Introduction of Weaving Drop Wires

What is Drop Wire?

Drop wire, also called drop pin or dropper, is an indispensable part on shuttleless loom; it indicates warp breakage and give signal to warp stop motion to stop weaving machine.

Function and Criteria of Drop Wires

1. The function of drop wires during weaving process

(1) Warp stop function. Warps pass through the thread eyes of drop wires in an orderly way, once warp breakage or lack of warp tension occurs, drop wires will fall due to gravity, warp stop motion will take function and stop the loom, to prevent fabric defect.

(2) Lease and impurity clearance. Warp passing through drop wire thread eye, so that warps are arranged orderly without twisting together. In the meanwhile, the change of warp tension during weaving process cause friction between warp yarn and thread eye, so as to clear out cotton impurities on the warp surface.

2. Criteria of weaving drop wires

(1)  Appearance and specification of drop wires should be consistent, so that automatic warp stop motion will react sensitively when warp breakage happens.

(2) Drop wires thickness should be even, and weight of each dropper should be same, so that all warps get same tension, making sure fabric quality.

(3) Surface of drop wires shall be flat and smooth, falling smoothly when warp breaks, and also can reduce flyings and impurities.

(4) Thread eye should be smooth without burr, to avoid harming warp yarn strength and causing breakage.

(5) Drop wires should have a certain elasticity, hardness and abrasion resistance.

Classification and Technical Requirements of Drop Wires

1. The classification of drop wires

According to way of warp stop motion, there are drop wires used for mechanical warp stop motion and drop wires used for electrical warp stop motion. According to drop wire structure, there are open type drop wires and closed type drop wires. According to shape of thread eye, there are U-type eye drop wires and R-type (round type) eye drop wires.

Due to high running speed of shuttleless loom, electrical warp stop motion is requested. And U-shape eye drop wires have relatively less abrasion on warps, shuttleless looms mostly use this type.

Warp Stop Motion E
Drop Wire Structure O     G
Drop Wire Code
U-type Thread Eye
R-type Thread Eye

2.     Technical requirements of drop wires

(1)   Below is the allowable tolerance for different grade drop wires;

Allowable Tolerance for Drop Wires

(2) Hardness requirement of drop wires


B Grade (HV0.2)

A Grade (HV0.2)

0.10, 0.20. 0.25









(3) Material of drop wire should be #55 or #60 carbon steel, or similar quality steel.

(4) Drop wires should have good flat, flatness for B grade should be 0.4mm, flat for A grade should be 0.2mm.

(5) Degree of symmetry between drop wire groove and center line should be 0.20mm.

(6) After galvanizing treatment, base metal of drop wire should not be exposed. Coating thickness of dropper in A grade should be not less than 0.005mm, in B grade should be not less than 0.015mm.

(7) Surface of drop wire should be smooth, thread eye should be round without burr, coating without defect.

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