Every spinning mill aims to produce a better quality of yarn with maximum efficiency. Now microprocessor technology and solid-state circuits have brought it on board, doing it faster than anyone imagined. Electronics helps to monitor machine speed, analyze downtime problem and compute efficiency of machines. The modern electronic control systems offer functions for optimal running and supervising of all machines thereby making step-by-step improvements in each yarn-making process.
- AUTOMATION IN BLOWROOM
In modern blow room, the line whole process is graphically indicated with the running mode of entire installation as well as that of individual machines. All relevant events are registered on the hard disc of the computer and can be recalled, printed, or transferred to a floppy disk at any time. In it, all machines are connected by LAN. Fiber Control Corp. offers a package of electronics that will continuously, visually monitor, and /or optionally record each weigh-pan dump in a central location. Uniflow, automatic bale opener processes raw material with up to groups of differing bale heights. Metal ejectors electronically detect magnetic and non-magnetic metals down 2.5 mm diameter and automatically ejects them from the material flow. Some selected electronic controls used in blow room are given in the next section:
1.1 Bale Height Measurement in Unifloc
The take-off unit of uniflow moves down until the light’s barrier is covered. Then a transport drive is switched on. The differences in height are measured constantly. As soon as a slight bump is detected and the light barrier is also covered, the take-off unit moves upward at low speed until the light barrier is free again, the height is registered.
1.2 Use of Proximity Switches
In blow room, proximity switches and limit switches are used at different places to provide safety operations, length measurement, collision protection, etc. Some of these functions are:
- Foreign body detection
- Length measurement
1.3 Use of Photocells
In spinning, control of linear density is very important, to ensure smooth working of the process. Optical sensing systems find useful applications in blow rooms. Photocells are installed at different places to control the level of cotton. Similarly, photocells are used in blending chambers and filling trunks to ensure the correct level of material.
- Electronic application in card
Crosol Ltd. developed electronics for chute-feed which uses electronic, logic systems to handle the event sequence. Zellweger Uster Ltd. markets card control which is a long-term autoleveller system. It monitors and corrects sliver-weight variation occurring longer than the correction length 25-30 m.
2.1 Measurement of cylinder speed
The cylinder speed is measured by using the perforated disk mounted over the cylinder shaft and the proximity switch generates a pulse whenever a hole passes in front of the proximity switch, these pulses are counted by an electronic counter for calculation of cylinder speed.
2.2 Measurement of Delivery Speed
The delivery speed is continuously measured using the same method as used for cylinder speed measurement.
2.3 Regulation of Doffer Speed
The control circuit serves mainly to automatically register the draft in the delivery and correct the speed of the delivery motors using the inverter drive.
2.4 Measurement of Distance Between Flats and Cylinder
Nowadays, an electronic system is used for the exact measurement of the distance between flats and cylinders. Measurement can be made with the cylinder in rest or running condition. For this purpose, a proximity switch is used.
2.5 Nep Control at Card
The optical online nep control was first introduced in the world by Trutzschler. In this system, the guide profile underneath the doffer roll is exchanged against the nep sensor. A small video camera passes through this profile, which is covered with a glass plate and takes five pictures per second on the web. The image analyzing software evaluates these pictures and differentiates between trash and neps and accordingly, indicates size and location.
It is used to measure the sliver thickness variation and then act continuously to alter the draft accordingly so that more draft is applied at thick places and less at thin places with the result that the sliver delivered is less irregular than it otherwise would have been. In addition to an improvement in the product appearance, autolevelling can waste and constant process conditions. The autoleveller is an online monitoring device in the spinning process.
- Electronics Application in Draw Frame
3.1 Stop Motion in Draw Frame
To ensure the smooth working of the draw frame, stop motion is a must. Suppose we are feeding 8 slivers in a draw frame, if one of the slivers gets broken then this sliver has different properties than the previous. If we are using a draw frame for blending, then their blend ratio will change. So, by use of electrical and optical sensors, we can eliminate this defect.
3.2 Draft Commander Functions
These are for example delivery speed, production rate, sliver fineness, CV values, single drafts, total draft, shift data, and rotational speeds. In case of malfunction, a detailed indication of the trouble source appears on the display. This reduces the time for fault detection and increases the availability of the machine.
