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Tips for Feed Millers – Rules for Die Handling


Die is a critical part of a pellet feed mill, die not only directly related to the pellet feed quality but also plays an important role in feed mill operating/running cost. According to the feedback from feed millers and statics, on an average - die accounts for more than 60 % of the total cost of mechanical consumables. Hence it is quite mandatory to follow the proper guidelines and instructions throughout the die life cycle:

Some of the Golden Rules for Proper die usage are as mentioned:

1. Selection of Die as Per Formulation: Broiler contain less fibers and more oil %age (soft formulation), which provides better pelleting properties, less frictional load on pellet die. Hence, we can use compression ratio of 1:12, 1:13 & even more.And using low compression dies in soft broiler formulation may lead to poor PDI (Pellet Durability Index –Pellet Strength).

As the layer feed is more fibrous and contains lesser oil percentage ,using high compression ratio for layer feed may leads to poor die life, die chocking, non-uniform PDI, more power consumption in layer feed, low output, more wear & tear.

Considering all above factors using separate die for both layer & broiler feed is a better and cost effective solution. For Layer feed – Minimum hole size for die should be or more than 3.5 mm. If someone wants to use same die for both formulation to avoid the die change over die; we have two options either we can use tapper fitment die to reduce the down time or we can select a balanced die having that configuration which matches both the formulations. But we have to compromise a little in Pellet PDI (In Broiler feed) and Die Life (In layer feed).

2. Die Fitment: The Fitment of die plays significant role in the life of the die. While changing die carefully examine the condition of the die seating surfaces with rear & front ring. If the rings have been used for a long period of time, operator must check the clearance between die and rear/front rings. Loose fitment of die and ring may leads to fatigue failure of die bolts and die.

3. Avoid using hammers: The use of hammers must be avoided to prevent the impact forces to the die.

4. Gap Setting in between Rollers & Die: There must be paper gap of 0.3-0.6 mm between die and roll shell(depends upon die hole size & feed formulation ), If it will increase it leads to die slippage and too little gap leads to the damage of counter holes.

5. Protecting against iron particles: Too much sand or iron impurities in the feed, can increase the wearing of the die & rollers. So it is important to remove the impurities in the raw materials before entering the die.

When any foreign particle comes in direct contact with the die surface, it blocks the die surface. When roll shells exerts pressure on the clogged surface extreme forces are generated which after some time may leads to die breakage. So it is always recommended to clean the magnets at regular intervals.

6. Starting a new die with new rollers set: Always start the new die with new set of Roll shell to have the proper impact and proper friction forces on the entire working pad of die.

7. Optimum life of rollers shells for better die life: Some time we use the consumable parts more than their standard life but loose much more in feed quality and life of other parts which directly related to them. Like for an average die life cycle it is recommended to use 5 pieces (2.5 set) of roll shells for a better die life and uniform PDI feed quality. Hence using the roll shells & beaters more than recommended life results in great losses in terms of grinding texture, conditioning, pellet quality and specific energy consumption also reduces the die life.

8. Preserving the dies for different applications: Some times its wise to keep few dies in stock after 50 % , 60 % , 70 % of their total life ; which can be used in emergency or as trial in other feed formulations to select the perfect L/D as per formulation without investing in new dies at that time.

9. Die Flushing: Always flush the die (with oil mixed rice bran)after use for better life.

10. Preserve the die when not in operation: The die should be kept at a proper location to prevent the die from being rusted /scaling.

11. Check for play in holder assembly: Worn out die holder/ bearing seats allow the die to move slightly during the operation. This may generates vibration in the pellet mill leading to fatigue failure, die rollover or premature end of die.

12. Die , rollers and scrapper settings as per wearing: To have a better die life , it should be mandatory to have uniform wearing of the die, that should be only possible when the proper gap should be maintained between die and roll shell , The deflector or scrappers setting should be good enough that it should deflect the mash on the entire pad which ultimately leads to uniform wearing.

The above information is based on data collected from our existing customers & internet sources and is only for your reference. As expertise in feed mill engineering only, Lark Engineering will not be responsible for any type of loss occur due to the above stated information.