What is Straight Bar Frame and Its Features?
Straight bar frame is a special type of weft knitting machine which is equipped with bearded needle. In this machine, operating speeds of a hundred courses per minute can be achieved. It has the following unique features:
- Straight bar frames is a specific type of machine having a vertical bar of bearded needles whose movement is controlled by circular engineering cams attached to a revolving cam-shaft in the base of the machine.
- The length of the machine is divided into a number of knitting heads (sections or divisions) and each head is capable of knitting a separate but identically-dimensioned fashion-shaped garment panel.
- The needles press their beards against a fixed pressing edge; loop formation prior to intermeshing is achieved by individually horizontally-moving loop-forming sinkers, and knock-over occurs when the needles descend below the knock-over bits.
- At either edge of each knitting head, a group of rackably-controlled points transfer loops to fashion shape the garment panel at the selvedges by widening or narrowing the knitting width. On completion of the garment panel, it is pressed-off the needles.
Straight bar frames are long, capital-expensive machines that, because of their multisections and in spite of their intermittent knitting action, are highly productive in a very narrow sphere of garment manufacture. The knitting width is rather restricted and fashion tends not to encourage full exploitation of the fashion shaping and stitch-transfer patterning potential of the machines.
The machines are noted for their production of high-quality garments as a result of the gentle knitting action, low fabric tension and fashion shaping, which reduces the waste of expensive yarn during cutting and is emphasised on the garments by carefully-positioned fashion marks.
The straight bar frame is the only bearded needle weft knitting machine that is still commercially viable, although it now faces serious competition from electronically-controlled V-bed flat machines.
Different Parts of Knitting Head of the Straight Bar Frame:
1. Bearded needle, having a cranked end for location in the tricked and drilled needle bar.
2. Sinker – only one between every other needle space – with a reinforced back and, at the front, a ‘catch’ to sink the yarn around the needles, and a ‘neb’ to separate the old and new loops until knock-over.
3. Divider, occupying each remaining space, usually having the same shaped front as the sinker but with an extended tail at the back.
4. Knocking-over bit – one directly beneath each sinker and divider – having a ‘throat’ for holding the loops and a ‘nose’ for knocking-over.
5. Needle bar, having a compound horizontal and vertical movement.
6. Striking jack, fulcrummed at its lower end, each one with its ‘nose’ resting on a sinker back, and a ‘spring’ exerting pressure on its ‘tail’.
7. Catch bar, extending the full width of the knitting head, having forward and backward, as well as vertical, movement.
8. Yarn carrier, which traverses in alternate directions across the head from one course to the next – up to six carriers may be available. The carrier is connected to a reciprocating carrier rail by friction, and when the carrier is arrested by its carrier stop, the carrier rail completes its full traverse, driven by the coulier cam and punching through the carrier friction.
9. Falling bar, which is a stop that cushions the advance of the sinkers and dividers.
- Knitting Technology by David J Spencer
- Understanding Textiles for a Merchandiser by Shah Alimujjaman Belal
- Fundamentals and Advances in Knitting Technology by Sadhan C. Ray
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.