3.2 Online Collection
Online collection of all operating data for a constant good sliver quality is done by a microcomputer. Spectrograms, spectrogram analysis, length variation graphs, sliver count diagrams, production data, shift reports, daily reports, and lot reports, efficiency and standstill analysis as well as trouble reports are readily available at any time. Every single meter of sliver is checked automatically and thus the need for lab sampling is eliminated.
- Electronics Application in Speed Frame
The flyers are aerodynamically balanced to a higher degree of precision and are enclosed in design. The building motion has also been improved to enable a better package with a minimum of stretch. As a result, breakage rates are reduced enabling a higher speed and productivity. A fluid coupling is introduced in the drive, which facilitates a soft start. The breakages at the time of jerky start are reduced and as the starting torque is lower, the motor HP can be reduced enabling power savings. Electronic oft start attachments are also offered by some parties where the full speed is gradually reached for 20 sec. The power consumption and maximum demand are reduced by such attachments. Positively driven clearers which are kept clean by an oscillating doctor blade, overcome the problem of stub-like defects due to the incorporation of fluff accumulated on clearer pads into the strand. Provision of pneumatic and stop motions also helps to minimize lashing in and of bobbins. Ball-bearing footstep bearing helps to reduce power consumption by 3%-4%. The suspended flyer is a standard feature in the latest speed frame as tills help to achieve higher flyer speeds and bring down doffing time.
- Electronics Controls in Ring Frames
Modern ring frames incorporate several innovative electronic controls that enable higher productivity with improved quality.
5.1 Variable Speed Drives
To keep breakage under control, at all positions of doffing. Spindle speed should be controlled. Speeds are kept lower at cop bottom and towards the end of the doff and at much higher at other positions of doffing to achieve spindle speeds.
5.2 Servo-Motor Driven Front and Back Rollers
Servomotor systems use an individual motor for spindle, front roller, and back roller which are computer controlled. So, by just feeding the draft and TPI we can change the yarn specifications very easily. The advantage of using servomotors is:
- Quick yarn specification change.
- Very easy to adjust yarn specification.
- No need to change gear
- Reduction of gear noise.
5.3 Roving Stop Motion
Roving stop motion detects the end break and stops the roving to that spindle arresting the back roller movement. Whenever yarn breaks optical sensors detect and gives the signal for further action.
5.4 Travelling Sensor
The sensor generates a magnetic field that is affected by the rapidly rotating traveler. If yarn breaks, rotation of the traveler ceases, and the sensor detects it and gives a pulse. The microprocessor already identifies the spindle from the travel time of the sensor.
5.5 Doffing Sensor
This sensor is mounted on the spindle rail to register the number of doffs and the time taken for each. The indication of end breaks using lamps, resulting in a reduction in patrol time, and the reports are made available at any moment and the shift end.
- Electronics Applications in Winding
6.1 Yarn Clearer
The electronic clearer monitors yarn quality in the yarn path at any winding speed. Released by a yarn fault signal, the yarn-cutting blade of the cutter executes cutting orders, preventing yarn containing thick or thin places or double ends from running onto the package.
6.2 Automatic Splicer
In modern winding machines winding head has its splicing unit which automatically joins the two yarn ends together after a yarn breaks or the bobbin changes itself. The two opened-up yarn ends are placed, overlapped, into an intermingling chamber. A jet of compressed air, which is adjustable according to the yarn characteristics, such as pressure and reaction time, joins the two ends together.
6.3 Controlling Yarn Tension and Winding Speed
The tension sensor continuously detects actual winding tension, positioned immediately before the drum. The tension discs rotate against the direction of the running yarn, thus preventing the build-up of dirt particles, abrasion or even entangling of the yarn at the shell surface.
6.4 Auto Doffing
Auto doffer unloads the package and places the empty cone and the reserve of yarn at the preset length suitable for the next process. Continuous communication between the computer and the heads sends the trolley, in sequence, to the next position when the preset length is about to be reached but before it is completed. There is an empty tube on the trolley ready for use, which is substituted during the doffing cycle time.
Electronics has made almost all the areas of the textile industry more reliable to improve the quantity and quality of the material.
- Advanced Spinning Systems, NCUTE Programme, IIT Delhi
- Electronic controls in textile machines, NCUTE Programme, IIT Delhi
Tanveer Malik, Ajay Shankar Joshi and T. K. Sinha
Faculty, SVITT, SVVV, Indore