Copyright Goodheart-Willcox Co., Inc. 180 CNC Manufacturing Technology 9.1 Introduction to CNC Mill Programming In this chapter you will learn how a print, read correctly (Chapter 5), can tell you exactly how to machine a part. You will also discover how complex operations and calculations are made simple through a variety of canned cycles in which the computer does all the work. You will learn how work- holding impacts part production. Think of the many aspects of machining a part that must be planned and communicated to the machine: What tools are available? How do you control where each tool goes, how fast it gets there, and how fast you can machine a piece of material? These are things that are all controlled by the CNC program, and ultimately by the programmer. This chapter will cover codes specifically for FANUC- and Haas- controlled machines. These two controller types, and all their different models, cover most machine controllers in the market. They use a type of programming referred to as G and M code. While other types of controls can also use G and M code, the codes used for FANUC and Haas are by far the most common, and in most cases interchangeable. Writing a CNC program is as simple as telling a story one tool at a time. Your most important tool is the creativity and planning you bring to the project before making even one keystroke toward writing a program. 9.2 Program Planning The most critical, and often overlooked, step in creating a successful CNC part program is the planning stage. Weak programmers will grab a print and start producing code, adding tools that make sense to them, which often results in programs that have not considered the complex issues of workholding or fixturing. A great programmer will spend time consider- ing the machines and tooling available, the most efficient workholding method, and the customers’ requirements. It is always a good idea to assemble a team when preparing to program a part and move it to production. A customer representative—possibly a salesperson or manager—someone from the engineering staff, a setup specialist, and an operator could all have helpful feedback in the plan- ning process to make a quality finished part. Every program produced and every part manufactured should provide end users a piece that fits their needs in a cost-effective manner, while giving your company a profitable solution. This quality customer service and smart planning takes a team of highly skilled and organized professionals. 9.2.1 Print Review Interpreting design intent is an important first step in reviewing prints. By examining the tolerances of fea- tures and the position from which tolerances are estab- lished, a print reader can gain an understanding of part function, what features are critical in manufacturing, and how this part can be machined. The simple print in Figure 9-1 provides an example. The block size is dimensioned as 6″ by 3″, with a total tolerance of .020″. A reader can determine from the print that this block could be manufactured from 3″-wide stock and that the 6″ length cannot be left as saw cut, but the Goodheart-Willcox Publisher Figure 9-1. A sample drawing of a 6″ × 3″ block with a 1/2″ hole.