What is prewinder? How do they work?

A prewinder (usually translated as yarn accumulator or pre-winding device) is a crucial auxiliary device in textile machinery. Its role is like a "transfer station" or "voltage regulator" between the loom and the large yarn bobbin.
To prevent high-speed looms from stopping due to yarn problems, the prewinder plays a vital buffering role.

● Main Components of a Prewinder

We can break down this device into several easy-to-understand parts:

Power Motor:

This is its "heart," responsible for driving the machine to rotate and pull the yarn from the large bobbin at the back.

Yarn Storage Drum:

A smooth cylinder, like a "temporary warehouse." The yarn is neatly wound in circles here, waiting to be used by the loom.

Winding Arm:

Like a hand constantly drawing circles, it rotates around the drum, evenly laying the pulled yarn onto the drum's surface.

Sensor Probe:

This is the machine's "eye." It monitors the amount of yarn on the drum and gives the motor instructions to "work" or "rest."

Yarn Tension Ring:

Located at the yarn exit. It acts like a "filter," ensuring that the yarn is pulled away smoothly without sudden jerks.

● How does a Prewinder work?

Its working process can be simply summarized as "front-end retrieval, back-end delivery, and intelligent regulation":

Pre-winding (stocking):

The loom grabs the yarn at a very fast and discontinuous speed. If the yarn were pulled directly from the large bobbin, the immense impact force would instantly break the yarn. The prewinder's function is to first use the motor and winding arm to smoothly unwind the yarn from the large bobbin and neatly wind it onto its own storage drum.

Inventory Monitoring (stock management):

The sensor probe continuously scans the yarn reserve on the drum. When the loom uses the yarn quickly and the inventory decreases, the sensor notifies the motor to accelerate winding; when the inventory is sufficient, the motor slows down or stops. This ensures that there is always enough "spare yarn" on the drum.

Smooth Yarn Release (Delivery):

When the weaving machine needs to insert the weft (i.e., pull the yarn into the fabric), it draws the yarn directly from the prewinder's drum. Because the yarn on the drum is already unwound and neatly arranged, the resistance is very low.  Combined with the tension ring at the outlet, the yarn flows smoothly into the weaving machine like a stream of water.

● Why use a Prewinder?

Protects the yarn:

Avoids damage to the yarn caused by high-speed pulling, reducing breakage rates.

Improves fabric quality:

Because the tension of the yarn fed into the machine is very constant, the resulting fabric surface is very smooth and free of imperfections.

Increases speed:

With a sufficient supply of "stock," the weaving machine can operate faster, significantly increasing production efficiency.