A Machining Method for the Internal Bore of Cylinder-Barrel-Type Parts
2026-03-11
Hollow cylindrical components typically have a large length-to-diameter ratio and thin wall thickness, with stringent requirements for internal bore accuracy and surface roughness. In existing technologies, the machining of the internal bore of such cylinder blanks begins with seamless steel tubing as the raw material: first, the tubing is cut to the required length; then the blank undergoes preliminary processing, including straightening and quenching-and-tempering; next, both ends are turned and bored using process locating shoulders and external welding shoulders; subsequently, external cylinder components are welded on; followed by rough boring of the internal bore; then finish boring; and finally, finish honing.
1. Introduction
The internal bores of cylinder barrel components typically have a large length-to-diameter ratio and thin wall thickness, with stringent requirements for bore accuracy and surface roughness. In existing technologies, the machining of these internal bores begins with seamless steel tubing as the raw material: the tube is first cut to the required length to form the cylinder blank; next, the blank undergoes preliminary treatment, including straightening and quenching-and-tempering; then the two end faces are turned and bored, using both internal locating shoulders and external welding shoulders for process alignment; subsequently, external cylinder components are welded on; followed by rough boring of the internal bore, fine boring, and finally honing. In the rough-boring stage, a single tool head—comprising both rough and finish boring tools—is usually employed to complete the entire internal-bore operation in one pass. The final honing is performed on a dedicated honing machine. However, this conventional method of boring the cylinder barrel results in a relatively high scrap rate.
This technology proposes a machining method for the inner bore of cylinder barrels, which can address the high scrap rate and high machining costs associated with existing methods for machining such bores.
2 Technical Solution
This method for machining the inner bore of the cylinder barrel comprises the following steps: pre-treatment of the barrel, turning and boring the end bores using process locating shoulders, rough boring of the inner bore, and finish boring of the inner bore. After completion of the finish-boring step, the inner bore of the cylinder barrel is subjected to roller burnishing using a roller-type burnishing head, thereby completing the machining of the inner bore. The rough-boring step and the finish-boring step
The upsetting and rolling steps must be performed on dedicated machine tools.
Rough boring and finish boring of the internal bore are performed in two separate steps, using a rough-boring tool mounted on the boring bar for the former and a finish-boring tool for the latter.
The roller-type rolling head comprises a boring bar, a pressure-bearing body, a roller holder mounted on the outer surface of the pressure-bearing body, and a plurality of rollers housed within the roller holder. The outer surface of the boring bar is provided with external threads, and the pressure-bearing body is connected to these external threads via internal threads. The pressure-bearing body is a cylindrical member with a conical outer surface, and a limiting pin is installed between the pressure-bearing body and the boring bar. The rollers are cylindrical, with smooth transitions between their cylindrical surfaces and end faces. The roller holder is located at the small-end face of the pressure-bearing body and is connected to a bearing cover fitted over the end of the roller holder via a thrust bearing.
The “set” referred to here consists of the end cap of the bearing housing fitted over the end of the roller carrier, with the end of the roller carrier in turn fitted over the end of the circumferential cover; the other end of the bearing housing is equipped with an adjusting nut mounted on the boring bar.
3. Specific Implementation Plan
The process parameters for the rough boring of internal holes are as follows: cutting speed of 70–80 m/min, cutting depth of 2–4 mm, and feed rate of 0.3–0.5 mm/rev.
The process parameters for the precision boring of internal bores are as follows: cutting speed of 90–100 m/min, cutting depth of 0.2–0.5 mm, and feed rate of 1.3–1.4 mm/rev.
The process parameters for the roll-forming step are as follows: the transition fillet radius between the cylindrical surface and the two end faces of the roller is 2.8 to 3.5 mm; the roll-forming speed is 90 to 100 m/min; the roll-forming depth is 0.05 to 0.1 mm; and the feed rate is 1.3 to 1.4 mm/rev.
Due to the adoption of the aforementioned solution, this technology achieves the following beneficial effects compared with the prior art:
1. By adopting this technical method, the scrap rate for internal bore machining of steel cylinders is reduced from the current 6% to 1%.
2. Adoption of this technical method reduces the processing cost per unit by 10%.
4. Example
A manufacturing process for producing a cylinder barrel with a bore diameter of 200 mm, a stroke of 1000 mm, and a pressure rating of 16 MPa.
Material preparation: Select 45# carbon seamless steel pipe with an outer diameter of 232 mm and a wall thickness of 18 mm as the raw material, and cut the seamless steel pipe into 1000-mm-long cylindrical billets in accordance with the design requirements.
Preprocessing: Perform quenching and tempering on the cylinder barrel billet and straighten it to ensure that the hardness of the steel barrel billet is HRC 28–32 and the bend does not exceed 3 mm; then machine process locating shoulders at both ends of the preprocessed steel barrel billet for镗孔, and weld the external components of the cylinder body.
Rough Boring: The inner bore is rough-bored on a dedicated machine tool. One end of the cylinder barrel blank is clamped by the chuck of the dedicated machine, while the other end is supported by the positioning support on the cylinder barrel holder of the same machine. The rough-boring cutter is mounted on the boring bar of the dedicated machine, and the boring operation is performed according to the following process parameters: cutting speed of 70 m/min, cutting depth of 4 mm, and feed rate of 0.3 mm/rev.
Fine boring: Remove the rough-boring tool, mount a roller-type burnishing head on the boring bar, and continue push-boring on the dedicated machine tool according to the following process parameters: cutting speed of 90 m/min, cutting depth of 0.2 mm, and feed rate of 1.4 mm/rev.
Rolling: Remove the precision boring tool, mount a roller-type rolling head on the boring bar, and continue rolling on the dedicated machine tool in accordance with the following process requirements: the fillet radius at the transition between the cylindrical surface of the roller and its two end faces shall be 2.8 mm; the rolling speed shall be 90 m/min, the rolling depth 0.05 mm, and the feed rate 1.4 mm/rev. After rolling, the inner bore of the cylinder barrel will be fully machined.
Keywords:
Machine tool,Spindle,Workpiece
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