Routine work time is the average time it takes per cow to complete the milking tasks, for example attaching clusters. It determines how many cows can be milked in an hour.
In a rotary, more work is automated compared to a herringbone, so cluster attachment is the main job, along with reattaching hoses, controlling the backing gate, or idle time if the platform is rotating too slowly.
A shorter routine work time will increase the number of cows that can be milked. The throughput (maximum number of cows able to be milked per hour) is calculated by dividing 3600 (number of seconds in an hour) by the work routine time.
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The number of bails, the speed of rotation and distribution of cow milking times within the herd will also affect how long it takes to milk the herd.
- A cow’s most common milking time is 6 minutes. If the rotation time is set at 10 min and it is a 50 bail rotary, this would give you a platform speed of 12 seconds per bail. (10 min × 60 seconds divided by 50 bails).
- The 10 minute rotation would mean about 7% of cows need a second rotation. Many farmers aim for less than 10% of cows ‘going around’ when setting platform speed. This can limit efficiency by adding idle time to the operator’s work routine.
- Most operators can consistently attach clusters at about 8 seconds per cow. This means that in this example, the operator is idle for 4 seconds a cow and is milking 150 cows/hour less than if the platform was rotating at 8 seconds/bail.
- The number of bails also affects the amount of idle time. There is generally less idle time in larger rotaries because there are more bails with a set amount of time.
- In a 40 bail rotary, an 8 min rotation will be 12 seconds/bail.
- In an 80 bail rotary, an 8 min rotation will be 6 seconds/bail.
- This means there is often idle time in smaller rotaries while larger rotaries may need two cuppers.
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Possible actions to take:
- Set your platform speed based on the operator’s ability to put the cups on, rather than the number of ‘go around’ cows. Go as fast as is sustainable for the operator, even if it means 15-20% of cows ‘go around'.
- Apply a maximum milking time (MaxT) which eliminates ‘go around’ cows and minimises idle time, letting the platform speed approach the maximum comfortable cupping speed.
- If you often have to stop or slow the platform because of empty bails or to encourage cows onto the platform, visit the design section for simple changes you can make to pipework aiming to improve cow flow.
