Can You Train a Machinist on a CNC Machine Tool?
By Professor Torbjorn Bergstrom, Operations Manager, WPI Manufacturing Laboratories
They say that a Swiss machinist's apprentice starts with a piece of steel, a file, and a micrometer. They are then told to make a cube. I don't know the truth of this assertion, but it has a sort of elegance. It can give the apprentice insight into measurement and metal removal. It also lets them appreciate the ease of using a milling machine later in their training to complete the same task in minutes. It brings to mind books like Ivanho, where we can almost feel what it is like to grow up in a feudal castle and go through the steps from page to squire and then knighthood or even apprentice, journeyman, and master.
When I started teaching people to program and operate machine tools, I was tasked with taking engineering students and enabling them to use the equipment to make something they have designed. I wasn't given seven years to take them through an apprenticeship program or even seven months to train them. I was given seven weeks and only four hours a week of lab time. We started on the first day making chips in a CNC lathe.
I knew that the "old-timers" insisted that students first understand how to use a manual machine before operating a CNC tool. They argued that you needed to have a feel for the process, with your hands on the handles controlling the feed, feeling the cutting forces and vibrations of the process. Since these were the "old-timers" that taught me, I believed them. The problem was I hadn't used a manual machine tool for 10 or 15 years and could barely remember how to turn it on. It wouldn't have been safe for me to teach them with a manual machine.
In that first 7-week term, the students and I taught each other how to program and use the machines. In the seven years since that first day, I've had hand in the instruction of thousands of students. Most are engineering students, although recently we've been using the engineering students to help train CNC operators and setup technicians.
Multimedia Teaching Lessons
The system we have developed involves the use of standalone multimedia teaching lessons. Any pair of students can step through the series of lessons, taking turns in the role of student and instructor. The lessons are intended to teach safe use of the equipment and to allow the students to become familiar and comfortable with the controllers and setup procedures.
The theory is that this system enables us to use students to teach each other the simple aspects of programming and using the equipment. This allows the staff to help them understand more challenging and nuanced issues dealing with complex fixturing and complicated tooling and tool path selection. The reality is the students end up handling the most complex setups with very little help as the staff members tend to be interrupted too often to concentrate on anything complex.
Manual Machines in Schools Only
Through the years I've traveled to meetings and met with instructors from all over the world. The training methods we've developed are frequently a topic of discussion. We almost always get to the question of the missing value of our students not getting a chance to feel the cutting forces through the handles. In the beginning I was a little defensive when taking these questions as it seemed there may be some validity. In all of these meetings we would tour the local teaching institutions and local manufacturing facilities. I began to quickly notice that the only places I saw row after row of manual machine tools was in the schools. Frequently, the manual machines had been donated to the school by a company that was closing or upgrading to CNC equipment.
With that realization forming in my mind, I began to look critically at our teaching methods and their lack of manual machine tools. The arguments for starting with manual always revolve around the idea that machinists need to have a feel for the process to understand the influence of changes in feed, speed, and depth of cut. They will tell you that you need to have this feel for the process to truly understand what is going on and make good parts. It reminds me of a story I heard about a WWI fighter pilot visiting a Messerschmitt factor at the beginning of WWII and telling the engineers that the first thing the need to do is remove the cockpit glass so the pilots can feel the wind in their faces. If the pilots can feel the wind they will know how fast they are going.
Time for a Change
All of the CNC machine tools I've used have a power meter, so I began to discount the wind in the face / feel the force arguments. It is not hard to convince the students that power is directly related to cutting force. The other argument I've heard returns us to the feudal system. You will appreciate the easier methods more if you've done the work the hard way. This argument even extends to the discussion of teaching G-code or CAM first. One of my colleagues likes to point out that is like saying you need to ride a horse from Boston to Worcester before you can appreciate the Mass Pike.
If we look critically at the real need and the value we can add to our students, we need to consider the types of jobs they are doing and the type of equipment they will be using. Just because I learned it that way doesn't mean I should teach it that way. In my experience, starting with CNC is faster, safer, and creates qualified machinists that meet the needs of today's industry. Auto technician training doesn't start with the Model T.