How It’s Made: Smooth Wall Straws
***All extrusion equipment utilized by SELA is of the highest quality available to make the very best straws available.***
Smooth wall straws are made in a continuous extrusion process where pellets of selected plastic material are fed into a plastic extruder, which heats the plastic (for this product to approximately 380 -460°F, depending on material type), it then compresses the molten plastic under high pressure to remove any air, and mixes any colorant into a homogeneous molten material and extrudes (pushes) this material through the appropriate sized pin and bushing (depending on I.D. and O.D. desired) into a vacuum tank for outer diameter final sizing. Wall thickness is a percentage of extruder screw speed to puller speed. An encoder on the puller monitors actual speed to allow for very accurate wall thickness during the product run. All SELA extruders are made in America.
SELA uses color feeders which are linked to the extruder drive with digital settings to precisely feed the correct amount of color pellets directly into the extruder instead of making batches and feeding the mixed batch into the extruder. This provides for very precise color control, color consistency during the run, and the ability to repeat the same color tint time after time. All SELA color feeders are made in North America.
The vacuum tank, Made in America, is flooded with chilled water and has a bolt in calibrator at the front which finalizes part O.D., with a series of 3 vacuum chambers separated by sized rubber orifices to allow a vacuum to be drawn in the calibrator chamber for outer diameter sizing along with vacuum drawn down stream in the subsequent chambers to maintain the roundness of the part during cooling. This tank is 15’ long and made of stainless steel.
If a product is hard to cool, SELA has a 21’ SS cooling tank to further cool the extruded item before cutter operation. SELA’s water tank was made in America.
SELA water cooled chillers are made in Italy and cools the vacuum tank, and water tank if needed, to bring the temperature of the plastic down from 380 – 460°F to approximately 70 – 85°F depending on material type while the straw is being sized, formed and cooled in the processes above. All SELA chillers’ are made in Italy.
SELA chillers are connected to an Italian made recirculating water tower which does NOT use evaporative cooling, which saves many thousands of gallons of water per month and eliminates the use of rust and microbial inhibiting chemicals from being discharged into the atmosphere as conventional evaporative water towers do. This water tower also utilizes inverter technology in the cooling fans to further save on electrical consumption. SELA’s water tower was made in Italy.
This water tower technology is the center piece of our green efforts as it saves electricity, water, and does not discharge chemicals into the atmosphere. Why do more companies not use this technology? Because it is much more expensive than conventional systems.
The puller literally pulls the continuous tube of sized plastic into the cutter. All SELA pullers are made in America
SELA uses two different cutters in the smooth wall line. One cutter is for diameters up to .380″ and the other is for diameters from .420 – 1.125”. All SELA cutters are made in America.