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What is cylinder boring?

Cylinder boring

Dry boring cylinder liner is excessive wear of the more common methods of repair. To replace the wet cylinder main piston – group liner repair mode. Computing

(1) the amount of boring. When the repair cylinder number determination, matching similar to a piston, is then calculated according to the amount of boring cylinder diameter and piston diameter. Piston and the cylinder with the gap 0.03mm suitable gasoline, diesel 0.15mm mill jar balance 0.02-0.04mm, boring an amount calculated by the following equation:

= amount of boring a maximum diameter portion of the piston skirt -. the minimum diameter of the cylinder piston and the cylinder with the gap + – Honing balance

(2) cylinder boring machine. Cylinder boring equipment used, there are two, fixed and mobile cylinder boring machine cylinder boring machine, since the mobile cylinder boring machine accuracy, low efficiency, has been replaced by a fixed cylinder boring machine.

(3) selecting a reference for positioning cylinder boring. In order to ensure quality cylinder boring in the operation should be noted first of all locating datum choice. Select positioning reference cylinder bore purpose is: to ensure the boring of the cylinder, each cylinder with the center line of the crankshaft main bearing hole center line in a plane and perpendicular to each other. Fixed cylinder boring machine to both main cylinder housing bore and the cylinder bottom surface for positioning the front and rear upper opening reference, which cylinder boring relatively high accuracy.

(4) determining the center of the cylinder boring. There are two concentric center given cylinder method and the eccentric method. Statutory concentric central portion is in an unworn centering cylinder, each cylinder can ensure the boring center line and center line of the same original. Statutory eccentric center is the largest in the wear parts of the centering cylinder, the cylinder axis is offset boring. The method of positioning a stationary cylinder boring machine is mounted on the boring bar in the centering rod performed. Centering rod is adjusted by a screw to a position corresponding to the cylinder diameter, and then the boring bar protrudes into the stepped portion of the cylinder ports is not worn (such a step is scraped cylinder port, the cylinder piston stroke needed to lower portion positioned below), the centering ball rod end of the cylinder from the top surface of 3-4mm. Where a uniform rotation of the boring bar to check the centering rod in contact with the surface of the cylinder. When the centering rod and cylinder wall is equal to four weeks gap, that is already very center.

In actual production, in order to reduce the amount of each cylinder boring boring, the method also eccentric to the cylinder bore. But only applies to insert through the liner and to allow the cylinder offset range. This is because the eccentric cylinder boring method will makeCenter deviate from the original center of the cylinder, when the eccentric is too large, the connecting rod small end is pressed against the side of the piston pin boss of the piston against the cylinder wall, the cylinder increases wear, it will shorten the engine life.

(5) to select an appropriate depth of cut. After boring determined amount, consideration should be given boring tool according to the number of the allowed amount of food each. Typically cast iron cylinder, a first knife cutting depth should be no greater than 0.05mm, because the hardened layer surface of the cylinder and cylinder uneven wear, excessive cutting tool, cutting force Guo cause vibration not only affects the quality of the processing cylinder, and detrimental to the cylinder boring machine, aggravated tool wear. Intermediate times can be a bit more, but not exceeding the cylinder boring machine to limit the maximum allowable depth of cut. Finally knife, the cutting depth should be controlled at 0.03-0.05mm, boring to ensure the accuracy and surface roughness.

Cutting cylinder boring requirements: For general hardness gray cast iron cylinder HB180-230, or YG8 YG6 using carbide tools; cutting speed of 125-150m / min; passes in an amount of 0.10-0.15mm / r; depth of cut as described above.

should be separated cylinders cylinder boring. The cylinder boring cylinder port to be processed into a 75 ° chamfer, so that the piston rod assembly mechanism, and note that the chamfer width should be specified.
Process
(6) of the cylinder boring and technical requirements. After the cylinder must cylinder boring holes, and other welding operation is completed, can be conducted, cylinder boring process steps are as follows:

The measurement results of the amount of the cylinder, the expansion tank is determined to increase the size of the repair.

The selected size with the size of the repair of the piston, with the weight of the piston group, should be the same size, cylinder boring amount determination performed by the following equation:

= amount boring piston skirt the maximum diameter – the minimum diameter of the cylinder piston and the cylinder with the gap + – honing balance

selection of the exact measurement of the diameter of the piston, in accordance with the cylinder gap, leaving a rough boring, finish boring and honing allowance I amount, determined from the size of boring, boring First infeed typically 0.03-0.05mm.

rough boring – boring finishing allowance left to 0.10mm.

fine boring – Honing left margin of 0.03mm.

honing – has reached a predetermined size and the surfaceRoughness.

Cleaning – careful cleaning of the cylinder, and the piston into the cylinder pair implement check the fit, and finally the coated cylinder oil rust.

After the honing, the cylinder wall surface roughness Ra not greater than 3.2 m, uniform irregularities formed on the liner surface traces (with a surface of the cylinder wall is visible moire 60 °, cylinder wall was grayish blue pan color) the circularity error of the cylinder should be less than 0.005mm, cylindricity error of less than 0.015mm; while ensuring the fit clearance between the cylinder and the piston of 0.03mm.

In the honing process should always pay attention to check the dimensions of the cylinder. Usually the amount of cylinder or piston table test with processing size changes. It should be noted that the cutting heat generated in the process, possible changes in the diameter of the cylinders, the factors to consider when measuring, for a test with a piston in a half hour after the honing. After the piston and the cylinder with a good, it should lay on top of the cylinder of the piston, to prevent confusion during assembly.

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