Are you using Computer Numeric Controlled (CNC) equipment in your shop? According to our most recent Babcox Machine Shop Market Profile Survey, 12 percent of engine builders said they own a CNC machining center (a multi-purpose machine that can do surfacing, boring, milling, drilling, etc.). The survey also asked what other types of equipment our readers own (boring & honing machines, surfacers, valve guide & seat machines, etc.), but we didn’t ask if the equipment was manual or CNC. Most shops (88 to 94 percent) own these types of machines, as one would expect since they make their living doing engine work. Had we asked for a breakdown between manual and CNC machines, the percentage of shops who are using some type of CNC equipment would likely be one out of four or maybe even one out of three. The point is the use of CNC equipment continues to grow — and with good reason.
Many of the CNC machines that are in use today are found in high-end performance shops, shops that work on a lot of late model engines, and shops that are doing specialized machining for both automotive and non-automotive customers.
The use of CNC shop equipment is growing because it offers so many advantages:
• It reduces the need for skilled labor. An operator doesn’t have to stand in front of the machine all day manually controlling its motions and babysitting processes. The automatic controls run the equipment, freeing up the operator to work on something else. CNC machines also don’t punch a time clock, don’t call in sick, don’t take vacations and are not interrupted by phone calls, nature calls, coffee breaks, parts deliveries or shop chatter. Any of these things can interrupt the steady flow of work in a shop and create distractions that reduce productivity and sometimes lead to mistakes.
Shop owners we’ve interviewed tell us that CNC allows them to do more work with the same number of employees, or in some cases to trim staff. One shop owner said, “We used to have seven people working in our shop. Now we do the same amount of work with just two people. It’s a huge cost savings in labor for us. Once a job has been setup, the automatic controls take over and do all of the machine work. If it’s a long job, the machine doesn’t stop working at 5 o’clock and go home. We can let it run all night if necessary, and start the next job first thing in the morning.”
• CNC offers a high level of accuracy and repeatability. A highly skilled operator who pays close attention to details can do the same thing, but everybody has a bad day now and then and makes mistakes. Late model engines have much closer tolerances than engines from a few decades ago, so you have to be right on when you bore, hone and machine critical components. There’s less room for slop, so once you have a process in place that delivers the accuracy you want, you don’t have to worry about mistakes messing up a job.
Once you’ve setup the basic machining perimeters for a job, the programming can be stored and reused or easily modified the next time a similar job comes in. For example, say you want to blueprint a small block Chevy engine. Once you’ve established the basic dimensions for locating and centering the cylinder bores, lifter bores, crank and cam bores, deck surfaces, etc., you have a digital map that be used over and over again for every engine you do.
• CNC provides a higher level of quality control through automation. Assuming the job is set up correctly the first time, the CNC machine can do the same job over and over with the same degree of accuracy each time. This takes the human operator our of the equation and delivers consistent results no matter who pushes the buttons on the machine.
• If you are currently sending out parts for CNC machining, you can keep those jobs in-house by installing your own CNC machine. This can give you greater control over your work and reduces the time it takes to complete a job by eliminating shipping and delivery delays.
• One of the most popular applications for CNC machining is for porting high-performance cylinder heads. This type of work usually requires a 5-axis machine that can reach all areas of the intake and exhaust ports for a seamless transition. But a CNC machining center can do more than heads. It can bore cylinders, line bore blocks and OHC heads, machine lifter bores, surface decks, lighten blocks and even fabricate custom billet parts from a solid chunk of metal.
• With a CNC machining center and some CAD/CAM design software, you can even make your own parts. A growing number of shops with 4-axis and 5-axis CNC machines are finding new markets where they can offer custom machining services. This includes copying parts, making custom automotive and motorcycle parts and even fabricating custom non-automotive components for a variety of industrial and agricultural customers.
A digital probe on a CNC machining center can be used to map parts, giving you a blueprint of all the key dimensions and surfaces on that part. If you then want to replicate a part out of solid billet aluminum (like a cylinder head, engine block, connecting rod, or crankshaft), you have the three-dimensional map for making it.
“If you can dream it, you can machine it,” said one CNC equipment supplier. With the proper software, you can digitally map and copy or modify parts, and you can design new parts from scratch. It opens up a whole new world of possibilities for expanding and growing your business.
CNC Fear Factor
In spite of all the advantages CNC offers, some shop owners are reluctant to embrace new technology — especially anything that involves computers. Old school machinists are used to pulling handles and turning knobs on their equipment, and watching the machine as it does its work. They enjoy the hands-on control over what’s happening and are reluctant to turn the controls over to a computer. What happens if the computer locks up or crashes? Can they still operate the machine manually or do they have to wait for a service technician to come fix it? These are legitimate concerns for anyone who is considering a major new equipment purchase.
“Those who don’t see a need for CNC equipment are living in the past,” said one shop owner. “As time goes on they’ll find their old school ways of doing things are no longer competitive with shops who have gone to CNC. It’s survival of the fittest.”
The resistance to computers is a generational thing, with younger shop owners and machinists being much more open and receptive to automation. Almost everybody has some type of smart phone these days, or own a tablet, laptop or desktop PC. Cars are packed with numerous control modules and even simple appliances now have computer chips inside them. So it’s not like its totally alien technology that’s being added onto shop equipment to make the equipment easier to operate, more productive and efficient.
