Vibratory Tumbler

Chapter 1: What is a vibratory tumbler, and how does it operate?

Vibratory tumbler is the equipment used in a vibratory finishing process, one of the most common methods in mass finishing. But how does a vibratory tumbler work?

A vibratory tumbler operates by placing workpieces and parts into a tub filled with specially shaped media pellets. The motor generates vibration force that moves the contents of the tub. Strong springs at the bottom of the tub support it during this motion. Additionally, a specialty finishing chemical may be added to the tub to aid in the finishing process.

The vibration causes the media and workpieces to rub and grind against each other, which polishes the workpieces. Although the tumbler shakes, both it and its contents remain stationary. A vibratory tumbler can function in either batch mode or continuous mode.

A vibratory finishing process is used to clean, deburr, deflash, descale, and polish workpieces. It can be used as a surface preparation step to enhance the bonding of coating, plating, and adhesive materials to the workpiece. It is typically performed after a machining process. It can also be used in slightly reducing the size or radiusing of irregularly shaped materials, and the workpiece maintains its original shape after the process. The results of this finishing method cannot be achieved using manual polishing and deburring.

Benefits of Vibratory Tumblers

Vibratory tumblers offer high throughput, making them ideal for processing large volumes of parts. They can deliver finished parts more quickly than rotary tumblers, though this depends on the nature and size of the parts being processed. They are capable of safely finishing the surfaces of plastic, metal, and ceramic workpieces, as long as the correct media, vibratory action, and finishing type are employed.

Vibratory tumblers come in various capacities, shapes, and sizes. Many models are highly automated to offer improved control over the finishing process and may even include features for drying the parts.

Products finished using vibratory tumblers are commonly used in aerospace, firearms, equipment parts, and orthopedic implants.

Chapter 2: What are the different types of finishing media used in vibratory finishing?

Finishing media, or grit materials, are used to polish parts during the vibratory finishing process. As the media rubs against the parts, it smooths and cleans rough edges and surfaces. The media come in various materials, grades, and shapes, and selecting the right combination of these factors ensures the highest quality finish for your parts.

The types of finishing media in vibratory finishing, categorized by material type, include:

Ceramic Vibratory Finishing Media

Ceramic media is the most common vibratory finishing media that has high density, tough, and durable; hence, they are ideal for deburring, edge radiusing, burnishing, and polishing hard metals such as steel, stainless steel, and titanium. They can be used in removing rust on metal parts. They are used in general-purpose finishing, though they are preferred if heavy or fast grinding is to be performed. However, ceramic media can chip due to wear and exposure to excessive forces, and loose ceramic particles can be embedded in the small holes of a part.

Ceramic media is usually composed of porcelain, aluminum oxide, silicon carbide, and silica. Aluminum oxide and silicon carbide are used for harder metals, while silica is suited for softer metals.

Steel Vibratory Finishing Media

Steel media, made from hardened carbon and stainless steel with high density, are known for their strength and durability. Their robust construction extends their service life and improves wear resistance. Steel media can exert significant pressure during vibration, making them ideal for heavy-duty burnishing and polishing. They are suitable for use with aluminum, brass, steel, stainless steel, and plastic parts. The finishing process with steel media results in a bright, burr-free, and smooth surface.

Plastic Vibratory Finishing Media

Plastic media are ideal for polishing, deburring, burnishing, and cleaning softer metals like brass, aluminum, and zinc. Being less dense than ceramic and steel media, plastic media can safely process threaded and delicate parts without causing damage. They are used for mild cutting and less abrasive finishing, resulting in smooth, bright surfaces and edges on the workpieces.

Plastic media are typically made from polymers such as polyester, urea, and formaldehyde.

Several formulations of plastic media are available to achieve specific results and to finish workpieces made from various materials.

• Low-density plastic media are used for deburring, flash removal, burnishing, and pre-plate or pre-coating surface preparation. They are used in finishing softer parts since they prevent their distortion and impingement.
• High-density plastic media are formulated to finish ferrous and non-ferrous metal parts and harder parts. The applications range from deburring hard metals to the fine finishing of intricate parts. They are used in fast-cutting applications.
• High-performance plastic media are used for finishing parts made of ferrous metals.

Organic Vibratory Finishing Media

Organic media are lightweight and typically made from walnut shells and crushed corn cobs. They are environmentally friendly, biodegradable, and durable, making them suitable for light to medium deburring tasks. These media are often used to dry parts after vibratory finishing and can produce a glossy surface on metal parts when used with polishing paste. They are also safe for finishing jewelry. Crushed corn cobs have the added benefit of absorbing oils and moisture from the workpiece surface, which enhances corrosion resistance.

The grades of vibratory finishing media are as follows:

Light Cutting

Light cutting media are among the most common finishing media used for minimal abrasion and a gentler finishing action. They are effective for deburring, deflashing, and burnishing workpieces, resulting in a smooth and bright surface.

Non-Abrasive

Non-abrasive or polishing media are designed to polish parts, creating a smooth and lustrous surface.

