Shear Rate (Injection)
Compute the shear rate of the molten plastic in a rectangular channel, γ = 6Q/(W·H²), from the flow rate (Q), the channel width (W) and height (H). It is a critical parameter of polymer processing: thermoplastic viscosity drops with shear rate (pseudoplastic behavior), and excessive rates degrade the material. It guides the design of runners and gates. Enter the flow rate, the width and the height of the channel.
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Shear rate (injection moulding)
When molten plastic is forced through a narrow channel, the fluid layers slide over one another — that sliding is shear, and its intensity is the shear rate γ. For a rectangular channel, γ = 6Q/(W·H²), a function of flow rate and geometry. Why does it matter so much? Thermoplastics are pseudoplastic (shear-thinning): their viscosity drops as the shear rate rises — the material turns 'thinner' and flows more easily the faster it is pushed, the same principle as ketchup that runs once the bottle is shaken. That helps a great deal in filling the mould, yet it has a limit: excessive rates generate heat through viscous friction and degrade the polymer chains, staining and embrittling the part. Every material has a maximum recommended shear rate, which guides the sizing of the runners and the gate. Enter the flow rate, the channel width and the channel height.
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Screw Channel Shear Rate
Calculate the average shear rate in an extrusion screw channel, γ̇ = (π·D·N) ÷ H, from the barrel diameter D (m), screw speed N (rev/s) and channel depth H (m). Shear rate is the velocity gradient the molten polymer experiences between the moving screw surface and the fixed barrel, and it is central to plastics processing for a key reason: molten polymers are NON-Newtonian pseudoplastic fluids whose viscosity DECREASES as shear rate rises (shear thinning). Knowing the shear rate lets you estimate the material's real viscosity in the machine (via the power law) and thus pressure, power and viscous heating. Very high shear can degrade the polymer (chain scission by shear and heat); too low leaves melting incomplete. Each polymer has a suitable range. This screw-channel shear rate differs from the (much higher) die shear rate at the exit restriction. It is a basic processing-rheology calculation. Enter the diameter, speed and channel depth.
Plastic Injection Flow Rate
Compute the injection flow rate by dividing the injected volume by the fill time, in cm³/s. It is the speed at which the molten plastic enters the mold — a parameter that controls the shear rate, molecular orientation, surface finish and defects such as jetting or flow marks. High flow fills fast but may degrade; low flow may solidify before filling. Enter the injected volume and the fill time.
Injection Shot Volume
Compute the shot volume of a plastic part by dividing the injected mass by the molten material density. The shot is the total volume of plastic injected per cycle (parts + runners), a parameter that must fit the injection barrel capacity. Together with the machine capacity, it defines how many cavities can be filled per cycle. Enter the injected mass (g) and the material density (g/cm³).
Crop Growth Rate (CGR)
Computes the crop growth rate, CGR = (W₂ − W₁) ÷ (Δt × A), the canopy's dry-matter gain per unit of ground area per day between two destructive samplings. Unlike relative growth rate, which measures efficiency per gram of existing plant, CGR measures the productivity of the LAND — it is what you compare across row spacings, seeding densities and fertiliser levels, because it answers how much biomass each square metre of field produces per day. Peak values in well-managed C4 crops fall around 20 to 30 g/(m²·day), and the integral of the CGR curve over the season is total biological yield. Enter the initial and final dry masses, the interval between samplings and the ground area sampled.
Email Open Rate Calculator
Enter emails sent, bounces and unique opens to get the rate on delivered mail: opens ÷ (sent − bounces) × 100. Above 30% rates as excellent.
Falling-Rate Drying Period Time
Computes the duration of the falling-rate drying period under the model where the rate drops linearly with free moisture starting at the critical moisture: t = m_s × X_c ÷ (A × N_c) × ln(X_c ÷ X₂). Moisture contents go in as free moisture on a dry basis, that is, with the equilibrium moisture already subtracted, which is why X₂ can never be zero — drying down to equilibrium would take infinite time, exactly what the logarithm says. Compared with the constant-rate period this is the expensive stretch: every kilogram of water removed costs far more time than in the previous stretch, because internal transport now sets the pace. Enter the dry solid mass, the critical moisture, the final free moisture, the exposed area and the constant rate at the critical moisture.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.