Turning is a broad machining process. It encompasses workpieces with diameters measured in feet and diameters of a fraction-of-an-inch. It’s a function of scale. On the fractions of an inch side of turning is a moving headstock automatic micro-screw machine from Freer Engineering (Simi Valley, California).

Billed as a JIT (just-in-time) machine, this little lathe is profitable producing quantities of a few or even one. The key to its application in short-run work is a low base price (under $70,000 tooled) and simple programming method.

Since the machine makes really small workpieces, an integral TV camera and monitor allow the operator to observe the metalcutting action. The camera and monitor also help the operator set tools and program the machine. A cross hair on the monitor screen registers the centerline for tool alignment. A joystick controls positioning of the head-stock and tooling axes. An operator can “teach” the control a program while walking the machine through the moves needed to make a part.

The Freer machine has a maximum 5/16-inch diameter through the spindle capacity. It cuts virtually any material including stainless and titanium. A moving headstock design, the spindle has three inches of travel. In operation, the spindle axis intersects a tool bar located perpendicular to the spindle traverse. From a plan view, the tool bar moves north and south while the headstock moves east and west. The tool bar is servo controlled and carries up to 18 tools. Powered attachments for milling can be used on the tool bar.

So far this machine has been successfully applied primarily in the medical arts industry. It’s used to make bone screws and biopsy cups. In one application an impeller for a dentists’ drill (450,00 rpm) was machined complete in one chucking on this machine. The operation was previously a multi-step machining process.

The machine, designated AM 2000, may be small but it is built to standards used on larger machine tools. For example, the spindle is heat treated, ground and lapped to provide an accurate mating surface for the Class 7, preloaded bearings used to support it. The head-stock is a stess-relieved, Meehanite casting. Both the tool and spindle axes travel on recirculating roller bearings over linear guideways. Ballscrews are preloaded and driven by stepper motors with ten-to-one micro-stepping.

Speed of changeover between jobs is vital to machining small quantities of workpieces profitably. This machine, says the manufacturer, can be retooled from one job to the next in a matter of minutes. Because of the relatively large carrying capacity of the tool bar, often more than one job can be tooled at a time. The MS-DOS based computer can accommodate numerous programs in its memory. Under ideal conditions, job changeover can be as simple as changing the material, selecting the program and hitting cycle start.

Freer offers the AM 2000 standard with at least two live tooling stations for sawing, cross-drilling or milling, and eight toolholders on the machine. Also included is programming and tooling for two to four workpieces. This parts runoff constitutes the buyoff criteria for the machine.

Micro-machining is growing in part because off increasing improvements in scaling down machine tools. Automating what was essentially a jewelers craft has opened many opportunities to contract manufacturers. In the area of medical arts, the application of advanced manufacturing technology, in the form of CNC machine tools and other automation, is making a reality of workpiece designs that could only be imagined a few years ago.