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The machining of the inner bore of a hydraulic cylinder generally involves boring and honing. Boring itself is typically divided into deep hole boring with roller burnishing and roller burnishing boring. In recent years, with the advancements in material cold drawing technology, and development of roller burnishing boring equipment, and the tremendous advantages of the roller burnishing boring process in terms of material utilization and production efficiency, roller burnishing boring is gradually becoming the main process for machining the inner bore of hydraulic cylinders.
Today, we will discuss the capabilities of these two processes in ensuring the straightness of the cylinder bore, and we welcome your comments and participation in the discussion.
I. Differences between the two processes
1. Processing principle
Deep hole boring + roller burnishing (e.g., push boring and roller burnishing): A two-step combined process. First, cutting (boring) is performed to correct the shape errors of the hole, and then roller burnishing is carried out.
Scraping and burnishing (scraping and roller burnishing): A single-step combined process. Cutting (scraping) and roller burnishing are performed simultaneously/continuously with a single cutting tool.
2. Requirements for the material
Deep hole boring + roller burnishing (e.g., push boring and roller burnishing): This process has a higher tolerance for the initial curvature of the raw tube, such as heat-treated and tempered raw tubes;
Skiving and roller burnishing (skiving and roller boring): This process is very sensitive to the initial curvature of the raw tube and requires higher quality raw materials, such as cold-drawn tubes;
3. Straightness performance
Deep hole boring + roller burnishing (such as push boring and roller burnishing): Better and more stable. It provides better correction of initial deviations and higher processing consistency.
Scraping and roller burnishing (scraping and roller boring): Performs well when the workpiece quality is good, but the straightness is easily affected when the workpiece is of poor quality.
4. Efficiency and Surface Quality
Deep hole boring + roller burnishing (e.g., push boring and roller burnishing): Multiple steps, relatively low efficiency. Good surface quality.
Scraping and roller burnishing (scraping and burnishing boring): High efficiency. Achieves excellent surface roughness, hardness, and wear resistance.
5. Key Data Support
A comparative study conducted (for φ400mm cylinder barrels) directly confirmed the above conclusions:
Dimensional consistency: After push boring and roller burnishing, the fluctuation (standard deviation) of the inner diameter of the cylinder barrel was only about 70% of that of the scraping and roller burnishing process.
Shape accuracy consistency: In terms of “cylindricity,” which reflects the uniformity of the hole shape, the fluctuation of push boring and roller burnishing was only about 65% of that of scraping and roller burnishing.
This set of data indicates that products processed using the “deep hole boring + roller burnishing” process have smaller dispersion in size and shape, and better consistency.
Abstract
This study investigated the time-dependent changes in the inner diameter and cylindricity of jack cylinders after push-boring and roller burnishing, and scraping and roller burnishing processes. Six 400 mm column cylinders were selected for testing, and the experimental data were analyzed using interpolation methods. The results showed that the inner diameter and cylindricity of the cylinders processed by push-boring and roller burnishing, and scraping and roller burnishing exhibited similar trends. The dimensional changes could be divided into oscillating, gradual, and stable stages. The changes in cylindricity were more pronounced than the dimensional changes, stabilizing after 168 hours of natural aging. The dimensional deviation and cylindricity dispersion of push-boring and roller burnishing were smaller than those of scraping and roller burnishing, with the standard deviation of dimensional deviation being approximately 70% of that of scraping and roller burnishing, and the standard deviation of cylindricity being approximately 65% of that of scraping and roller burnishing. A natural aging time of around 168 hours is recommended.
II. How to choose the right process?
1. If processing reliability, high yield rate, and adaptability to raw materials are the top priorities: “Deep hole boring + roller burnishing” (push boring and roller burnishing) should be prioritized, especially suitable for processing longer cylinder tubes with average raw material quality.
2. If processing efficiency and optimal surface performance are the top priorities, and high-quality raw materials can be guaranteed: “Scraping and roller burnishing” can be chosen, suitable for high-quality, large-volume production.
Before making a final decision, it is best to conduct small-batch trials comparing the two processes using specific raw materials (including material type, initial curvature, etc.), and measure key indicators such as straightness and cylindricity. This is the most reliable method. Meanwhile, recent technological advancements in scraping and roller burnishing equipment and tooling are also gradually improving the quality of this process.
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Contact: Nancy Zhu, Sales manager, JW GROUP.