First, the choice of grinding beads:
1, the chemical composition
According to the different grinding media materials can be divided into glass beads, ceramic beads (including zirconium silicate beads, zirconium dioxide beads, aluminum oxide beads, rare earth stabilized zirconia beads, etc.), ball and so on.
As the chemical composition and manufacturing process determines the difference between the crystal structure of grinding beads, crystal structure of dense bead to ensure a high strength, high wear resistance and buy low, sell oil. Percentage content of various components of the grinding beads of different proportion of the decision, the high proportion of the ground provided a guarantee for high efficiency; grinding beads in the grinding process the chemical composition of the natural wear and tear in the performance of the slurry will have some impact, so in addition to consider the low wear rate, the chemical elements are also factors to be considered. Tape such as grinding paste powder or other electronic components, metals Fe, Cu and other elements should be avoided, CuSO4 and other ingredients containing Fe2O3 or not in the choice of the grinding beads the list, so choose zirconium beads are often a popular choice in this industry; such as grinding pesticides , medicine and biochemistry, heavy metal elements as scruples, and PbO is the most common ingredients. Beads determined the chemical composition of some physical properties (hardness, density, abrasion resistance) and wear their own pollution in the slurry is to choose the grinding media to be taken into account.
2, the physical properties:
2.1 density grinding beads
Density in the usual proportion of the documents is (true specific gravity) and the bulk weight (apparent specific gravity), using the various oxides of molecular weight and percentage composition of the density determines the ground, the density of common ground in the following table.
Type
Glass beads
Zirconium silicate beads
Zirconium beads
Alumina beads
Ball
Rare-earth zirconium beads
Proportion
2.5
4.3
5.5
5.7
7.8
6.1
Loose weight
1.5
2.5
3.2
3.4
4.
3.7
Typically, the greater the proportion of the grinding beads, the greater the impulse, the higher the grinding efficiency, and contacts on the sanding machine (within the cylinder, scattered disk, etc.) wear relatively large, so the slurry viscosity and flow with a Key. Low-density grinding beads slurry for low viscosity, high-density grinding beads suitable for high viscosity paste.
The hardness of grinding beads 2.2
Mohs hardness (Mohs) is commonly used indicator, the greater the hardness of the grinding beads, beads in theory, the lower the wear rate. Such as grinding beads from the contacts of the sand mill (dispersion plates, pins and rods within the cylinder, etc.) wear situation, the grinding bead hardness wear resistance of contacts, although a little bigger, but can be filled by adjusting the amount of beads , slurry viscosity, flow and other parameters to achieve the best optimization point.
Grinding bead diameter of 2.3
Determines the size of abrasive grinding beads beads and the amount of contact materials, small size of the beads under the same volume of more points, in theory, the higher the grinding efficiency; the other hand, the larger abrasive particles first test materials, for example, 100 microns for the slurry, D = 1mm beads may not win with, because the volume of small red beads disperse the energy of less than full, and you should use a larger size beads.
3, the first use of grinding media notes
3.1. High and low viscosity of the material chosen by zirconium beads or glass beads
3.2. Particle size of raw materials and products according to the required fineness select the appropriate size of the beads.
3.3. Check the grinding machine or a sieve separator choose the right aperture is set, the gap should be one-third the diameter of the smallest beads. For example: Using the 1.2 ~ 1.4 mm of the bead, the gap should be 0.4 mm.
3.4. Try to avoid open ground in the dry state machine, resulting in unnecessary loss of beads and accessories.
3.5. Do not mix different brands of beads.
3.6. Try to avoid mixing the size of beads.
4, how to determine the particle size of zirconium beads:
4.1. Grinding equipment requirements:
1) mesh separation: the minimum diameter of beads gap * 1.5 = screen;
2) ring separation: the smallest bead diameter = ring slot * 3;
4.2. Process requirements:
1) The initial diameter of materials: beads, the minimum diameter = initial diameter of the material * 30 ~ 50;
2) The final material bead diameter = diameter.
