In the past articles, we discussed about mechanical and metallurgical concepts of rotary-swaging.
We also mentioned about peculiar features, possibilities of use, technical advantages in using this technology when producing parts, from the simplest-, to the most complex-ones.
Now we want to come back to those concepts by extending the argument.
We'd like to release some details to get "deeper" into rotary-swaging technique, so that to allow our readers to better evaluate some possible applications. A comparison will be made oftentimes towards most
commonly used machining methods (of chip removal).
With the purpose to make this article more comfortable and interesting (if possible), we have set it as F.A.Q. (Frequently Asked Questions), that we may have collected from engineers and production-managers involved - at the beginning of a project - in the design of a machine component.
Some other questions come from R.& D. departments when it takes to reduce the cost of a given part, maybe already manufactured in a
conventional way. In current days, we all know how it can be critical to keep our own company "on the front edge", both to match old- and new-competitors, and to offer our clients a more performing product, or - why not ? - even a less expensive solution.

May I save some money on the cost of raw materials ?
Precision rotary swaging is a working technology which preserves the initial volume of the blank.
Generally speaking, this feature is typical of (cold) metal forming, as the blank and the finished part have the very same weight. This means we may get from rotary-swaging a great saving of material in comparison with machining, and no need to remove metal chips, nor even generally associated lubrication / cooling products.
As a general rule, we may say the saving in weight of a typically swaged part - made from tube - compared with the same component - made from a solid bar - ranges from 30% to 50%.
Sometimes is also possible to choose a less sophisticated (thus less expensive) raw material, as parts take advantage from the natural
improvement of mechanical properties coming from rotary swaging (natural work-hardening).
Some parts - being symmetrical by rotation - can be conveniently manufactured out of tubes, while saving material and getting - at the same time - a better functionality. In facts, cold-forming brings to a favourable flow of metal fibres (all along the length of the blank),
providing - at the end - more rigidity, more strength, etc. This fact should be taken in consideration in the design of parts.

Which are the "ecological factors" to be considered?
In comparison with most chip-removal manufacturing methods (but also compared with some cold-forming systems), parts made through rotary-swaging do not need lubricant, and the coolant - whenever necessary - is filtered, conveyed, end continuously re-cycled, therefore minimizing the environment impact, and reducing the risks for operators' health.
In most cases, final washing of parts can be eliminated, too.
Disposal of metal chips is also a very limited and minimal problem. Most of times, chips come only from cut-to-length operation, and from eventual facing, or chamfering of blanks. These operations are anyway not
strictly connected to the cold swaging process itself.
Of course, we cannot make any comment about the electric consumption required by a swaging process vs. a metal machining, as too many factors may be involved in the comparison.
When talking about "environmental impact and operators' health", we must say the new generation of rotary-swaging machines have
dramatically reduced the amount of vibrations and noise-levels, thanks to most recent studies on the design of internal components.
Beside that, recent developments in the technique of noise-reducing
protections and sound-proof materials, have also brought most swaging machines to be introduced into a low-noise emissions rooms. This
concept is valid both for stand-alone equipment, and for more complex transfer-lines.

What kind of operational flexibility is offered by rotary-swaging?
Operational possibilities offered by precision-swaging allow the designer to get a wide flexibility in the selection of shapes, sizes and materials, that is generally higher than other metal-forming techniques. Flexibility applies both to external- and to internal-profiles.
Through precision-swaging is possible to get quite complex hollow-parts (with precision degree of a finished component), sturdy connections between components without welding, etc.
A natural advantage of rotary-swaging is to lay metal-fibres into a favourable flow, thus improving the resistance of the piece to withstand both static-, and dynamic-loads.
At the end of the swaging process, blanks generally preserve enough elongation and ductility to allow for other cold-forming operations (such as thread-rolling, roll-grooving, etc.), without the need of intermediate annealing, yet with a very low roughness of the surfaces.
It's interesting to remark that, oftentimes, through the same rotary-swaging machine, many different parts can be produced by simply changing related dies. Finished swaged parts may vary because of their cross-section, profile, length, materials and final applications, even starting from the same raw material (outside diameter and wall thickness).

Can we avoid some heat-treatments (hardening) and grinding?
It's indeed the high quality of the surfaces to be checked and appreciated as further advantage of precision-swaging. This fact brings to another saving of costs in the production of a given piece, as - sometimes - our process can make the part suitable to support heavy-loads without having to introduce some expensive heat-treatments, and consequently with no need to make final grinding at the end. (Specific needs have to be considered time-by-time, anyway).
If we think deeper at this technique, we may find some further advantages in the reduction of manufacturing times, of logistic costs, and because we have less risks of defects on parts coming from heat-treatment
(problems of distortion, non-even hardness, etc.).
In fact - as we said - many of these operations can be made within the precision swaging routine, yet with a close control of the process.

