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Full screen hammer mill
Hammer Mill
Why to use a Hammer Mill
In industry where we need to reduce the particle size of a product so as to use it effectively, we use different machines to solve the purpose which include hammer mills, grinders, roller mill's etc.

In hammer mills high speed rotating impact force of hammer is utilized to crush a material.

Though our Hammer mills are being used in many industries with different design features, here we will discuss regarding hammer mills being used in animal feed industry.

Animal feed consists of different ingredients to make a balanced diet in terms of proteins, carbohydrates, fats, vitamins, minerals and medicines etc. There are few ingredients which are already available in powder form while the others like grains and cakes (by products of oil extraction plants from soya, groundnuts, mustard etc) need to be reduced to the required particle size to help to achieve to following :
Expose greater surface area for digesting.
Improve ease of handling of some ingredients.
Improve mixing characteristic of ingredients.
Increase Pellet efficiency and pellet quality.
Basic Hammer Mill Design

A typical hammer mill consists of a horizontal rotor assembly fitted inside a metal housing.  The rotor assembly includes a shaft and several circular plates mounted on it with equal spaces between plates. Plates are having holes on its outer PCD to accommodate hammer pins on which swinging hammers are fitted. A perforated metal screen is forming either a full circle or half circle fits around the rotor assembly. The diameter of hole in screen is selected to match the desired particle size.

A material inlet is typically located at the housing top and a material outlet is located below the housing. A flow deflector is mounted below the material inlet to deflect the material either way to assist grinding.


The Grinding Theory

The product entering from the top of hammer mill, fall at the moving speed of 30 to 60 ft per minute. The product comes in contact with very high speed moving hammers at the top of their swing. The entering product can be assumed almost stationery as compare to very high tip speed of hammers. Due to huge difference in relative speed of each other, when contact is made, due to high impact force product is shattered in particles.

After this action, hammers begin to pull material into acceleration zone where the particles will increase in velocity to attain hammer tip speed.

As soon as the particles attain the exit velocity, they are thrown out of grinding chamber.
  Full Screen Hammer Mill
  As its name implies, Full screen hammer mill have 80 % screening area as compare to 50 % in half screen hammer mill. This machine is an     answer to many fine or coarse grinding problems that we usually face. Our Full screen hammer mill has so many other features also that make    it an ultimate choice.
  Efficient Grinding by maximum grinding surface
  Dynamically balanced rotor means vibration level minimum to the Standard norms. Forward and Reverse  rotation of     rotor allows utilization of cutting points of hammers without wastage of time. Further hammers and  hammer holding     rods are heat treated for prolonged life and static balanced to avoid viberations.
  Quick span Locking mechanism
Quick Span Locking Mechanism
  Quick span Locking mechanism of doors makes accessing the grinding chamber for screen changing etc.very easy.
  Interlock Sieve pressing Device
Interlock Sieve Pressing Device.
  Interlock Sieve pressing Device makes sieve changing quickly, without any tools and eliminates unevenness of sieve.
  Direct Coupled Motor
Direct Coupled Motor
  Direct Coupled Motor with grinder means no slipping of belts and no loss of power.
  Rotary Feeder
Rotary Feeder
  Rotary Feeder for uniform feeding of product into the mill. For maximum safety of mill, rotary feeder is equipped  with     self  cleaning magnet for removing metal objects etc., which can be cleaned within 10 seconds.
  Gap adjustment by dual position of hammers on rotor allows hammer tip to screen gap-adjustment which are fit for normal grinding and fine     grinding.
  For safety reasons Hammer mill doors interlocked with main motor.
  Technical Specifications
Model CapacityKgs/Hr. Maize Grinding CapacityKgs/Hr.Mixed feed Grinding Capacity Kgs/Hr. Power (H.P.)
  Starter 4mm Grower 5mm Finisher 6mm Starter 4mm Grower 5mm Finisher 6mm Millet grinding
FSHM 1015
2500 4000 5500 1800 10 - 15
FSHM 1525
3200 4500 6800 2600 15 – 25
FSHM 2040
6500 8500 11000 4500 20 - 40
FSHM 3075
8000 10000 13000 8000 30 - 75
FSHM 50120 8500 10500 12000 12000 14000 16000 10000 50-120
  In most feed manufacturing facilities, the grinding operation is first or second largest energy consumer .So an efficient machine that can grind     the material to the required fineness with minimum of power, will not only cut the cost of grinding but also play significant roll in producing     quality pellets by helping to improve mixing, conditioning and pelleting process .
  Lark introduces model FSHM-1015, a hammer mill specially designed for small feed mills. It can run on 10 HP motor     and has solved the problems of fine grinding. It has given outstanding results on millet grinding and can  be used as     separate unit. For normal grinding it has provision to shift to coarse grinding. It is supplied with Inlet  hopper, outlet     hopper, vibration dampers.

  Lark introduces model FSHM-2040, a hammer mill specially designed for feed mills with 4-6 MT/hr mash. For  pelleting     operation it can crush 3-4 MT/hr on 40 hp with 3mm hole screen.

  It can run on 20 to 40 HP motor and has same features as model-1015.
  Lark introduces model FSHM-3075, a hammer mill specially designed for feed mills with 8-10 MT/hr mash. For     pelleting   operation it can crush 6-8 MT/hr on 60 hp with 3mm hole screen.


  Lark introduces model 50-120 of patented design which is specially suitable for fine grinding in pelleting  operations. It     is capable of grinding 10-12 ton per hour easily on 3mm hole screen using just 100 h.p only ,   besides it has other     features also.