4.3. Beads 1.5mm in diameter is a better choice.
Second, the grinding of broken beads
1, the causes of broken beads
The market is popular glass beads, zirconium silicate beads and pure zirconium beads, to the production process, the essentially two kinds of fused method and sintering. Beads in hot air, cold air or the electrolyte in the molding, such as a key technical parameters did not control well, will produce the following delicate beads:
1.1, bubble beads
1.2, snowman beads
1.3, tail beads
1.4, flat (oval) beads
2, the beads determine the normal wear and broken
Work for a period of time grinding beads become smaller, the surface smooth and not with the edges and corners, which should be normal wear beads; such as beads which appear with a edges and corners, chip shaped beads created when it should be broken beads.
3, broken beads causes
The one hand, the quality of beads, on the other beads or strength of such material can not win with some type of sanding machine. Such as Switzerland's Dyno-mill ECM horizontal sand mill and the DCP German Drais vertical sand mill, because of the input energy density is relatively high, often recommend the use of zirconium beads.
Grinding beads in the sand under the machine to work, to be about 1 kg of pressure, relative glass beads can withstand the force of about 5,000 kg and 9000 kg of zirconium silicate beads, the grinding beads in the sanding machine in the force is negligible Therefore, the reasons for broken beads should focus on equipment and workmanship, and take the appropriate solution.
4, broken beads solution
A. equipment
1). Scattered disk: install anti-dispersing plate, loose or crack damage.
2). Separation devices: Dynamic screen ring is chipped, broken screen.
3.) Feed pump: Gear pump suddenly turned off, the sand inside the beads back pressure to the pressure pump. Can be avoided by installing one-way valve, while maintaining the regular cleaning of feed pump.
4). Within the cylinder: the cylinder is defective points.
B. operational aspects of the production:
1). The size of mixed beads: this situation was beginning to improve grinding efficiency of the signs, but with the grinding time longer, resulting in a large bead mill case of beads, and finally the deformation as well as speed up the broken beads. The solution is to make use of uniform size beads.
2.) Beads in the mix of different brands: for a variety of beads, hardness, density and other inconsistent, prone to eat the soft beads beads hard situation, and should put an end to this form.
3). Slurry viscosity is too thin or too thick: the relative terms of a certain density of the grinding beads, beads so easily lead to the accumulation and direct contact with the sanding machine is accelerated wear parts wear and broken beads.
4.) Rapid flow of materials: This will result in the backlog of the materials exit the beads, and speed up the beads and the sand here wear accessories. The solution is to boot using the method of intermittent backlog of grinding beads to loosen and re-distribution, re-adjust the material flow.
5, how to solve the crushing grinding beads
If the particles are relatively smooth, not like the broken glass that have sharp edges and corners, which is the natural wear and tear of the beads. These beads may be ground into various shapes such as discoid, oval, or a smaller ball. This situation can be called wear, just wear different.
The force from the point of view, scattered disk transfer energy to the beads, if the liquid viscosity is low, such as when cleaning with solvents or water sanding machine, the material of the thrust is not big enough, but there may be exposed to the beads scattered disk and have broken. This is what we recommend cleaning time as short as possible is an important reason. If the cleaning machine with a low viscosity liquid, then the beads will wear beads or other contact sanding machine parts. To make grinding beads, sand mill to obtain the longest life, best to use the resin in the production process for cleaning and maintaining sufficient viscosity of the material. Discard the old beads met many new beads into the post-test broken beads. The following analysis of this issue and explore solutions.
1). Sand inside the contact, not installed correctly: loose or scattered disk scattered disk angular edges, sanding inside a foreign body, loosening the valve inside, these situations can cause grinding beads broken.
2). Sanding machine wear contacts or not installed correctly: Dynamic separator or screen may be worn, the screen may be broken open or loaded upside down, and if so grinding media and into the separator through the feed pump, pump before being blocked or shut down the beads will be crushed.
3). Back pressure: When the feed pump turned off, sanding the residual pressure inside the beads pressed into the pump, so that when the pump starts again, it will crush the beads. Not necessarily reliable, and sometimes one-way valve to allow the beads through the valve before closing.
