Amongst the various surface treatments, barrel finishing is one that is attracting a lot of attention as a polishing technique for aluminum parts. What is barrel finishing, and how does it differ from buffing as most riders know it? Discover how barrel finishing can be combined with powder-coated color clear for a customized look that you may never have imagined.
Barrel finishing involves stirring the parts to be polished in the polishing media.
Barrel polished and powder-coated wheels for a 1987 Suzuki RG250 Gamma. The stock wheels are painted in a subtle mag or beige color scheme.
CARVEK's MURAMASA three-dimensional barrel finishing machine pushes parts attached to a motor into the polishing media in a 600-liter bucket and polishes them by interlocking rotational, vertical, and swinging motions. Two buckets contain media for rough grinding and finishing, and the buckets can be changed according to the grinding task. In terms of size and price, this is equipment for shops and factories.
The operation of the polishing head is set by the program, and the operator does not have to do anything after pressing the start button, and it does not get dirty with buffing cloth or abrasive. This image shows finishing polishing in progress, where the polishing media grain size is small. Although it depends on the shape and condition of the part, rough polishing takes about 20 minutes and finish polishing takes about 10 minutes to complete.
Many riders will know that aluminum parts, whether machined or cast, shine beautifully when polished. Aluminum alloys are prone to oxidation as a characteristic of the element, so they are often commercialized with anodized aluminum, which creates a forced oxide film, but cast products such as engine crankcase covers and front fork outer tubes, for example, can be made to shine beautifully with metal polishing chemicals.
The best-known method of polishing aluminum parts is buffing, as described below. However, for industrial products manufactured in large quantities, there is a more efficient method. This is barrel polishing.
When we try to polish a part, whether it's a wheel or an engine cover, we apply the polish to the part with our own hands and scrub it with a microfiber cloth.
Barrel finishing, however, is the opposite: the parts to be polished are placed in a container of polishing media and polished using vibrations or other means. In the case of pre-surface polishing of tableware such as spoons and tools such as spanners and sockets, the material is often placed in a large tank filled with polishing media. Barrel means a barrel. In industry, there are several types of polishing machines, such as rotary, vibratory and centrifugal, which are used to remove burrs during molding and to prepare the surface for plating.
As you can see, barrel finishing is a technology used only in the intermediate process of mass production, but Carvek has commercialized this technology for the aftermarket by offering a variety of products and technologies related to surface treatment such as gun coating and powder coating.
The company's MURAMASA 3D barrel finishing machine differs from standard barrel finishing machines in that the parts to be finished are mounted on a motor and rotated in a polishing media bath. The rotation is not as simple as attaching the part to the end of a drilling machine and spinning it around, but rather up and down or swinging the part around in the tank so that the finishing media makes even contact with the part, even if it has a complicated shape.
Although the MURAMASA is factory equipment and not a product that motorcycle users can purchase individually, it is possible to order polishing from Carvek, the manufacturer, and other shops around the world that have installed the machine.
- Point 1: In barrel finishing, the parts to be polished are put into a tank containing polishing media, and polishing is performed by the constant contact between the media and the parts.
- Point2: Carvek's barrel finishing machines perform efficient polishing in three dimensions: rotary motion, vertical motion and swinging motion.
What is the difference between buffing and barrel polishing, which are the standard methods for polishing aluminum parts?
Paint wheels that look like ochre will shine amazingly with barrel polishing. From stripping off the old paint to polishing, the cost per wheel starts at around 30,000 yen, and while you can do it yourself, the quality won't be as good.
The advantage of barrel finishing is that it does not shine excessively like buffing for a mirror finish, but gives a uniform and moist finish like OEM parts. That's because barrel polishing is also used for many genuine parts with a polished finish.
Whether it can be polished or not depends on whether the polishing media can touch it or not. If you want to polish a narrow space, you can't beat a thin tool like a pencil rheuter, but if you want to make it as shiny as genuine parts, barrel polishing is the best.
Whereas barrel polishing cannot be done by an individual, buffing is a popular means of polishing that can be done in a garage. Buffing is a standard technique for customizing and dressing up aluminum and stainless steel to make the surface shine by polishing it with an abrasive buff.
It depends on the condition of the material, but in the case of aluminum casting parts, the base is made while gradually making the grit of sandpaper finer. As an example, the order of sanding is 600, 800, 1500. It is like erasing scratches made by coarse paper with fine paper. After that, apply abrasives to a buffing pad attached to a grinder, drill or luthier and polish it up to a mirror-like finish depending on your patience.
It is the abrasives that are of interest here. While sandpaper is used to polish the aluminum itself, abrasives are used to rub it in. It is true that the abrasive reacts with the aluminum surface to make it shiny, but it is also a process of applying the oil in the abrasive, like wax.
