Patent Application
20050132569
The present invention is directed to a method of repairing a part and, more particularly, a method of repairing piston ring grooves using a laser cladding operation.
Typically, an internal combustion engine commonly includes a crankshaft and a plurality of cylinders sized to receive a respective piston. A connecting rod couples each piston to the crankshaft. Each cylinder includes a combustion chamber that contains the high pressure gases formed during the combustion process of the fuel within the combustion chamber. To ensure that the combustion process occurs in an efficient manner, it is important that the interface of the piston and combustion chamber be sealed. This is typically accomplished by the use of one or more piston rings that are placed within piston ring grooves provided on the piston crown. Over time, the piston ring grooves will wear to a point that they are outside of design specifications. This wear can result in the loss of sealing of the combustion chamber thereby decreasing the efficiency of the combustion process.
Those engine components that sustain damage or wear are oftentimes recycled or, as it is typically referred to, “remanufactured”. This assumes the component is not beyond repair and a suitable method to repair the component exists. Traditionally, repairing of the piston ring grooves was accomplished by machining the worn grooves so that they became larger than what the original specification called for. These “oversized” piston ring grooves then required “oversized” piston rings which may result in requiring different rings for the same piston. The use of different rings for the same piston could subsequently result in a mis-matching of the rings with the ring grooves during assembly and/or installing the wrong ring or rings.
The present invention is intended to overcome one or more of the problems set forth above.
In accordance with an embodiment of the present invention, a method of repairing a part, having a damaged portion that has deviated from an original configuration, by using a laser cladding process is provided. The process comprises the steps of applying cladding material to the damaged portion, and irradiating the cladding material with the laser beam until such time as the cladding material substantially bonds with the part thereby forming a repaired area having a configuration substantially the same as the original configuration.
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If it is determined that repair is needed (as depicted by decision block 505), the process then moves to block 508 where the faces 300 that are in need of repair are pre-machined, by using the above-identified laser cladding machine 400 or other like machine, a pre-determined amount, such as 0.020 inch, so as to provide for a uniform geometry of the face 300. Prior to the laser cladding operation, the process proceeds to block 509 in which the piston crowns 101 are degreased to remove any remaining oil or contaminants.
Once the pre-machining and cleaning is complete, the process proceeds to block 512 where the piston crown 101 is attached to the laser cladding machine 400 and the laser 404 is oriented to direct its beam 405 onto the face 300 in need of repair. For the exemplary process described herein, the diameter of the beam 405 is selected to be approximately 0.040 inches at a power level of approximately 1350 watts which has been found to be an acceptable power level in this application to provide sufficient fusion between the cladding material 408 and face 300. The cladding material 408 is then fed into the beam 405 at a rate of approximately 3.45 grams per minute and the cladding material 408 and the face 300 are irradiated by the beam 405 for a length of time required to cause the cladding material 408 an the face 300 to bond together. Depending on the diameter of the piston crown 101 being repaired, the speed of the piston crown 101 in the laser cladding machine 400 should be selected to provide a cladding bead 409 of approximately 0.040 inches on the face 300. During the cladding process, the shielding gas 412 such as Argon is supplied to the area being clad at a rate of approximately 1 cubic foot per minute. Additional beads 409 are then applied in such a manner as to be stacked on the preceding bead until the face 300 extends past the original specification location. In other words, the distance between the two faces 300 of a ring groove 102 are less than they were when the ring groove 102 was originally formed in accordance with the original specifications (e.g., the width of the ring groove 102 is less than the original width of the ring groove 102). When the face 300 has been built-up to a pre-determined amount, an additional pass with the laser 404 may be used to temper the repaired face 300. An additional pass with the laser 404 to temper the heat effected area of the piston crow 101 may be performed at this time, either with or without cladding material 408, using a predetermined wattage to achieve a proper temper.
Once the laser cladding process is complete, the process proceeds to block 513 where the faces 300 that were repaired are again machined using the laser cladding machine 400 or other like machine to original print specifications. After this machining step, the process proceeds to block 516 where the piston crowns 101 are tested for any cracks using any suitable method such as, for example, magnetic particle testing. Finally, as shown in block 517, the piston crowns 101 are again washed and any needed assembly, such as installing pin bushings (not shown), is completed. Shown in
If it is determined that repair is not needed (as depicted by decision block 505), the process then moves to blocks 520-523 where the pistons 100 are, respectfully, cleaned, reassembled by installing new pin bore bushings (not shown), tested for cracks again using a suitable process such as a magnetic particle testing method, and finished washed.
Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.
