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CNC Equipment: Should Your Shop Make The Leap
By Brendan Baker
When the great American pioneer Eli Whitney invented mass production, little did he know that more than 200 years later his ideas of uniform parts and production efficiency would still hold true. Through his innovations and inventions (he also invented the first milling machine) he helped spark the industrial revolution.
Today, in the information age, the computer is changing everything, including manufacturing, as we know it. Computer Numerical Control machining centers (CNC) have made smaller operations more profitable with less manpower and with better quality than ever before. CNC machines are not new to machine shops; many shops have been using them for years. But, is it a must have machine tool or is it a luxury item that most shops don’t need to remain competitive?
"At the present time CNC machines have a lot of interest from engine builders and many other industries as well. Is the expense worth it, though, and will it pay for itself?" asks Norm Brandes, owner of Silver Lake, WI-based Westech Automotive. "The short answer is, yes, especially if you are doing repeatable things. But when you look at these machines and see their price tags – some well over $100,000 on up to $500,000 – it can seem out of reach for most shops."
There are many things you can do with a CNC machining center but the price of a new one can be a barrier to the small custom engine rebuilder (CER) building many different styles of engines. It is questionable whether or not these shops would benefit from owning one.
There are several differences in CNC machines. There are CNC machines that are designed to do strictly automotive work – mainly cylinder heads and blocks. These machines are very good at what they do and can be programmed like any other CNC machine. More versatile industrial-style CNC machine centers can be used for a variety of uses (even non-automotive uses). However, a CNC machine center is not inexpensive and has to be adapted for automotive uses. Additional fixtures and tooling will need to be purchased to make it operational for engine building. If you’re only doing blocks and heads and not manufacturing special pieces or don’t need all of the versatility, a full-capability CNC machine center likely is not the best choice for your shop. This said, there are options for shops on a budget looking at purchasing a CNC.
Many manufacturers offer affordable entry-level machines. And there is a good market for used equipment as well. "Haas Automation offers an entry level machine called the Toolroom Mill for just under $20,000," says Brad Harris, manufacturing engineer for Haas CNC Racing, a NASCAR Winston Cup race team. "It’s CNC controlled with 3-axes and can even be adapted to a fourth-axis. It’s similar to a Bridgeport in that it is an open design and features manual controls as well as CNC controls. It’s not much more expensive than a standard manually controlled Bridgeport machine." Harris says Haas also makes CNCs that can accommodate up to 150-inches of "x" travel (left to right).
According to Harris, HCR uses CNC machines to manufacture just about everything on its race cars. There are many uses for a CNC machine center in race shops and automotive machine shops, he explains.
Dr. Larry Wilkins, president of ERL Performance, Miami, FL, says from his standpoint there are no downsides to using CNC. ERL Performance has had extensive experience with CNC for work in other industries because it started out doing work for the aerospace industry and then manufactured parts for railroad companies. "But after 9/11, the railroads just stopped," says Wilkins. "We scrambled to find work until we joined forces with Miami, FL, based-South Florida Performance and Frank Smith. Through this affiliation we can take little Honda 4-cylinder engines and make them into 800 hp monsters!
"Very early on we got into CNC because I thought we could use it to set us apart from the competition, even back then in the ’80s," Wilkins explains. "When we started we were making aircraft parts and we bought a Sheldon Lathe. I mortgaged everything I had to purchase this machine.
"Now, our whole company would shut down if we didn’t have CNC machines. We just couldn’t function as well. What we’ve done over the years has been to keep upgrading the machinery. You’ve got to find ways to be more productive all the time because labor costs continue to go up. And this is one way to be able to keep up.
It Does What You Tell It To
If a shop’s primary business is doing two engines a week, does CNC make sense? Probably not, says Wilkins. If, on the other hand, a shop wants to expand its production capabilities without necessarily adding more staff, then a CNC may be a solution. However, there is a significant learning curve to overcome in the beginning.
Wilkins warns that for those that do go this direction there will be plenty of challenges ahead. "In three months he or she is going to think that, ‘this is the worst mistake I’ve ever made in my life! It won’t ever pay off.’ And honestly, it may be closer to 12 months before it starts to make sense. Tools and engines will likely be broken during this process. The machine tool builder will often get blamed, but 99 percent of the time it is the programmer who did something wrong. Therefore, you can’t say CNC is right for everybody but it is a very effective way to increase production efficiencies," he says.
There is definitely a learning curve involved with CNC machining. However, most machinists make very good CNC operators and programmers because of their experience and ability to visualize the toolpaths that the machine will take.
