Discussion created on 12/20/2021

Issues with extrusion

We trial products with high fat. The fat before extruding around 7-8%. Using a single screw with high shear screw configuration and with die design for floating fish. The issue with the product is the size between the front and end is not symmetrical. What is the root cause of this issue? Is that from machine process or raw material?

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Influencers "Likes": Sankaran Suresh Sundaram
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Faizan Ali Faizan Ali
Student
December 20, 2021

What's the moisture of the mix before extrusion?

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December 21, 2021
Faizan Ali
The moisture
before extrusion 22-26%
after extrusion 18-22%
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Faizan Ali Faizan Ali
Student
December 21, 2021

Tanatat. Could you please state the moisture of the mix before the preconditioner? Have you included any starch source for firm texture?

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December 24, 2021
Faizan Ali
The mix moisture around 8%.
The starch source we use normally starch like from corn.
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Faizan Ali Faizan Ali
Student
December 24, 2021
Tanatat you can play with the potato or topioca starch for more firm structure of pellet or texture with 1 to 2 % and see results..
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March 12, 2022
I should think the die design could be the problem in the cutter,
If extrusion process is complete and cooking has taken place to the desired extent then the vagaries of pellet shape front being larger than the rear might not have anything to the recipe.
Dry Extrusion can process recipe vontsining just 7 to 8 % without any problem.
Also the thickness of the die plate would be minimal and therefore the time taken for the extrudate will not alter unless the moisture content various in the feed stock.
The only way it can happen is when the die has a taper where each hole for drilled has a taper in the wrong direction.
Usually a taper is provided but if the product expands then the die holes need to be looked into
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March 12, 2022
Sankaran Suresh Sundaram On extrusion cooking being completed the starch should bind the product string enough not allow any variation in expansion.
However it is very unlikely that product expansion alone is the problem. One would have to look at the die plate and die holes more closely.
Take a product like kurkure, which has multiple expandable starches will surely have this same variation.
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June 2, 2022
Sankaran Suresh Sundaram For the die plate I'm not sure that which factor is the main one that i should change to solve this issue. Like the picture above we use die diameter 7 mm with 33 holes and the die land about 4 mm. thckness.
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December 23, 2021
I think that shape variations will be come due to die hole land position may be wornout or land height is not sufficient for bigger dia extruder pellets..
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December 24, 2021
D.V.Sambasivarao
Land height you mean same as land length right?
Do you have number criteria for big diameter to be sufficient?
We used diameter around 7 mm.
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December 25, 2021
Tanatat
Yes..land height is nothing but a land vertical length..need to use land height more than normal for bigger dia pellets....and also it will depend on fat level and type of extruder ( single or twin screw)...you can use 5 mm land for 7 mm dia die in fat levels between 4% to 6%..
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December 29, 2021
D.V.Sambasivarao
Ok thanks for your information.
If the fat in formula is more(more than 6%) i have to increase the land length more right?
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December 25, 2021
Yes
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June 2, 2022
D.V.Sambasivarao Last time i testing more with the longer land length from 4 mm to 6 mm but the issue not been solve.I'm not sure that other factor that i need to be checking more?
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Giuseppe R. Bigliani
Giuseppe R. Bigliani
Bachelor of Science, Mechanical Engineer. Maste...
  Cumming, Georgia, United States
 
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