Motion Without Limits

®

Example 3 A feeding mechanism incorporates an R44-612-R90 slide ring segment andFCP-44-612 fixed center carriage. This mechanism has a paddle which pushes components onto a manufacturers of conveyor via a curved path. The pusher is powered by a rotary actuator which engages on a pin on the center of the carriage plate, 70mm above the center line of the V’s. The mass of the carriage assembly is 10kg and the center of mass is 70mm from the system center. When the mechanism is pushing products onto the conveyor, the pushing force F

P

is 200N which acts 100mm from the center of the systemand at a height of 60mm from the center line of the V’s. The length of travel is 150mm and the system is lubricated by lubricators supplied with the fixed center carriage.The application is slow speed and low acceleration, so centrifugal and inertial forces can be ignored for the calculation. L

1

= 10kg x 9.81m/s

2

(g) = 98.1NL

2

= 0Reaction force on carriage pin = F

P

x mechanical advantage = F

P

x [(306 + 100) ÷306] = 200 x 1.327 = 265NM = 265N x 0.07m – 200N x 0.06m = 6.55NmM

V

= 200N x 0.1m = 20NmM

S

= 98.1N x 0.07m = 6.87Nm

L M
V +M
S +L
1 +=L
2 20656.5565
F =+MM
(max) M
V(max) M
S(max) L
1(max) L
2(max) ++= +98.116006.8735 +01600 0.67

900km or 6 million strokes . Reading from the nomogram on page 25 we see that the linear life corresponding to an L

F

value of 0.67 is1200km, however, due to the short stroke the system should be derated by applying the short stroke correction (see note 3 on page 25). The life from the nomogram must therefore be multiplied by 0.15 ÷0.2 = 0.75. The cor- rect linear life of the system thus calculated is 1200 x 0.75 = Example 4 A textile cutting machineuses a

PRT

track systemconsisting of 1 x TR76-799- R180/C; 1 x TNL-76-B2040 – 2xAK; 1 x TR76-799-R180/C; 1 x TNL-76-B2040 – 2xAK; 1 x FCP-76-799. The carriage carries a knife which experiences a resistance force of 200N at a distance of 100mm from the system center, and the blade is offset by 60mm from the centerline of the V’s.The carriage is driven by a timing belt suppliers whichengages a pin in a yoke on the side of the carriage. The line of the force is offset by 110mm from the system cen- ter. The carriage and knife assembly weighs 15kg and travels at 1 m/s. The knife only cuts while the carriage is on the lower of the two straight portions of the track. This system is lubricated. On lower straight section:

L

1

= 0L

2

= 15kg x 9.81m/s

2

= 147.2NCutting force = Driving forceM = 200N x 0.06m – 200N x 0.025m = 7NmM

V

= 200N x 0.10m + 200N x 0.11m = 42NmM

S

= 147.2N x 0.04m = 5.9Nm

L M
V +M
S +L
1 +=L
2 421657165
F =+MM
(max) M
V(max) M
S(max) L
1(max) L
2(max) ++= +038005.9140 +147.23800 0.38

The corresponding life figure from the lubricated nomogram on page 25 is 6000km.On the curved sections there is no cutting force and the driving force will be small, but there will be a centrifugalforce = DV

2

/R = 15kg x 1

2

/0.3995 = 37.5N plus the weight of the carriage. On the top straight section there is onlythe weight of the carriage acting. The worst case loading anywhere in the system other than on the lower straight portion occurs on the bottom of the curved sections where the various load components are as follows:L

1

= 0L

2

= 15kg x 9.81m/s

2

+ 37.5N = 185NM = 0M

V

= 0M

S

= 185 x 0.04m = 7.4NmFrom these figures, a life factor of 0.10 can be calculated, as above. This life factor corresponds to a linear life of140,000km. Because the life calculations show that the expected life on the section where the cutting is done is 23times shorter than on the return section of the track, the wear on the return section can be ignored for the purposes of this approximate life prediction. On this basis the system will last for 6000km ÷2040mm = 2.9 million circuits of the track.

Notes In applications where a ring slide or track system experiences a range of loads within a cycle which all significantly contribute to the wear,an appropriate allowance should be made. Calculations for such duties fall outside the scope of this catalog. Consult BWCfor details. © Bishop-Wisecarver Corporation 2008. All rights reserved.

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