Indian Journal of Fibre & Texti le Research Vol. 3 1 , September 2006, pp. 465-466

Suitabi l i ty of cycloidal cam in shedding mechanism

Sal i l Kumar Bhattacharya" & Kisalay Das

Govt. College of Engineering and Texti le Technology, Serampore 7 1 2 20 I, Hooghly, I ndia

Received 1 February 2005; revised received and accepted 21 July 2005

A suitable cycloidal cam has been designed and compared with the simple harmonic cam to study the behaviour of warp yarn tension and warp breakage rate. Electronic tensiometer was used to measure the tension of the warp yarn during weaving with and without shuttle for both types of cam to understand the effect of shuttle propulsion on warp yarn tension. I t is observed that the warp breakage rate is comparati vely less in case of cycloidal cam. The tension behaviour is also found to be smoother in case of cycloidal cam.

Keywords: Cam follower, Cycloidal cam, S imple harmonic cam, Shedding cam, Weaving

IPC Code: I nt. CI.8 D03C5/00

Shedding motion is one of the basic motions in weaving machine. Due to rotation of cam in shedding motion of the loom, harnesses are moved up and down to form shed for weft insertion. The displacement-time relationship of the fol lower governs the shape of the cam. Sever<1l attempts have been made to modify cam profi le. Gu t attempted to minimise the lateral force to the bowl for which i t causes the side thrust and ware o f the mechanism. H e also showed that lateral force o n the bowl for cycloidal cam i s i n i tially less than that for s imple harmonic cam over the change periods. H inkle2

described that the dynamic force exerted by a cycloidal cam to the fol lower follows purely sinusoidal curve. Grossberg3 showed the movement of the fol lower for both types of cam through one unit of d istance in one radian of cam rotation from which i t can be concluded that the in i tial displacement i s slower in cycloidal cam as compared to that i n simple harmonic cam, resulting in low in i tial heald velocity for cycloidal cams. The gradual displacement becomes h igher by gaining higher velocity but fi nally

"To whom al l the correspondence should be addressed. E-mai l : sal i lctts@hotmail .com

the follower again reaches the end point slowly in case of cycloidal cam. This heald movement behaviour has an obvious effect on warp yarn tension variation and abras ion of warp with picking elements. In the present work, keeping al l other cam parameters unaltered as compared to existing s imple harmonic set of cams for a particular loom, a set of cycloidal cams has been designed from the profile which is drawn with the help of computer program written in c­programming language with graphics interface. After manufacturing the cam, the comparative displacement of cam followers was studied along with the warp breakage rate, and basic tension and its variations in a standard mi l l loom-shed.

From the computer programming and graphics, the actual profi les of the cycloidal cams were drawn and accordingly the casting of cams was made. These were then machined and case hardened.

Actual displacement of the cam follower for both the sets of cam was measured to get the actual heald displacement behaviour for simple harmonic and cycloidal cams.

A powerloom with negative tappet attachment was chosen wi th warp(48 ends/inch) and weft(42 picks/inch) counts of 24 Ne. Number of warps in the beam was 2500 and the loom speed was 1 65 rpm for the plain woven cotton fabric. The w idth of the loom was 1 20cm with negative let off attachment. Heald level was kept at 2900 as the warp yarns were comparati vely weaker.

Variation i n warp tension for both sets of cam was measured by Rothschi ld Tensiometer with measuring head of 0- 1 00 cN in the position between back rest and lease rods. To el iminate h indrance from shuttle during actual weaving process on l ine, the tension of warp was measured for both the sets of cam, firstly without using shuttle and then by i nserting shuttle to get the actual cam behaviour.

Warp breakage rate was studied for both types of cam sets on the basis of breaks per 1 000 warps per 1 0000 picks (Table 1 ) .

Figure 1 shows the displacement behaviour of two types of cam. It can be seen that cam fol lower of cycloidal cam starts in a slower and smoother fashion as compared to simple harmonic cam follower and then it moves faster compared to s imple harmonic

466 INDIAN J . FIBRE TEXT. RES. , SEPTEMBER 2006

Table I---Comparative study of breakage rate

Type No. of No. of Time of No. of Breakage Average of cam obser- breaks study picks rate/ breakage

vations min inserted 1 0,000 rate picks!

1 000 ends

Simple I 4 60 7500 2. 1 3 harmonic 2 5 70 9000 2.22 cam 3 3 60 6200 1 .93 2 . 1 1

4 4 60 7300 2. 1 9 5 6 80 9700 2.06

Cycloidal I 4 55 7900 2.02 cam 2 3 60 7600 1 .58

3 5 90 1 0200 1 .96 1 .94 4 4 60 7800 2.05 5 3 40 5700 2. 1

OO.-------------------------------r-----� � 50

. 40 t:: � 3O 5 � 20 � '0

-+- 51 "'vI --6- Cycloida]

6 O ����������,,��������� � � $ � # � � � � � � , � � � � � � �

c. S. Rotation, dcg

Fig. I-Displacement of cam fol lowers

motion cam fol lower and at the last part of the d isplacement, the cycloidal cam follower stops comparatively more gradually.

F igure 2 shows the dynamic tension on the warp yarn by keeping the loom running wi thout i nserting the shuttle, which shows during the change period of healds that the change i n tension on the warp i s smoother at the beginning and end part o f the change period. The same behaviour is also retlected in Fig. 3 when tension i s measured dynamical ly during normal loom runn ing. Highest tension values at beat-up zone and higher tension level at the bottom position of heald as compared to that at top posit ion is i n accordance with the findings o f Talukder.4

When comparative breakage rate wi th both types of cam is studied (Table 1 ), it is observed that the breakage rate is comparatively lower by more than 8% in case of cycloidal cam. Thi s i s because of the fact that the smoother cam follower movement at the

50

40

Z � u 30 .:" � .,. 0 V "'--.� 20 �

1 0 -+- 511M -6- CycloiJal

0 0 90 1 80 270 380 450 540 630 720

C. S. Rotation, deg

Fig. 2-Warp tension variation without shuttle propulsion

60

50

Z 40 u S 30 . Yi � 20

1 0 -+- 5HM 0 -.- Cycloidal

0 90 180 270 360 450 540 630 720 C. S. Rotation, deg

Fig. 3--Warp tension variation during normal running of loom

start ing and finishing zones enables better stress d istribution of the warp yarn.

It is concluded that the tension on the warp yarn i s marginally smoother i n case of cycloidal cam as compared to that i n case of s imple harmonic cam. Breakage rate of warp yarn is found to be comparatively lower i n case of cycloidal cam as compared to that in case of s imple harmonic cam, but the large scale trial is required to substantiate the fact.

Acknowledgement The authors are thankful to MIs Jayashree Texti les,

Rishra, Hooghly, West B engal, for provid ing the scope to carry out the experiment.

References I Gu H , Text Res J, 58 ( 1 988) 444. 2 H inkle T R, Killematics of Machilles ( Prentice-Hal l , Inc,

Japan), 1 960, 1 34. 3 Grossberg P, All Introduction to Textile Mechallism (Ernest

Benn Limited, London), 1 968,98. 4 Talukder M K & Sriramulu P K, Weaving- Machilles­

Mechallism-Mallagement (Mahajan Publishers Private L imited, Ahmedabad), 1 998, 1 38.