One of the reasons why some riders have found it essential to clean buffed parts afterward is abrasive. One of the reasons for this is abrasive. The oil in the abrasive oxidizes in the air, causing a whitish discoloration, which can cloud the mirror surface. Oily abrasives also have the ability to fill small scratches in the substrate, so spraying parts cleaner to remove fogging may degrease the surface and reveal the underlying condition. This is one aspect of buffing which can be remedied by re-polishing.
In contrast, barrel finishing uses polishing media from start to finish and does not use chemicals. The shine of the parts after polishing is the shine of the aluminum material itself, so wiping with parts cleaner or degreaser will not change the texture.In addition, while buffing involves polishing each part that comes into contact with the buffing cloth, barrel finishing, which involves pushing the part into the polishing media and turning it, has the advantage of being able to polish a large area uniformly and evenly. Also, since no oil is applied to the surface, it is possible to paint over the polished surface.
Not a few automotive custom shops have taken notice of these features and are utilizing barrel polishing machines as a necessity for wheel customization.
- Point 1: Buffing brings out the luster by coating the parts with the oil in the polishing agent, whereas barrel finishing brings out the luster of the part material itself.
- Point 2: After barrel finishing, the parts are in a solid state, so the surface can be painted.
Powder coating the barrel polish to turn it into an anodized aluminum look.
Powder coating paint is a fine powder that adheres to the metal surface using static electricity in its powder form. When the powder is then heated to a temperature of 180°C or higher, the powder melts and forms a coating that adheres to the part.
Powder coating is suitable for painting frames because the coating film is thicker and sturdier than urethane coating. You may misunderstand that you can choose only plain colors for frames, but Carvek offers powder coating paints in 80 different colors such as solid, metallic, candy and neon.
Candy yellow powder paint is sprayed on the wheel polished by barrel polishing. The powder paint sprayed out from the gun adheres to the wheels like static electricity.
Since the powder remains in powder form until it is baked in the dryer, it can be easily blown off by air blow. This is another unique feature of powder coating that liquid paints do not have.
Powder coating paints are made of powdered polyester, epoxy polyester, acrylic, or other resins, and even if the finished color is candy yellow, it appears solid in its powdered state. Similarly, clear, which becomes transparent after baking, is white when sprayed.
By layering colored clear powder coating on top of the barrel polished shine, a luster with depth is achieved. The same effect can be achieved by applying candy yellow over the silver paint, but it is different from the metallic luster by polishing. Also, since only one color of candy yellow is used (so-called one coat), the edges of each part are sharper than with two coats of candy on top of silver.
The cast surface of the wheel is polished by barrel polishing, but not by sandpaper, so the genuine look is maintained.
Here is an example of wheel customization based on the difference between barrel finishing and buffing, and the features of Carvek's 3D barrel finishing machines.
Here we have a 1980's 3 spoke cast aluminum wheel. The stock version has a painted finish, but when this is stripped and sandblasted with a stripping agent and barrel polished, it gives the wheel a beautiful aluminum sheen that makes it look like a custom wheel.
Wheel polishing is often carried out by buffing, but the use of sandpaper or belt sanders to prepare the buffing surface can remove the pearly cast surface. While polishing the pearl surface has the advantage of enhancing the custom look, barrel finishing does not significantly alter the texture of the material itself. This means that the surface texture and the edges of the maker's or size stamp will not be cut away and become dull, while still shining.
The shine of a painted wheel is a great customization effect, but you can also change the image of the wheel by adding a few extra touches. As mentioned above, barrel finishing is not a chemical or oil-based process, which means that the wheels can be painted after polishing. As Carvek also sells powder coating equipment and paints, you can choose from a wide range of paints in candy yellow for a transparent finish.
The candy color of the powder coating is transparent to the substrate so that the finish looks like gold anodized aluminum. The gold powder coating is just that, gold, but by choosing a candy color, you get transparency and depth, and by barrel polishing the wheel itself, you get the anodized look. If you're a rider interested in surface treatment, you'll know that cast aluminum and anodized aluminum don't mix well, so you'll probably be asking yourself "why anodize a stock wheel? you may ask.
Customization by replacing special parts is rewarding, but the combination of different surface finishes can also produce unexpected effects. As well as customization, it is worth remembering that barrel finishing can be used to great effect when restoring out-of-print motorcycles with polished crankcase covers and headcovers.
- Point 1: Unique custom effects can be obtained by combining barrel finishing and painting.
- Point 2: Barrel polishing is the best for customizing and also for polishing parts when restoring an out-of-print motorcycle.
