If 3D Printing Is Additive, Then Is Reverse 3D Printing... Machining?

Posted by: 20. September 2014


3D Printing, an all-the-rage additive technology, was prominently displayed at IMTS. I saw a full scale printed car, a seven foot rocket, and dozens of more practical part samples that are routinely finding their way into the part manufacturing mainstream. Additive applications tend toward smaller parts and excel where complex part geometries confound conventional subtractive machining.

New technologies never end with one new product or process change.  Innovations as radical as 3D printing are disruptive (perceived in both negative and positive ways, depending on how you currently make a living) and always spawn other new products and processes.  In the short lifetime since the introduction of 3D printing, dozens of machine builders have sprung up.  Unlike machining and turning centers that cut away material to finish parts in essentially the same way, there are many different types of 3D printing processes that add material to create parts. In short, additive technology has opened the flood gates to product and process disruption that is just getting started.  An inflection point is nigh, or maybe we’ve already turned the corner on parts being converted from subtractive to additive processing. Only time will tell.

But new product and process capabilities related to 3D printing or more broadly, additive manufacturing, are now being offered even by long-established traditional machining center manufacturers such as Mitsubishi, DMG MORI SEIKI, and Kitamura.

DMG MORI offers the Lasertec 65 3D, laser deposition welding and integrated milling machine. This machine combines 5-axis milling and welding via laser deposition at speeds, that the the company claims are up to 10 times faster when compared to the powder bed method. Workpiece envelope on the model is up to 19.7” diameter. This hybrid style machine enables areas of parts to be machined that would otherwise be impossible to access. In other words, machining occurs first, then material is added on, through the laser welding process, in areas where the machining had already been performed.

The Matsuura Machinery Lumex Avance-25 metal laser sintering and high-speed milling machine is said to be the world’s only one-machine, one-process system capable of manufacturing complex molds and other parts by merging metal laser sintering (3D SLS) technology with high-speed milling technology. Using powdered metal to add on material and the high speed milling spindle to cut metal away, this machine can now produce very complex, highly accurate parts in one operation that were either impossible or very difficult to make before now. MC Machinery is the exclusive sales and service agent for the machine in North America.

Kitamura’s XrossCut, (pronounced “Cross-Cut”) high-speed, bi-lateral vertical machining center doesn’t actually perform 3D printing like the other two models.  In fact, Kitamura uses the term “reverse 3D printing” to describe the process.  So, if 3D printing builds up material, then reverse 3D printing should imply subtractive machining, just like the process performed by a conventional machining center, right?  Right. This machine’s capability’s does not include 3D printing. But the process that Kitamura has integrated into a standard machining center has been inspired by the emergence of 3D printing and the many opportunities that have sprung up along side the process. In this case, Kitamura has developed a directly integrated software program that interfaces between a scanner and the machine control. Users can first scan a 3D model or even a 2D image with the scan device connected to the machine. The software converts the scanned points (which can be set by the operator for higher or lower resolution) to a program the machine can run. Then the machine cuts the 3D object or 2D image from solid material. Typical applications include mold creation or even repair without having to program complex shapes.  A particularly impressive capability on this machine is the extremely high cutting feed rate (over 4,000ipm). This rate can be doubled due to the design that uses two parallel X axes (bi-lateral), one moving the spindle and one moving the table. While feeding one of these components in the plus direction and simultaneously feeding the other in the negative direction, cutting rates are doubled to over 9,000ipm.  And for light cutting in aluminum or plastic or other soft materials, very rapid cutting rates can dramatically reduce machining time. 

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