Medium Cutting

Medium cutting media are used for efficient general-purpose deburring, providing both faster cutting and a good level of surface brightness on the part.

Fast Cutting

Fast cutting media are used for heavy-duty finishing applications. They apply a significant amount of abrasive force, enabling them to deburr, grind, and burnish workpieces quickly.

The shape and size of the media influence the finishing process of the workpiece. The commonly available shapes and sizes, along with their suitable applications, are as follows:

• Rounded Media (spheres, oval, and cylinders) are used for light deburring and provide delicate finishing action. Since they have no sharp edges, the chances of rounded media getting stuck on parts are low. They also have low chipping rates.

  

  
  

• Sharp Media (triangles, wedges, and arrowheads) are used for polishing and deburring hard-to-reach sections (e.g holes) and are suitable for complex parts. Their flat edges enable them to finish the sharp corners that are present on the parts which cannot be reached by rounded media. However, these media have higher chipping and wearing rates compared to rounded media.

  

  
  
• Small media have greater contact with the part, which can be used in polishing and deburring hard-to-reach sections. These media produce a smoother and brighter surface.
• Large media are used for tougher grinding, including the quick removal of burrs and rounding sharp edges. These media produce a rough surface.

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Chapter 3: What are the types of vibratory tumblers?

Before discussing the types of vibratory tumblers, let’s first explore dry and wet vibratory finishing.

Dry Vibratory Finishing

In a dry vibratory finishing process, the finishing is accomplished solely by the media, without the use of specialty chemicals. Typically, non-abrasive media, such as organic media, are used. This process is effective for drying and polishing, resulting in a bright and lustrous finish on the surface of the part.

Dry vibratory finishing is generally less expensive than wet vibratory finishing. However, dry media can become contaminated with dirt, oils, and metal oxides after several cycles, reducing finishing performance and potentially contaminating the parts. Harder and denser media, such as ceramic media, may also scratch the workpieces. Additionally, dry media wear out after multiple finishing batches, necessitating the installation of a dust or particle collector. Dry finishing operations can also generate significant noise.

Wet Vibratory Finishing

In wet vibratory finishing, a fluid such as water or specialty chemicals assists in the process. The fluid acts as a lubricant and coolant, reducing the heat generated from the rubbing of the workpiece. It also helps in removing oxides and surface contamination, leading to a cleaner and more polished part. The media absorbs some of the liquid, which minimizes part distortion and reduces debris generation and deposition on the media. However, wet vibratory finishing is generally more expensive than dry finishing and generates waste from spent chemicals that requires treatment.

A wet vibratory finishing process can be performed using media of nearly all material types, with the exception of organic finishing media.

Wet vibratory finishing offers a broader range of finishing capabilities compared to dry finishing, which contributes to its greater popularity.

The types of vibratory tumblers are:

Continuous Vibratory Finishers

A continuous vibratory finisher is a type of vibratory finishing machine where parts are fed into one end of the machine and move along with the media throughout the finishing process. The finished parts are continuously discharged at the other end at a consistent rate.

Continuous vibratory finishers provide high productivity by finishing and conveying parts to a designated location or downstream equipment simultaneously. This combined process significantly reduces cycle time.

Vibratory Bowl

The vibratory bowl is the simplest configuration of vibratory finishing equipment. It is composed of a bowl lined with polyurethane. The lining reduces the coefficient of friction between the bowl and the media, thus protecting them from wear. The bowl can be equipped with adjustable and removable dividers to process small and sensitive parts separately, which prevents part-to-part friction.

Vibratory bowls come in various shapes and sizes, including rectangular and bowl-shaped tubs. Some models feature narrow central sections designed to handle large products. These different bowl geometries allow you to select the vibratory bowl that best fits your specific application.

Vibratory bowls can accommodate both small and large production batches. For smaller capacity finishing, portable and bench or table-mounted vibratory bowls are available.

Vibratory Dual Finishing Machine

The vibratory dual finishing machine features an inner chamber and an outer chamber for performing wet and dry finishing steps, respectively. Heavier-duty processes such as deburring, radiusing, and polishing, often aided by finishing chemicals, are carried out in the inner chamber, which is lined with polyurethane to minimize wear and friction. The outer chamber, which is heated, handles the drying and cleaning steps. A stable partition separates the two chambers to prevent the transfer of contents between them.

After wet finishing is completed in the inner chamber, the media is screened and retained in the bowl, while the parts are transferred to the outer chamber for drying and cleaning.

A vibratory dual finishing machine is a cost-effective solution because it combines both wet and dry finishing processes in a single unit.

Vibratory Dryer

Vibratory dryers feature an elliptically shaped tub filled with heated drying media that dries parts following a wet finishing process. Additionally, this equipment provides extra polishing to the parts.

Vibratory dryers can handle both small and large volumes of parts and are available in both batch and continuous modes. They can also be used in in-line manufacturing, where finished parts are conveyed directly to downstream equipment.