Can we avoid a broaching-operation, or a welding-operation?
In some cases, rotary swaging is the only (rational) way to go for a certain piece, but - since it's not yet a well-known technology - designers may look at other manufacturing systems, or they may try to change even some of the coupled parts. Sometimes, project-engineers are forced to modify the dimensions of the single piece, or the lay-out of the complete assembly, by using conventional manufacturing systems, more material, etc., which may result - at the end - just more expensive.
Let's think - for a while - to an hollow shaft with some internal splines, or to a blind hole with a poly-angular cross-section inside. Or - for instance - to a complete closure of a tube at one end, to an internal restriction in the middle of a hollow-section, without having the possibility to weld anything, and without possibility to introduce another piece in the assembly.
All of these could be some typical cases to go for rotary swaging.
Through rotary-swaging technique is possible to get a very strong mechanic-connection between a metal bushing and a tube, or bar, without having to make a welding operation.
With the same idea is also possible, for instance, to mechanically lock a hollow-coupling, or spherical-joint at the end of a safety-cable, using the concept of metal-to-metal interference.

Is rotary swaging convenient also for quite complex parts, having different operations?
When we talk about mass productions, automatic rotary swaging transfer lines are generally more convenient than most conventional
machining systems. In fact, even for shafts needing, for instance, of facing-, thread rolling-, grooving-, chamfering-, beading-, or bending-operations, is generally possible to link all related working units, one after the other, inside the linear transfer in order to get - at the end - the finished parts required.
Lay-out of transfer-lines where rotary-swaging is the main application is generally more compact, more economic, and more versatile than a corresponding working-cell where conventional machines are put in a circle. In addition to that, automatic handling of parts made by pick-and-place devices is more rational, and it doesn't need robots, nor other very complex automation facilities. Specific output of a typical swaging line is also (on average) much higher than the output we can get from
conventional machining equipment.
Human labour is generally reduced to the minimum. It is generally required just to feed / un-feed the materials from the transfer line, or to check their quality, when these operations aren't fully automatic as well. By
following this automation concept, scrap parts related to human errors are practically close to zero, because the whole manufacturing routine is controlled within the process.

What is the "time-to-market" we may expect for a new rotary- swaged part ?
Back to the previous question, if our new component requires simple operations such as cutting, chamfering, swaging (and eventually a new facing of formed-ends), we can say that just a few weeks are enough to design and the produce the tooling. After that, prototyping is possible, where "prototyping", in rotary-swaging, means sometimes a few
hundreds, or a few thousands of parts.
Delay depends - of course - from how complex is the shape to be produced, from current working programs, and it starts always from the technical definition of the project.
This time could be a lot different if a component is very complex, and if it needs several machines, or working units with special tools; maybe it requires first the construction of a dedicated transfer- line, when production volumes are important. In this last case, from the technical definition of the project, one can wait even 10 or 12 months in order to get the equipment fully engineered, assembled and tested, prior to be able to start the production at required rate. However, a.m. procedure should not be considered as a problem, if
required volumes are expected to grow step-by-step, and commitments are taken with necessary time in advance.

Where's the border-line from purchasing a swaging equipment, and sub-contracting parts?
What's the minimum number of parts where one should consider rotary-swaging ?
It depends from many factors, please talk to a specialist. You should refer to a company, or to a group, being able to make prototyping of your components first, by manufacturing a temporary tool to be tested on your genuine materials, using already existing machines. An ideal scenario would be when the same supplier can offer even consistent and regular deliveries of semi-worked parts, even in considerably high volumes, when necessary, as a precise and qualified sub-contractor.
Even better would be if selected partners have on their shoulders, or
co-operate in a synergic way with a company who can supply the very same production equipment on demand. In this case, the end-user may be able - after a while - to produce the components inside its own company, due to strategic reasons, to preserve its own know-how, for logistic problems, production volumes, or again for different reasons.
Minimum number of parts where one can use rotary-swaging also depends from different factors, among which: the shape to be produced; how complex is the part; what kind of conventional-machines (as alternative solution), or which kind of swaging-machines are necessary; price / performance targets; and from other factors already discussed above.
Once again: please consult a specialist.
Lifetime of tools used in rotary-swaging is very high (degree of wearing depends on how critical are the operations, and on tolerances required). It is so high that sometimes costs of re-machining, or re-make of tools are not even considered in the cost of the process, if volumes are also important.
Thanks to the special tool-steels (or carbide-metals) recently developed and used with the experience of the specialists, sometimes the first set of tools may last for the whole life of the industrial component to be manufactured.