SCREW MACHINE

SCREW MACHINE

A screw machine is a metalworking machine used in the high volume manufacture of turned components.
In operation, a screw machine is similar to a lathe. Essentially a screw machine is an automated turret lathe.
Screw machines have been replaced by CNC lathes to some extent. However, for high volume production of turned components nothing is as cost efficient as a screw machine.
In the hierarchy of manufacturing machines, the screw machine sits at the top when large volume of product is needed. An engine lathe sits at the bottom, taking the least amount of time to set-up but the most amount of skilled labor and time to actually produce a part. A turret lathe has traditionally been one step above a lathe, needing greater set-up time but being able to produce a higher volume of product and usually requiring a lower skilled operator once the set-up process is complete. Screw machines may require an extensive set-up but once running, a single operator can monitor the operation of several machines.
The advent of the CNC lathe or more properly: the CNC turning center, has blurred these distinct levels of production to some extent. The CNC turning center most appropriately fits in the mid-range of production, replacing the turret lathe. However, it is often possible to produce a single component with a CNC turning center more quickly than can be done with an engine lathe. To some extent too, the CNC turning center has stepped into the region traditionally occupied by the screw machine. The ease of set-up of CNC machinery makes it attractive alternative to the screw machine. However, in nearly all cases, a screw machine, once set-up, can outperform any other turning machine in speed and cost of production.
As CNC components and controllers have matured, CNC has moved into the world of screw machines as well. Multispindle CNC screw machines have opened up possibilities for producing a number of parts per hour that was not obtainable before. CNC screw machines and rotary transfers are a recent, and highly expensive manufacturing option. The number of axes which must be controlled can number over a hundred, and as a result, programming is highly complex. The costs in initial purchase and tooling plus ongoing programming costs relegate this flexible, high-end piece of equipment to only the largest manufacturing operations.

turning machine

CNC TURNING MACHINE SMALL UNIT,

HISTORICAL OVERVIEW OF CNC MACHINE

HISTORICAL OVERVIEW


CNC was preceded by NC (Numerically Controlled) machines, which were hard wired and their operating parameters could not be changed. NC was developed in the late 1940s and early 1950s by John T. Parsons in collaboration with the MIT Servomechanisms Laboratory. The first CNC systems used NC style hardware, and the computer was used for the tool compensation calculations and sometimes for editing.
Punched tape continued to be used as a medium for transferring G-codes into the controller for many decades after 1950, until it was eventually superseded by RS232 cables, floppy disks, and now is commonly tied directly into plant networks. The files containing the G-codes to be interpreted by the controller are usually saved under the .NC extension. Most shops have their own saving format that matches their ISO certification requirements.
The introduction of CNC machines radically changed the manufacturing industry. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to produce, and the number of machining steps that required human action have been dramatically reduced.
With the increased automation of manufacturing processes with CNC machining, considerable improvements in consistency and quality have been achieved with no strain on the operator. CNC automation reduced the frequency of errors and provided CNC operators with time to perform additional tasks. CNC automation also allows for more flexibility in the way parts are held in the manufacturing process and the time required to change the machine to produce different components.