What is CNC File in Steel Industry?

CNC (Computer Numeric Control) is a method by which a steel fabricator sends information to specific semi-automated machinery to perform certain fabrication tasks. These tasks may include cutting members to length, drilling or punching of holes and cutting plates to size, beam copes, long slots, etc.

CNC is not new to the fabrication of structural steel. It has been provided by what is referred to as interactive methods. In the past shop drawings were sent to the fabrication shop and numeric information was entered into a computer by hand or interactively. The classical method can and does provide for the possibility of making mistakes. 

The programmer /operator, typically someone in what is called the "template shop", would then provide tapes or some other means of transferring the information to the individual CNC pieces of equipment. With this digital information the machinery would, when the material is loaded, perform the indicated operation.

In today's world of electronically produced shop drawings CNC information can be provided automatically by the detailing software. If the detailing software being used is being capable of providing CNC information, the need for a programmer in the shop to transfer the required data from the shop drawings to the computer is eliminated. CNC also reduces the possibility of an error in data transfer.

This will, for the most part, eliminate the need for a programmer in the shop, but it also means that the shop drawings must be made accurately and to scale. Furthermore, all holes, cuts, lengths, and other fabrication criteria must be incorporated electronically for inclusion with the CNC information. If shop drawings are plotted and changes are made to these plotted/hard copies, then the automatic CNC information may be rendered useless.

In today's market these hand changes are rarely performed when accurate CNC information is required. If for some reason drawings are not made to scale, the CNC information is corrupted and cannot be sent to the shops for fabrication.


CNC is a great tool providing speed of fabrication and better quality control. If fabrication information is transferred digitally from the detailing computer directly to the CNC control computer, either through a network system or stored data on some sort of digital media, there is little room for error and quality control is greatly improved.