to the poor rotation accuracy of the T611C, only the cantilever bore can be selected. During the cantilever boring process, it will be subjected to the cutting torque, the cutting force and the weight of the mast. The rod produces elastic distortion, which mainly affects the surface roughness of the workpiece and the life of the cutter ; the cutting force and the self-weight cause the elastic deformation (flexure deformation) of the mast, and the influence on the machining accuracy of the hole system is particularly serious.
(2) Influence of machine feed mode There are two feed modes for the bore: one is the direct feed of the mast, and the other is the feed of the table on the machine guide rail. The influence of feed mode on the machining accuracy of the hole system has a great relationship with the hole punching method. When the mast and the machine tool spindle are floatingly connected with the die hole, the feed mode has no obvious influence on the machining accuracy of the hole system; When the rod and the main shaft are rigidly coupled to the cantilever bore, the feed mode has a great influence on the machining accuracy of the hole system.
When the cantilever is directly fed by the mast, as the mast is continuously extended during the boring process, the deflection of the tool tip becomes larger and larger, and the hole to be processed becomes smaller and smaller, resulting in cylindricity. Error; similarly, if the hole is directly fed into the processing coaxial line, the coaxiality error will be caused. Conversely, if the mast is extended in length and fed by the table, the deflection at the tip of the tool is unchanged during the boring process (assuming the cutting force is constant). Therefore, there is no influence on the geometric accuracy of the hole to be machined and the mutual positional accuracy of the hole system.
However, when feeding with the table, the straightness error of the machine guide rail will cause cylindricity error in the hole to be machined, causing coaxiality error in the hole on the coaxial line. The parallelism error between the machine guide rail and the spindle axis causes the cylindricity error of the hole to be machined; in the section perpendicular to the axis of rotation of the mast, the hole to be machined is a perfect circle; and in the section perpendicular to the feed direction, the hole is machined Is an ellipse. However, the resulting cylindricity error is extremely small in general and can be ignored. For example, when the machine guide rail and the spindle axis are inclined by 1 mm at 100 mm, and the machined hole having a diameter of 100 mm, the roundness error is only 0.005 mm. In addition, the matching clearance between the workbench and the bed rail has a certain influence on the machining accuracy of the hole system, because when the table is fed in the forward and reverse directions, it is usually in contact with the guide rail at different parts, so that the workbench will follow The change of the feed direction is yawed, the larger the gap is, the heavier the work table is, and the larger the yaw amount is. Therefore, when the coaxial hole system is used, the coaxiality error is generated; when the adjacent hole system is used, the hole distance error and the parallelism error are generated.
It can be seen that it is easier to ensure the processing quality of the hole system than the mast feeding by feeding the worktable and adopting a reasonable operation mode. Therefore, in the general overhanging bore, especially when the hole depth is greater than 200 mm, the table is mostly fed.
(3) Influence of cutting force and clamping force When roughing, a large amount of cutting heat is generated. The same heat is transferred to the different wall thicknesses of the tank, and different temperature rises occur. Therefore, after roughing, the workpiece is sufficiently cooled before finishing to eliminate the influence of thermal deformation on the workpiece.
If the clamping force is too large or the force point is improper in the pupil, clamping deformation is likely to occur. When the box body is machined, if the clamping force acts on the machining hole, the hole of the blank is deformed, and the hole is rounded after the boring. After the clamping is released, the aperture is elastically restored and deformed, and the roundness error is generated in the machined hole. Similarly, the clamping deformation of the casing will also affect the mutual positional accuracy of the holes. In order to eliminate the influence of clamping deformation on the machining accuracy of the hole system, the clamping force should be appropriate when it is fine, and should not be too large; the force point should be selected at the real point.
Through the above analysis, combined with the actual situation, the cantilever boring is used in the processing, the table is fed, and the rough finishing is combined. The corresponding process measures are used to ensure the machining accuracy. The worm seat is not removed and directly combined with the workbench. Processing on the top. The specific processing process is discussed below.
(1) Adjustment of equipment The operation accuracy and rigidity of the trampoline and the wear in long-term use will directly affect the processing quality of the workpiece. Therefore, the necessary adjustments must be made to the machine during the finishing process. Specifically, the adjustment of the sliding seat, the upper sliding seat, and the spindle box are adjusted properly; the tension of the motor belt; the clearance of each clutch; the clamping screws of each pressure plate, and the geometric precision of the machine tool together with the mechanic Inspect and adjust to meet the machining accuracy requirements of the part.
