The sinking of the saddle means that the saddle of the ordinary lathe is reduced in the correct position in the machine due to wear, resulting in a decrease in the position of the relevant components (middle carriage, knife holder, slide box), and even loss of normal working performance. A phenomenon. The sinking of the saddle not only makes the lathe lose its normal working performance, but also causes the precision of the workpiece to be processed to be reduced or even worse, and it will cause the working position of the longitudinal pinion on the slide box to change, and the angle α is inclined in the vertical plane, in the horizontal plane. Tilting the angle β causes the pinion and the bed rack to not mesh with the full tooth width, which not only accelerates the tooth surface wear, but also easily generates vibration due to the reduced contact rigidity, and the surface roughness of the workpiece to be processed is increased. When the saddle sinks seriously, the three bars (light bars, screw bars, and steering cymbals) cannot rotate, and even the longitudinal pinion gears are separated from the rack racks, which makes the machine tool lose its working ability.
1 Increase the longitudinal gear small gear displacement coefficient method When the amount of saddle sinking of the ordinary lathe is small, the position of the relevant parts related to the saddle (the middle carriage, the knife holder, the slide box) is decreased, but absolutely The smaller amount has less influence on the working performance of the machine tool. At this time, the meshing quality of the longitudinal cutter pinion and the bed rack has been greatly affected. There are three main aspects: First, the meshing height is small, which will accelerate the wear of the longitudinal gear pinion and the rack; When the saddle moves longitudinally, the starting impact is large, which increases the possibility of the rack and the longitudinal cutter pinion teeth being broken (toothing). Thirdly, when the hand crank is used for the longitudinal movement of the saddle, the handle is too idling and feels. not good. Therefore, it must be repaired. At this time, the method of increasing the longitudinal gear pinion displacement coefficient can be used.
Increasing the longitudinal travel pinion gear displacement coefficient method only needs to increase the longitudinal travel pinion gear displacement coefficient without changing the scale of the longitudinal movement dial.
The main technical parameters of several conventional lathe longitudinal cutter pinions are shown in Table 1.
The key to increasing the longitudinal gear pinion displacement coefficient method is how to determine the new displacement coefficient. Remove the ordinary lathe slipper box, wipe the A and B sides clean, and measure the h' value directly with the depth vernier. Note that the measurement position should be roughly near the center of the saddle.
Then there is a saddle sinking amount Δh: Δh=h-h' The saddle sinking amount Δh and the increased displacement amount should be equal, ie: Δh=Δx?
M∴Δx=(h-h')/m The relocation coefficient of the redesigned longitudinal cutter pinion is: x=x 0+Δx=x 0+(h-h')/m(1) where: x 0?? The displacement coefficient of the original design longitudinal cutter pinion is shown in Table 1.
Δh???The saddle sinking amount h??? The original design theoretical value, the value of which is shown in Table 2.
h'???measured value m??? The modulus of the original design longitudinal cutter pinion, the value of which is shown in Table 1.
Δx??? should be increased to become a coefficient.
When x>0.5, it is not advisable to increase the longitudinal gear pinion displacement coefficient method.
2 increase the number of longitudinal gears and small gears. The lathe of ordinary lathes has a large amount of sinking. It has certain influence on the three bars (light bars, screws, and steering cymbals), but the cutting process has little effect. The redesigned longitudinal knives are small. When the gear displacement coefficient x>0.5, it is not advisable to adopt the method of increasing the longitudinal cutter pinion displacement coefficient method. At this time, the method of increasing the number of teeth of the longitudinal cutter pinion should be adopted. Increasing the number of teeth of the longitudinal cutter pinion often requires proper displacement of the new gear.
Preparation and measurement methods are the same as before.
The original design longitudinal cutter pinion index circle diameter is: d = mz 0 + 2mx 0 set: x 1 is the displacement coefficient of the newly designed longitudinal cutter pinion.
z' is the number of teeth added.
The diameter of the index circle of the newly designed longitudinal cutter pinion is: d'=m(z 0+z')+2mx 1∴Δh=h-h'=(d'-d)=m(z 0+z')+2 mx 1!
"-(mz 0+2 mx 0
$) After finishing: x 1=x 0+Δh/m-z'/2(2) Obviously, the displacement coefficient of the newly designed longitudinal cutter pinion consists of two parts, one part is “increasing the longitudinal cutter pinion†The coefficient of the displacement coefficient method becomes: x=x 0+(h-h')/m When x≤0.5, the method of increasing the longitudinal gear pinion displacement coefficient should be adopted; when 0.5<x≤2 When increasing the number of teeth of the longitudinal cutter pinion, check the corresponding new number of teeth z' according to Table 3. When x>2, the machine tool performance is often lost due to the too large amount of bed saddle sinking. The recovery bed saddle height method is adopted.
The other part is the adjustment of the displacement coefficient of the newly designed longitudinal cutter pinion.
∴ (2) becomes: x 1=x-z'/2(3) The x value is calculated by the formula (1), and the z' value is obtained from Table 3, and the number of teeth of the newly designed longitudinal cutter pinion is :z=z 0+z' Calculate the value of x 1 from equation (3), which is the value of the displacement coefficient x 1 of the newly designed longitudinal cutter pinion.
