Monday, 24 August 2009

Advantages and Disadvantages of Warp Knitting Tricot and Raschel machines

Tricot machines Characteristics

• Compound sinker bar (2-point knockover).
• Warp beams are placed mainly at the back of the machine or perhaps above the machine.
• Needles can be changed from the front side of the machine.
• Up to 5 guide bars are used at the moment.
• Use of compound needles.
• Starting-up without fabric take-up possible.
• Only pillar loops cannot be knitted (only by support through inlay motion),(lateral 2-point knock-over)
• Angle between incoming yarn sheet and fabric take-up is 90° (considerable needle stress).
• Simple machine construction.
• Short run-in of the threads because of the beam positions.
• High number of courses possible up to total stop of the beams (for pleats) because working without fabric take up is possible.
• High yarn run-in is possible (overfeed).
• Handling of the knitting elements from the knitter's side possible.
• Piles for terry effects are possible.
• Simple construction of pile fingers for plush.
• Soft fabric touch.

Disadvantages of Tricot machines

• Problems with small number of stitches and reduced yarn run-in (fabric take-up 90°) (high tension for the needle, loose selvedges lead to yarn twisting and fault).
• Processing of elastomeric yarn mainly possible only as loop.
• Net constructions are difficult to be made since the knock-over of the wales connection is not possible
(lateral 2-point knock-over).
• Processing of filler yarns is very difficult (see fabric take-up,90°).
• Common machine gauges from E 24 to E 40.

Raschel machines Characteristics

• Separate knock-over bar (trick plate) 3-1point knock-over and stitch comb bar.
• Warp beams are placed on the top of the machine.
• Needles have to be changed from the back side of the machine (due to the knock-over comb bar).
• Nowadays up to 78 guide bars are possible.
• Usage of compound needles and sometimes of latch needles.
• Loop formation without fabric take-up is not possible;main knockover at the front edge (take-up).
• Angle between incoming yarn sheet and fabric take-up is 170°(low needle stress).
• High take-up tension allows the production of open fabric structures and the manufacture of elastomeric inlays (powernet) as well as the production of elastic pleated fabrics.
Vertical laying-in (filler threads) can be processed (170°fabric take-up).
• The high yarn tension does not affect the needles directly. Hence, low stitch densities and short yarn run-in possible at high fabric stability and low needle stress.
• Various materials can be used: film tapes, glass,aramide, carbon, metal wires.
• Wide range of gauges.

Disadvantages of Raschel machines

• Starting-up only with fabric take-up possible.
• Loose yarn run-in (overfeed) and high stitch densities(velvet, pleats) are not possible fabric touch less soft.
• Longer yarn path due to beam positions.
• Changing of needles only from the back side.


Anonymous said...

Would you explain of Compound sinker bar (2-point knockover).

Warp Knitting said...

Already describe at,

2 points knock over (on tricot machines)
1st knock over 0 degree.
2nd knock over 60 degrees holding down.
Please read also stitch forming process on raschel machine.

3 points knock over (on raschel machines)

1st knock over 285 degrees.
2nd knock over 345 degrees.
3rd knock over 0 degrees,with additional part which no available on tricot machine i.e knock over bar (trick plate bar).

by the way, would you like to introduce your self please,thank you.

Anonymous said...

My name is Soewarso, I've been working in knitting Factory (1984-2001)in Bandung Indonesia, in spare part provisioning and maintenance department.I want to obtain a deep understanding of The process on tricot and raschel warp knitting also warping. Nowadays I supply some spare part for some knitting factory. Thank you for your kindly.

Warp Knitting said...

Dear Mr.Soewarso,thank you for introduced your self and visiting our site.

Soewarso said...

Dear sir,In tricot machine starting-up without fabric take-up possible. but in raschel machine starting-up only with fabric take-up possible. is it the causes of feeding device of that two kind machine are different? Would you explain about it. Thank you

Warp Knitting said...

the capability on tricot machines start-up without take up not cause of the yarn feeding system but cause of the knock-over system (2 points knock over)allowed the loop release from the needle without need to pull by take up roller.(can run with high courses per cm).