The Evolution of Automatic Screw Machines
Fully automatic, high-speed lathes are commonly known as automatic screw machines. It could even be considered a highly developed type of turret lathe due to the fact that the cutting tools are carried in a turret of some form. They operate on a vertical or horizontal axis, depending on the machine tool style.
The machine tool itself is automatic in that it uses the cutting tools to automatically cut into the turning stock to form any quantity of duplicate parts. The machine operates mechanically, but the operator can set the machine up to form parts either by using mechanical controls or CNC controls depending on the style of machine. CNC stands for computer numerical controls
Automatic Screw Machine History
The first automatic screw machine was patented in 1865 by Brown & Sharpe and then by Christopher Spencer in 1873. The idea was taken from the turret lathe and was created as a way to produce small turned parts more efficiently.
The idea was to create a turning machine that could make the exact same turned part automatically and repetitively. It was called the screw machine because its intended use was to create screws and pins.
The first automatic screw machine had a single spindle; multiple spindle models were introduced in the later 1800’s. The multi-spindle machines were not widely used until the coming of World War I, since manufacturing efficiency became extremely important.
The design feature, predominate to the use of the turret, and making the automatic screw machine truly automatic is the use of drum cams. Drum cams are fixed upon a series of removable cam components. These are compatible with the size of the workpiece and parts to be formed. The cams allow the automatic movements of the different operative machining tools to be performed. It is the action of these cams that give this machine tool its automatic classification.?
This particular machine tool was initially designed to make screws, pins, and other small parts from bar stock, which was passed through the hollow spindle from the rear of the machine. When the chuck opened up large enough for the bar stock to be fed through it was pushed forward until it hit a stop located in one of the turret’s tool holes.
The bar feeding device was operated automatically by weight, and was called a wire feed because screws were once made from portions of straightened wire. This same machine tool is now capable of feeding rather large bars of stock, much larger than thought possible in the early years of machine development.
The Modern Automatic Screw Machine
Many modern automatic screw machines are equipped with multiple spindles and are capable of operations such as index drilling, screw slotting, threading, counter boring and more. They are also capable of operating by more than purely mechanical means; modern machines utilize hydraulic, electric, or CNC. Again, CNC stands for computer numerical controls.
Additional Automatic Screw Machine capabilities include:
- Automatic loading of the workpiece
- Automatic ?starting of the machine and coolant
- Automatic changing of the tools, speeds and feed rate
- Automatic inspection and measurement of the part
- Automatic? unloading of the finished part
- Automatic operation restart
Some screw machines can be equipped with a hopper or magazine in which metal parts can be fed. When they pass into the chuck, they will be gripped and machined according to operator specifications. This machine tool process is completely automated, meaning that the only thing required of the operator is to ensure that the hopper stays full and that tools stay sharp.