After increasing the number of teeth of the longitudinal cutter pinion and increasing the number of teeth of the longitudinal cutter pinion, the original design longitudinal cutter scale device is invalid due to the faster cutter speed, and the dial scale must be redesigned.
The vertical lathe dial of a conventional lathe is generally 300. The number of grids turned by the dial is proportional to the number of teeth of the pinion, so there are: n:z=300:Z 0 The number of the new dial scale n is: n=300×Z 0(5)3 Recovery bed height method When the equipment is overhauled, the saddle sinking is severe, or x>2, the above two methods are obviously not applicable, and the height of the saddle must be restored. Although the restoration of the saddle height method is more complicated, it is the fundamental method to solve the problem of sinking the saddle.
To restore the bed saddle height method, it is necessary to repair the bed rails and the fine planer saddle lower rails. After the bed rail is ground and the bed is polished, the h' is measured and Δh=h-h' is obtained. Since the bed rail adopts a "mountain-flat" type structure, the vertical component of the sinking amount of Δh on different rail faces is different. The vertical component of the sinking amount on the flat rail surface is Δh. The mountain type guide rail has 90° symmetrical and asymmetrical forms, and the 90° symmetrical guide rail is most commonly used. The vertical component of the sinking amount on the two rail surfaces of the 90° symmetrical mountain rail is equal, that is, S=Δhsin 45°=0.707Δh(6)90° The vertical components of the sinking amount on the two rail surfaces of the asymmetric mountain rail are not equal. The vertical component on the narrow guide surface is: Sa = Δhsin 25° = 0.423 Δh (7) The vertical component on the wide rail surface is: S b = Δhsin 65 ° = 0.960 Δh (8) Restoring the saddle height, actually It is to eliminate the vertical component of each of the above sinking amounts.
Generally, the radiation-grafted polytetrafluoroethylene (referred to as filled F 4) is used as the main material, and the wear-resistant adhesive (commonly known as AR double-tube adhesive) is bonded to the lower rail of the saddle, and the saddle height can be restored to obtain satisfactory results.
The process of restoring the bed saddle height method is: (1) grinding the bed rail to repair the bed rail according to the standard of the lathe bed guide precision, to restore the accuracy of the guide rail, the smaller the grinding amount, the better, otherwise the rail surface will be The hardened layer causes damage. If the guide rail wears seriously, the grinding amount exceeds 0.5mm, and the surface is quenched after grinding.
(2) The planer saddle rail first grinds the upper dovetail rail of the saddle to restore the accuracy, then flips the saddle 180°, the lower rail faces up, and the dovetail rail surface as the reference, the planer saddle rail. When planing, the left front side of the saddle (the most severe wear) can be cut to minimize the amount of shaving. The relative values ​​of the mountain-flat rails should refer to the original design data.
(3) Measurement 1) Use the bridge and level measurement method to place the lathe bed horizontally; 2) wipe the bed and the saddle rail surface with oil washing and wiping cloth; 3) fasten the bed saddle to the bed On the guide rail, measure the joint gap at both ends (six places) with a feeler gauge, and insert the 20 mm with a 0.05 mm feeler gauge. A light hammer on the bed saddle should not have a "empty" feel; 4) a h' value is measured with a depth vernier with an accuracy of 0.02 mm.
(4) Determine the height to be restored According to the h' value, determine the height dimension of each rail surface to be restored according to formulas (6), (7), and (8), and select the corresponding bonding thickness.
(5) Bonding and filling F4, restoring the height of the saddle 1) Cleaning the lower rail surface of the saddle with acetone; 2) Separating the two pairs of AR double-tube adhesives of A and B according to the volume of about 1:1 in a clean steel plate Or evenly spread on the glass plate, respectively applied to the filled F4 surface and the saddle rail surface of a certain thickness cut according to the size of the guide surface. The thickness of the adhesive layer is about 0.05-0.1 mm, the rubber layer must be even, naturally dry, waiting for compaction. Curing; 3) Applying oil on the bed rail and attaching the newspaper; 4) Turning the saddle that is naturally open for about 15 to 30 minutes and pressing it 180° on the rail of the bed for bonding, pay attention to its own weight. Add a certain weight (about 100 ~ 200kg), press tight, after 36 ~ 48h, turn the saddle over, scrape the bottom corner of the F4 surface, hit the oil hole, avoid opening the oil tank, avoid tearing. The scraped and discarded F4 layer is about 0.02~0.05mm, and the corresponding precision requirements are met.
Because the graft filling F4 has the advantages of small friction coefficient, oil content, soft texture, anti-vibration, wear resistance, and absorption of tiny dust particles, the use of this method greatly improves the working performance of the machine tool and slows down the saddle sinking. speed.
4 Conclusions In the daily repair and the saddle sinking is not serious, there is no need to repair the machine guide rails. It is usually possible to change the technical parameters of the longitudinal cutter pinion and the longitudinal movement of the dial scale on the slide box to improve the longitudinal cutter pinion. The repair effect of the method is limited, but it has the advantages of simple and easy operation, less technical difficulty, short repair period and low repair cost. For daily maintenance, it can be used to increase the vertical. The method of shifting the pinion gear displacement coefficient or increasing the number of teeth of the longitudinal cutter small gear; when the saddle sinks seriously, or when the machine tool is overhauled, the method of restoring the height of the saddle is adopted.
(Finish)
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