Mixer grinders needs no introduction! We all have grown up listening to its high-pitched grinding noise. Over the years, with technological advancements, mixer grinders also have gone through various changes. Be it in terms of looks, stability, ease of use & of course the motor power. But when it comes to choosing the right mixer grinder, it always seems to be a difficult task. For better selection and understanding, we have elaborated the basic features that one must look for while buying a Mixi.
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Compared to older times, today's mixer grinders are not just confined to mixing and grinding. They can do the jobs quicker, cleaner and also come with Fruit Filters for making juices from soft fruits or making tomato puree. When it comes to getting a mixer-grinder that does the basic tasks with ease, there will be many options available. Glen has been selling a range of mixer grinders for over 2 decades now. These have been accepted well in the market and offer many advantages over other mixer grinders available in the market.
FEATURES TO CONSIDER WHILE BUYING A MIXER GRINDER:
Before zeroing to any mixer grinder, you must consider its motor power. Higher the power the faster it will do the job! A mixer grinder ranging from 500W to 750W power is good enough to do all the mixing grinding effortlessly. Glen offers a variety of mixer grinder options between 500W & 750W. You may select as per the requirement and type of usage. Also check that the Motor has 100% copper winding for better strength.
These are the ones that do all the work, so it makes sense to verify their quality. Make sure that the material is stainless steel and preferably rust free if can be of SS 304 grade its wonderful. High-quality steel blades retain their sharpness for a longer period.
Overload Protector helps in saving the motor from damage in case of overload of ingredients or electricity fluctuation. All Glen mixer grinders comes equipped with overload protector.
The size & number of jars should also be taken into consideration while looking for a mixer grinder. The bigger size allows processing of more ingredients in one go. Also, the separate jars for liquidizing, grinding & chutney making allows ease of operation. Glen gives you option of 2/3/4 jar mixer grinders, depending upon your usage and requirement.
The Revolutions Per Minute of a mixer grinder is also a deciding factor, as it tells you how fast the blade can rotate per minute. For efficient dry grinding a minimum of RPM is required.
Usually all mixer grinders comes with 3 speed settings that allow you to achieve the desired consistency of ingredients while processing. But, you must also look for the incher or pulse function in the mixi allows in processing of delicate ingredients which otherwise on normal speed may lose their texture.
BEST MIXER GRINDERS OPTIONS:
750W ISI: It comes with three jars (liquidizer, dry grinder & chutney). There are 3 speed settings and pulse function. An impressive design feature is that is comes with a 6 way coupler between the jar and base unit ensuring secure fit.
This model comes with 5 year warranty on motor. This model has its other variant Plus with Glass Jar.
500W ISI: This is an ISI Certified mixer grinder that comes with 3 jars ' liquidizer, dry grinder & chutney to minimize your manuals efforts.
It has 500W heavy duty motor to handle heaviest of loads. The model has 3 speed settings with pulse function.
550W ISI: This model comes with 550W motor for effortless mixing & grinding of ingredients. There are three jars (liquidizer, grinder & chutney) to minimize your efforts.
The 3 speed settings with pulse function allows to achieve best results.
TIPS ON USING A MIXER GRINDER:
HERE ARE SOME WAYS TO CLEAN YOUR MIXER GRINDER:
Conclusion:
Justifying the fact that there are number mixer grinders available in the market from various brands but it certainly gets difficult to make a choice while buying one. However, if you select a MG, and all the above-mentioned basic features are met as per expectation, then you are good to go. In case, if you still have doubts or confusion in mind for the MG, then you may reach out to us via social media or our helpline number for best assistance.
Closed Loop
Figure 5. Oversize material is separated and then returned to the mill.Oversize material is separated and then returned to the mill.
MILL SELECTION
Dry grind processing is ideal for products with particle size specifications of 2'3 microns average or larger. Dry grinding offers many potential cost savings. It can cut transportation costs because materials can be shipped without additional liquid weight. It also can reduce production costs and energy because there's no need to remove liquid from the final product. In addition, dry grinding can eliminate costs associated with waste liquids' disposal, which has become increasingly expensive due to stricter environmental regulations.
Attrition mills can operate in either batch or continuous mode and suit harder-to-grind material such as metal powders, metal carbides and glass frits. Their shaft speed runs from 75'500 rpm and media generally range in size from 5'13 mm. Feed material can be as coarse as 1/2 in., while end product size can be as fine as 2'3 microns if the mill operates in a batch mode.
Dry grind mills also are used to make dispersion strengthened metal (DSM). In this process (known as mechanical alloying or cold welding) the grinding media break the metals and additives into small particles first, and then beat them together to form agglomerates. Repeating the process evenly mixes and disperses the various metals to form the DSM.
Pigment makers also use these mills to develop color in pigments.
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High-speed attrition mills rely on small (2'3-mm) media and operate at a much higher speed, generally from 400'2,000 rpm. Proprietary design features such as shaft/arm configuration and side discharge screens allow these mills to continuously produce fine powders, which are discharged by centrifugal force. However, the small media size used limits feed materials to 40 mesh and finer. The end products from these continuous mills generally are in the 2'5 micron range.
