Neuman Aluminium Impact Extrusion

A Subsection of Cold Forging

What is aluminium impact extrusion?

The words themselves give a good description of the process.  An aluminium disk or blank, which can be round, rectangular, or virtually any shape, is automatically fed into a die.  A punch, with several hundred tons of force behind it, impacts the disk.  The material is placed under high pressure and may only escape through a thin gap between the punch and die.  In a reverse extrusion, this forms a can or shell shape.  When you watch this happen, you get the impression that the material is not only deforming, but is also actually “flowing” into a new geometric state.  Because the slug is at room temperature, impact extrusion can be considered a cold forging process.

History of aluminium impact extrusion

Impact extrusion was originally developed for manufacturing collapsible aluminium tubes and many tubes are still made this way today.

However, impact extrusion has developed substantially from a technical perspective alongside traditional tube production. Considerably more complicated geometries can now be produced in medium and large sizes by using modern simulation software and significant expertise in material science and tool construction.

What is a typical impact extrusion component?

This isn’t an easy question to answer. We would often say: “It very much depends on the geometry of the part itself.” An extremely simplified description would be: “An impact extrusion component is a direct extruded part with a base or bottom. This base may be in any position across the length of the extruded part.”

To learn more, let’s look at the three main types of impact extrusion in more detail:

Reverse Impact Extrusion

The punch motion and the flow of material are in opposite directions. Once around the punch, the material moves in one direction with no friction.

Forward Impact Extrusion

The punch motion and the flow of material are in the same direction. Both hollow and full body parts can be created.

Combination Impact Extrusion

A combination of the two previously mentioned processes. The material flows both backwards and forwards. Both hollow and full body parts can be created.

One common feature of most impact extrusions is that the material flows in one direction. It is always a consideration as to how to get the extruded part out of the die. This point makes radial undercuts or radial fins impractical.

Impact extrusion products from Neuman

There are a multitude of impact extrusion parts available from Neuman. We have been technological pioneers in this forming process for decades and we are always looking for new applications.

Heat sinks
Heat sinks manufactured using the impact extrusion process have 30% greater heat conductivity, which allows the components to be produced so that they are both smaller and lighter.
The cooling fins can be different lengths and different shapes (e.g. circular or star shape). Complicated geometries can be formed on the back of the part for circuit board mounting, etc.
These parts are predominantly used in LED headlights in modern automobiles.

Advanced Driver Assistance Systems (ADAS) sensor housings
The number of sensors used for (semi-)autonomous driving is dramatically increasing.  More computing power is installed directly in the sensors and as the electronics get smaller and more concentrated, there is a growing need to dissipate more heat more quickly using a smaller package.  Impact extruded parts with complicated internal geometries (e.g. pins for mounting circuit boards) combined with a very thin-wall housing dissipate heat quickly due to the material properties.

E-motor housing
The demand for innovative component solutions for electric motors and drives is rising with the increase in electrification.

Structural components
Aluminium impact extrusion components really shine wherever the focus is on lightweight construction and high demands are placed on the material. These include yokes, outer guides of air springs and ball joints for wishbones.

Further applications (automotive, machine construction and consumer products) 

  • Airbag ignition housing
  • Microgas generators
  • Pump component
  • Belt tensioners
  • Pressure vessels
  • Drive components
  • Air-conditioning system parts
  • Battery housing
  • Hydraulic components
  • Cartridges (e. g. for two-component adhesives)
  • Pyrotechnic parts (e. g. tracer housing)
  • Kitchen control dials
  • Capacitor cans
  • Gas tank connections

Which raw materials are used in impact extrusion?

The slug is mainstay for raw material in global tube production, impact extruded aerosol cans, and technical impact extrusions. 90% of slugs are round or rectangular.  However, slugs of virtually any profile can also be produced.
The two main alloys used are the 1000 series (close to pure aluminium) and the 6000 series (AlMgSi1-alloys).
Other alloys can also be used with consultation.  We can also process copper and magnesium.
Ultrasonic testing of the raw material is available at the customer’s request.

What are the benefits of impact extrusion? How does it differ from other procedures?

Efficiency of the manufacturing process
Impact extrusion usually utilizes horizontal knuckle-joint presses. They are considerably faster and more precise than conventional hydraulic presses. This type of press is the most efficient manufacturing process for medium and large series components.  There is a high degree of deformation with good throughput.  Neuman Aluminium has the world’s largest horizontal knuckle-joint presses with a maximum pressing force of 2000 tonnes. For very small components, our presses reach cycle times of up to 300 strokes/min.

Thermal conduction
Impact extruded parts are very good at dissipating heat. The thermal conductivity is up to 30% higher than that of die casting (the silicon added in die casting that ensures the melt is continuously cooled down has a negative effect on thermal conduction). Therefore parts made with our process can be smaller and lighter for the same heat transfer.

