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CNC Machining Advantages

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Who Is Using CNC?
It’s hard to come up with an exact number of automotive machine shops that are using CNC equipment. One CNC equipment manufacturer estimated that probably one out of five top quality shops are using CNC. Another said the number might be as high as 50 percent. But for smaller mom and pop custom shops, you might find CNC in may one out of every 25 or 30 shops.

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. After that, the general purpose CNC machining center that can bore and surface heads and blocks is high on the “must have” list for many shops.

The biggest stumbling block to adopting CNC is its cost. The price of the equipment varies greatly with its capabilities, with many CNC machines costing several hundred thousand dollars up to a million dollars or more for industrial high volume production equipment. Figure on spending at least six figures for some type of 5-axis CNC equipment and the tooling that comes with it. By comparison, you can purchase a Bridgeport mill with CNC controls for under $25,000, but such a machine won’t have the capabilities of a multi-purpose CNC machining center.

CNC Retrofits
What about retrofitting older manual equipment to CNC?  A number of companies have CNC retrofit kits that can be installed on existing machines to automate their operation. The cost of some of these CNC retrofit kits can be as low as $5,000 for upgrading an older Bridgeport machine – if you do the installation yourself, which they say isn’t that difficult. They even have online videos that show you the step-by-step retrofit process.

Others feel more comfortable having a local distributor/ installer to do the CNC retrofit. Either way, retrofitting an existing machine or a used machine is much less expensive than buying new equipment. A CNC retrofit can add features an older manual machine never had, like the ability to digitize the profile of a work piece, and to automatically control tool zeroing and positioning. It can also automate what used to be a manual process to free up the operator’s time so he can perform other tasks in the shop.

Others say retrofitting older equipment to CNC may not be the best way to spend your money. It may be a step up from manually operated equipment, but it’s never the same as new CNC equipment. If you want all of the advantages of CNC machining, then buy new equipment that was designed to be CNC controlled from the start. Most CNC equipment has precision ball screws and better antifriction materials on the ways, along with liner ball ways for more accurate machining.

Some CNC machines even come with a webcam, Wi-Fi and software that allows a service technician to log onto your machine remotely via a phone connection to help you troubleshoot a problem. So if improved accuracy, speed and capability are important, new CNC equipment will give you more bang for your buck than a simple CNC retrofit.

Custom Work
One of the main benefits of 5-axis CNC is that it gives you total control over the movement of the tooling and the workpiece.  Once you have created a digital model of a surface (which many machines can do for you with a digitizing probe), you can easily modify or customize the profile of almost any work piece as needed. That’s one of the main reasons why CNC has become an absolute must for high performance head porting.

It’s very difficult and time-consuming to replicate a given port profile with a die grinder by hand with a high degree of consistency.  CNC duplicates the port profile exactly whether it is one cylinder head or a hundred cylinder heads. And if you need to tweak the port profile a bit for a slightly different engine application, it’s a simple matter of entering the new data and letting the CNC machine do the rest.

Shopping For CNC Equipment
If you are considering a CNC machine purchase but aren’t sure what to buy, talk to the various equipment suppliers to find out what kind of CNC machines and tooling packages they have and what type of equipment best suits your needs.  Do you really need a more expensive 5-axis CNC machine, or will a 3-axis or 4-axis CNC machine provide the capabilities you need for particular set of tasks.

Ask the equipment suppliers about the potential Return On Investment (ROI) their CNC machines are capable of achieving by boosting productivity and accuracy.  Do the numbers make sense for your business and the type of machine work you are doing now or want to do in the future?  Most shops can’t afford to buy an expensive toy.  They need a productive piece of equipment that will make them money from the get go.

One CNC supplier we interviewed said engine block work probably offers the best profit potential for CNC machining today because 5-axis high performance head porting is so competitive. There are lot of people porting heads with CNC equipment, but not as many who are doing blocks.

Some suppliers also offer a “try before you buy” opportunity to test out their CNC equipment in your own shop for 30 or 60 days.  This type of offer is usually only extended to shops that already have CNC equipment or experience rather than first-time buyers.  Better to find out a certain machine is or isn’t right for your business before you sign on the dotted line.

One supplier said you should look for a CNC machine that provide the most functionality and accuracy that you can afford.  A relatively basic 3-axis or 4-axis CNC machine that fits your immediate needs now may not have the features or capabilities that would allow you to expand your business later on.

Installation
The equipment supplier from whom you buy your CNC machine (or their local distributor) will usually handle the installation and initial setup of the equipment. One thing that should always be checked is your power supply. You want relatively “clean” power with no noise or erratic changes in the frequency or voltage as this may cause problems with the functioning of the computer controls. The power supply to the CNC machine should be on its own electrical circuit. CNC control software is updatable and usually downloadable from the equipment supplier. 


The following companies responded to requests for input to this article:

Centroid CNC
www.centroidperformanceracing.com

Okuma America Corp.
www.okuma.com/americas

Mazak Corp.
www.mazakusa.com

RMC Engine Rebuilding Equipment
www.rmcengine.com

Rottler Manufacturing Co.
www.rottlermfg.com