Dry grind mills can be used in conjunction with air classifiers or screeners to form a closed grinding process loop (Figure 5). By continuously classifying out fines and returning oversize material to the mill, such systems can very efficiently provide sharp particle-size-distribution grinds.
As a rule of thumb, dry grinding generally will achieve particle sizes of 3'5 microns. To mill to sizes below that range requires wet milling. Today, the trend clearly is to produce nanoparticles.
Wet grind processing can be done in batch, continuous or circulation modes. In recent years, many paint and mill manufacturers have focused much of their attention on a "new" type of "high circulation rate grinding" to achieve superior dispersions. In actuality, this type of grinding has been used for many years.
These units combine a grinding mill with a large holding tank equipped with both a high-speed disperser and a low-speed sweep blade. The entire contents of the holding tank pass through the milling chamber at least once every 7.5 minutes or about 8 times per hour. This high circulation rate results in a uniform dispersion, narrow particle-size distribution and faster grinding.
There are two types of high circulation mills ' one uses 3'10-mm media to process material down to sizes of a few microns, the other uses 0.1-2-mm media to achieve sub-micron and nano-size products.
MEDIA SELECTION
Choice of grinding media depends upon several factors, some of which are interrelated.
' Specific gravity. In general high-density media give better results. The media should be denser than the material to be ground. When grinding some slurries, media with higher density may be required to prevent floating.
' Initial feed size. Smaller media can't easily break up large particles.
' Final particle size. Smaller media are more efficient when ultrafine particles are desired.
' Hardness. The harder the media the better the grinding efficiency and, consequently, the longer the life.
' pH. Some strongly acidic or basic material may react with certain metallic media.
' Discoloration. Certain applications require, for instance, white material to remain white.
' Contamination. Material resulting from media wear shouldn't affect the product or should be removed by a magnetic separator, chemically or in a sintering process.
' Cost. Media that may be two-to-three times more expensive may wear better, sometimes lasting five-to-six times longer ' and therefore may justify their extra cost in the long run.
For attrition milling, media size ranges from 1/8 in. to 3/8 in., with smaller media generally resulting in faster particle reduction ' because for a given volume there'll be more impact and surface contact. As media becomes smaller than 1/8 in., mass is significantly reduced, resulting in less impact force and thus longer grind times. When ultrafine grinding isn't needed, larger diameter media may prove to be faster and more efficient because of their greater mass. Here is a summary of the advantages and limitations of attrition milling:
Attrition Milling in Perspective
Advantages
1. Fast, efficient and reliable fine grinding
2. Versatility of the grinding process
3. Low power consumption
4. Mills come jacketed for heating or cooling
5. Easy and safe to operate with minimal operator attention
6. Low maintenance
7. Compact design requiring small plant area
Limitations
1. Maximum feed material size of 13 mm generally
2. Heat generation from dry milling
3. Multiple mills likely needed for large quantity production
Keep These Hints in Mind
Here're a few practical pointers to help you succeed with attrition milling. First, the smaller the feed size and the more uniform the feed size the higher the efficiency. Beyond that, the type of milling raises a number of specific issues.
Dry Milling '
Tips:
1. Minimize moisture content of feed material; high moisture content (over 2%) can cause material to cake inside the milling chamber.
2. Continously add grinding aids or additives, whether in powder or liquid form, while size reduction is taking place. Most dry milling processes require such materials. Their function is to do one or more of the following:
a. minimize the effects of moisture inherent to the material being processed;
b. change the electrical charge on the surface of particles;
c. reduce the negative effects of static charge that may develop;
d. function as a lubricant between particles; and
e. act as a partitioning agent between particles to prevent agglomeration.
Trap:
1. Avoid over-grinding material that's already smaller than desired size. Remove this fine material as soon as possible by some form of classification. This will increase process throughput rate and efficiency.
Wet Milling '
Tips:
1. If needed, use wetting agents or surfactants. They serve several purposes:
a. helping to neutralize electrostatic charge;
b. lowering surface tension; and
c. assisting in improving the solution's rheological properties.
Traps:
1. Ensure material is properly dispersed before adding to the mill. This will help to prevent agglomeration and clogging of the discharge screen.
2. Don't choke the mill by starting with solids content that's higher than the mill can process. A rule of thumb is to start with 50% solids and adjust as needed. Remember that as particle size is reduced surface area and viscosity will increase, which may require lowering the percent solids.
Keep in mind that no single mill will grind large particles to a very fine size efficiently by repeating or prolonging the process in the same unit. A specific type of mill (with fixed media, operating conditions or equipment parameters) is most efficient in grinding a particular material with a certain feed-size range. A ratio of feed size to desired particle size of greater than 100:1 requires a two-step milling process. The first step should rely on larger media to reduce particle size to a level that can be handled in step two with smaller media. Whenever possible run a laboratory test at the mill manufacturer's facility. This will demonstrate the feasibility of the milling system and provide valuable scaleup information for larger throughputs.
ROBERT E. SCHILLING, P.E., is national sales manager for Union Process Inc., Akron, Ohio. him at [ protected].
Reference
1. Moir, D. N., "Size Reduction," p. 54, Chem. Eng. (Apr. 16, ).
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