Rebuilt Extruder Screw


Last Updated on Wednesday, 13 April 2011 09:41 Written by Administrator Friday, 15 January 2010 11:20

Thanks to Mr. Samy Bahgat of Trust Engineering Co, our authorized Magna distributor in Egypt and our Senior Marketing Consultant, Mr. Mahmoud Labib, we are delighted to release this success story about the excellent performance of Magna 480 (3.17mm diameter) on rebuilding a worn extruder screw of a blown film extrusion machine at Abu El Naga & Co. in Egypt.


Plastic resins are fed to and melt in an extruder. Molten plastic material that comes out of the extruder then enters a tubular die. Air is blown into the die which expands and stretches the material like blowing a balloon. This blown-up material is called a film tube. The air flow pushes the tube upwards as it expands and cools. From there, it enters a sizing basket made up of small rollers to regulate the size and shape of the tube. The tube is then forced to form a flat sheet by the collapsing guides. The nip rolls presses the sheet and acts to pull the tube upwards in the entire process. The folded tube then travels down a series of rollers before it is being wind-up into rolls. The extruder screw (circled in red in the diagram above) is an important component in the extruder. The screw (with thread that is used for conveying plastic material within the extrusion barrel) is exposed to abrasion, chemicals, and high temperatures & pressure. In this success case, the screw needed to be re-built was extremely damaged on the surface due to this kind of harsh operating condition.


The Success Case

Initially, the end-user, Abu El Naga & Co., failed to rebuild the worn extruder screw - Length: 176cm / Diameter: 55mm (as shown on the right) with a 7018 type of electrode. They thought of replacing the screw, but it would cost them USD5,000. Instead, they asked Trust Engineering, with reputation of providing effective and efficient solutions to the Egyptian plastic industry, to rebuild the worn screw. After inspection of the worn screw, Mr. Samy Bahgat of Trust Engineering recommended Magna 480A to rebuild the screw. By skip welding at minimum 80 amps setting and peening in between passes while deposit was still red, the welder successfully rebuilt the screw. This successful repair job consumed only about 3 Kgs of Magna 480 costing several hundreds US dollars to the end-user. However, it saved the end-users few thousand US dollars and potentially a few days of downtime. In addition, by introducing this successful case of applying Magna 480 to rebuild extruder screw, Trust Engineering managed to capture a few more orders of quality Magna 480 in 2010.