The automatic controls on most CNC machines use either keyboard or touch screen inputs. The interface is Windows-based so anyone who knows how to use a computer should have some familiarity with the controls. The software that actually runs the equipment ranges from easy to learn to very complex. CNC software designed for industrial applications is usually more difficult to learn than CNC software which has been developed exclusively for automotive machinists. Learning how to navigate numerous drop down menus, prompts and other inputs to set up the equipment takes some time.
Industrial CNC machines are typically programmed using G-code or M-code commands entered on a keyboard or touch screen. These are special codes that tell the tooling how to move in the X, Y and Z planes. To make life easier for automotive machinists who are not engineers or who have not taken a CNC programming training course, many automotive-oriented CNC machines use “conversational programming.” The operator enters basic instructions that tell the machine what he wants it to do, how deep he wants to cut, mill or surface, and any other important information that has to be input before the machine can start the job. Some software even has built in safe guards so if the information entered doesn’t make sense or would overextend the tooling, it prevents the operator from proceeding and saves the embarrassment of making a costly mistake.
Conversational programming is much easier and faster to learn than traditional G-code and M-code programming. So with minimal training, a CNC machine can be up and running and making you money.
In fact, the more training a CNC supplier offers, the better. And the more specific the training is to the type of work you do in your shop, the better. If you’re making a major investment in something like a CNC machining center, you want all the training you can get. If an equipment supplier can’t provide adequate training, find another supplier who can.
If you want to use CAD/CAM software to custom fabricate parts, the learning curve will be longer. It takes time to learn the nuances of CAD/CAM software if you’ve had no previous experience designing parts on a computer. This may require taking a CAD/CAM training course at a votech school or community college. But once you’ve mastered the basics and have gained some experience, the sky is the limit as to what you can do.
Another point to emphasize is that today’s CNC machines are not the CNC machines of a decade ago. The software has evolved over the years, and each new generation of upgrades has brought with it more features and capabilities. Inputs are more intuitive and user friendly, and displays are easier to read and more informative.
Upgradability is another advantage CNC has over manual machines. Upgrades can be installed by a simple download. If you need a new button to perform a new function, there’s no wiring to rewire, no new switches or buttons or other components that have to be connected to the machine. It’s all done through the software and user interface. Like a smart phone upgrade, new icons or buttons can be added to an existing display screen or touch screen to provide new functions or information.
Can You Afford It?
The question is not “Can you afford it?” but “How can you not afford it?” Given all of the advantages that CNC has to offer, how can you remain competitive in today’s market without this type of equipment?
CNC machines are not cheap. They require a sizable investment: it can cost you up to six figures depending on what you buy. With five year financing, the payback can come fairly quick, according to CNC suppliers. Your return on investment will depend on what kind of work you are doing, how many jobs per day, week or month you are doing, how much you are charging for your work, the time and labor savings you realize from automating processes, and any additional savings that result from better quality control (fewer comebacks and do-overs that cost you money).
For CNC custom work, some shops charge by the piece or the batch. Others charge by the time it takes to complete the job. Rates are usually variable and depend on who the customer is and what they want. It’s not the same as charging a flat fee to mill a head or surface a block. Consequently, there’s a lot more opportunity for profit because you’re not competing against the shop down the street.
Manual Or CNC?
If you are considering a new equipment purchase and are debating whether to go with traditional manual controls or CNC, your equipment supplier may offer the capability to upgrade from manual to CNC at a later date. It’s usually less expensive to go with CNC now rather than later because costs usually go up over time.
If money is an issue, buying a manual machine and delaying a CNC upgrade may seem like your best option for now. But why would you want to postpone the labor savings that CNC offers by putting off a CNC upgrade to a later date? You should cash in on the savings that CNC offers by going with CNC from the get go.
One equipment supplier said the difference in cost between a manual machining center and a CNC machining center is about $40,000 ($100,000 versus $140,000). That sounds like a lot of money, and it is. But consider this: a skilled machinist earns $50,000 to $60,000 a year (wages plus benefits). The labor savings can add up very quickly if a CNC machine multiplies the work he can do, or it can save money by reducing the number of employees needed to do the work. Either way, you come out ahead.
Older equipment can often be retrofitted with CNC controls to automate certain processes, but you won’t get all of the advantages that a new CNC machine can provide. You’ll be limited by the capabilities and accuracy of the old machine. Most new CNC machines use precision ball screws and have better materials on the ways to improve machining accuracy.
The cost of a retrofit usually starts around $5,000 and goes up from there depending on what the retrofit includes and who installs it. Some retrofits can add features such as the ability to digitize the profile of a work piece, or to automatically control tool zeroing and positioning.
Maintenance & Upgrades
Like any type of shop equipment, CNC machines require a certain amount of maintenance. Certain components need to be cleaned and oiled on a regular basis, filters have to be changed and backlash should be checked and adjusted as needed once a year (recommended but not mandatory).
Backlash is the amount of play in the machine tooling. It needs to be minimized to assure consistency and accuracy. A laser is used to verify machine travel in all axis directions, and a correction table is generated so the control software can compensate tooling travel as needed. This is usually performed by a service technician as part of the service contract.
Some equipment suppliers provide a free service contract for a given period of time after the initial purchase. Others charge a flat fee for their annual service contracts — which may or may not include software upgrades.
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