In the world of machining, additive manufacturing (popular with hobbyists owing to the advent of 3D printing) has long been shunned due to its relative lack of precision. Though additive manufacturing—which relies on building material up in very fine layers to create a shape—is perfectly adequate for ‘makers’ who have the time to individually finish each piece they produce, the world of commercial machining demands far more efficiency.
Mitsui Seiki, a machine tool builder that builds custom tools for CNC machine shop use, aims to change all this, however. Though the decision came as a shock to many given the firm’s reputation for creating highly accurate machines, Mitsui Seiki is now offering machines which have additive manufacturing as a capability.
Rob Hudson, the technology and business development manager for the firm, believes in a future of compromise for the CNC machining industry: Though nothing is likely to replace conventional CNC machining, putting additive manufacturing on the CNC machine shop floor will give designers much more freedom, says Hudson. He believes that coupling the precision offered by subtractive machining with the creative options inherent in additive manufacturing will strike the perfect balance for CNC machine shop workers; in addition to adding more diversity to part designs, additive manufacturing capabilities will consolidate parts processing. Parts will no longer need to be handled as much, reducing the chance of human error during manufacturing (as parts will be processed within a single machine).
To achieve this lofty goal, over the last year Mitsui Seiki’s engineers have been working on creating a single machine tool which can perform both metal cutting and deposition—without sacrificing an iota of the precision the firm is famous for. The company has thus far been successful, paving the way for a new era of hybrid CNC machining. The new hybrid tool they have created performs additive metal manufacturing through a technique known as ‘laser cladding,’ wherein metal powder is melted by a high-powered laser so that it can be deposited in successive layers. Once metal has been added in this way, it can be refined through standard machining processes.
This is not to suggest, of course, that engineering a hybrid CNC machine was easy; as Mr. Hudson himself explains, coolant and lasers are poor bedfellows, causing the company to have to innovate a great deal. According to Modern Machine Shop magazine, Mitsui Seiki had to invent a process for using flood coolant ‘extensively within a cycle that also includes additive layering. In this process,’ explains MMS author Peter Zelinski, ‘An air blow-off operation removes much of the volume of coolant still clinging to the part, followed by the laser applied at a wide focus to evaporate the rest. The surface, dried in this way, is ready for a new feature to be grown onto it through laser cladding.’
Additionally, Mitsui Seiki had to incorporate additional measures to protect their hybrid machines from the threat posed by escaping metal powder, which could easily damage the sensitive mechanical systems within the machine. Fortunately, the company’s experience with graphite milling machines helped them to come up with a sufficient guarding system.
Over time, Mr. Hudson hopes that hybrid machines will become the norm, gradually leading to greater efficiency and less waste. A great deal of interest in hybrid machining has already been expressed, particularly from within the aerospace industry, so while this technology is still in its infancy, Mitsui Seiki’s hopes remain high.
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