Method and device for operating a drawing line or drawing unit

1. A method for driving a drawing line or drawing unit for drawing of tows having polymer filaments comprising a plurality of driven drawing rollers for drawing the tows and a plurality of separately controllable drive units, one of the plurality of separately controllable drive units being operably connected to each of the driven drawing rollers for individually controlling the torque on each drawing roller, said method comprising:

comparing a measured torque on a given drawing roller of the plurality of drawing rollers to a setpoint torque for the given drawing roller; and

controlling the drive unit controlling the given drawing roller to bring the measured torque closer to the setpoint torque,

wherein said individually controlling the torque on each drawing roller is done automatically through gradual approximation based on a setpoint torque curve or a setpoint torque characteristic,

wherein each drawing roller is controlled to run at a specified rotational speed based on a current control,

wherein said individually controlling the torque is continued until the torque on each drawing roller meets the setpoint torque and each drawing roller reaches the specified rotational speed,

wherein torques of the separately controllable drive units are controlled until a same torque is given throughout, and

wherein a first of the plurality of driven drawing rollers is driven at a fixed rotational speed and the rotational speed of the other of the plurality of driven drawing rollers increases until reaching the specified rotational speed.

2. The method according to claim 1 , wherein each drawing roller is assigned a speed sensor.

3. The method according to claim 1 , wherein the separately controllable drive unit is an asynchronous motor having an assigned frequency converter.

4. The method of claim 1 , further comprising:

registering an actual torque of a given one of the plurality of drawing rollers;

comparing the actual torque to a given setpoint torque; and

controlling the given drawing roller based on a relationship between the actual torque and the setpoint torque.

5. The method of claim 1 , further comprising shutting down one of the drawing rollers if a speed or torque of the one of the drawing rollers exceeds a given value.

6. A method for driving a drawing line or drawing unit for drawing of tows having polymer filaments comprising a plurality of driven drawing rollers for drawing the tows and a plurality of separately controllable drive units, one of the plurality of separately controllable drive units being operably connected to each of the driven drawing rollers for individually controlling the torque on each drawing roller, said method comprising:

comparing a measured torque on a given drawing roller of the plurality of drawing rollers to a setpoint torque for the given drawing roller; and

controlling the drive unit controlling the given drawing roller to bring the measured torque closer to the setpoint torque,

wherein said individually controlling the torque on each drawing roller is done automatically through gradual approximation based on a setpoint torque curve or a setpoint torque characteristic,

wherein each drawing roller is controlled to run at a specified rotational speed based on a current control,

wherein said individually controlling the torque is continued until the torque on each drawing roller meets the setpoint torque and each drawing roller reaches the specified rotational speed, and

wherein torques of the separately controllable drive units are controlled until a same torque is given throughout,

the method further comprising:

driving a first one of the plurality of drawing rollers at a previously determined speed;

determining a speed of a subsequent one of the plurality of drawing rollers and a draw ratio of the first one of the plurality of rollers and the subsequent one of the plurality of rollers;

starting the drawing line at a free selectable starting draw ratio;

for a set of intermediate drawing rollers between the first one of the plurality of drawing rollers and the subsequent one of the plurality of drawing rollers, setting the speed of each intermediate drawing roller to be between the previously determined speed and the speed of the subsequent one of the plurality of drawing rollers;

placing a tow on the plurality of drawing rollers and initiating a torque optimization process by monitoring and adjusting the torque on each of the intermediate drawing rollers so that the torque on each of the intermediate drawing rollers approaches a setpoint torque for said each intermediate drawing roller; and

accelerating the rollers of the set of drawing rollers to a final speed.

7. The method of claim 6 , further comprising:

recording the final speeds of the intermediate drawing rollers;

registering the final speeds in a setpoint curve; and

using the registered final speeds for a subsequent starting process.

8. A method for driving a drawing line or drawing unit for drawing of tows having polymer filaments comprising a plurality of driven drawing rollers for drawing the tows and a plurality of separately controllable drive units, one of the plurality of separately controllable drive units being operably connected to each of the driven drawing rollers for individually controlling a torque on each drawing roller, said method comprising:

comparing a measured torque on a given drawing roller to a setpoint torque for the given drawing roller; and

controlling the drive unit operably connected to the given drawing roller so that the measured torque on the given drawing roller of the plurality of drawing rollers approaches the setpoint torque for the given drawing roller,

wherein said individually controlling the torque on each drawing roller is done automatically through gradual approximation based on a setpoint torque curve or a setpoint torque characteristic and wherein said individually controlling the torque is continued until the torque on each drawing roller meets the setpoint torque,

wherein torques of the separately controllable drive units are controlled until a same torque is given throughout, and

wherein a first of the plurality of driven drawing rollers is driven at a fixed rotational speed and the rotational speed of the other of the plurality of driven drawing rollers increases until reaching a specified rotational speed.

9. The method according to claim 8 , wherein the plurality of separately controllable drive units are operable to drive the plurality of driven rollers at different speeds.

10. The method according to claim 8 , wherein the plurality of driven rollers are driven at different speeds.

11. The method according to claim 8 , wherein the plurality of separately controllable drive units comprise a frequency converter configured to set a rotational speed of the plurality of driven drawing rollers.

12. The method according to claim 8 , wherein the plurality of separately controllable drive units comprise a field-oriented converter configured to set a rotational speed of the plurality of driven drawing rollers.

13. The method according to claim 8 , wherein the first of the plurality of driven drawing rollers and a last of the plurality of driven drawing rollers are driven at the fixed rotational speed to determine a drawing ratio and the rotational speed increase is distributed among the other of the plurality of driven drawing rollers in a linear manner or a freely selectable manner until reaching the specified rotational speed.

14. The method according to claim 8 , wherein final speeds of the plurality of drawing rollers are recorded and registered in the setpoint curve for use in a subsequent starting process.

15. The method according to claim 1 , wherein the first of the plurality of driven drawing rollers and a last of the plurality of driven drawing rollers are driven at the fixed rotational speed and the rotational speed of the other of the plurality of driven drawing rollers increases until reaching the specified rotational speed.