A bobbin winder transfers yarn onto a rotating package while a guide distributes it along the spindle. This calculator compares the circumferential speed, spindle rate and effective package diameter. The animation shows a flanged bobbin and a continuous path from feed cone to take-up.
Bobbin Winder Interactive Calculator
Set circumferential surface speed and spindle RPM to calculate the corresponding effective package diameter. Inspect the rotating bobbin and traversing guide below. The illustration is a normalized winding station, not a particular machine specification.
Equation Used
- No slip between strand and package in the circumferential direction.
- Effective package diameter is constant for this calculation; package growth is not solved.
- Illustrative traverse and slowed spindle motion explain the parts; numeric RPM and time per revolution report the actual entered rate.
- Input bounds are exploration limits, not ratings for a particular winder or bobbin.
Compare bobbin surface speed while following the strand from the stationary supply cone, through the tension and traverse guides, to the rotating bobbin. Circumferential surface speed differs from the total yarn velocity when the guide also moves along the bobbin.
Following the yarn path
Yarn leaves the stationary feed cone over its end, passes through a fixed guide and tensioning device, and reaches the moving yarn eye. The eye traverses along the rotating bobbin to distribute the strand over its working length.
The enlarged drawing shows one winding station. A spindle drives the take-up bobbin and the guide moves on a separate linear rail. Real machines use different guide drives and tension controls. The SSM FM1 is one manufacturer example of flanged-bobbin parallel winding with electronic yarn laying.
Different scales of bobbin winding
Sewing bobbins and industrial yarn packages share the transfer principle but have different holders, dimensions, drive systems and operating limits. SINGER/PFAFF instructions show the supply spool, thread eyelet, tension disk and take-up bobbin. SSM describes industrial winding with individually driven spindles and controlled yarn laying. This generic drawing is not a specification for either product.
Surface speed and yarn speed
For effective diameter D in millimetres and spindle rate N in revolutions per minute, circumferential surface speed is V = pi D N / 1000 metres per minute. Rearranging gives D = 1000 V / (pi N). The circumference is pi D, revolution frequency is N/60, and time per revolution is 60000/N milliseconds.
When the guide traverses axially at speed U, ideal total strand speed is sqrt(V² + U²). Equivalently it is V/cos(alpha), where alpha is the winding angle measured from the circumferential direction. The two-input calculator reports the circumferential component; it does not infer an unentered traverse rate.
Example using the calculator inputs
At 1800 m/min circumferential speed and 25000 rpm, the required effective diameter is approximately 22.92 mm. Circumference is 72 mm, revolution rate is 416.67 per second and one revolution takes 2.4 ms.
This is a kinematic example, not an approved operating point for a sewing bobbin or an industrial machine. Halving RPM while retaining the same surface speed doubles the required diameter.
What this calculation leaves open
The relationship between diameter and speed does not determine yarn tension, package density, bearing load, motor torque, flange clearance or a safe maximum rotational speed. The required diameter must fit the chosen core, flanges, holder and machine. A growing package also requires a changing RPM if surface speed is to remain constant.
Frequently asked questions
Why does lower RPM increase the required diameter?
Each revolution must carry more circumferential length to preserve the selected surface speed.
Does the bobbin grow in the animation?
No. The selected effective diameter represents one instant during winding. The drawing is normalized for clarity.
Is the animation playing at the entered RPM?
No. It is slowed for inspection. The outputs report the actual revolution rate and time.
Does the calculator include cross-winding angle?
No. It calculates the circumferential component. Total yarn speed also includes traverse motion.
Manufacturer references
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