In part one of the weaving preparation, an introduction was made to the preparation processes for both warp and weft yarn prior to the weaving process, figure 1.
In this part we will discuss the warping process and its types and stages. Warping is defined as the process aimed to prepare the weaver’s beam with a certain number of yarns with a certain length at a certain density to be set up on the weaving machine.
Warping has the following operations:
- -A certain number of warp yarns are wound at a desired length.
- -Arrange the warp yarns according to the required design and colours.
- -Produce the weaver’s beam with the needed density, length, arrangement and number.
The weaver beam might contain thousands of yarns, which is always higher than the capacity of the creel, thus the beam cannot be wound directly from the creels to the weaver’s beam in a single operation. For this warping process has two phases; phase 1, when the yarns are unwound from the cones to an intermediate carrier till the required number is achieved. Phase 2 takes place to rewind all the yarns simultaneously from the carrier to the weaver’s beam. Depending on the intermediate carrier there are two different types of warping.
- -Sectional / Dresser Warping: where the yarns are wound into a conical drum.
- -Direct / Beam Warping: where the carriers are preparatory beam warping.
All warping machines have the same parts, creels, headstock and control devices.
They are the metallic frames, where the yarn cones are fitted / organized to be fed to the intermediate carrier. The creels are usually fitted with sensors for yarn tension and yarn breakage. The creel capacity is an indication of the number of the cone fitted on it, it is parameter that determines the number of section of beams. The capacity usually between 800 – 1200 cones.
Different designs of creels are available to overcome the problems of consuming time and space. Figures 3, 4, 5 and 6 shows different types of creels with their advantages.
This creel is formed by trolleys that can be fitted in the creels, which save time and space.
This type of creels are used when similar types of warps are needed to be prepared. Two cones are used, one operating and one as reserve.
Similar to the mobile creel, this type consists of trolly parts that can be turned from one side to other side when the first one finish. When one side is operation the other side can be fitted with cones.
In this creels the cones are fitted on endless chain, one side of the chain is operating while the other can be fitted with cones. When the operating side finished the chain rotates to bring the other side to the front to be operated. This creel reduces the tension on the yarns and produces uniform tension across the beam.
Some references say that creels are independent of the warping system, but others say that parallel creels used for sectional and direct warping and the V-shaped creels are used for direct warping because it allows high speed productivity.
The winding process requires extra attention to tension of the yarns and the headstock is equipped with precision direct drive, advanced electronics, smooth doffing and programmable breaks. Also measuring roller connected to control devices.
In the sectional warping, the headstock consists of the drum, trolly, warping carriage, leasing device and beam carrying chuck, figure 7. 1 is the drum, 2 the leasing device that splits the layers of the yarns to separate them for later processes, 3 is carriage bearing, a is the expandable comb that control the section width and position the section on the drum, b is the guide and metering roller, which measure the tension on the and give the feed back to the pressure control on the creel and c is the leveling roller to carry out winding at low tension and have a compact winding. the carriage feed the yarns to the drum in the conical shape with its traverse motion. The carriage also move with every new section, the creel has to move to keep the threads perpendicular to the drum.
The headstock for the direct warping is simpler than the previous one, figure 8. It consists of expanding comb, pressure roll and beam. The expanding comb is a zigzag comb place the yarns at the required width and order. The pressure roll works to ensure a cylindrical beam. The beam, figure 9, is where the yarns are wound onto.
As mentioned earlier the tension should be applied equally and fully controlled during the warping process. The control devices are to ensure this. Beside the controls the exist on the headstocks, the creel has a control over the tension for single yarns, figure 10. The disc tensioner apply tension on the yarns, the new tensions can be controlled separately by mean of aerodynamic and connected to the main machine computer.
Also the yarn break sensors, figure 11, to stop the machine when there is a yarn break.
1 – Sectional Warping
The conical shape dresser or drum is the mark of this type of warping. See figure below.
As mentioned before, the warping process here is carried out by parallel sections in certain sequence on the conical drum. This method is cost effective for short and striped warps. The warping speed is up to 800 m/min.
If this equation did not produce a correct number then the number of sections is adjusted to a bigger corrected one with a change in the total number of the yarns being warped.
As soon as all the section are being wound, the on the dresser, the second phase to produce the weaver’s beam starts. The sections are unwound from the drum to the beam at the same time, this process is called beaming.
2 – Direct Warping
This warping is done on two separate stages, first to wind the yarns onto beams, then unwind these beams and wind the yarns on the weavers beam as described below. The speed in this type is 1200 m/min.
Figure (13): Beaming, adapted from Weaving Reference Books of Textile Technology, 2000.
There are other types of warping and different warping calculations in regard with calculation and carrying out the warping process it self, we will discuss in other different articles.
- -Weaving Reference Books of Textile Technology, 2000.
- -Handbook of Weaving, 2001.
- -Weaving Technology and Operation, 1995.