Statistical Quality Control(S.Q.C) | Function of Statistical QualityControl(S.Q.C) | The Significance of Statistical Quality Control(S.Q.C)in the Textile Industry

Statistical Quality Control(S.Q.C)
It is the application of statistical tools in the manufacturing process for the purpose of quality control. In SQC technique attempt is made to seek out systematic causes of variation as soon as they occur so that the actual variation may be supposed to be due to the guranted random causes.

Statistical quality control refers to the use of statistical methods in the monitoring and maintaining of the quality of products and services. 

Basic Categories of Statistical Quality Control(S.Q.C):

All the tools of SQC are helpful in evaluating the quality of services. SQC uses different tools to analyze quality problem.

1) Descriptive Statistics
2) Statistical Process Control (SPC)
3) Acceptance Sampling

1. Descriptive Statistics:

Descriptive Statistics involves describing quality characteristics and relationships.

2. Statistical process control (SPC):
The application of statistical techniques to determine whether a process is functioning as desired

3. Acceptance Sampling: 

The application of statistical techniques to determine whether a population of items should be accepted or rejected based on inspection of a sample of those items.

Variations of Statistical Quality Control(S.Q.C):

1. Allowable or cause variation
2. Assignable or preventable variation

Function of Statistical Quality Control(S.Q.C):

1. Evaluation of quality standards of incomeing material, product process and finished goods.
2. Judging the conformity of the process to establish standards taking suitable action , when deviation are noted.
3. Evaluation of optimum quality, obtainable under given condition.
4. Improvement of quality and productivity by process control and experimentation.

Main purpose of Statistical Quality Control(S.Q.C):

The main purpose of Statistical Quality Control(S.Q.C) is to divide statistical method for separating allowable variation from preventable variation. 

The Significance of Statistical Quality Control(S.Q.C) in the Textile Industry:

1. The expected quality of product can be produced and hence customers satisfaction can be achieved which brings higher profit.
2. It is very easy to separate allowable variation from the preventable variation by this.
3. It ensures an early detection of faults in process and hence minimum wastage.
4. With its help one can easily defect the impact of chance in production process in the change in quality.
5. It ensures overall co-ordination.
6. It can be use in the interpretation control chart.

Crochet Machine | Knitting Elements of a Crochet Machine

The Crochet Machine
In hand crocheting, a hook is used to draw a new loop through the old loop with the chains of loops being joined together at intervals. On crochet machines, the warp chains are separate from the weft inlay and it is the latter threads that join the chaining wales to each other. 

Knitting Elements of a Crochet Machine

• A single horizontal needle bar whose simple reciprocating action can be used to operate individually-tricked latch, carbine or embroidery needles. The patent or carbine bearded needle is used for fine structures and has a sideways crimped beard placed in a permanently-pressed position. Although warp threads can only be fed into the beard from the left (necessitating a unidirec-tional closed overlap), the old overlaps are automatically cleared and landed by the movement of the needle. It is still the most frequently used needle, achieving speeds up to 2500 rpm. Reduced machine speed and high needle wear make its use uneconomical for knitting single end cotton yarns.

• No sinkers; instead a fixed hold-back bar is fitted in front of the knock-over verge to prevent the fabric moving out with the needles. 

Knitting Elements of a Crochet Machine

• Closed lap pillar stitches and inlay threads controlled and supplied as separate warp and weft respectively. Each needle is lapped from below by its own warp guide, which is clipped to a bar whose automatic one-needle overlap and return and underlap shog is fixed and is controlled from an eccentric cam whilst its upwards and downwards swing is derived from a rocker-shaft. The warp yarn is often placed low at the front of the machine. 

• The weft yarn, often placed above and towards the back of the machine, supplying the carrier tubes, which are clipped to the spring-loaded inlay bars.These bars are fitted above the needle bar and are shogged at the rate of one link per course, from pattern chains around a drum at one end of the machine.There are usually up to two warp guide bars and up to 16 weft inlay bars, which may be electronically controlled.

• Special attachments are available for producing fancy effects such as cut or uncut fringe edges, pile, braiding (equivalent to fall-plate) and snail shell designs.

Crochet machines, with their simple construction, ease of pattern and width changing, and use of individual yarn packages or beams provide the opportunity for short runs on coarse- or fine-gauge fancy and open-work structures and edgings, as well as the specialist production of wide fancy fabrics or narrow elastic laces.

Knitting Action of the Compound Needle Warp Knitting Machine | KnittingAction of the Compound Needle Tricot Machine

Needle rise and guide bar swing: 

With the sinkers forward holding down the fabric, the hooks and tongues rise, with the hook rising faster, until the head of the latter is level with the guide holes and is open.The guides then swing through to the back of the machine.

2. The overlap and return swing:
The guides shog for the overlap and swing to the front of the machine; immediately, the hooks and the tongues start to descend with the tongues descending more slowly, thus closing the hooks.

Fig.  Knitting action of a compound needle tricot machine

3. Landing and knock-over:
The sinkers start to withdraw as the needles descend so that the old loop is landed onto the closed hook and then knocked-over as it descends below the sinker belly. At this point the underlap occurs before the needles begin their upward rise and the sinkers move forward to hold down the fabric.

The Karl Mayer tricot model HKS 2–3 E is designed to knit elastic fabrics and has a maximum speed of 3300 cpm with reduced noise levels and energy consumption.The vertical staggered arrangement of the guide bars enables the stroke to be reduced.The bars are hollow section which reduces their weight and expansion due to heat.

Features of the Latch Needle

Latch Needle

Fact and fiction envelopes the invention of the latch needle in a similar manner to that of the bearded needle. Pierre Jeandeau patented the first latch needle (also known as the tumbler needle) in 1806 but there is no evidence of its practical use.There is also no evidence that the pivoting of a broken pocket knife blade led to the development of the latch spoon.

The latch needle has nine main features (Fig. A):

1 The hook, which draws and retains the new loop.

2 The slot or saw cut, which receives the latch-blade (not illustrated).

3 The cheeks or slot walls, which are either punched or riveted to fulcrum the latch blade (not illustrated).

4 The rivet, which may be plain or threaded.This has been dispensed with on most plate metal needles, by pinching in the slot walls to retain the latch blade.

5 The latch-blade, which locates the latch in the needle.

6 The latch spoon, which is an extension of the blade, and bridges the gap between the hook and the stem covering the hook when closed, as shown in broken lines.

7 The stem, which carries the loop in the clearing or rest position.

8 The butt, which enables the needle to be reciprocated when contacted by cam profiles on either side of it, forming a track. Double-ended purl type needles have a hook at each end; whilst one hook knits, the inactive hook is controlled as a butt by a cam-reciprocated element called a slider.

9 The tail, which is an extension below the butt, giving additional support to the needle and keeping the needle in its trick.

Fig.A. Main features of the latch needle.