Big-name automakers, heavy vehicle/truck manufacturers, as well as those producing marine craft, are all under pressure to develop engines that are more fuel-efficient and expel less harmful emissions. And most often, engine designers achieve these stringent efficiency goals using an emissions reduction technique known as Exhaust Gas Recirculation or EGR.
EGR involves reducing emissions by manipulating how fuel is injected into engines. And while the technique is quite effective, it has had a significant impact on the design of certain engine components, mainly those cast from aluminum. As a result, heavy vehicle engine component castings have become much more challenging to produce, not only because of complicated shapes for EGR purposes, but also due to the fact that multiple components once separate and mounted to engines are often combined into one big extremely intricate casting.
As heavy vehicle engine component castings grow increasingly complex and unique in their designs, efficiently processing them requires equally sophisticated machine tool technology - a fact that Ward Corp. in Fort Wayne, Indiana, knows all too well.
Ward, founded by Vern and Marion Ward in 1964, began from a foundry pattern shop that grew and added its own foundry. Initially, the company's largest customer was General Motors, but Ward soon took on work from other major vehicle makers such as Harley Davidson and Cummins Inc., designing and pouring aluminum castings. At that time though, Ward wasn't machining its castings for customers.
In 1985, Ward's relationship with Cummins strengthened considerably. And it was then when Cummins requested that Ward also machine the castings, a development that lead to Ward becoming the vertically integrated company it currently is.
Today, with Pattern & Engineering, Casting, Heat Treating and Production Machining divisions, Ward is a full service aluminum castings provider and manufactures over 100 unique part numbers for Cummins alone, with quantities for those numbers ranging from 50 to 100,000 pieces per year. And its list of customers has multiplied to also include Chrysler/Dodge, Dana Holding Corp., Allison Transmission Inc., Navistar Inc., Eaton Corp., Mercury Marine and others involved in the manufacture of heavy vehicles and diesel engines.
For all its customers combined, Ward's production output runs from 50 to 100 different part numbers per month, and quantities vary from 50 to more than 150,000 pieces per year for those numbers. And over 60% of all castings produced require machining done in Ward's Machining Division that is equipped with 15 CNC machine tools, about half of which are from Mazak Corporation and acquired through and supported by Mazak distributor Shelton Machinery in Fishers, Indiana.
Ward's Mazaks include three HORIZONTAL CENTER NEXUS 6800-II Machining Centers, a VARIAXIS 630-5X 5-axis Vertical Machining Center, a HORIZONTAL CENTER NEXUS 5000 Machining Center, two VERTICAL CENTER NEXUS 510C-II Vertical Machining Centers, and a VERTICAL TRAVELLING COLUMN 200C. The company also has Mazak's QUICK TURN NEXUS 250 and 300 model Turning Centers along with a Multi-Tasking INTEGREX 200-II SY.
The bulk of the engine component castings Ward processes on its Mazaks are complex pipes, manifolds and air-intake connections for diesel engines, those used in heavy vehicles/trucks and marine craft. Pipes - either air, fuel or other liquid related - are core castings that involve turning, drilling and tapping operations, while manifolds and air-intake connections that are even more complex require full 5-axis machining.
"Many of our engine component castings are complex and specialized, that a lot of other shops wouldn't even attempt," said Tim Atkins, a vice president at Ward Corp. "Adding to the challenge is the fact that many of our castings are poured from 356 alloyed aluminum that then get heat treated to Brinell hardnesses of 80 - 100, which adds another variable to the machining process."
He pointed out that the Machine Division's toughest part, to date, is a Cummins casting that is a combination of three previously separate casted components. This intricate, extremely tight-toleranced casting is machined in multiple operations done on two Mazaks, the HORIZONTAL CENTER NEXUS 6800-II and VARIAXIS 630-5X. Total machining time for this casting approaches one hour, while machining times for the shop's other castings typically average around five minutes.
