What is the recommended high and low hardness range for the rubber covered pressure roll? Generally what life may be expected in working hours?
It depends to the type of product, for rotary molder product we are able to work with large range of % of fat and sugar. More the % is high more flexible is the recipe but for product with hard dough (low level of fat and sugar.... for rotary moder product), my experience is that is better with 30 to 50 shore of hardness, for other until 65. In general the shelf life of the rubber roller is around 10000 -12000 hrs
Shore Hardness of a rubber roller should be 70. Some difficulties may be evident if hardness drops to 65 but should never be below 55.
Some manufacturers use dual hardness rollers where a standard inner coating is used with a harder 75 outer skin. Personally have not found this to be any advantage and would recommend a standard 70.
For high fat content biscuit dough rubber roller shore hardness should be between 65 to 70 . Over a period of time fat seeps into the rubber coating and reduces the hardness. If the hardness drops rapidly an extra amount of pressure by lifting the rubber roller will have to be applied to extract biscuits onto the endless web and may lead to tailing of biscuit shapes.
Life of the roller will depend on hours of usage per day and the fat content in the biscuit dough
1. Shore hardness for soft dough biscuits--60 to 70mho and hard dough or fermented dough biscuits its is 70-80 mho.
2. On regular usage it will run for one year to one and half year. If you want to maximize the utility then by a hardness meter and check the hardness at various points on monthly basis then you can until you measure a less value in any the point.
In my opinion and experience shore value should not go below 70 mho on the outer layer / surface . More is better up to 80 mho.
Life is depending on the speed of the roller or the volume of production.
I have run high speed line with 12000 + hrs.