Increased surface wear (of screws, barrels, etc.) is caused by a continuously increasing percentage of fillers in plastics (e.g. glass, mineral fillers, flame retardants, etc.) which are included in 20 % up to 60 % of total volume of plastics.
Armouring surfaces with hard metal materials shows several times higher mechanical and chemical resistance to wear in comparison with nitrided parts (according to the type of hard metal overlay and the kind of material to be processed). Armoured areas acquire increased resistance to excessive wear, high temperatures and pressures as well as to all non-plastic materials.
Armoured overlay of hard metal material of thickness up to 2,5 mm (according to the type of armoured layer) shows in its whole thickness a uniform indicating high hardness and resistance to wear compared to the nitrided layer (thickness of approx. 0,3 to 0,5 mm) showing higher hardness only on the surface compared to the remaining cross section of the layer. With increasing nitration depth the hardness of the nitrided layer decreases. Service life of armoured parts is min. three times longer in comparison with the nitrided parts of higher qualities.
One of the options for renovation of the worn-out nitrided set consisting of the screw and barrel is grinding through and honing the inner diameter to the net diameter (to the largest possible worn-out diameter) with consecutive new nitration and welding on the appropriate screw by means of the hard metal material on the dimension in accordance with the renovated barrel.
Welding technology allows to carry on further repeated consecutive repairs (number of revisions depends on the way of wear, basic material, chosen type of hard metal overlay, etc.).
Welding screws is performed not only on the upper part of the screw thread but also on the side part and on the screw body.
We constructionally design new shapes of screws and barrels. These constructinal designs can increase output even of older extruders by 10 % up to 30 % of melt (kg/hour) and improve its mixing.
As our free of charge service we check measures of parts (e.g. outer screw diameters, inner barrel diameters by means of specially prolonged subites with an accuracy of hundredths of a milimeter etc.) in your firm and provide suggestions for several consecutive repair options.
Our company has been involved in welding technology with consecutive grinding of inner barrel diameters, as one of a few such companies in Europe