Quality control in weft knitting:
The dimensions of a weft-knitted fabric are determined by the number ofstitches and their size, which in turn is determined by stitch length. Most knitting
quality control therefore reduces to the control of stitch length; differences in mean
stitch length give pieces of different size; variation of stitch length within the piece
gives appearance defects, by far the most common one being the occurrence of
widthwise bars or streaks owing to variation in stitch length between adjacent
courses.
1. Measurement of stitch length, l
• Off machine (in the fabric):– HATRA course length tester
– Shirley crimp tester.
• On machine (during knitting):
– Yarn speed meter (revolving cylinder only)
– Yarn length counter (both revolving cylinder and cambox machines).
2. Control of stitch length, l
• Positive feed devices:– Capstan feed: cylindrical or tapered
– Nip feed: garment length machines
– Tape feed: (Rosen feed) circular machines producing plain structures
– Ultrapositive feed: IPF or MPF
• Constant tension device: Storage feed device: flat, half-hose, hose and circular
machines producing either plain or jacquard structures.
• Specialised positive feed devices:
– Positive Jacquard Feeder MPF 20 KIF
– Striper Feeder ITF
– IROSOX Unit (half-hose machines)
– Elastane Feed MER2
– Air controlled feeds for flat and fully fashioned machines.
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