4). Grinding beads backlog: If grinding beads deposited on the sand bottom and work speed of the pump led to excessive grinding beads are concentrated at the exit of horizontal sand mill, would lead to this situation. The solution is to start sanding machine - off - on - off point of moving around first loosen the backlog of grinding beads.
5). Scattered disc wear: This may be difficult to determine. Scattered disk edges worn very uneven ground, and scattered its edge is the largest scattered disk rotational speed place and may form a strong vortex.
In addition to vertical grinding machines, grinding beads scattered due to weight concentrated in the lower part near the edge of plate. All these factors together, there may cause grinding beads broken. Scattered disk wear too much largely because the feeding pump speed is too slow, grinding bead density excessively. Can be powerful by replacing worn parts, and then into the same batch of grinding beads to solve this problem.
6). The different manufacturers of grinding beads mix. In the density of products from different manufacturers may be different. This will increase wear and tear each other between the beads. The solution is to never mix different manufacturers of grinding beads. If you suspect have been mixed, it can only be drained them all.
7). Because they do not accidentally used the old beads added to the sanding machine.
8). Rubbish or some small beads are worn: there is often a waste or some small beads attached to the screen worn line, shaft, bracket, or some other corner of the machine. When adding a new grinding beads, these little things may come loose from the attachment sites of the beads mixed into Xin Tian. This would result in a new illusion of beads right away, broken, and in fact, just before you see some of the natural wear of the beads. If the problem is not too much, you can let these small things in a certain time after the natural discharge. Otherwise, you must be thoroughly drained the old beads, change into the new grinding beads.
9). Cleaning formula selected beads Keyi water, cleaning solution or resin; cleaning should be kept low, should be grinding machine "- up and close" button for the intermittent cleaning.
6, fill the principles of grinding media
Found to reduce the efficiency of the grinding mill, is to add beads may signal. User Keyi own conditions, to grasp the actual loss rate of beads, and beads for the regular screen and add. Too small beads will be screened out with a sieve, mesh size of two-thirds the diameter of the beads. (Example: use of 1.2 ~ 1.4 mm of the bead screen should be 0.8 mm), thing to add, the difference between the beads.
7, how to fill grinding media
As beads of the natural wear and tear, will become increasingly smaller size of the beads, in order to maintain the unity of fine bead filler content and to avoid clogging or enter separation unit should be in accordance with the life of grinding media and the users themselves process conditions used to screen and add some beads the amount of grinding media. After 100-200 hours of work proposed screening of the new beads and adding some beads.
Third, the grinding media trends:
1, with a smaller particle size the more
Grinding equipment from the world's first computer with a larger particle size stirred ball mill grinding balls (Attritor) the birth and development to the smaller size of the grinding beads with vertical sand mill, horizontal belt sanding machine and various improvement features a new generation of ultra-fine grinding sanding machine, grinding media used in more and more small size. There are two main reasons for its promotion:
◆ micron material grinding fineness of the end: As the material inside the mill through the movement of the grinding media contacts for dispersion and grinding, grinding media, the smaller the particle size of more points, and finally reach a higher and better grinding effect small fineness. If a certain brand of 2mm diameter zirconium silicate beads, approximately 20,000 pieces per liter, while the particle size is 1mm to about 80,000, which is 4 times the former. When using large diameter zirconium beads for grinding of a product, regardless of the number of channels through the sand, the material has not been able to achieve the required particle fineness; and when to switch to smaller particle size of grinding beads, the effect that has been markedly improved.
◆ improved sanding machine separation device using ultra-fine grinding beads as possible: the minimum allowed size of grinding beads has become a balanced assessment of a sander and an important indicator of quality grades. Design and production of material separation devices every revolution, have brought the use of abrasive particles smaller beads a leap. Separation unit from the static network to the traditional flat Nickel Johnson beams with triangular network and to the dynamic separator ring and sleeve Cartridge network, in addition to longer life, the size of grinding media can be used less and less while not significantly affect the flow of materials. Sleeve-type Cartridge Network representatives (such as the U.S. Premier of the speed of Po grinding) the smallest beads used to 0.2mm; ring separator representatives (such as Switzerland, Dyno-mill lab model) can also be reached 0.2mm diameter beads . The company began development of the Swiss Buhler centrifugal separation devices, the principle of separation of beads from the distinction between particle size and density of the size of the beads into distinction, leaving the grinding beads to a new minimum size limit.
