• Regen­er­a­tion of screws

We regenerate worn screws and cylinders

Screws or barrels that have reached their wear limit belong in the hands of WAFO. We have 25 years of experience in the regeneration of wearing parts.

We first remove the worn base material from the screws. Then we create new screw flights by build-up welding a special, highly wear-resistant armour alloy. For special cases, the base and flanks of the worm can also be hard-faced. Subsequent straightening, grinding and polishing gives the screw its final geometry. It is therefore better protected against wear than standard, new, nitrided screws.

Hardfacing is usually cheaper than a new screw. And - a decisive plus is the improved service life. 
If the screw and barrel are regenerated at the same time, cylinders made of nitriding steel can usually be honed and then intensively nitrided.

We take the increased cylinder diameter resulting from the honing process into account when regenerating the screw; the screw and cylinder fit together again afterwards.

We drill out the worn barrel to remove the bushing. Using a process developed by us, we insert a wear-resistant bushing that is fixed and torsion-proof. The cylinder is restored to its original diameter and you can use a screw with the original diameter as before.

The material available for the bushing is either chrome steel, particularly wear-resistant and corrosion-resistant powder metallurgical materials or bimetals.

Special hardfacing for rubber extruders

In a large number of cases, hard facing with conventional coating materials, such as stellite, has not proved successful.

During rubber processing, a very high surface pressure occurs between the screw flight and the barrel wall. This is caused by unequal force balances when the usually only slightly pre-tempered rubber strips are drawn in.

The resulting compressive stress, also known as sigma stress, far exceeds the limits of stellite.

Sometimes an armoured screw with stellite has only half the service life of a normal nitrided screw.
For this reason, we use a nitrided armour material.

This material already has a basic hardness of approx. 50 HRC after welding and is then nitrided.
The support effect resulting from the high base hardness in relation to the nitrided layer significantly improves the wear behaviour compared to normally nitrided screws.

Screw regen­er­a­tion in 4 weeks

Highest quality
  • Repro­du­cible armour­ing with PTA welding machines
  • Multi-layer system armour­ing
Lower prices
  • High level of auto­ma­tion in produc­tion
Short delivery times
  • Collec­tion and delivery by our own lorries
  • Decom­mis­sion­ing of your machine at the agreed time, there­fore no replace­ment set neces­sary
Optimum service
  • Free wear and material analyses
  • Compre­hens­ive customer support

WAFO's answer to screw wear

Since 1997, we have had a modern screw service centre at our disposal to enable us to regen­er­ate screws with increased value through wear-resist­ant web armour­ing in the shortest possible processing time.
We use a CNC-controlled plasma powder welding system (PTA) of the latest gener­a­tion for the welding process. The process enables high-quality and repro­du­cible web, flank and solid armour­ing.
The mech­an­ical processing to new worm condi­tion is carried out on machines, some of which we developed ourselves.

WAFO screws Armour­ing mater­i­als
Char­ac­ter­ist­icsMaterial type
 Stellit 6Stellit 12Stellit 1Colmonoy 56WP 88
Hardness of the armour HRC38-42 43-4948-5548-53 56-60
Wear resist­ance✪✪✪✪✪✪✪✪✪✪✪✪✪✪✪
Corro­sion resist­ance✪✪✪✪✪✪✪✪✪✪✪✪✪
Relative wear during assembly
ScrewStellit 6Stellit 12Stellit 1Colmonoy 56Colmonoy 56WP 88

Other armour mater­i­als and special surfaces on request!
Stel­lite® is a trade­mark of Deloro Stellite Holdings Corpor­a­tion.

The WAFO special armour

The bar armour­ing first used by WAFO as a pioneer 30 years ago has become estab­lished world­wide over the years.

The mater­i­als we use, Stellite, have proven them­selves in thou­sands of WAFO recon­di­tioned screws.

But nothing is so good that it cannot be improved. Our answer to this chal­lenge is WT 50, an armour material that produces even better results in special cases. WT 50 is an armour material specially adapted by WAFO. Special armour­ing
This material consists of a very hard and there­fore very wear-resist­ant inter­metal­lic compound, which is embedded in a soft nickel matrix. This alloy is char­ac­ter­ised by excel­lent sliding prop­er­ties and very good corro­sion and wear resist­ance over a wide temper­at­ure range.

The hardness is around 50 HRC. We also use our armour material WT 60 as a supple­ment to this.

This is a cobalt-based material with the same prop­er­ties as our WT 50, but with a hardness of approx. 58 HRC.

Thanks to a special plasma welding system, we are able to apply highly wear-resist­ant armour­ing with a Ni-Cr matrix and a high propor­tion of extremely hard tungsten carbides to screws.