"A CNC machine does what you tell it to do," says Westech’s Brandes. "If you give it a point in space to machine, it will. On the other hand, if you give it the wrong point in space (coordinate) to machine, it will do that, too."
Brandes practiced his programming skills on wood in the beginning for a number of reasons, with cost being a big factor. "Home Depot, Menards, they were my core suppliers during this training phase," he laughs. "You can use wood or plastic on a CNC with an end mill or any other tool. The downside is you will make a lot of chips but the upside is you won’t ruin any tooling either. It’s the cheapest practice session you can have," he adds.
Practicing on inexpensive materials can help you get a little better understanding of what the program controls are like, what they do, and it lets you see if the final product looks anything like what you expected. Mistakes are common in the beginning, says Brandes: "A typical mistake is when the programmer forgets to retract the drill after drilling a hole. It’s easy to forget that you’re not just drilling a hole but retracting the drill bit back out far enough to clear the piece and move to the next task. Otherwise, the machine says, ‘now move to the next step,’ and breaks the bit right off!"
Most CNCs run only as they are programmed. And the programming is also the most difficult part to learn. Most of the machine work is designed on a desktop computer in some type of Computer Aided Design (CAD) program. This allows the programmer to work out the dimensions and measurements before running it on the CNC. From there, the programmer converts the blueprint to CNC code. G-code, a series of letters and numbers that represent certain tasks or movements on a coordinate system, is the most common language used to program CNC machines.
"Once you’ve written and verified a program, practically a floor sweeper can take parts in and out of the machine as it operates virtually unattended. You still need someone to oversee the machine as it’s running, but that person doesn’t have to be an experienced machinist. Most of the skill required to run a CNC is in the programming and designing phase. There are times, however, that you’ll need a machine attendant to change inserts or tooling, so experience is helpful," explains Mike Schaefer, president of Southern Illinois Crankshaft, Red Bud, IL, and AERA’s 2003-2004 chairman.
Most of our experts agree that it probably requires less labor force to run a CNC but that you will need a few highly skill and trained CNC operators and programmers to help run it all.
"It does take longer to run an engine through the CNC the first time because you have to be a little more careful at first," says ERL’s Wilkins. "We do a dry run first without an engine, then we have a very skilled operator watch the first run with an engine to make sure everything is working as it’s supposed to."
Wilkins says that there are even machine tools that can be taught to learn the toolpath by physically driving it on the path it should follow. According to him, some robotic welders have this feature. This idea could make sense for very low volume shops that don’t want to take the time to learn the code. Using the machine tool to teach or test programs sounds less costly, but often is not.
"We don’t want our guys to program code on our really expensive machine tool," says Wilkins. "We prefer all the bugs to be worked out on a computer at a desk instead. The desk didn’t cost much. And if the program can be worked out right at the programmer’s desk, it costs less."
Versatility Is A Virtue
A testament to how versatile CNC machine centers really are is illustrated by Wilkins’ experience with them. In the time that his company has owned CNCs he has gone from working in aerospace, railroads and doing contract work for General Electric to manufacturing his own parts and building 800 hp Honda sport compact engines. "We had all of our machining centers except one before we even got into the engine building business," Wilkins points out.
"The versatility of the CNC machine is the beauty of it. With the old world way of running production, even low production, you had to make all kinds of jigs (drill jigs, bore jigs, etc.) that were specific to that particular part. Now, the only thing that’s specific to that part is the set of tools you have selected the program that you use with it and the mounting fixture that you use. That’s why CNC is so prevalent today: you could literally cut out a plastic toothbrush and then bore an engine with it."
Haas CNC Racing’s Harris agrees that CNC’s biggest asset is its versatility: "I come from the automotive aftermarket and the companies that I worked for always wanted to be as versatile and flexible as possible. The more capability you have the more potential you have to find other sources of revenue," he says.
A CNC machine center is most ideally suited to the shop that is doing some engine work and also manufacturing a few custom pieces for their engines. Southern Illinois Crankshaft does both engine building and parts manufacturing. Currently SIC designs and builds a custom tractor pulling crankshaft in house. "It takes about two days from design to completion to run a crankshaft through one of our CNCs," says SIC’s Schaefer.
Speed And Accuracy
"The speed improvements over manual operating machines is just huge," says ERL’s Wilkins. "And you can’t believe how precise and accurate these machines really are – and repeatable, too. We can hold tenths of thousandths of an inch tolerance – and that’s part-to-part even!"