(2) Processing of the workbench According to the original process, the remaining amount of each hole is 2mm from the ordinary boring machine, and then the precision is processed by the coordinate boring machine to the process requirements. Now that the two processes are combined, it is necessary to ensure that the parts are not deformed due to excessive cutting force or excessively high processing temperatures. The measures taken include: small cutting amount, multiple infeeds; sufficient cooling, and then finishing; appropriate pressing force, after roughing, the loose pressing plate restores the elastic deformation caused by the clamping, and then the smaller The clamping force clamps the workpiece.
This workpiece has two clamping positions during processing. For the first time, the bottom surface of 655mm is placed on the surface of the boring machine. The f190mm worm wheel hole and the mounting surface face the boring machine spindle. Since the upper surface is guaranteed to be parallel to the bottom surface by 0.01mm during the processing of the previous process, it is directly corrected by the dial gauge. The surface is perpendicular to the horizontal direction and has a tolerance of 0.01 mm or less. The reaming worm seat joint surface is within 0.01 mm in the horizontal direction. Press the workpiece to correct the center of the f190mm inner hole, the height is not moving, move the machine table to the left and right, and do it on the ribs.
Two holes of f10h6 require drill, boring and hinge to ensure that the joint surface with the worm seat is parallel to 0.01mm. Loosen the plate and perform the second clamping.
The second time, repair the 470mm underside burr with oil stone, place it on the table top under 470mm, the end face of f95mm hole to the main shaft, correct the top of the table, within 0.02mm tolerance of the direction of the bed rail and the direction of the sliding seat, you can add on the bottom surface. The padding paper is leveled, and the f10mm measuring rod is installed in the two f10mm process holes, and the working table is moved along the direction of the bed rail. The side tolerance of the two measuring rods is within 0.01 mm. Clamp the platen at the four mounting hole locations of the part. This clamping allows the process reference to coincide with the assembly and design basis to ensure machine assembly accuracy. Use the dial indicator to find the center of the f10mm rod to determine the center of the worm wheel. There is one point to note here: that is, the spindle box must be locked when looking for the center, so as to eliminate the gap between the headstock and the bed column. The spindle headbox is also locked at the time of boring, so that the hole pitch error can be avoided. Next, take the standard block, move the headstock down 205.393mm from the worm wheel mounting surface, and move the upper table 127.28mm to the left to determine the center of the (1) group. The semi-precision f95mm hole and the f72mm hole have a remaining amount of 0.7mm, 镗f138mm hole to the size, and the bottom of the hole has a remaining amount of 0.2mm. The remaining holes are finished by semi-finishing. Make each flat hole to the size, leaving a 0.2mm margin on the bottom of the hole. During processing, several problems should be noted: when moving the machine table, move from left to right in one direction, do not move back and forth to avoid the hole spacing error caused by the table gap; if both ends of the hole are blank, before the hole Chamfering prevents damage to the tip during boring. Loosen the plate, the workpiece does not move, the isothermal temperature is about half an hour, moderately compact, re-correct the workpiece and the center of the worm wheel, and use the universal boring head to flatten the bottom surface of the hole. The remaining pupils are left with 0.1~0.15mm margin, and the holes are machined into coarse and fine hinges to meet the size requirements. Here, one thing to note is that the headstock is moved upward by 0.03mm at the original center height when the rear end is f72mm hole. The purpose of this is to overcome the parallelism error caused by the mast overhang. This was confirmed in later tests.
(3) Selection of tools during machining Due to the self-weight and cutting force of the mast, the deflection caused by the deformation has a significant influence on the geometric accuracy of the holes and the mutual positional accuracy. Therefore, it is necessary to select a suitable mast when boring, which is not too thin, too thin and not good in rigidity; nor too thick, too thick and too heavy. After practice, the mast of f50 ~ f60mm is adopted. The use of new types of boring tools ceramic, a material easy to wear such tools have high hardness, so that in processing ensures the dimensional stability of the holes, indirectly improve the processing efficiency. In addition, in the finishing process, the cutting amount should be selected as basically as possible to reduce the influence of cutting force.
In summary, as long as we are in the processing of the box parts, fully consider the various influencing factors, adjust the machine tool , use the appropriate tool , careful operation, precision measurement , and complete the finishing of the box parts on the ordinary trampoline. To make it meet the requirements of the pattern.