According to the requirements of the size of the underwear of the customer, choose a suitable caliber on seamless curcular knitting machines, and then adjust the line speed, tension and suction on the equipment to achieve the required size according to the requirements of the finished clothing. Because of the special nature of seamless underwear, there is no way to accurately achieve the size of the finished product through drawing board cutting. Therefore, seamless underwear has a certain size error range, but the actual producer will often exceed the allowable error range.

Below are the main reasons:

Weaving and dyeing reasons

1.1 Human factors

a. Weaving workshop employees have insufficient quality awareness of size issues and ignore quality management.

b.Dyeing technicians and operators are weakly aware of the size problem and ignore the effects of the pre-shrinking process before dyeing, dyeing temperature, dyeing time, and dyeing pH on the size.

1.2 Machine equipment

The selection of the caliber is unreasonable; the standard of equipment between the same caliber is inconsistent, such as tension and linear speed, which causes the difference in size; the linear speed is out of control, which causes the change of the coil length; poor tension control or inaccurate tension meter causes The suction of the equipment is not well controlled. Due to the unsmoothed suction pipe or different pipeline strokes, the suction of each equipment is uneven, which affects the stability of the size; the process parameters in the pre-shrinking and dyeing process are not consistent. Stable, resulting in instability in size; the capacity of the dyeing equipment varies, the size of the small tank dyeing will be smaller, and the large tank dyeing will be slightly larger.

1.3 Raw materials

a.The choice of raw materials is not good. For example, the raw materials provided by the factory are unstable, the tension and elasticity of the inner and outer layers are not consistent, and the elasticity of the yarn is easily damaged. The batch number of the raw materials is unstable and may be changed halfway, which causes some products to fail to achieve the standard size.

b.Improper selection of dyes and auxiliaries, especially oxidants, reducing agents, and acidity and alkalinity, such as the concentration and amount of hydrogen peroxide in oxygen bleaching, pH value, alkalinity during reduction cleaning or peeling, and the amount of insurance powder, etc. Affects size.

1.4 Improper processing methods

The size test was not accurate before putting into production, but it was probably cooked a bit. The size was not tested according to the large-scale dyeing process in the dyeing workshop. The mechanics disturbed the relevant parameters when repairing the equipment. Line speed, tension, and suction occurred. Changes did not readjust, which affected the size; some operations such as changing the line did not pay attention to the parameters that affect the size in time, which affected the size; the pre-dyeing process design before dyeing was not reasonable and did not play a role The effect of stable size; the design of the pretreatment and dyeing process is unreasonable, especially the formulation of the dyeing temperature, dyeing time and pH value of the dyeing process is not reasonable.

1.5 Environment

The instability of temperature and humidity in the workshop causes fluctuations in size, and the change in temperature and humidity directly affects the size of the product; the negative pressure in the workshop causes uneven suction.

Prevention and improvement measures

1. Select a good material, especially the quality of the core-spun yarn, and it is required that the batch difference is stable, and the density, tension and elasticity of the inner, middle and outer layers should be consistent.

2. After choosing a seamless clothing machine, it is necessary to ensure that the number of rows of products of the same caliber and the same size is the same. It is important to ensure that the products of the same number of rows are the same. This is the first condition to ensure the stability of the product size.

3. Keep the coil length consistent, keep the line speed, and the yarn feeding tension consistent. It is required to regularly check the coil length, line speed and wire tension. When the operating status of the equipment changes, the above parameters must be measured in time, and adjustments should be made in time if changes are found.

4. Strictly control the suction and record the size of the machine. If there is a change in the size of the machine, immediately find the cause and adjust it.

5. Control the temperature and humidity of the weaving workshop. The temperature and humidity of the workshop should be recorded regularly to keep the temperature change within the allowable range. If there is a large range of fluctuation, it should be adjusted in time.

6. While controlling the size of the machine, it is best to have someone to test the size every day. When testing the size, it should be dyed in a large cargo.

Dye improvement and prevention measures

1. The main purpose of steaming is to stabilize the size. The steaming temperature is generally higher than the dyeing temperature.

2. Select the dyeing equipment and try to dye on the same type of dyeing equipment as possible. Find out the difference in the size of the product after the size of the dyeing tank.

3. The influence of PH value: strictly control the pH value in the dyeing process, and maintain the minimum damage to elastic fibers such as spandex by acid and alkali. The required pH value is between 4 and 10.

4. Influence of oxidant: Control the oxygen bleaching process of cotton and spandex products, such as the amount of hydrogen peroxide, pH value, temperature and time of oxygen bleaching.

5. Influence of reducing agent: Reductive powder is used after the product is repaired and stripped, and the dye is washed with disperse dyes. The powder is liable to cause elastic damage to elastic fibers and spandex. Therefore, the use of reducing agents should be avoided as much as possible, the amount of reducing agents should be reduced as much as possible, and the treatment process during reduction cleaning and peeling should be controlled.

6. Water quality: Iron or iron ions are still present in the water. If the content is too high, spandex will be damaged. Therefore, a water quality test should be performed before pretreatment and dyeing. If the iron ion content is too high, a water quality treatment should be performed.

Conclusion

In seamless underwear processing, the instability of size is a common problem and the most difficult to control. There are two main countermeasures: First, strengthen management. The second is to control weaving, pre-forming and dyeing processes.