Tightness / No blowholes
Impact extrusion components are free of porosity and impurities, so our parts can be used in safety applications and for vessels for storing pressurized media (gases, etc.). Our parts are always smooth, shiny, and free of pits and craters, while cast parts sometimes have these defects due the tool tearing grains from the surface.

Shape tolerance
Because the aluminium slug is at room temperature during impact extrusion, there is very little shrinkage after the deforming procedure.  Shape tolerances of the finished part correspond closely to those of the tool. This reduces the need for further processing steps.

Low tool costs
Impact extrusion has low tool costs in comparison to other methods of manufacturing. We are constantly working on making tools that are more robust. They are produced in our in-house toolmaking facility using state-of-the-art equipment.

Thin walls
Depending on the component size, very thin walls (down to 0.5 mm) with consistent mechanical properties can be impacted. This leaves more installation space for the inner workings of the housing. Combine that with the high thermal conductivity for dissipating heat and the multiple advantages are apparent.

Strength and ductility
Aluminium impact extrusion can be considered as cold forging. Significant plastic deformation at room temperature results in cold work hardening due to the movement and displacements in the grain structure. This results in an increase in strength (+15%) and a simultaneous decrease in ductility.

If higher demands are placed on the material, we can employ a customized heat treatment.

Comparison of impact extrusion with other procedures

Various aluminium production processes can be used for a certain component geometry. We only recommend impact extrusion to our customers if we believe it is the right fit for their intended use. Having said that, here is how impact extrusion stacks up against other methods:

Alternative to aluminium die casting
Aluminium die casting is in many cases a cost effective solution for many part applications. However, impact extrusion offers the following benefits compared to casting:

  • Very thin walls can be produced
  • Zero draft
  • Closer tolerances (no shrinkage after cooling)
  • Tool costs and tool follow-up costs are low (low temperature load)
  • No porosity or cavities (can be used as a safety component)
  • Shiny, smooth surface, free of pits and craters

Alternative to deep drawing
Impact extrusion is preferable to deep draw when

  • the component length is more than twice the diameter.
  • the base must be thicker than the side walls (i.e., a heavy, complex bottom),
  • the component geometry incorporates lugs, bosses, projections, recesses and raised areas.
  • the component requires several draws.

Impact extrusion is also superior to deep draw if there are medium-sized quantities, because deep draw tooling is very expensive and only pays off with very high quantities.

Alternative to CNC milling / turning
For smaller quantities, it often makes sense to mill/turn components out of solid material. But with larger quantities, creating impact extruded “near net shapes” (parts that are much closer to the final shape of the finished design) can dramatically reduce turning scrap and also significantly decrease machining times.

Alternative to hot forging
Impact extruded parts are usually lighter than their forged counterparts and have better surface properties for subsequent coating processes. Tolerances can be more reliably maintained, as there are always shrinkage effects involved in hot forging.

What about additional processing?

Impact extrusion is our area of expertise. Upon reviewing each new customer drawing, we always offer suggestions to make the geometry “impact friendly” and save material. We devise a master impact extrusion for each part that minimizes the secondary operations required.

Once optimized in the impact, we also have a great deal of experience in secondary processing to meet your needs:

  • CNC 3-axis to 5-axis
  • Turning/Milling
  • Automated roundtable machining
  • Punching
  • Thermal treatment
  • Blasting (deburring)
  • Cutting
  • Conventional part cleaning and fine cleaning (including clean room)

We also work with our experienced partners in the field of anodizing and coating.

Neuman Aluminium impact extrusion – part of the Neuman Aluminium Group

Neuman impact extrusion is part of the Neuman Aluminium Group with ten sites worldwide, 3.000 employees, and approximately € 570 million in annual revenue.

In addition to impact extrusion, our areas of expertise in aluminium also include billet and rod casting, direct extrusion, bending (PWG) and hot forging (Raufoss).

There is an age-old tradition of metal production at our sites in Marktl (nestled in the Lower Austria Traisental, Austria’s aluminium valley) and Raufoss, Norway.

All of our factories are united by the advancement of the versatile material aluminium with its numerous technical applications. One of our main aims is to continue to stretch the limits of our prowess in aluminium.

While doing so, we strive to constantly reduce our CO2 footprint. Although the production of primary aluminium is associated with the use of a high level of electrical energy, a good portion of our raw material is secondary recycled aluminium.  A much greater amount of aluminium is recycled worldwide than steel.

We are active in the development of new, innovative alloys and heat treatments. We cooperate with universities throughout Europe, North America and China and regularly receive research awards for these partnerships.

Light material - hard facts

Because aluminum is not always actually aluminum, you can find all the technical details, multiple certifications, quality seals and other interesting facts to read and download here.

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Your Partner for impact extrusion in your area

With our production facilities in Austria (Marktl), Slovakia (Zarnovica), Germany (Rottenburg), USA (Waynesboro, VA) and China (Xinhui) and our high level of on-site availability, a Neuman partner is always close by.

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