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INTRODUCTION

I’m spoiled. With few exceptions, I now put everything I can now on the CNC machines. In most cases, jobs are less labor intensive, less prone to error, and can be completed sooner than when using conventional machines. With the user-friendly CNC technology available today, even making one or two simple parts is often easier and more efficient than conventional machining.

Does that mean the end of conventional machining is near? I don’t think so. There are certain tasks you can do with conventional machines that CNC machines are just not good at, such as “blending.” CNC machines can’t blend flawed features very well simply because they don’t have eyes. They run on numbers. Many jobs that come through the door don’t have exact numbers to work to or any documentation for that matter.

Often parts that need rework are so beat up, worn out, or outdated that, even if you had a print, there’s a good chance the dimensions on the print won’t match the part. Maintenance machining and mold repair jobs come to mind as jobs that often need rework and manual blending of some sort.

There are craftsmen in our shop who know little about CNC machining and CNC people who are not craftsman. The funny thing is that often these people imagine the other as having some kind of God-like abilities. The fact of the matter — little would get accomplished it weren’t for these two groups working together.

CNC machining involves a combination of three things:

1.Machining knowledge

2.Controller familiarity

3.Programming knowledge

Machining is the art of cutting away material in the proper sequence, selecting and sharpening cutters, setting feeds and speeds, measuring, and determining how you are going to hold the work. The planning and cutting characteristics of conventional and CNC machining are quite similar with the exception that you can machine parts a lot faster using CNC machines because they can read numbers quickly and move accordingly. They also don’t take coffee breaks.

Programming is essentially the art of making the machine move the way you want it to.

CNC programming, at its core, is simply point-to-point programming which in turn obliges the cutter to move from point to point. You don’t have to be especially adept at doing mental gymnastics to program CNC machines because almost all the instructions you give the machine are sequential. CNC programs are a lot like driving instructions: “Go north three miles then turn left.” “Go west ten miles then turn right.” Etc.

My previous book Machine Shop Trade Secrets deals mostly with conventional machining.

The practice of starting out on conventional machines to learn machining may be shifting now as CNC machines become increasingly more popular, less expensive, and easier to use. If you are an experienced conventional machinist, you’ll have the advantage of being able to concentrate your efforts on learning the controller and how to program. I don’t believe it is essential to have experience on conventional machines to learn CNC machining. However, a person with a strong conventional machining background will likely have an easier time getting good parts consistently.

To the untrained eye, CNC machines may look complicated. They did to me at first. I was so accustomed to machining everything conventionally,; I couldn’t imagine how anybody could machine parts simply by pressing buttons on a control panel.

When I signed up for a CNC programming course years ago, I asked the instructor how long he thought the average person would need to be able to set up and operate a CNC machine. His answer surprised me. He said “ a couple of days.” In my ignorance, I figured it would take at least a couple months of intense training. As it turns out, he was much closer to being correct than I was.

The other day while running a job on the CNC mill, I took some time to look over the list of G codes posted on the controller. To my surprise, I wasn’t familiar with a lot of the codes. I have literally programmed and run thousands of different parts through these machines. “How can that be?” I asked myself. The only logical conclusion I was able to come up was this: You don’t have to know “everything there is to know” to be able to make parts on these machines. It is sort of like using Microsoft Word. You don’t have to know everything there is to know about Microsoft Word to be able to write a letter.

This book is written from a machinist’s perspective. I work as a machinist in a small support shop. What I strive for and demand of myself is being able to accomplish whatever machining job comes through the door. If I don’t know some aspect of doing a job such as thread milling, I’ll learn it. I’m stubborn in that regard. I may forget what I learned a few weeks later, but that’s another story.

I have always preferred learning something new by doing a project. By doing a project you immediately to start to separate what is important from what is not.

The first chapter talks about planning jobs. The planning stage is where you may save countless hours of time and frustration later on. The second chapter is devoted to “work holding” which is often a challenging aspect of machining. The third chapter discusses ways to avoid crashes. Nobody likes to crash. The fourth chapter goes into some detail about applying edge dressings to parts. The fifth chapter discusses something dear to my heart, which is helping designers and engineers help us. The sixth, seventh, and eighth chapters are devoted to familiarizing yourself with CAD/CAM systems and G code. Once you get over the pain of learning a CAD/CAM system, you’ll never want to go back. In these chapters we’ll be modeling, programming, and machining a simple part. The methods applied to make this part are used over and over in shops and provide a solid base of knowledge from which to expand.

The ninth chapter provides an overview of the commonly used controls on CNC machines. The tenth chapter provides miscellaneous tips that may help you through your day in the shop.

The CNC machines and controllers discussed in this book are primarily Haas. The only reason for that is because Haas is what we use in our shop. The setup and programming procedures discussed are specifically for Hass machines, but will likely be useful in a generic sense for other brands of CNC machines. Nevertheless, if you don’t use a Haas right now, chances are you will in the future. At this time, Haas is outselling their competitors three to one.

Let’s get started.