Do you need a barrel for an extruder or injection moulding machine? Euro-Stel specializes in both bimetallic and nitrided barrels for all types of injection moulding machines and extruder.
The choice of a bimetallic or nitrided barrel depends, of course, on the application and the materials to be processed, but also on the metallurgy of the screw. The metallurgy of the screw and barrel must be matched so that both have an equally long lifespan.
Bimetallic barrels differ from each other due to the alloy used to manufacture their core diameter. For example, there are bimetallic barrels with resistance to abrasion and/or corrosion. To handle wear under the most extreme loads, we use bimetallic barrels made with tungsten carbide alloys. These resist extreme abrasion and are corrosion resistant too.
In addition to the classic one-piece barrels with a filler opening, Euro-Stel also supplies barrels with C-clamp joints and melt units equipped with a separate filling area with interchangeable bushes. These retractable bushes are supplied with grooves that differ in geometry according to the type of plastic to be processed. If the grooves are worn, you only need to replace the retractable bush.
All our barrels and filler zones can be supplied with water cooling (if necessary). Water cooling can also be fitted to flanges. We supply, according to you wishes and requirements, thermocouples, pressure transducers, resistors, heating cartridges and all kinds of other peripherals with our barrels.
Euro-Stel does not only repair and recondition screws – of course we handle barrels too. High pressures in injection moulding and extruding will not only cause wear on the screw; it affects the barrel too. Screw and barrel wear profiles are congruent, but the degree of wear varies. It is less in the barrel because it has a larger surface area compared to the screw. There are several methods of repairing and reconditioning barrels. The appropriate option depends on the actual wear and damage, and on the barrel metallurgy.
There are four possibilities for reconditioning barrels:
- Applying bushing in the metering zone.
- Full length bushing (only for barrels with a complicated or expensive contour)
- Barrel honing (making oversized)
- Partially renewing the barrel
Applying bushing in the metering zone
This method is only recommended when the wear in the remaining part of the barrel is not too severe. The bushing in the metering zone will again provide dimensional accuracy in the barrel emission and therefore also restore the closing ability of the non-return valve.
Full length bushing
Full length bushing is a solid and highly professional solution but it is also more expensive. This method is only interesting for barrels with complex outer contours.
When you compare the price of bushing to the alternative (i.e. buying a new bi-metal barrel), a first repair is uninteresting in the case of a normal barrel with a smooth outer side. Full-length bushing will not be economical until the second time the barrel is bushed. It is possible to use hardened tool steel, bi-metal or powder metallurgy for bushing.
Reconditioning by honing the barrel can be used in cases with larger dimensions. The advantage is obvious – honing costs considerably less than a new barrel. Unfortunately, there are also some disadvantages.
- Honing increases the diameter of the barrel, so the original non-return valve is no longer usable. This can be corrected by adding a new lock ring sized according to the new diameter of the barrel.
- If the barrel is very worn, there is a risk that the honing tool will not run fully axial and thus the bore will no longer be aligned (the honing tool always looks for the path of least resistance and can only be centred to a limited extent!). This is why honing barrels should only be used in cases of minor wear. Reference point: Max 1% of diameter
- Excessive barrel honing (more than 2% of the diameter) not only changes the barrel, but also the screw, and actually in its geometry. Changing the diameter changes the flank height.
We would like to point out that, during each repair, we carefully examine whether technical changes can be made that will extend the life of the barrel, and we offer a proposal if this is the case.
Partially renewing the barrel
This applies in cases where the barrel is not worn but damaged by conditions, e.g.cracking at the intake or ejection sides. We carefully carry out an examination, for each part separately, into how the barrel can be repaired.
A good thing to know: Each reconditioning task requires thorough analysis of the worn parts by an experienced Euro-Stel expert, so that we can propose the most appropriate method (economically and technically).