For the manufacturing of various aerospace and defense industry components, flowforming and hot-spinning techniques are unsurpassed production methods. In light of the Repkon innovative

Date: Issue 33 - February 2012

Flowforming method is used to manufacture parts in the form of pipe with rotary symmetry and complex geometry. During flowforming process; length of the pre-form material is extended by reduction in the wall thickness. Advanced CNC control of the machine makes it possible to have thickness variation at different part sections during the forming process.

Hollow cylindrical pre-form material is rotated by fastening on a mandrel. During rotation, forming rollers apply radial and axial force on the outer surface of the pre-form creating pressure to form the material between the mandrel in the inner surface and the rollers on the outer surface.

During the process material undergoes a cold hardening effect, due to which microstructure of the end product is very similar to ones in forged products. Furthermore use of flowforming technology makes it possible to achieve excellent geometrical tolerances even on very thin-walled parts. Thanks to geometrical advantages provided by the flowforming technology, it may be possible to obtain a near net shape of the product without further machining.

This decades-old wondrous technology has been raised to a whole new level by REPKON?s patented (Registration No: 2 127 775) innovation ?free flowforming.? ?Free? flowforming minimizes the relative motion between the material and the mandrel, which is inherent in the classical flowforming techniques; thus eliminating the unwanted frictional disadvantages of the conventional methodology. In comparison, ?free? flowforming technology provides significant increase in the forming speed while enabling the production of parts with enhanced precision sensitivity.

In addition, development of this new technology prompted elimination of numerous geometrical limitations on the parts that can be manufactured. In other words, some of the part forms which are not possible to manufacture with current technologies are now plausible for manufacture with the cutting-edge ?free? flowforming technology.

Due to its unique advantages, flowforming technology is being used in defense, aerospace and nuclear industries for many years. With the development of REPKON?s new technology now it is possible to produce parts with much complex profiles with robust structure. This technology allows for manufacture of parts which have never been possible to produce using the flowforming technology before. Furthermore using this technology we can now produce parts at much higher speeds and with much precise tolerances.

Although this development is important for wide-ranging industries, it provides a distinct benchmark for aerospace, defence and nuclear manufacturing, where the precision of parts are amplified and manufacturability of new geometries are now made possible. This technology can trigger development of new generation weapon systems where lighter shells and much better weight distribution can be achieved. This would result in longer ranged, more robust and much more accurate weaponry systems. The recurrence of geometrical tolerances and weight distribution enhancements would result in repetition of excellent expected final results.

Hot spinning

Using hot spinning technology it is possible to manufacture many of the extreme forms of missile warheads.

The section of the part to be formed is heated to desired temperature using an induction coil, and then this part is rotated by means of fixing the part to the main spindle. Rotational and axial motions of the forming rollers deform the part in to the desired shape in several steps.

There are numerous advantages of manufacturing ammunitions and missile warheads by using the hot spinning technology.

In order for ammunition to have superior hit rates, all comprising parts should have excellent geometrical tolerances. Especially weight balance of the ammunition is crucially important. In order to obtain this, wall thickness distribution of the part must be homogenous. Ammunition consisting of wall thickness variation on the rotational cross-section will cause disturbance to the balance of the part, resulting in its deviation from the target.

Hot spinning process entails forming while the part is in rotation, consistently generating a very homogeneous wall thickness distribution. Consequently, mass centre of gravity can be reached within the targeted area with significant repeatability. Parts manufactured using this process do not require any additional turning operations in their inner sections.

Another important criterion that contributes to the success of ordnance is the correct manufacturing of the internal volume of the part vis-à-vis the design specifications. Internal volume of the parts produced by using hot spinning technique has the desired values with a very high rate of repeatability.

The combined use of flowforming and hot spinning technologies in ammunition manufacturing brings radical improvements to the product?s grain structure. This improvement in grain structure provides the possibility of designing and manufacturing lighter weight and durable ammunition bodies.

In comparison with conventional methods, another advantage gained by the combined use of flowforming and hot spinning technologies to replace the conventional techniques is the significant material savings. For example, if a product to be manufactured by conventional press + ironing + machining method, to start with, we would require about 80 kg of raw material. However with the introduction of flowforming and hot spinning processes for the same product initial requirement would be as low as 52 kg.