When choosing the most suitable mass finishing machine, you must take into consideration the size of the workpiece, material (hardness), shape, and purpose of finishing. Production volume, time taken in the mass finishing process and the state before mass finishing also must be considered.
Mass finishing machines are mainly divided into the following five types. Also available are Gyro finishing machines, Recipro finishing machines and High-Spin finishing machines as special-purpose machines. However, a description of these is omitted here.
Hi-Gravitational Barrel Finishing Machine
Function
This is an original product developed by us.
Just as in centrifugal barrels, the barrel tub of this finishing machine repeatedly rotates and revolves. Although a centrifugal force of 2 to 4 times that of centrifugal barrels is applied (whereas the centrifugal force of a centrifugal barrel is 7 to 10G, it is roughly 15 to 40G in a hi-gravitational barrel), its rotation speed is slower by 1/10 to 1/2. As a result, the sliding layer becomes "low-speed, high-pressure flow," hopping of mass as in "high-speed, low-pressure flow" of centrifugal barrels disappears and flow is calm.
Method of Use
Abrasive media, water and compound are charged in the same way as in a rotary barrel finishing machine.
Advantages
- Finishing capacity is extremely high, capacity of 40 to 100 times that of rotary barrel
- Wear of abrasive media can be reduced by 20 to 50% of centrifugal barrels
- Little deformation, impingement, chipping and cracking of workpieces
- Improved surface roughness results in extremely high gloss
Disadvantages
- Difficult to automate as the barrel tub must be covered and shut tight
Centrifugal Barrel Finishing Machines
Function
On these machines, barrel tubs having a hexagonal or octagonal cross-section are located on the periphery of a rotating turret, and a sliding layer is formed on the surface of the mass and workpieces are finished by each barrel tub rotating in opposite directions while revolving around the turret, in other words through planetary motion.
Method of Use
Abrasive media, water and compound are charged in the same way as in a rotary barrel finishing machine.
Advantage
- Finishing capacity is extremely high, capacity of 30 to 40 times (max. 60 times in some conditions) that of rotary barrel
Disadvantages
- Deformation and impingement on workpieces easily occur due to strong flow
- Difficult to automate as the barrel tub must be covered and shut tight
Centrifugal Disc Finishing Machines
Function
The barrel tub is made up of cylindrical stationary tub and a bowl-type rotating disc located at the bottom edge of that tub, and the workpiece is finished while the entire mass flows as a result of the rotating disc rotating.
Method of Use
Mass amount
40 to 50% of barrel volume is charged as a standard amount
Water amount
Water is charged 10 to 20 mm above surface of settled mass
Compound amount
1 to 2% of water amount
※The reason to take 40 to 50% as the mass charging amount is because the mass flow is less likely to occur if the mass amount is greater than this. Alternatively, if the mass charging amount is less than this standard amount, output may drop and deformation and impingement on workpieces may increase.
Advantages
- Machining capacity is high, capacity of 10 to 15x that of rotary barrels
- Easy to automate as upper part is open
Disadvantages
- Deformation and knocks on workpieces occur relatively easily
- As fine abrasive media and thin sheet workpieces easily get in between the gap (also called "clearance") of the fixed tub and rotating disc, these sizes are limited
Vibratory Barrel Finishing Machines
Function
A curved bowl tub and vibratory motor placed in the vertical direction at the center of the bowl are supported on springs, and the action of the vibratory motor causes the mass to vibrate in three dimensions. The workpiece is finished while the entire mass flows as a result of this vibration.
Method of Use
Mass amount
100% of bowl volume is charged as a standard amount
Water amount
3 to 5% of the mass amount
Compound amount
1 to 2% of water amount
※Satisfactory flow can be obtained for the first time when a mass amount of 90% or higher of the volume of a vibratory barrel is charged. When an amount below 90% is charged, flow is easily disrupted, which may prevent a satisfactory finishing amount from being obtained.
Advantages
- Large workpieces can be finished as there is little deformation and impingement on workpieces
- Productivity is high as volume efficiency is high
- Easy to automate as upper part is open
Disadvantages
- Flow is easily disrupted when fine granular abrasive media is used
- Very noisy
Rotary Barrel Finishing Machines
Function
This is the most basic of mass finishing machines. When the octagonal cross-section barrel tub is rotated, a sliding layer is formed on the surface of the mass of workpieces and abrasive media inside the tub, and the workpieces that slide down through this mass rub against the abrasive media to be finished.
Method of Use
Mass amount
50% of barrel volume is charged as a standard amount
Water amount
Water is charged 10 to 20 mm above surface of settled mass
Compound amount
1 to 2% of water amount
※The reason to take 50% as the mass charging amount is to strike a balance between throughput and grinding amount. In other words, this takes into consideration the fact that, at above 50%, throughput increases but the grinding amount drops, and, at below 50%, throughput decreases but the grinding amount rises.
Advantages
- Almost all workpieces can be finished
- Equipment is low-priced
- Continuous operation over a long time is available
Disadvantages
- Finishing capacity is low
- Difficult to automate as the barrel tub must be covered and shut tight
Model Comparison Table
This table compares the benefits of the above five models.
| Rotary Barrel Finishing Machines | Vibratory Barrel Finishing Machines | Centrifugal Disc Finishing Machines | Centrifugal Barrel Finishing Machines | Hi-Gravitational Barrel Finishing Machine | |
|---|---|---|---|---|---|
| Finishing Capacity Comparison※ | 1 | 1.5～2 | 10～15 | 30～40 | 40～100 |
| Mass Charging Amount in Relation to Barrel Volume | 40～60％ | 90～100％ | 40～50％ | 40～60％ | 40～60％ |
| Target Workpiece Size | Small～Large | Medium～Large | Small～Medium | Small | Small |
| Difficulty of Automation | Difficult | Easy | Easy | Difficult | Difficult |
| Price | Low-priced | Medium-priced | High-priced | High-priced | High-priced |
※In the finishing capacity comparison, the capacity of a rotary barrel is taken to be "1".