Traditional powder mixers' advantages and disadvantages

       Traditional powder mixers' advantages and disadvantages
  Mixing is an indispensable production technology in modern industry. With the continuous development of China's industry, the development of hybrid systems and hybrid equipment will become more and more powerful. The mix covers the entire industrial sector, such as chemicals, foodstuffs, building materials, pharmaceuticals, fertilizers, and at least one step in the process of mixing the products we use every day.         A wide range of powder mixing equipment, this paper mainly on mechanical mixing equipment commonly used in the Chinese market for analysis.         1, double-motion mixer          Advantages: ① ultra-fine mixing to achieve uniform particles and particles.                     ② can solve the light weight, ultra-fine powder mixing problems.                     ③ uniform operation time-saving, energy-saving, using horizontal structure much more.                     ④ uniform operation on the original appearance of small damage powder.                     ⑤ mixed materials no dead ends.                     ⑥ dual-motion mixer can be made into a large mixer, such as a -liter mixer.         Disadvantages: for the time being no obvious shortcomings of the device. 2, Three-dimensional mixer (gravity convection diffusion hybrid)         Advantages: ① multidimensional space motion can make the material fully mixed macroscopic.                    ② Mixing process without centrifugal force.                    ③ Without dead ends.         Disadvantages: ① microscopically difficult to do fine mixing.                    ② Kinetic energy is too large, ultra-light powder, ultra-fine powder easy to float easily mixed with the main powder.                    ③ Mixing a long time, more power consumption, loading rate is low.                    ④ Operating acceleration, there are bad records broken shaft, due to safety equipment is not easy to enlarge.                    ⑤ Equipment difficult to do more than 1,000 liters of large equipment. 3, V-type mixer          Advantages: ① No dead ends.                     ② When the mixed powder fluidity, similar physical properties, you can get a better mixing effect.          Disadvantages: ① microscopic powder is not easy to mix well.                     ② Ultra-fine powder, ultra-light powder is not easy to mix into the main powder.                     ③ Gravity lifting exercise, so high power consumption.                     ④ Throwing smashing movement, will destroy the powder shape. 4, Single cone double helix mixer          Advantages: ① Simple structure, easy to do mainframe.                     ② On the heat-sensitive materials will not produce overheating.                     ③ Can add spray device and heating.          Disadvantages: ① Long mixing time, Low efficiency.                     ② Equipment height is too high. The same mixing capacity, double helix device requires twice the height of other equipment or even higher.                     ③ Equipment at the bottom of the dead ends, the middle part of the material required for the bottom of the material mixed repeatedly, to avoid dead ends.
5, groove ribbon mixer          Advantages: ① Loading factor, equipment, small footprint.                     ② Within the shear blade can reach the microscopic uniform mixing.                     ③ According to the demand for production equipment can do mainframe, the price is cheaper than other mixers.          Disadvantages: ① Barrel fixed material will exist dead ends.                     ② Equipment start-up load is particularly large, full load start difficult, time-consuming electricity.                     ③ There are residual material. 6, Horizontal gravity-free mixer          Advantages: ① Speed, high mixing efficiency, sealing operation, economic and environmental protection.                     ② Can add flying knife, to achieve with the fiber material mixture.                     ③ Open the door out of material, a short discharge time, discharge clean, compact structure.          Disadvantages: ① can not solve the problem of mixed material weight disparity.                     ② Dead ends.                     ③ Easy to damage the particle shape of the powder.
7, Double cone mixer          Advantages: ① Double cone-shaped cylinder to adapt to mixed materials without dead ends of the mixing requirements.                     ② Gentle operating speed will not damage the fragile materials.                     ③ To meet the production of large quantities of the combined batch.          Disadvantages: ① Can not achieve the refinement of mixing.                     ② Lower mixing efficiency, mixing time longer.
8, Square cone mixer          Advantages: ① Innovative design, compact structure, beautiful appearance, mixed effect in general.                     ② Fine polishing mixed without dead ends.                     ③ Cone side of the bucket can replace the material storage silo with convenient operation.                     ④ Convenient and easy cleaning material bucket.          Disadvantages: ① Can not achieve the refinement of mixing.                     ② Not easy to enlarge.                     ③ Complex and cumbersome equipment, equipment, high cost.
9, Planetary mixer           Advantages: ① Not only the internal revolution, while it is still its own rotation, fine mixing and high uniformity.                      ② Fine polishing mixed without dead ends.           Disadvantages: High speed powder particles destructive.                      ② Due to equipment constraints is not easy to enlarge.                      ③ Due to the complexity of the structure is relatively high cost.

Manufacturers carefully consider the pros and cons when selecting a process to produce their products. Their goal is to achieve high quality while keeping costs low.

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Why does the powder metallurgy (PM) stand out?

In this blog, I’ll tell you the advantages and disadvantages of powder metallurgy.

What is PM?

PM technology is famous for its high raw material utilization, low processing energy consumption, and superior production efficiency.

This process mainly consists of 4 stages.

• Powder production: Metal powders are produced by atomization, reduction, or electrolysis.
• Mixing and blending: Mix powders and binders evenly
• Compacting: The compaction machine presses powder metal into a mold to form the green compact.
• Sintering: The sintering furnace heats the green compact at a temperature below the melting point of the metal.

Advantages of Powder Metallurgy

Minimize Material Waste

You must want to improve material utilization and reduce waste.

