Planetary Strander: A cage strander with backtwist. Planetary strander makes two twisting action at the same time. Pay-off cradles rotate around their own axis while whole cage is rotating in opposite direction. With this backtwist , planetary strander saves the round shape of stranded material and maintain the best stranding used in cable production.
Backtwist ratio could be fixed or variable between 0-100 percent and even more upto 135 percent. Cradles also can be locked to rigid mode. If Cradles' position locked, Planetary strander works as a rigid strander. Disadvantage of Planetary strander is speed and limited number of pay-off units. Cage rotation speed maximum 100-150 rpm range. As the pay-off spool size increase rotation speed decreases to minimum 6-10 rpm range.
The number of cradles determine maximum number of strands can be achieved in one pass. Starting with three cradles minimum for insulated cores. Six , twelve, eighteen and twentyfour cradles are most used.
A classic Planetary strander line is completed with a belted or pulley type capstan and a take-up unit. Other auxiiliary units such as die holder, tape/yarn applicator head, lubricating equipment and chalk applicator may be added as well. If necessary more than one cage could be used in one line. It depends on how many cradles are in one cage. Twisting lay is adjusted by the ratio between capstan speed and rotation per minute of cage. As the capstan speeds up lay length increases.
Planetary strander is used for :
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OPGW,ACSR conductors
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Fibre Optic and sub-marine cables
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Overhead Lines and conductors
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Insulated conductors of power cables with Class I or Class II conductor strand
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Armoured cables
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Signal and Special cables.
Best For:Hard drawn bare wire stranding. Insulated conductors where backtwist is a quality issue. Planetary Strander is the best quality stranding solution for all. However, it is not cost effective due to low speed. Labor cost can be compensated if 16 square millimeter and above either bare conductor or isolated cores are stranded. It is best for multi core cables with more than one layer stranding required.
Versatility:In compare to SingleTwist and Doubletwist buncher , Planetary strander has no weight issue of take-up drum. Auxiliary equipments are easy to add. It can work either with or without backtwist. A planetary line project must be configured for possible future needs. Because once whole line is configured , it could be real hastle to add more cradles or changing pay-off spool size. Thus, maximum number of strands has limited at first.