"Like all our castings, these complex parts for Cummins have to be machined to the highest quality and done as quickly as possible, so we need consistently fast, reliable and precise machine tools," said Atkins. "When we add machine capacity, it's often driven by new work, and we brought in our third HORIZONTAL CENTER NEXUS 6800-II specifically for the Cummins casting."
Ward's HORIZONTAL CENTER NEXUS 6800-IIs and its HORIZONTAL CENTER NEXUS 5000 are basically dedicated to two part numbers, one of which is the complex aluminum casting for Cummins. Equipped with 1,000-psi high-pressure coolant systems for extended tool life and standard two-pallet systems, the machines frequently run 24/7 at Ward.
Featuring a 10,000-rpm, 50 hp integral motor spindle, the HORIZONTAL CENTER NEXUS 6800-II delivers a rapid feed rate of 2,362 ipm at 0.8G acceleration for quick starts and contouring. Its pallets measure 24.80" x 24.80" and easily handle Ward's larger size castings, while the company's HORIZONTAL CENTER NEXUS 5000 with pallet size of 19.68" x 19.68" delivers spindle speeds up to 18,000 rpm with 47 hp.
The Cummins castings are machined on all six sides and involve compound angles and deep, tight toleranced bores. The HORIZONTAL CENTER NEXUS 6800-II does the majority of operations first, and the VARIAXIS 630-5X finishes the castings. But if needed, Ward will run the castings complete on the VARIAXIS 630-5X.
Ward's VARIAXIS 630-5X, with a tilting/rotary table and pallet size of 24.80" x 19.69", gives the company multiple-surface, full 5-axis simultaneous machining capability. The high-precision machine quickly and easily handles the most difficult castings with its spindle speed of 12,000 rpm and 30 hp and offers continuous operation with its optional 80-tool capacity.
Chris Thierry, a Ward Machining Division supervisor, said the Mazak machines are very precise and consistently hold the shop's part tolerances that can range from 0.05 mm to 0.25 mm. But most importantly he indicated that they provide the speed and power the shop needs.
"Our castings require everything from high-rpm face cutting to high-torque roughing, so we use the Mazaks to their full capabilities," said Thierry. "We do a lot of metal removal, and often we will machine over 10 lbs of material from a casting. Plus, surface finishes are critical on all the castings we produce, and the Mazak HORIZONTAL CENTER NEXUS 6800-II and the VARIAXIS-5X easily allow us to exceed the 3.2 Ra surface finishes that are required."
Ward uses limited automation, but instead optimizes casting production operations with the standard two-pallet changers on the HCN 6800-II and VARIAXIS-5X - running the same part number on both pallets or a different job on each. The shop also increases casting output by utilizing as much machine tool table space as possible - fixturing the individual tables of its two VERTICAL CENTER NEXUS 510C-II machines and the table on the VERTICAL TRAVELING COLUMN 200C machine for either multiple different part numbers or for the sequential operations of one part number.
On the VERTICAL CENTER NEXUS 510 C-II for example, Ward sequentially completes the three operations of diesel engine pipe castings that will advance from one fixture to the next on the machine's table. As parts move out of fixture one and into number two, a new part is loaded into fixture one, and parts coming out of fixture three are complete. And because the machine is so accurate, Ward is able to machine the ends of pipe O.D.s using an end mill and circular interpolation to avoid having to transfer the parts to a turning machine for that operation.
The table on the VERTICAL CENTER NEXUS 510C-II measures 21.65" wide and 51.18" long and accommodates part loads up to 2,640 lbs. The machine's 1,417 ipm rapid traverse speed in X, Y, Z allows Ward to quickly move from one part operation to the next.
When it comes to the Mazak VERTICAL TRAVELING COLUMN 200C machine, Ward often loads its table with two different casting part numbers, such as diesel engine valve cover castings and engine pipe castings. The machine's 20" wide, 79" long stationary table features a partition that allows for uninterrupted machining with a 12,000 rpm, 25 hp spindle at one end while operators safely load or unload parts at the other end.
