Your shop owns many thousands of dollars worth of machining equipment, but if the newest one is more than a dozen years old, is it still up to the task for the jobs today?
Looking back on some of Engine Builder’s past articles on surfacing equipment, one thing you’ll notice is that the OEMs have decreased tolerances and surface finish profiles, but some machine shops that service these engines may have been lagging behind in the machine tool department.
However, equipment manufacturers are continually looking for ways to help you turn a more significant profit by simplifying the processes. Instead of doing everything by hand, for example, multipurpose CNC machine centers can do the job of several machines (and people), almost automatically.
Most equipment manufacturers will be the first to tell you that decades old surfacing machines won’t cut it with today’s more complex engine technology. An older machine, for example, may not hold tight enough tolerances needed to achieve really low surface finishes on late-model production and performance engines. After many years of use (and sometimes abuse), these machines wear out and start to lose the rigidity in the fixture, have free play in the table ways, cutter head or spindle. These issues can stack up quickly, allowing too much tolerance for a quality shop to stand behind.
With racing engines, smoother finishes are critical to squeezing out the last bit of horsepower. Even NASCAR engines are running MLS gaskets today, and they typically run a surface finish in the single digits! Surfacing equipment must be extremely rigid to produce an ultra-smooth finish for racing and other high-end applications. If your current machine can’t get below 60 RA, you may need to upgrade, regardless of the type of engines you work on.
Gasket makers say the head gasket is the most critical seal in the engine. The head gasket must hold the cylinder pressure generated during combustion, plus handle high-pressure oil and hot engine coolant without any leaks. To withstand high temperatures and casting movement, the head gasket has to hold a seal. Many variables contribute to both the horizontal and vertical motion that occurs between the cylinder head and engine block. However, even the best head gasket can’t seal a surface that is improperly prepared.
The block and cylinder head must be inspected and resurfaced to the proper spec before installing a new head gasket. A surface that is too smooth can cause the gasket to slip and leak. However, if the surface is too rough, the gasket may not conform to surface imperfections and could also leak. Surface finishes can be checked using a digital profilometer, which most machine shops should have in their arsenal of tools by now.
A stand-alone surfacing machine may be a good choice for larger shops that do a lot of head work and milling jobs. However, many shops are condensing their footprint with multipurpose machines that will mill as well as bore. A 5-axis CNC machine center can do all of this and make fixtures and other tooling to do more jobs. You can port cylinder heads and line bore on the same machine!
Boring and honing are some of the most common jobs performed in a machine shop. The equipment needs to hold up to rigorous use. While boring operations can be performed on multipurpose CNC machines or vertical CNCs, most shops have a dedicated honing machine because the final finish is that critical. The latest honing machines are much more automated and precise compared to older equipment.
Manual machines are available from some manufacturers and can be a very viable option for some smaller shops. For shops working closer to the cutting edge (no pun intended), there are higher performance automated machines that you can practically turn on and walk away, but the price tags are much higher as you might expect.
There are boring machines to fit every engine bore size so look for one that best fits your needs. If you primarily build smaller engines then a machine capable of boring a diesel engine may not be the best choice for you. Many of the automated boring machines have programmable boring and an automatic centering features, which helps speed the workflow.
The latest boring equipment uses air-float boring bars that float across the ways and centers itself over the cylinders. Many old-style boring bars bolted down to the deck of the block and were portable. New machines use indexable cutter bits instead of brazed-on cutter bits. Today’s machines are better designed and made with better materials so they will run circles around an older machines most of the time.
If you use a portable boring bar it is best to pair it with a stand and an air-float system. It is not recommended to mount a portable bar to the deck of an engine block with thin-wall casting because it could cause bore distortion.
Multi-purpose machines are being used in many shops today because they take up less space and you get a piece of equipment that is very flexible for any job that comes in the door. Many smaller shops don’t really need the speed they need precision and flexibility.
Honing improves the bore geometry and surface finish. It smooths the rough edges down to the optimum level for oil retention and ring load. Some machines use a type of spindle that allows you to control the stroke speed and hone head speed separately. Honing machines that use a pneumatic stroke can be spongy and leave an inconsistent finish. Base level honing machines, without the bells and whistles, have many of the same features as high-end machines, minus the automation, and can be a good choice for smaller shops. Whereas automated honing machines with computerized screens that show where you are in the honing process and that automatically dwell if necessary may be a good investment for a large or low-volume high-performance shops.
And don’t forget about the abrasives. Diamond abrasives last longer than conventional cutters and bore more consistently for the life of the tool. But final plateau hone will be necessary to remove the folded edges and debris left over from the diamonds.
Surfacing equipment today can be as computerized or as basic as you want. The high-end equipment is much more automated and precise than the machines from 30 years ago; however, some shops won’t need all of these features.
Machines are available for surfacing everything from the largest locomotive components to the smallest landscaping equipment. For the most part, the market is demanding automated equipment for specialty and performance applications, so if you want to move your shop up a notch or two above the competition, now’s a good time to step up. ν