Wilkins says the only thing ERL does on a non-CNC machine is make prototypes. He wouldn’t even dream of running production on a product unless he did it on a CNC. "We’re going to run our production on a CNC or we’re not going to be competitive. And we’re not a high volume shop at all," he states.
Like many shops heavily involved in a niche market, ERL has less variability in its production runs because it only machines certain Honda engines. ERL uses elaborate fixtures to lock the engines and heads into position for machining very quickly.
"If you haven’t had a CNC you may think it’s normal to do long set ups and changes to get the part into position to begin machining. With a CNC, it’s time you can’t afford to be down because the equipment is so expensive. You’ll want to keep the CNC in production as much as possible to take advantage of its strong points," says Wilkins.
Because of ERL’s fixtures, it can run a Honda B16 and then right behind it run a Honda H22 without any changes to the set up. This is because the programs are already loaded in the CNC and all that has to be done is to select the proper program for the corresponding engine.
"We already know what tools are in the tool holder; they’ve been written into the program. So we can easily run two different engines back-to-back and have it work just as fast as if it were the same engine because the program is there and the tools are there," Wilkins explains. He says his two-man shop is capable of cranking out 8 engines a day utilizing his CNC machining centers. All together ERL has three Haas CNCs, three Sheldons and four vertical machine centers; plus, a few CNC controlled lathes and crank grinders, too.
There’s no question that on the manufacturing side a CNC is a must have piece of equipment. "The CNC machining center for our manufacturing side of the business has definitely taken us to another level," says SIC’s Schaefer. "We’re producing parts the industry needs at a reasonable price. And we couldn’t have made it economically viable any other way."
Schaefer still does all his align boring and honing work on manual machines. But adding the CNC for manufacturing purposes and profiling pistons has added a new facet to his company. "I’m pretty certain that to justify owning a CNC several things have to happen: you have to be in some sort of niche market; you have to make/sell a large enough volume; and you have to be in a niche that is free of foreign competition. This is because if you make a part that’s made by many manufacturers and there is a lot of competition, a foreign company will likely make it for much cheaper, and it’ll put you right out of business."
Although Schaefer says his manufacturing needs justified the decision to purchase a CNC, not all engine builders feel that a CNC is a necessity for their shop.
"The way I look at it right now is that it would be about a $1,200 a month pet for me, says Westech’s Brandes. "Not that I wouldn’t make a go of working with it and all. But it takes up a lot of additional time to learn and to work into your workflow. It isn’t a situation for me where I’m going to buy one to save my business. It’s really no different than owning a flow bench or a dyno. You have to grow into it."
The high cost of a full-blown CNC machining center is difficult for the average automotive machine shop to justify unless there is a real need. If you’re a production engine remanufacturer (PER) or you’re a CER that does a lot of the same engines, a CNC can be a big advantage. You can use it to do many repetitive tasks, and hold near perfect tolerances, which are some of its greatest strengths. Additionally, you will be able to reduce labor costs because the machines virtually run themselves.
With a CNC the sky is the limit. Yes, there are hurdles to overcome, but what you can gain with a CNC cannot be matched by any other machine tool.
From Model to Metal: Programming a Typical Part
Todd Bastian, Production Manager for Alan Johnson Engineering, a manufacturer of cylinder heads and other performance parts, is the company’s primary CNC programmer. "The process typically begins when Alan sketches out the geometry for a new design in ESPRIT (a CAD/CAM program from DP Technology)," Bastian says. "Then he shoots the file over to me and I am responsible for finishing up the detailed design. When I have finished the design, I may ask Alan to visit me at my workstation while I rotate, pan and zoom the model to make sure that it matches his concept. Once we have agreed that the model is correct, I specify the tools to be used and the cutting feeds and speeds. In most cases, this is simply a matter of opening the appropriate technology page that defines the standard tools and the most common machining parameters for that particular machine. Standard tools are used whenever possible but custom tools are also available as a menu selection.
"For a typical cylinder head," Bastian says, "I begin with a 3D roughing cycle using either a flat-end or ball-nose end mill. I usually go through several cycles of roughing and semifinishing with successively smaller tools. I reduce the scallop height on each pass to the point that the next tool won’t be overloaded. This takes a lot less time than you might expect because of the fact that the technology pages define each tool and the machining parameters. Then I define semi-finishing, taking advantage of optimized math algorithms in the software that reduce the time required for 3D tool path calculations. The final step is cleaning the corners of the workpiece, in which I take advantage of unique capabilities of the software to isolate and machine just the horizontal surfaces. Then, I simulate the machining operations on the screen to ensure that the final results will be exactly what we have defined. Within an hour or two we are ready produce the part."