Extrusion Output Rate, Line Speed, and Draw-Down

Cross-sectional area times line speed times melt density is the whole of it, and its value is that the two numbers are set by different people looking at different gauges. The exact annular area is used here rather than the thin-wall approximation, because on a heavy wall the approximation runs several percent high and that error lands directly on the output figure. THE DIAGNOSIS THIS SUPPORTS IS THAT COOLING USUALLY GOVERNS, NOT THE SCREW. An extruder rated well above what the bath can solidify does not produce more good product; it produces product that leaves the bath soft, ovalises under the puller, and drifts dimensionally. Adding extruder output to a cooling-limited line buys nothing at all, and the money goes to bath length, water temperature, or a vacuum tank rather than to a bigger machine. The operator's instinct when the product comes out soft -- slow the line and leave the screw alone -- makes it worse, because it puts more material in every foot and more heat in the bath. Draw-down is the reason line speed and output are not independently adjustable. The die is deliberately larger than the finished product, and the material is drawn between the die and the calibrator, which orients the polymer and changes properties as well as dimensions. Changing the speed without changing the output changes that ratio, so a line that is running well is running at a particular combination rather than at a particular speed. This is a mass balance on entered geometry and density. It does not size an extruder or a screw, model die swell (which is why the die is not simply cut to the product size), compute the cooling actually required or the bath length that provides it, address melt temperature, pressure, or the screw's plasticising capacity, or handle non-uniform wall or profile shapes -- the annulus here is a round pipe or tube. Melt density is entered because it differs from the solid density and varies with temperature. The extruder and die manufacturers' data, the material supplier's melt properties, and the line's own production records govern.

output = cross-sectional area x line speed x melt density, with the EXACT annular area pi/4 x (OD^2 - ID^2); line speed inverts it, and draw-down is die opening over product size.

The extrusion mass balance. The exact annulus is used rather than the thin-wall approximation pi x OD x wall, which runs several percent high on a heavy wall and puts that error directly onto the output figure. Melt density is ENTERED because it differs from solid density and varies with temperature.

One mass balance on entered geometry.

Estimate. AHJ and licensed professional govern.

Field names used by the API: product_od_in, wall_thickness_in, line_speed_ft_min, melt_density_lb_in3, extruder_output_lb_h, die_opening_in, cooling_capacity_lb_h, shift_hours, area_in2, lb_per_ft, output_at_speed_lb_h, speed_at_output_ft_min, draw_down_ratio, shift_pounds

• Exact annulus, round product only profiles and non-uniform walls are a different areathe product drawing
• Melt density is entered differs from solid density and varies with temperaturethe material supplier's melt data
• No die swell which is why the die is not cut to the product sizethe die manufacturer's data