Vibratory Trough Finishing Machine

A vibratory trough finishing machine is composed of an enclosed, long U-shaped tub lined with polyurethane with divider plates inside the tub, which can be removed and adjusted manually. This machine is used in vibratory finishing of long, large, irregularly shaped parts and of delicate parts. The divider plates create compartments inside the tub that separate each delicate part in order to prevent the rubbing contact of each part during finishing.

Vibratory trough finishing machines are capable of performing nearly all finishing operations and can process large quantities of products. They are highly versatile and come in standard sizes with various combinations of lengths, widths, and capacities. Both batch and continuous vibratory troughs are available to meet different production needs.

Chapter 4: What considerations should be taken into account when selecting and operating a vibratory tumbler?

Here are additional considerations for selecting and operating vibratory tumblers:

Media-to-Parts Ratio

The media-to-parts ratio refers to the volume of finishing media relative to the total volume of the parts. For sensitive or soft parts, a higher media-to-parts ratio is preferred to minimize scratching caused by part-to-part contact. When working with delicate products, using a divider plate is recommended. This ratio helps determine the appropriate volume for your application, with the total part and media volume ideally occupying 90% of the tub's capacity. The characteristics of the parts will influence the media-to-parts ratio. The table below outlines various media-to-parts ratios and their specific applications:

Frequency and Amplitude

Frequency and amplitude are key properties that define the intensity of vibration. Frequency refers to the number of vibration cycles per minute (CPM), while amplitude measures the maximum distance the vibrating object moves from its stationary position, typically in millimeters. Vibratory tumblers can operate with frequencies ranging from 900 to 3600 CPM and amplitudes from 1 to 8 mm. Amplitude can be adjusted using the motor's controls.

The surface finishing of delicate and fragile parts is best achieved using high frequency with low amplitude vibration. Conversely, processes such as burnishing, deburring, and radiusing require larger amplitudes.

Chapter 5: How do vibratory tumblers compare to barrel tumblers?

A Barrel tumbler is another type of tumble mass finishing equipment. It works by rotating the parts, the media, and the finishing chemical inside a barrel. The rotational movement causes the parts and the workpiece to rub against each other. Like vibratory tumblers, barrel tumblers also perform a variety of finishing processes, from heavy cutting actions like burnishing, deburring, radiusing, and deflashing to surface improvement such as polishing, cleaning, and drying. Barrel tumblers typically operate in a batch production mode, though continuous or in-line configurations are less commonly found.

We will now compare vibratory tumblers and barrel tumblers across various aspects.

Types of Parts

Vibratory tumblers are effective for finishing nearly all types of parts, including delicate, soft, and fragile ones. They are particularly recommended for such parts because divider plates can be used to prevent part-to-part contact. Vibratory tumblers help maintain the original shape of the parts as the tub remains stationary during operation and can also handle long parts. In contrast, rotary tumblers are better suited for smaller, harder parts.

Finishing Media

The media used in rotary tumblers wear out more slowly compared to vibratory tumbler media, lasting about twice as long. However, rotary tumblers require more time to achieve the same finishing results as vibratory tumblers. Additionally, rotary tumblers typically consume more media.

Cycle Time

Vibratory tumblers produce finished parts more quickly than rotary tumblers.

Finishing Tasks

Rotary tumblers are well-suited for heavy deburring, radiusing, and size reduction, as they can deform parts to some extent and shape rough, irregularly shaped parts into smooth, rounded forms. On the other hand, vibratory tumblers are ideal for polishing, cleaning, and drying, though they are also capable of handling heavy finishing tasks.

Initial Cost

Vibratory tumblers are generally more expensive than rotary tumblers because of their robust construction, versatility, and additional features. They also require more floor space. In contrast, rotary tumblers have a lower initial cost.

Noise Control

Vibratory tumblers can be quite noisy during operation due to the strong vibration force causing the contents to oscillate against the tub. However, advanced models offer noise control features. In contrast, rotary tumblers produce less noise.

Summary

• A vibratory tumbler is equipment used in the vibratory finishing process, one of the most commonly employed mass finishing processes.
• The operation of a vibratory tumbler involves placing the parts in a tub filled with finishing media and a specialty chemical (for wet vibratory finishing processes). Vibration force is applied to the tub, which causes the part and the media to rub against each other. This action deburrs and polishes the part. Vibratory tumblers can perform many finishing tasks.
• The types of finishing media used in vibratory finishing are classified into material type, grades, and shapes.
• Vibratory finishing may be a wet or a dry vibratory finishing process. A wet vibratory finishing process is aided with water or specialty chemicals.
• The types of vibratory tumblers are vibratory bowls, vibratory trough finishing machines, continuous vibratory tumblers, vibratory dual finishing machines, and vibratory dryers.
• The media-to-parts ratio and the frequency and amplitude of the vibration must be considered in selecting and operating vibratory tumblers.
• Vibratory tumblers have lower cycle time and consume fewer media compared to rotary tumblers. They are ideal for finishing delicate, fragile, soft, and long parts.

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