Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Patent
1997-11-17
2000-02-22
Larson, Lowell A.
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
72108, B21H 502
Patent
active
06026666&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for manufacturing parts with internal teeth.
DE-A1-24 20 014 describes a cylindrical flow turning method according to the species in which a tubular workpiece is subjected to a rotating extrusion process. Plastic deformation and/or a pointwise softening of the material takes place. This method is basically different from rolling, hammering, or deep drawing, since in this case only work hardening of the material takes place.
In the flow turning method described, the workpiece is located on a rotatably driven pressure mandrel, with one or more pressure rolls abutting the workpiece during a lengthwise movement. Flow shaping of the metal takes place between the pressure mandrel and/or a shaping tool and the pressure roll and/or pressure rolls, with the wall thickness of the workpiece being reduced and its length being increased.
SUMMARY OF THE INVENTION
The goal of the invention is to improve a flow turning method sufficiently to guarantee mass production.
This goal is achieved by making the distance of the shaping tool from the point at which the pressure mandrel is mounted in the machine so great that the shaping tool can undergo a certain degree of deflection relative to the machine axis.
This guarantees that the shaping tool can center itself by deflection of the mandrel under the pressure of the pressure roll as it engages the circumference uniformly. The automatic centering of the mandrel (and hence of the shaping tool) results in reliable manufacture without constant tool breakage caused by stresses imposed by the outer-roller pressure.
The shaping tool according to the invention consists of materials containing chromium and molybdenum (for example according to DIN 1.2343, 1.2344, and 1.2606) and is quenched and tempered as well as surface-hardened. Preferably, it is then polished. As a result of these measures, the shaping tool is extremely durable and suitable for continuous use.
The distance of the shaping tool from the mounting location of the mandrel is preferably 200 mm or more, preferably 500 mm. This dimension of course depends on the stability and size of the machine. In any event, assurance must be provided that the shaping tool can undergo a certain degree of deflection.
The pressure rolls are preferably made of HSS steel or hard metal. In addition, the run-in angle of the pressure roll or pressure rolls in a preferred embodiment is between 5 and 45.degree., the run-out angle is between 0 and 20.degree., and the outer roll radius is between 0.5 and 25 mm.
Another feature according to the invention provides that the workpiece is pushed onto the shaping tool as a pre-turned or pre-forged pot-shaped blank. As a result, the workpiece is firmly anchored to the shaping tool.
In order for the pressure rolls to engage the workpiece better, a constriction is advantageously provided on the outer face of the workpiece, the depth of said constriction being 0.2-0.6.times.S where S is the thickness of the wall of the workpiece. Advantageously, the constriction blends with the outer circumferential surface of the workpiece at a maximum angle .delta. of 45.degree..
In one preferred version, flow turning can also be performed by the opposed turning method. A tailstock guided in the machine is placed so that it adjoins the shaping tool, so that the mandrel, shaping tool, and tailstock form a unit. The workpiece is then clamped as a pot-shaped blank between the shaping tool and the mandrel.
In another preferred embodiment, to produce parts with double-sided internal teeth, a combination of the synchronous turning method and the opposed turning method is employed, with a double-sided pot-shaped blank being located between the two shaping tools as a workpiece, a pressure roll adjacent to the tailstock in the opposed turning method is advanced from the end of the blank toward the center and a pressure roll adjacent to the mandrel is advanced from the middle of the blank in the direction of the mandrel in the synchronous turning method.
Advantageousl
REFERENCES:
patent: 1665286 (1928-04-01), Stroh et al.
patent: 2220757 (1940-11-01), Engle et al.
patent: 3535910 (1970-10-01), Connolly
Stein Bernd
Zimmermann Jurgen
Zimmermann Willi
Dynamit Nobel Aktiengesellschaft
Larson Lowell A.
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