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Extrusion Basics Part 3 – L/D Ratio

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Extrusion Basics Part 3 – L/D Ratio

When you check the internet about manufacturers of extruder barrels and screws then you will often see the abbreviation L/D ratio. It stands for Length/Diameter ratio, so if you want to buy a screw of 40mm Diameter and a length of 1000mm (39,37 inches) then the L/D ratio will be 25:1

Length = 25 x 40mm Diameter

Like I mentioned already in the Extrusion Basics Part 1 I recommend you to get used to such technical terms and it is because of the same reason like I explained in Part 1. A year ago I already looked a couple times on the internet for extruder screws and when I asked for a quotation then I told the seller the length of the screw in mm. And at that time I did not know much about extruders and then clever international sellers will notice very quickly that your know-how is not really firm because you do not use common technical terms and so they probably will give you quotations where you just shake with your head. One extreme example: A seller really quoted me at that time for a 40mm Diameter L/D ratio 25:1 a price of 7,000.00 USD for a standard nitrated 3 zones screw (and this was not a typo!).

Just to give you an idea about the discrepancy about the prices: Currently I get quotations between 200-800 USD for a new single nitrated 40mm Diameter 3 Zones Screw L/D ratio 25:1. So put effort in your supply chain and never source such parts on ebay, they are in 80% of all cases used and overpriced, rather spend some money on a professional buyer if you do not have the time or (culture-/language-)skills to do it by yourself.


Dieser Text ist auch in Deutsch verfügbar.

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  • Fernando
    Posted at 10:16 pm, February 16, 2017

    Does each plastic (PVC, HDPE, PP AND PS) has or requires an specific l/d ratio?

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