Butt Shear Blade

The Damatool butt blade has a longer and a more precise cutting angle. In this way, a more even cutting process can be performed by applying lesser force. And the butt shear is designed according to the easier operating principle. It has a reliability of nearly 100%. The butt shear moves at 5/8 of the cutting path.

The cutting is performed clean and close since the butt shear is operated by hydraulic pressure. It uses a linear stress differential converter in order to perceive the movement. The butt shear equipped with a sensor will automatically stop the operation of the press in case of serious problems like die breakages etc.

The dual guides minimize the deviations at large shaft bearings. These can be adjusted to the front and back separately and thus there is no need to play with the adjustment of the blade.

The Damatool butt shear with a very durable structure designed for heavy work reduces “cutting squeezes” to a minimum.  The Damatool butt shear is designed very reliable and such to provide an easy maintenance.

The alloy gets conical during the pressing of the billet towards the container by the stem and the dummy block during the extrusion movement. The metal which flows to the backside of the container constitutes a dead metal zone like a funnel. Oxides and other contaminated materials coming from the surface of the billet are accumulated here. Therefore, the extrusion process should be stopped before the contaminated alloy mixes with the product. The part adhered to the back of the die stack is called “the butt”.

The container is opened in order to dispose the butt after the extrusion of each billet. The butt must be cut prior to closing the container again and loading the next billet.

A part of butt may continue to adhere to the back of the die stack when this process is not performed efficiently and properly. This will prevent the container from getting fully closed.

Nearly definitely serious problems will be caused when this situation should not be detected prior to the next extrusion movement.

The necessary butt thicknesses may show considerable variations. This depends primarily on the alloy to be subjected to extrusion, the state of the billet and the final usage of the extruded product. For example; products can be extruded with a butt of lesser than 5% of the billet length made of AA6060 which is used for non structural window frames to be painted and with a smooth surface at least acceptance formation. This can be 2 cm or lesser at many presses and discoloration of the product due to contamination is not faced with.

On the other hand, when an AA6061 billet is being extruded into forms with structural usages, 10-20% of the billet must be left at the butt in order to avoid that the exterior part penetrates inside the profile and not to cause any faulty look.

Lubrication is very important in order to easily separate the extruded part of the dummy block from the butt at the moment of pulling it from the die.

Frequently hydrocarbon lubricants are used in order to prevent an adhesion of the butt to the blade or the die stack. These can be efficient when they are used economically. Contrary to this, they will cause blisters when they are used excessively. In the same way, these lubricants will result in faulty profiles both in the transverse and the length when they meet the holes of the die.

At present, the best lubricant regarding the facilitation of butt shearing is boron nitride. Boron nitride is not only for its unmatched lubrication features, but also for its application easiness and costs the ideal lubricant. Environmental issues are eliminated and scrapping due to blisters is reduced by its utilization.

The butt shear must of course have the sufficient power in order to cut the thickest butt made of the hardest alloy. The shear blade has to move by maintaining a definite distance to the die stack since the shear moves directly towards the die stack. This distance is approximately 0.5 mm.

Due to the extruded range from light architecture AA6060 profiles to AA6061 rods with a large diameter at many presses, the shear blade must of course have the sufficient power in order to cut the largest sizes made of the hardest alloys. The optimal design of the shear blade varies according to the press size and the alloy-dimension combination.

The form of the cutting edge of the Damatool blades are designed and customized according to the individual needs of the extrusion facility. Damatool blades are tempered to a durability to resist against chippings and to provide an extra long life-time.

The importance of the optimal thickness of the butt, application of appropriate lubricants and cutting clean and efficient is taken for serious by many extruders. Though that, the costs can be very high when the necessary care is not shown. We as Damatool are 7/24 in your service at press stop causing butt shear failures.