First, we need to know what kind of Mould it is Cold Runner or Hot Runner.
If it is Hotrunner, No of cavities (layman words number of parts to be filled) multiplied by each part weight is Total shot weight or Shot Size.
if it is a cold runner, No of cavities multiplied by each part weight added to Runner weight is Shot weight or Shot Size.
Remember the shot size mentioned by the Machine manufacturer for PS. If your material other than PS, then you have to identify the specific gravity of the material to be processed and then multiply it with the Total shot weight of the machine mentioned in the catalog.
Multiply machine shot by two if maximum injection screw stroke is less than four.
Multiply machine shot by 1.4 if maximum injection screw stroke is greater than or equal to four
Divide the result by the melt density for polystyrene.
Multiply the result by the cycle time of molding.
Theoretical injection capacity = (injection molding machine) cylinder cross-sectional area screw stroke, injection weight = injection capacity melting density of raw materials injection efficiency coefficient (generally 0.86).
Theoretical injection weight is 91% of PS theoretical injection capacity.
Calculate the shot size in an injection moulding machine
1.According to the weight of injection molding machine products, Calculate the injection volume that the injection molding machine
When the injection molding machine product is made of polystyrene, the injection volume that the injection molding machine should have is Wps. Wps = (product weight + total gate system weight) ÷ (0.75 ~ 0.90) that is Wps = (1.3 ~ 1.1) x (product weight + gate system total weight) When the product quality requirements are high, the above formula The coefficient of should be a large value.
If the product is another plastic named X plastic), imitate the above method. First, calculate that it should have the theoretical injection volume of this plastic as Wx. Wx = (1.3 ~ 1.1) x (product weight + total weight of the gate system). But the WX value cannot be simply used to determine the injection volume of the injection molding machine. It must be replaced by the Wps value. The conversion formula is Wps=Wx x (1.05 ÷Vx) In the formula, Vx ― an example of the specific gravity of a certain plastic. Suppose an injection molded product is made of polyethylene (PE). The product itself has been calculated to weigh 180 grams. And it is estimated that the gate system weighs 20 grams.
Calculate the weight of the product itself to be 180 grams, and estimate the weight of the gate system to be 20 grams. Use the above formula to first calculate: Wx = 1.2x (180 + 20) = 240 grams. It is found from the manual that the specific gravity of the PE material is Vx=0.92, so Wps =240x (1.05÷0.92 )=273.9.
2.Calculate the clamping force according to the shape of the product.
Calculate the clamping force p according to the vertical projection area of the injection molding machine product on the template (fixed template or movable template): clamping force 2 clamping force constant x product projection area p 2 KpS were p ― clamping force (t) S ― a projected area of the product in the vertical path of the template (cmZ) Kp ― clamping force constant (T / cmZ).
Plastic name PS, PE, PP, ABS, PA, POM, PMMA Other Kp (T / cm 2) 0. 320. 320. 320. 3-0. 480. 64-0. 720. 64-0. 720. 65 A 0.80.6 A 0.85 .The mold opening stroke of the injection molding machine is determined by the product height. The mold opening stroke Zx product height + nozzle length.
3.According to the material of the product and the wall thickness of the product, select the screw model general plastics such as PE, PP, PS, ABS, etc., for the products with thinner wall thickness, choose A and B screw engineering plastics such as PC, PMMA, PPO, etc. For products with thicker walls, choose B and C-type screws.
4.According to the contour size of the mold, the inner spacing size of the tie rod (guide pillar) of the injection molding machine is determined. The mold width of the minimum mold thickness and the inner distance of the tie rod (10-20) mm. The minimum modulus of the plastic injection molding machine.