It has unique feature of Quick Gap Adjustment between hammer tip to screen which plays a crucial role in efficiency as well as quality of grinding .We can get fine feed for pelleting as well coarse feed for finisher /parent flock with equal ease.
Manually operated rotor break mechanism provided to stop the hammer mill quickly without wasting any time while changing of screens etc.
It can run on 2800 rpm or 1400 rpm as per requirement of quality of grinding required.
It is ideally suitable for 14-16 MT per hour Mash feed Plant and 10 MT per Hour Pellet Plant.


Inventing this technology is one more feather to our cap and a total grinding solution for all types of grinding. “Quick-Gap-Adjustment” QGA, as its name implies this technology is a boon for grinding different sizes of products as fine/ Medium/ coarse by quick change of gap between hammer tip and screen, thus creating ideal parameters for optimum grinding of  product.
  Grinding different sizes of product (fine/ Medium/ coarse)

In poultry feed, we need different particle size of feed referred to as fine or coarse to feed a day old chicks to full age broiler/ chicken. For optimum grinding we need different parameters for fine grinding or coarse grinding.

In simple hammer mills, the required particle size is obtained by changing the hole size of screens while the other parameter of hammer mill such as tip speed of hammer mill, gap between hammer tip to screen, remain same.

In modern hammer mills, to obtain coarse/fine grinding following step are taken.

Screen of smaller hole for fine and bigger hole for coarse feed is used.
Speed of motor can be changed by fitting a VFD (Variable frequency drive) or dual speed motor or D.C. motor.
Gap adjustment between hammer tip to screen is varied by changing the position of hammers on different PCD on circular plates of rotor.
  Our Modifications:

Our Modifications relates to point III Gap Adjustment between hammer tip to screen.

In prevailing method of gap adjustment, as the no. of hammer on rotor goes on increasing with increase in size of hammer mill. Particularly on bigger hammer mills it wastes so much time to remove all the hammers from one position and fitting in other position. Sometimes, requirements are there to shift from one setting to other many times a day. So practically it is not usually possible to always change the gap by altering the position of hammer for varying quality of feed because it causes huge production loss as well as trained person are required for it. So usually only changing of screen is done to achieve the target. It result compromises on quality of feed and production loss.

If a hammer mill is set for smaller gap say 10 mm for fine grinding with 3 mm hole screen. It will not give required coarseness of feed, if 6 mm hole screen is employed until gap is increased to suit 6 mm hole. By increasing hole size of screen, uneven grinding is achieved.

Similarly if a hammer mill is set for coarse feed with say 25 mm gap with 6 mm hole screen for coarse feed, it will get jammed if operated on 3 mm hole screen or otherwise will give poor output.

In our modified design, gap adjustment can be done in two ways: -

Fixture on Screen: - a) for coarse grinding clamping is fixed inside of screen so as to provide more gaps.

b) For fine grinding clamping is fixed on outside of screen to give small gap.
Fixture on screens for coarse grinding only:- In this design simple screens are used for fine grinding with no clamping/ fixtures on it. But for coarse grinding screens with inside clamping are used. To increase the gap to accommodate coarse screen, top & bottom screen holding assembly is moved either mechanically using cam shafts or pneumatically or hydraulically. Adjustment in clamping device is also provided to compensate for bigger gap screen.

  Different Models in QGA series

  All our full screen models as mentioned above are available with optional QGA feature.


  Rotary Feeder:

Even if a hammer mill is properly designed and well matched to its required job, it may not perform well if it not fed properly.

A typical hammer mill feeder is expected to meet following requirements.

The feeder must provide a "UNIFORM CURTAIN" of materials to hammer mill grinding chamber.
This curtain of material must be fed FULL WIDTH across the Grinding chamber of hammer mill.
Our latest designed Rotary vane type Hammer Mill Feeder has following features:
Conventional vane type feeder has 6 or 8 vanes across the width of grinding chamber which has the drawback of feeding in slugs that causes uneven feeding.

But our modified feeder has long vanes converted into multiple cups that provide instead of 6 discharge points to 24 or more depending on size, which results more even feed rate and distribution of material across full width of mill intake.
Feeder Drive Panel: In this variable frequency drive (VFD) is used to control the speed of feeder .It has following features:

(a) In auto mode VFD controls the feeding rate automatically with respect to load of main motor. This drive communicates the "Load" or "Amperage" of Hammer Mill main drive motor to the feeder motor to adjust the feeder speed. This ensures that the feeder does not supply the mill more material than Hammer Mill main drive motor can tolerate.

(b) In Manual Mode, we can control feeding manually through a potentiometer.
Incase of any major problem in electronic Feeder Drive Panel , we have provided a direct mechanical bye pass mechanism which allows gravity feeding through slide gate control to keep the plant running.
Fuel Width self cleaning type magnets provided to prevent iron thrash entering the mill with collection tray.
Line Diagram with dimensions
dimensions of sketch in mm
Type of FSHM
Dimensions Approx.weigth in kg.(without Moter) Voulume Seaworthy packing Cu/m
1280 2470 452 2025 2325 450 1592 525 315 41 1300 915 704 175 2218 575 250 - 1219 11.5
785 1990 - 2005 2280 412.5 1247 525 315 41 1200 915 704 175 2178 575 250 - 1000 6.4
777 1841 215 1295 - - 962 430 220 - 1200 915 704 175 1630 420 215 307 520 4.5
  1525 777 - 215 1005 - - 962 - - - 1000 750 - - 1347 268 214 191 415 2.3
  1015 642 - 197.5 827.5 - - 235 - - - 1000 750 - - 1110 222 160 172.5 230 1.5
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