Additive manufacturing in a cutting (edge) environment

The know-how from subtractive manufacturing as ideal entry into additive manufacturing!

Do you fabricate parts on machine tools? Then cutting metal on CNC machine tools is your core competence! This know-how represents a great launching pad for additive manufacturing. With additive manufacturing you can ideally prepare yourself to address new challenges in the domain involving parts and components that you have been fabricating up until now.

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Additive manufacturing – perspectives when it comes to conventional cutting

What are the fundamental perspectives relating to additive manufacturing in the machine tool landscape?

 

The trend to increasingly individualized products means that batch sizes are decreasing at a rapid rate. By using additive manufacturing, many parts can be fabricated faster and more efficiently, for instance, individual semi-finished products can be directly built-up in a machine.

 

This clearly addresses sustainability issues that are becoming increasingly more important. Many parts and components can be manufactured with less materials and in turn using lower amounts of energy.

 

Not only this, additive techniques allow parts to be fabricated that would not be possible with purely subtractive techniques. For instance, various materials can be combined in one part.

Applications

We will now take a look at the basic application areas of additive manufacturing in the context of metal cutting. Terms such as "rapid tooling" quickly come to mind. Here, structures are additively created, for example press molds from plastic, which previously required the fabrication of cast blanks – a time-consuming and expensive process.

 

Or also "rapid repair", which involves repairing metallic workpieces by specifically adding material to just damaged locations.

In both cases, the following applies: What is applied to material additively is generally post worked to remove material and finish the part in a conventional way. This closes the know-how loop around CNC and the machine tool – irrespective of whether the "additive" and "subtractive" process steps are distributed over two machines or whether a hybrid machine is purchased that combines both processes.

 

An additional application area involves material combinations, coatings and local alloying procedures: Additive manufacturing can be used to coat component surfaces and create material structures i.e. applying alloys, which are difficult to machine or cannot be machined at all.

 

This makes additive manufacturing an ideal incubation chamber for additional business opportunities that smartly complement classic machining.

Suitable additive manufacturing techniques

Which additive manufacturing techniques are predestined for conventional machining landscapes?

 

Directed energy deposition – also known as DED – is the first technique that should be mentioned. Laser metal deposition is probably the simplest and fastest way to explain just how DED works. When all is said and done, energy is introduced – mostly using a laser – to melt metal, provided in the form of powder or wire, which is then applied in tracks. This procedure allows metal structures to be completely rebuilt or they can be applied to existing parts and components.

 

An additional technique, predominantly used for "rapid tooling", is the "screw extrusion additive manufacturing", also known as SEAM. This involves a technique from the material extrusion group, where any component structure can be applied in tracks using an extruder and the associated plastic granulate. Functional surfaces must generally be subsequently post worked, for example using a conventional milling process. 

Post working frequently required

Whether directed energy deposition (DED) or screw extrusion additive manufacturing (SEAM): In both these cases, material is applied in tracks. Here again, we loop back around to CNC. CNCs are precisely built to move a tool or an AM unit as quickly as possible, with absolute constant path velocity and absolute precision in a machine. DED and SEAM techniques just wouldn't be able to be deployed in the first place without this intelligent motion control.

CNCs are completely at home in the kinematic transformation domain. The name of the game is to maintain the AM unit in an absolute perpendicular orientation to the workpiece surface, even if this is being traversed using multi-axis robot kinematics and additional round swiveling table.

 

Precisely when dynamic, high-precision path control is teamed up with complex machine kinematics, Sinumerik CNCs with their comprehensive selection of CNC system features are the first choice. In fact, they are frequently the only CNC in town that can do the job.

Onboard programming for prismatic applications – CAD/CAM link for complex parts and components 

But who tells the CNC how it has to move when it comes to additive manufacturing workflows? Fundamentally, there is no difference to programming CNCs in conventional machining environments.

 

If it involves pure prismatic parts structures, for example when repairing brake discs using direct energy deposition, CNC program code can be written by hand using the resources available at the CNC user interface. There is no way around a CAM system when it comes to complicated component shapes, for example, for rapid prototyping of tools for presses.

 

Many machining facilities already have CNC job planning departments that work with CAD/CAM systems, and many users already feel at home using CAM systems. The question still remains as to which CAM system also supports additive manufacturing. The focus then quickly switches to the NX system.

 

To complement many subtractive machine techniques, NX-CAM also comes with techniques required for additive manufacturing, for example "multi-axis deposition". NX offers machine simulation using a virtual Sinumerik CNC that precisely replicates the underlying process. Here again we make a full circle back to a real Sinumerik in the machine.

Production strategy that is fit for the future

Machine tool and additive manufacturing working as a team has the potential to be taken to a new level. 3D printing in a powder bed, i.e. an AM technique that doesn't necessarily require a CNC system can be ideally combined with classic post working using traditional subtractive machining on CNC machine tools. There are no limits to the possibilities.

 

You can find additional information on many specific examples from the additive manufacturing landscape in the area of machining with CNC machine tools under:

From the CNC4you magazine, edition 2022-2

Author: Andreas Groezinger

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