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Attachment Workpiece Finger mg μF μF F F Check the gripping force. LEHS20 25 20 15 10 5 0 14 0 20 30 40 60 80 100 LEHS20 Pushing speed is satisfied at the point where 70% of the pushing force and 30 mm/sec of the pushing speed cross. Note) Confirm the pushing speed range from the determined pushing force [%]. 110 100 90 80 70 60 50 40 30 0 10 20 30 40 50 60 Selection Procedure Step Example Guidelines for the selection of the gripper with respect to workpiece mass Although conditions differ according to the workpiece shape and the coefficient of friction between the attachments and the workpiece, select a model that can provide a gripping force of 7 to 13 times Note) the workpiece weight, or more. Note) For details, refer to the calculation of required gripping force. If high acceleration or impact forces are encountered during motion, a further margin of safety should be considered. Example) When it is desired to set the gripping force at 13 times or more above the workpiece weight. Required gripping force = 0.1 kg x 13 x 9.8 m/s2 . 12.7 N or more Gripping force F [N] Gripping point L [mm] Pushing force 100% 70% 40% When the LEHS20 is selected. A gripping force of 14 N is obtained from the intersection point of gripping point distance L = 30 mm and pushing force of 70%. Gripping force is 14 times greater than the workpiece weight, and therefore satisfies a gripping force setting value of 13 times or more. Gripping point distance: 30 mm Pushing force: 70% Pushing speed: 30 mm/sec Workpiece mass: 0.1 kg Pushing force/Trigger level [%] Pushing speed [mm/sec] Pushing force and trigger level range Calculation of required gripping force When gripping a workpiece as in the figure to the left, and with the following definitions, F : Gripping force (N) μ : Coefficient of friction between the attachments and the workpiece m : Workpiece mass (kg) g : Gravitational acceleration (= 9.8 m/s2) mg : Workpiece weight (N) the conditions under which the workpiece will not drop are 3 x μF > mg and therefore, F > With “a” representing the margin, “F” is determined by the following formula: Number of fingers mg 3 x μ F = x a mg 3 x μ When μ = 0.2 When μ = 0.1 F = x 4 = 6.7 x mg mg 3 x 0.2 F = x 4 = 13.3 x mg mg 3 x 0.1 7 x Workpiece weight 13 x Workpiece weight “Gripping force at least 7 to 13 times the workpiece weight” . The “7 to 13 times or more of the workpiece weight” recommended by SMC is calculated with a margin of “a” = 4, which allows for impacts that occur during normal transportation, etc. . Even in cases where the coefficient of friction is greater than μ = 0.2, for reasons of safety, select a gripping force which is at least 7 to 13 times greater than the workpiece weight, as recommended by SMC. . If high acceleration or impact forces are encountered during motion, a further margin should be considered. Note)