CNC vs. Manual Machining
By: Colton Anders
Importance of Machining
Machining is a very important aspect of our daily lives. Every that we touch or interact with has been touched by a machine or machinist in one way or another. The phones in your hand have hundreds of components that have been made by and possibly put together by machines, but without machinists they wouldn't exist. There are two main groups machining can be broken down into; Manual machining and CNC machining.
Manual Machining is when an individual operates a machine controlling every movement by hand. In the picture above this machinist is using a lathe to cut a circular part down to a particular size. This process can be very time consuming depending on what kind of metal you are cutting and how you are trying to cut the part. Manually using a lathe is now, for the most part, inferior to CNC lathe operations. CNC lathes, which are lathes controlled by a program that has been written for a certain part, are much quicker and more efficient than their manual counterparts, but manual lathes are much better for quickly fixing a part or changing how the part looks.
Manual Milling has its pros and cons. Manual milling can be very slow and very tiring depending on the size of the part. The cause for this is that each full turn of the handle to move the table is 200 thousandths of an inch. The good part of manual machining is that it is very quick and easy to set up parts and you do not have to write long and complex codes telling a machine what movements to make. It is also very good for quick adjustments or repairs to parts because you can just throw the part in a vice and quickly machine whichever area of the part you need to.
CNC Machines have made manufacturing faster, cleaner, easier(in some ways), and cheaper(in some ways). CNC stands for: Computer Numerical Control. Which means that you use number to maneuver the machine around it X, Y, and Z axis (Cartesian Coordinate System). CNC machines can cut metal faster than a regular mill because they can spin cutting tools faster, and the tables can move at a faster more constant speed than a person rotating a handle. These machines are also cleaner than regular milling because all the metal chips are confined inside the walls of the machine and there is also a coolant system that flushes the chips to the bottom of the machine, where they are then pushed out of the machine into a selected bin to be recycled. this is much safer and easier than using a regular mill because the hot metal chips are not flying at the operator and then all over the floor. This type of machining has also made manufacturing a lot easier because once a program is written for a part then you can mass produce the parts one after another just by simply taking out the finished one and putting in a raw piece of metal. CNC's also make it easy to make all the parts match and be with tenths of thousandths of an inch of each other, and it makes cutting more complex lines easier. The not so easy part is the process of writing the program for complex parts. Some simple programs even can have thousands of different lines of codes. CNC's have made it faster to make parts thus making them cheaper. But the down side to faster production is the price of the machines. The machine pictured above is just a base model 3 axis (X,Y,Z) CNC mill and it cost around $35,000 brand new.
The picture above shows the control panel for a CNC machine. This panel controls everything that the CNC does. these panels are good in the case that a quick change needs made on a program to make it run smoother. The fact that these controls are so complex means that it takes countless hours of learning the format of the software to use them and what the different controls stand for and what function they do. Since training takes time which means spending money. This also inclines that the operator will cost more than a manual machine operator because they are more highly trained.
Retrofit CNC Mill
A retrofit CNC is when a computer and servo motors are fitted to a manual lathe or mill thus turning it into a CNC. The computer is connected to the servos, and the servos are mounted to the table of the machine and can control the movements of the table. The servo motors also have handles on them so the lathe or mill can still be used as a manual machine. These retrofits are good for small shops that cant afford CNC's, outdated machines, and for machinists who are just leaning to use a CNC. The retrofitted machine can now control the X, and Y axis automatically and do basic functions like cutting lines, arcs, and pockets. The one major downside to a retrofit is that they are very expensive. The whole setup itself cost $10,000. The shiny aluminum piece in the middle of the machine actually encases a glass scale which measures the height of the Z axis and it alone cost $3,000.
Fixing and Fabricating
Being a manual machinist entails more than just operating a machine. You must also know to how to use hand tools to fix the machines when they break down. When a CNC breaks down a specialists has to come in and fix the machine and this process can take weeks and cost a lot of money, while fixing a manual machine can take as little as 30 minutes. Manual machines have much simpler parts than can easily be fabricated or modified right there in a machine shop with various hand tools. In the picture above a machinist (Sam Ferrington) is fixing a drawbar,which is the bar that is turned to tighten a tool into the machine, by pressing a spacer onto the bar to make it better fit the machine it was being used in.
Besides the usual measurement tools that both a CNC and a manual machinist use, a manual machinist must learn to use multiple other tools in a proper manner. Some of these tools are very common tools outside of the industry such as: Ball Peen Hammers, Protractors, Files, Shears, Hack Saws, and many other hand tools. Some of these tools are used in many occupations and are found in many peoples garages, but they must be used in certain ways when being used from a machinist standpoint. These tools are the equivalent of a CNC machinists control panel. They both need training, one more than the other, but once they are trained they can do anything imaginable, to a certain degree.
Precision Machinists tools
A manual machinist also uses very precise tools like: taps; for threading holes, dyes; for threading outside diameters(pictured above), micrometers; measuring within .0001 in., gauge blocks, dial calipers, etc. These tools are all very delicate and expensive and must be taken very well care of but they can last lifetimes and be passed down through generations. These tool are used for when a process needs to be handled with more care than what a machine can do like with more fragile materials such as plastic and carbide
CNC Machining vs. Manual Machining
Even though there will always be a need for both types of machining I believe that CNC will continue to grow and take over the industry due to the fact that it takes less people to run multiple machines, and in the long run will save shops a very large sum of money and expand there horizons for bigger and better opportunities. Some things are almost impossible to attempt on a manual machine. The image above would be an example of this. These long board trucks took multiple hours and multiple different setups to complete on a CNC which would take days or weeks to do on a regular mill.