Personal 3D printers are definitely here, but for some parts, 3D printed ABS or PLA is not always a viable solution. Many makers need to make parts made out of phenolic, Delrin, wood or aluminum, and need tolerances or finishes not obtainable with most 3D printers. Years ago, before makers were called makers, personal 3D fabrication belonged to a class of desktop CNC milling machines like those from Sherline and MaxNC. Makers are now again looking at personal CNC milling machines. In fact, the inexpensive, lightweight construction of the Makerbot has inspired, to a large degree, the new class of desktop CNC routers like ones from ShapeOko and Zen Toolworks. These machines are great for working on mostly flat workpieces, but they lack the versatility of the venerable Sherline desktop mill.
The Lobo CNC milling machine is an open-source project I launched to bridge these two worlds. Rather than the typical flat-bed CNC router design, which has limited Z-axis motion and has limited stiffness for cutting harder materials, the Lobo mill uses a traditional bed-type mill configuration which has a larger Z-axis range and greater stiffness. While the old-school CNC mills cost a few thousand dollars, the Lobo mill uses laser-cut and folded steel to create low-cost, but very accurate, X, Y and Z axes. It also uses a high-speed router suitable for doing detail work in woods and plastics.
Almost all low-cost CNC machines use “open-loop” stepper control, where you hope the motor actually goes where you told it to go. For the Lobo mill, I designed a closed-loop servo controller that works with stepper motors with encoder feedback. The encoders on the motors let the controller know exactly where the motor is at all times, and the controller can take corrective action if the motor gets out of position. You can also turn off the motor drivers altogether and position the mill by hand – the controller will still continuously display your exact position. Closed-loop servo control is whatʼs found on almost all industrial CNC machines. A Lobo mill with servo control can be built for less than $900. If you opt for traditional stepper control, it can be built for less than $750. (The prefabricated folded metal parts, the assembled motor controller board and pre-wired motors can all be purchased, or they can fabricated from plans.)
I started using my prototype Lobo mill for making aluminum acoustic guitars – bridges carved out of wood, saddles carved out of bone, and sound holes cut out of aluminum. It also gets used for a ton of other stuff: FRC robot parts, electronics enclosures, modifying existing parts, and also for making the occasional objet d’art. In the space of low-cost 3D fabricators, itʼs a new class of machine that in turn lets makers create new classes of things.
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