"Our goal is to always fixture parts as few times as possible for the most amount of operations, getting as much of a part done with the least number of machines involved," said Atkins. "But sometimes, schedules will drive part flow, and if we're busy, it can be more advantageous to switch parts from one machine that's needed for a rush job to another machine that's not as booked."
"We are very flexible when it comes to how and on what machines we process parts. The Mazaks give us that flexibility - in table size and machining capabilities. And all of them are equally precise and fast."
One of the Mazak machines he said has provided extreme amounts of processing flexibility is the shop's Multi-Tasking INTEGREX 200-II SY. As the company's first Mazak, the machine allows Ward to process certain parts, such as air connector castings, in single setups, using hand-off part-transfer operations with the machine's twin spindles. Castings are milled and drilled and come off the machine complete.
According to Atkins, Ward has been utilizing multi-tasking machine technology for over 10 years and was one of the first Northern United States shops to purchase a Mazak INTEGREX. "At the time, we needed turning capabilities, but when we saw the INTEGREX 200-II SY with its Y-axis capability, second spindle and optional tooling capacity of 40 tools, we realized that multi-tasking could easily apply to several of our other castings for further improving throughput," he explained.
While most of Wards machine tools are organized as standalone systems, the shop does have two cells, one of which consists of its Mazak QUICK TURN NEXUS 250 and 300. A cell that pumps out the thousands and thousands of smaller size diesel engine pipe castings Ward produces. Pipe ends get turned in the Mazak machines, then drilled and tapped. Both the QUICK TURN NEXUS 250 and 300 models give Ward 10" chuck sizes and maximum machining diameter capabilities of 13.78" and 16.54", respectively. Main spindle speed for the two machines are 4,000 rpm with a maximum torque of 321 ft-lbs for the QUICK TURN NEXUS 250 and 596 ft-lb for the QUICK TURN NEXUS 300.
Atkins said that the castings they process on their Mazak machines will continue to become more complex, spurring the need for even more advanced machines from Mazak.
"We're expecting the day when one of our customers asks us to cast an entire engine, with all its components, as one big casting, then want us to machine it," commented Atkins.
Whether or not such a casting request ever comes in, Ward plans to expand and further diversify, maybe into different materials and markets. But Atkins noted that the company is well entrenched in the niche market of aluminum cast parts.
"It's our specialty, and manufacturers know that and will come to us," he said. "And to meet those demands, we will continue to rely on the advanced machining capability and increased productivity the Mazak machines provide and on the service and support we get from Shelton Machinery."
Challenges Of Machining Aluminum Castings
At Ward Corp., machining aluminum castings is challenging not only due to the increasing complexity of casting designs, but also because of the wide assortment of variables that come into play. The main one is porosity caused by non-consistent solidification during the casting process.
Porosity leads to aluminum casting defects that, unfortunately, are not usually found until the machining stage of processing components. Ward does employ the latest in X-raying equipment and other such equipment to test all its castings prior to machining, but some aluminum casting defects are so slight that they are undetectable until cutting into the casting.
"Our challenge is to produce defect-free castings all the time," said Tim Atkins of Ward Corp. "But when machining uncovers certain defects we will try to salvage the casting. However, most often the casting is scrap and is melted down and recycled. And while we continuously strive for a zero PPM, the variables of aluminum castings make it practically impossible, but we are currently well under a 500 PPM.
In addition to porosity, castings are often heat treated to either increase their hardness or ductility, both of which create machining challenges. When a casting is more ductile, it's softer and can gum up drills and taps. For these softer castings, Ward depends heavily on the high-pressure coolant systems of its Mazak machines to prevent the problem.
Chris Thierry, of Ward Corp., said that machine speeds and feeds must also be closely watched when machining aluminum castings. He explained that excessive speeds and feeds can generate tool chatter, which transfers to machined surfaces and produces poor finish quality. Or if the speeds and feeds are too fast, they can cause parts to flex.