While vibratory finishing process focuses on the batch-to-batch consistency and low cost per components, Isotropic finishing process focus more on the flexible production with a smaller production lot.
Centrifugal barrel finishing is one of the popular methods to achieve fast processing of smaller batches with higher surface finishing requirement.
The term Isotropic Finishing refers to creating a smooth surface that has some physical characters in all directions. Therefore, peaks, grinding marks, burrs from machining, casting or grinding process is removed after isotropic finishing process. The entire part surface is uniform in all area.
The Challenging in Centrifugal Barrel Mass Finishing
3D printed parts surface finishing:
The 3D printed parts are made by an additive manufacturing process which creates a very rough surface. This rough surface needs to process a very long time if use conventional vibratory finishing process.
The isotropic finishing centrifugal barrel process takes only a fraction time of vibratory finishing or barrel tumbling. Moreover, it offer a smooth surface that acceptable for industry standard. Therefore, it would not be a bottleneck for 3D printed parts industrialization.
Titanium based aerospace turbine blade
The Titanium material itself is a very hard metal. In addition, the turbine blade used in aerospace is hardened with heat exposure.
The isotropic finishing process significantly removed any surface defects and shorten the process time that required in vibratory finishing.
Medical parts Deburring and Polishing
The medical parts have a very high surface requirement and the surface is very demanding. Usually, these parts are made from Titanium alloy which is hard and tough.
Centrifugal barrel finishing process brightens the surface of the parts and removes imperfection of parts in a short period of time. This high-energy process is ideal for high-quality and low-tolerance production.
The Features and Benefits of Isotropic Finishing
To satisfy the higher industrial requirement, nowadays, centrifugal barrel finishing is introduced with several steps from the raw parts to a fine polished surface.
Now, let’s take the example of rough machined stainless steel parts. First, we use ceramic tumbling media to remove the machining marks of the steel parts. The micro peaks and ridges are cut down and the surface becomes smooth but still rough.
Second, we use plastic tumbling media to improve the improve surface smoothness into the next step. Once the surface is smoothed and Ra value reduces to a certain level, we can use non-abrasive tumbling media to brighten the parts.
The centrifugal barrel finishing machines usually have four barrels. Each barrel you can put different parts with different media. Also, you can put the same parts with different finishing stage.
Reduce surface skewness
Unfinished parts have high surface peaks density above the mean line, showing a positive skew. These positively skewed surfaces are unwanted, impairing the performance of parts in applications for example in racing, bearing, and motor parts. Centrifugal Isotropic finishing eliminates undesirable skewed surfaces and offers more contacting area.
Surface Texture Pattern
The texture pattern of parts is greatly important for parts wear performance and life time.
The parts after machining have a directional pattern in nature which creates by tools. However, the parts life can be greatly improved if the surface texture can be changed into a random pattern.
Therefore, we use mass finishing media in a high-energy centrifugal barrel finishing process. As a result, parts machined pattern changed from directional pattern into an isotropic pattern. These isotropic surfaces reduce parts wear and fatigue at long-term mechanical running.
Residual Stress Removal
All mechanical processes tend to develop residual tensile stresses in part surfaces. These stresses make parts are likely to harmed by premature failure. The isotropic finishing improves surface stress conditions and replaces with compressive stress.
If you are the manufacturing the parts and you make a record of your parts performance you will find that centrifugal barrel finishing not only provides a burr-free and smoother surface, they also make a surface that has a longer life and less likely to have fatigue failure and exhibit better tribological property.
For example, the spring that treated with centrifugal barrel finishing process show a lifetime of 400,000 cycles. And the spring that processed with conventional vibratory finishing process shows a lifespan of 250,000 cycles. This show a 60% extend in parts lifetime.
In this article, we discussed the term “Isotropic Finishing” and its application. The Isotropic finishing is mostly related to the centrifugal barrel finishing process. This isotropic surface means a homogeneous surface that have same physical properties in all directions.
The next, we show three major applications for isotropic mass finishing, which includes 3D parts post process, aerospace turbine blade as well as medical parts finishing.
Later, we show 5 significant feature and advantages of isotropic centrifugal barrel finishing. This process is multi-step, flexible, remove surface skewness, change the surface pattern and improve parts lifetime.
This high-energy process is increasingly popular with high demand in small lots, fast processing. It is also well received for the predictable result.