Burnishing Process is an age-old technique that transforms metal surfaces through the gentle touch of a small, sturdy tool. Also known as ballizing or rollerizing, this artistic process compacts metal to create a radiant finish. This helps in elevating both aesthetics and durability. Join us on a journey through the secrets of burnishing, as we explore its techniques, materials, and diverse applications. Unleash the hidden potential of this captivating art, revealing captivating finishes and heightened micro-hardness. Let us discuss about it in detail.
What is burnishing?
Burnishing is an advanced finishing technique that doesn’t produce chips or remove material from the workpiece surface. It involves pressing a rolling tool against the surface, causing plastic deformation through sliding contact with another object. This process relies on local contact stress surpassing the material’s yield strength.
Burnishing can be performed using various methods, involving the application of force while rubbing the tool against the workpiece to induce plastic deformation. It can be done using a dedicated machine or on a regular lathe/milling machine.
In dedicated machines, the burnishing tool is affixed to a motor that revolves around the workpiece, which is secured to the machine using a wise or magnetic table. The rotational motion of the burnishing tool exerts force upon contact with the workpiece. This helps initiating the burnishing process as the workpiece moves from left to right. Two primary methods are used for inspecting and evaluating the burnishing process:
- Surface inspection by the naked eye
- Direct measurement using specialized instruments.
Direct measurement offers the advantage of determining a numerical value for the surface finish, enabling effective comparison with other burnishing processes. The widely used instruments for this purpose are stylus probes, operating on electrical principles. As the stylus moves, it generates a voltage signal, while pneumatic elements are employed to precisely measure the actual surface finish. This approach ensures accurate and quantifiable assessments of burnished surfaces.
Types of Burnishing
Following are the two main types of burnishing:
- Roller burnishing
- Ball burnishing
Roller Burnishing is a cold working process technique that utilizes hardened rollers to move or turn on the material’s surface, resulting in a super-fine and highly polished finish.
Ball burnishing is a specialized technique that achieves a super-fine finish, particularly sought after when aiming to create specific colors or luster on the workpiece surface. This process involves pressing a hard ball against the workpiece surface, imparting a desired sheen and texture.
Applications for Burnishing
Following are the main applications of burnishing:
- Cutting tools – Enhancing tool surfaces for improved performance.
- Turbine blades – Enhancing turbine efficiency and durability.
- Air foils – Improving aerodynamic performance in various applications.
- Curved pipes – Enhancing surface smoothness and functionality.
- Medicine – Improving medical device performance and safety.
- Capillary tubes – Enhancing flow characteristics in small-diameter tubes.
- Sanitary pipes – Ensuring smooth and hygienic pipe surfaces.
- Optics – Improving optical component precision and quality.
- Food industry – Enhancing food processing equipment surfaces.
- Needles – Improving needle sharpness and performance.
Guidelines for Burnishing
- Surface roughness value (Ra) measured between 0.04μm and 0.8μm.
- Burnishing process yields roughness from 0.8mm to 2.5mm.
- Deformation varies with pressure in non-machined burnishing.
- Irregular shape and texture achieved with burnishing.
- Non-working surface irregularities impact burnishing results.
- Lay direction depends on the chosen method.
Economic Aspect of Burnishing
- Minimal equipment costs; may not need specialized tools.
- Low production rate; unsuitable for high volumes.
- Possible automation for increased output but higher production costs.
- Low energy consumption.
- No material wastage; potential for cost savings.
- No lubrication required, reducing overall costs.
- More cost-effective than hot working process.
- Significant time savings compared to other processes.
Advantages of Burnishing
- Reduced process time.
- Zero material waste; no material removal.
- Easy control over all process steps.
- Low noise levels.
- Suitable for all machine tools.
- No additional lubrication needed.
- Increases tool durability.
- No bearing wear or slide way needed.
- Minimal dimensional changes.
- No coolant required.
- No dust or mud generation.
Disadvantages of Burnishing
- Unsuitable for all ordinary finishing tasks; consider conventional techniques.
- Cost implications when compared to traditional methods.
- Not suitable for mass production with wise/magnetic tables.
- Numerical assessment needed to evaluate finish smoothness.
Burnishing is a surface modification process utilizing a precision metal finishing tool, which can be a ball or roller. This tool smooths metal peaks over valleys without material removal.
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Burnishing is a process where a smooth hard tool, with enough pressure, rubs against the metal surface, flattening high spots through plastic metal flow.
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