2, with a larger proportion of the more
Comparison of common grinding beads
Type
Glass beads
Stone beads
Zirconium silicate beads
Zirconium beads
Chrome steel ball
Specific gravity
2.5kg/dm3
2.9kg/dm3
4.5kg/dm3
6.1kg/dm3
7.8kg/dm3
Mohs hardness
6
6.5
7.7
9
7
Compressive strength
0.45KN
0.50KN
0.75KN
2.0KN
0.6KN
Universal grinding beads such as glass beads, stone beads, zirconium silicate beads, zirconium beads, and gradually increased the proportion of chromium steel ball, and their hardness, compressive strength and wear resistance than chromium steel ball outside also were increased. From the kinetic formula P = mv we know that the impulse beads and bead quality of P m is proportional to the energy density, the greater the greater the movement of beads, grinding efficiency is relatively higher.
The toughness of high inorganic pigments (such as carbon black, phthalocyanine blue, iron oxide, etc.) need to fine grinding, in addition to the pursuit of higher grinding efficiency and the ideal gloss, high-density grinding beads has become a solution . The sanding machine manufacturers to coincide with this requirement, mainly in the following two reasons make this possible:
◆ high input energy density of the production of sanding machines: the development trend of the modern sand mill grinding chamber is one of the smaller size, while the larger configuration of the motor power, the input energy density to increase sharply. Relevant control parameters are as follows.
Item
Representatives of the traditional sanding machine
Representative of the modern sanding machines
Brand
American Premier
Switzerland
Model
HM-15
Buhler K60
Grinding chamber volume
15L
4.8L
Motor power
15KW
20KW
Energy density
1KW / L
4.2KW / L
The energy density of modern sanding machine sanding machines for the traditional 4 times or more. This makes effectively promote high-density grinding beads (such as zirconium beads) as possible. At the same time due to the high grinding energy distribution region, only the high compressive strength and wear of the grinding media (such as zirconium beads) to win with.
◆ sander improve the quality of contact materials: contact sanding machine parts (such as inside the tank, spread plate, bar sales and separation devices, etc.) using a hard wear-resistant carbide (such as tungsten carbide) and ceramic (eg, silicon carbide, zirconia, etc.) and other high performance material that can withstand such pure zirconium beads due to their high energy and high hardness, impact and abrasion caused by friction.
3, more and more small beads of diameter deviation
For sanding machine, grinding beads uniform reflect the size of its superiority, on the one hand is the fineness of the narrow distribution of materials has contributed greatly to the other side is greatly reduced the production of broken beads reduced wear contacts sanding machine and avoiding contamination of the product. General resistance on the market today promise to keep the grinding media size deviation of 0.2mm. Beads because of the production process even more complicated, so the market price is relatively high.
Four other
1, zirconium beads criteria:
Item
Indicators
Components
ZrO2 58%, SiO2 37%, other 5%
Proportion
4.0 g / cc
Loose weight
2.4 g / cc
Mohs hardness
> 7
Sphericity
"90%
Air content
0
Compression strength
> 9710 bar
2, particle size zirconium beads:
0.6 ~ 0.8 mm
1.2 ~ 1.4 mm
1.8 ~ 2.0 mm
0.8 ~ 1.0 mm
1.4 ~ 1.6 mm
2.0 ~ 2.2 mm
1.0 ~ 1.2 mm
1.6 ~ 1.8 mm
2.2 ~ 2.4 mm
3, safety devices
Contact with the inlet pressure gauge, fitted with contact thermometer at the exit near the sensor switch is not installed in the ground to prevent the cylinder or the front cover of the case of the machine running. Adjacent capacitance switches for monitoring the mechanical seal in the liquid cleaning solution, contact type pressure gauge for monitoring the pressure shaft seal.
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