CNC machining like turning, milling, and drilling removes excess parts from solid materials. This leads to a great waste of raw materials. What’s worse, the waste materials cannot be reused

PM is able to achieve material utilization of over 95%, a level unmatched by other processes.

Why can powder metallurgy do this?

This is because PM uses metal powder as the raw material. Defective green compact could be crushed back into powder for reuse. Any unused powder material will be utilized in the next production run.

PM is a near net shape technology, which is especially important when machining precious metals like titanium alloys.

Cost-effectiveness in Mass Production

Powder metal parts are formed at room temperature and sintered at lower temperatures than casting, consuming less fuel. In addition, powder compaction presses are able to operate quickly, and compact about 30 parts per minute.

Precise Forming Ability

The powder metallurgy mold, which includes the upper and lower punches, die, and core rod, is designed with tight tolerances. As a result, the pressed products realize high precision.

For the sintered metal product with a radial dimension of 25 mm, the tolerance is generally 0.13% (32.5μm) to 0.20% (50μm). This falls within the ISO standard tolerance of IT8-IT9. After the sizing process, the tolerance improves from 0.05% (12.5μm) to 0.08% (20μm). This is consistent with ISO standard tolerances IT6-IT7.

Batch to Batch Consistency

The mold tolerance, compacting pressure, and sintering temperature in PM could be precisely controlled. As a result, the consistency of products across different batches is high. Batch-to-batch consistency is of great significance for stable and reliable product operation.

Less Secondary Processing

Metal powder products are formed by pressing once, with less secondary processing. This not only shortens the production time but also decreases the production cost.

The transmission gear of the gearbox is a typical example. The size of the gear manufactured by the powder metallurgy process is the final product size after sintering. In addition, powder metal gears do not have excessive flash and burrs.

Due to the large number of teeth, machining gears is slow and generates a lot of material waste. The forging process is also hard to produce gears. Moreover, forging requires multiple secondary processing steps such as trimming, punching, and straightening.

Complex Shapes

PM allows for producing parts with internal features directly. These parts are applied for fluid flow, cooling systems, or wire ducts.

It also has the capability to produce components with sharp edges and thin walls, often applied for cutting tools or gear teeth. PM also can creates parts with stepped geometries in a single operation.

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Green Manufacturing Process

Powder metallurgy technology contributes to the green development of the manufacturing industry. Unlike die casting, powder metallurgy technology consumes less energy and emits less wastewater and exhaust gas. The stamping process wastes a lot of materials, while the material utilization rate of powder metallurgy technology reaches as high as 97%. These are conducive to saving resources and protecting the environment.

Controlled Porosity

The pore size of powder metal components could be controlled, offering two advantages.

First, the pores in sintered components are filled with oil through the impregnation process to achieve a self-lubricating effect. This is known as an oil-impregnated bearing. Second, powder metal parts are employed as sintered filters due to their uniform pore size.

Automation

Did you know the whole powder metallurgy process can be fully automated? Automated machines can run 24 hours a day, which makes production faster. They also reduce the need for workers, so labor costs go down. Robotic arms help avoid mistakes made by people. Besides, the automated system makes the product quality more consistent.

For example, a fully automatic sizing press can press parts at 50 pieces per minute. The sintered parts can be automatically transferred by a robot arm during sizing process.

Capability to Process Multiple Materials

It is quite difficult to machine metals with high melting points and hardness. Powder metallurgy has the capability to process these metals.

Titanium alloy is one example. As we all know, titanium alloy is resistant to high temperatures, and corrosion, has good tensile strength, low density, non-toxic.

Also, PM can process superalloys such as Inconel 718.

In addition, it has the ability to produce immiscible composite materials such as tungsten-silver, tungsten-copper, and molybdenum-copper.

Disadvantages of Powder Metallurgy

Limited Size

For powder metallurgy, manufacturing larger parts is more challenging. This is due to the limitations of powder compacting equipment.

Most metal powders are pressed at pressures between 300 and 800 MPa. If the cross-sectional area of the workpiece exceeds 200 square centimeters, the tonnage of the forming machine will exceed 1,600 tons. Such equipment is extremely expensive.

Therefore, most powder metal parts are within 250mm in diameter and 75mm in height.

Also, PM can’t make the production of tiny products (20g or less), but metal injection molding can.

Limited Shapes

For parts with particularly long shapes, such as sintered filter cartridges, isostatic pressing is commonly used. Similarly, for those with complex 3D features, PM is not suitable. Metal additive manufacturing process is a better option.

Low Mechanical Properties

Powder metal parts have many pores inside, while castings and forgings are fully dense. This leads to the strength, toughness, and fatigue resistance of sintered parts poor.

Expensive Powder Metallurgy Mold

Why are powder metallurgy molds so costly? There are two main reasons.

On the one hand, the mold needs to withstand high pressure and wear from metal powder. Therefore, it must have good strength, hardness, and wear resistance. You can use tool steel, high-speed steel, or tungsten carbide. These materials are expensive.

On the other hand, the mold tolerance is tight and the manufacturing time is long. This also increases the cost of the mold.

Costly Equipment

PM demands a large amount of equipment investment, which is important to the entire process. These equipment include mixers, powder presses, sintering furnaces, shaping machines, and automation devices.

Surface Roughness

The surface roughness of sintered components is not enough good, around Ra 0.8-1.6 μm. In contrast, machining can achieve a surface roughness of Ra 0.6 μm or even Ra 0.4 μm. To improve the surface roughness of powder metal components, you may need secondary processing or sizing process.

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