The term “screw machine” broadly refers to those machines that produce a high volume of turned parts via either CNC technology or cams. Screw machine products are found in many sensitive and critical applications, such as appliance parts, automotive tools, electronics components, laboratory tools, military parts, and precision medical tools. Through a variety of cost-effective machining methods, screw machines produce both standard and custom bio implants, fittings, miniature medical instruments, metal knobs, specialty fasteners, spindles, splines, threaded rods, tired gauges, and many other metal parts, machined to precise tolerances. Read More…
The most common types of screw machines and CNC screw machines and CNC lathes, or turning centers. CNC technology offers many benefits to the turned product manufacturers, including greater precision, more uniform parts and higher production rates. Typically, CNC screw machines and CNC lathes can both machine up to six parts at once.
In addition to CNC-run machines, screw machines may use mechanical means to work. More traditional screw machines, also known as Swiss screw machines, have successfully been mass producing screw machine products since their invention in Switzerland in the late 1800s. Mechanical screw machines typically consist of eight or more simultaneously operating spindles, metal bar stock attached to the spindles’ spring collets, a main drive shaft, a bed lead work shaft, two front cam shafts, a motor, and controls. The main drive shaft controls the front two cam shafts and powers the bed lead work shaft.
Meanwhile, the motor, which is found at the machine’s base, provides power to all operations. Its horsepower varies per the size and speed of the machine it powers and the stock the machine forms. During operation, the metal bar stock, which may be square, round, or hexagonal, are spun as they encounter any number of automated tools, such as drilling, cutting, notching, or knurling tools, that are attached to the screw machine. These tools drill, shave excess, and smooth the stock, thus forming them into parts. Often, these tools are arranged in stations, set at a variety of possible axes, including turret, horizontal slide and vertical slide.
Manufacturers select different surfacing processes in order to achieve different looks or functions. Knurling tools, for example, engage in the process of knurling, which is a process that produces a patterned texture on a metal’s surface in order to provide grip. This process is used to finish metal flashlights, nuts, knobs, tool handles, and more. Thread forming and thread forming processes, on the other hand, are used to form screw heads.
Both processes employ cold forming and therefore do not require the high heat of some other forming processes. Because threading is time consuming, it is more commonly used with lathes rather than screw machines. Another common process used to finish screw machine products is rotary broaching. Rotary broaching uses a saw-like cutting tool, called a rotary broach or wobble broach, to cut irregular shapes into metal.
They are used to create parts like splines and keyways. When performing these processes, screw machines may use any number of metal materials, the most common being aluminum, brass, stainless steel, steel and, for sanitary or medical tool applications, titanium.
The choice of whether to use a mechanical screw machine or a CNC screw machine may prove a difficult one, as both machine types have their advantages and disadvantages. For example, traditional screw machines are less expensive on the outset and can produce high volumes of product. Also, they are not inherently slower than their CNC-operated counterparts.
CNC screw machining and turning, on the other hand, can create more uniform, complex and precise parts. Some manufacturers bridge the gap between the two styles by building hybrid machines, such as multi-spindle CNC screw machines. Multi-spindle CNC screw machines take time to set up, requiring part design, CAD design, and general system programming. However, once set up, they prove quite cost effective, especially during long production runs.
The precision and tolerances reached by screw machining are hard to match. Rarely do parts created through other metal fabrication and forming processes approach the quality of screw machine products. Screw machines are perhaps the best devices out there for turned parts formation.