PNEUMATIC CYLINDER:Following points are needed to be considered while selecting a pneumaticcylinder1. Cylinder Thrust: The cylinder thrust is a function of pistondiameter, operating air pressure and the frictional resistance (though in thecase of static thrust, the frictional resistance is zero). Cylinder thrust can be calculated by thefollowing formula. Let, Ff =Cylinder thrust for forward stroke in kg. Fr= Cylinder thrust for return stroke in kg. D = Diameter of piston in cm. d = Diameter of pistonrod in cm. P = Operating air pressure in bar For Upper Cylinder (10*16cm)Ff= ?/4 * 100 * 3.
1 = 247.47kgfFr= ?/4 * (100-6.25) *3.1 =228.25kgfFor Lower Cylinder (5*8 cm)Ff= ?/4 *25*1.
7 =33.37kgfF= ?/4 *(25-4)*1.7=28.03kgfThe aim is to reduce manual pressure From standard table we got the values for thrusts as, 628kgf in forwardstroke and 590kgf in return stroke. This values are maximum from calculatedtherefore design is safe.
2. Air consumption The air consumption data for cylinder isrequired in order to estimate the compressor capacity. The calculations includeair consumption during forward as well as return stroke. The theoretical airconsumption calculated from following formula, Let, Cw = Air consumption for forwardstroke in liters.
Cr = Air consumption for returnstroke in liters.D = Diameter of piston in cm.d = Piston rod diameter in cm L = Stroke length in cm.P = Air pressure in bar. Free air consumption= piston area x (operatingpressure + 1.013) x strokeFree air consumption in liters for forwardstroke:- Free air consumption in liters for backwardstroke:- For Upper Cylinder,Cf=5.
15lit, Cr=4.83litTotal air consumed = 5.15+4.83=9.
98litFor Lower Cylinder,Cf=0.42lit,Cr=0.35 litTotal air consumed = 0.42 + 0.35 = 0.77lit3. Type of Mounting Mold Opening Stroke: Mold opening stroke is the displacement of the movingplaten from mould close to mold open. Mold opening stroke determines themaximum height H of the molded part the machine is capable of.
The relationshipis Mold Opening Stroke >= 2H + LL- Sprue Length In a hot runner system, L = 0. Mold Height (Mold Thickness)-? In a toggle clamp Injection Molding Machinespecification, mold height is expressed as a range, from the minimum to themaximum mold height the machine could accommodate. The difference is the moldheight adjustment the machine is capable of. ? In a direct hydraulic clamp Injection Molding Machinespecification, mold height is expressed as a number, the minimum mold heightthe machine could accommodate. The actual mold height must be bigger than themachine minimum mold height for the mold to be closed and clamped. Otherwise, asmaller machine (to be exact, a smaller clamping unit) is called for.? Therefore, the minimum mold height = 5cm? Maximum Daylight ? The maximum opening between the fixed and movingplatens when the clamp is wide open.
It is related to mold opening stroke andminimum/maximum mold height as follows. ? For a Toggle Clamp Machine, Maximum Daylight=Mold Opening Stroke + Maximum Mold Height. ? For a direct hydraulic/pneumatic clamp machine, Maximum Daylight = Mold Opening Stroke + Minimum Mold Height.
Part Weight (in gm) = xSpecific Gravity of material (gm)Shot size (gm) = (PartWeight x Number of Cavities) + Runner WeightClamp force (Tons) =Projected Area (in2) x No. of Cavities x Injection Pressure