Walter's "smear milling" relies on high cutting speeds and feedrates to eliminate the "salt and pepper" porosity that plagues aluminum engine components.Click image to enlargeby Kip Hanson

Competing in today’s automotive market requires high performance tooling

Maybe you don’t mill engine blocks or turn crankshafts. That doesn’t mean the cutting tools used to produce these and other automotive components are of no value to the average shop. Quite the contrary, the technology spillover from Canada’s auto industry favourably impacts manufacturers of all sizes. High tech carbide grades, advanced cutting tool coatings, ingenious insert geometries–these are just a few of the tooling advancements that, properly applied, can make the difference between robust business growth and simply “staying afloat.” 

 

Stair Stepping
One of these technologies is burr-free machining. By vertically staggering the inserts on one of its face milling cutters, Sandvik Coromant engineers were able to produce a tool that leaves virtually no burr on abrasive aluminum cylinder heads, increasing tool life and production output in the process. According to milling products and application specialist Brian MacNeil, the M5B90 superfinishing tool was first developed for the European market and has only recently been introduced to North America, but its design is now being leveraged for a wide array of spin-off tools.  

Sandvik Coromant’s M5C90 face mill in action machining the deck face of an aluminum engine block.Click image to enlarge“The M5B90 tool uses PCD inserts so is suitable for any kind of aluminum, not just the alloys used in automotive,” he says. “Because of the radial and axial positioning of the inserts within the cutter body, it works similar to a rotary broach, able to handle heavier cuts than many traditional face mills but with the last insert acting as a wiper, removing the last 50 microns or so of material to generate a very smooth, burr-free surface.”

Sandvik Coromant has taken this successful face mill design and run with it. By adding a series of roughing inserts along the tool’s periphery, engineers developed the M5C90 combo tool, a “direct finishing” solution that eliminates potential problems when material is encountered unexpectedly during a finishing pass, which could possibly destroy the tool. Similarly, the M5F90 Nano direct finisher is intended for smaller part features, and uses a brazed tip disposable cutter design, while the M5Q90 is designed for high volume “cubing” operations on cast aluminum components.  

Aside from higher rates of metal removal and the potential for reduced roughing and semi-finishing operations, these solutions save time in the tool crib as well. Since each insert is ground to a tolerance of 10 microns (0.0004 in.), they cut effectively right out of the box–there’s no need for manual adjustments as with some face mill designs. “I worked with a customer recently that was spending two hours on a presetter dialing in their old face mill,” MacNeil says. “Instead of individually setting 28 separate cartridges, the M5C90 has 10 roughing and 5 finishing inserts. You just screw them into the pockets and go. It’s a big timesaver.”

 

Smear Milling
The push for tools that support fewer operations isn’t unique to Sandvik Coromant. Walter USA LLC application engineer John Jansen was recently tasked with optimizing the production of bi-metal, 5.3 liter V-8 engine blocks containing CGI (compacted graphite iron) cylinder liners surrounded by cast aluminum. 

“As you can imagine, the problem here is that the cast iron likes to chip away when the cutter hits it,” he says. “Then the chips are either pushed into the softer aluminum or dragged across the surface, scratching it. I had good results with one of our F2010 eight-flute face mills equipped with CBN inserts, but a lot of it came down to using the right tool path. I found that by dropping down and semi-finishing the liners first, I could come back with a couple of light cleanup passes and get a nice, repeatable finish.”

Jansen says CGI is challenging enough even without the surrounding aluminum. He’s conducted numerous tests, machining more than 1,700 kg (3,800 lb) of test plates so far this year. He’s found that solid CBN is the hands down winner in terms of tool life and throughput, not only in milling applications but also holemaking, where B4212 indexable insert drills were used to drill nearly 5,000 linear mm (196 in.) of test holes. 

Jansen also participated in tests with so-called smear milling, which eliminates the use of up-sharp PCD cutters in favour of a Walter V650 300 mm (12 in.) diameter shoulder mill. By running the tool at surface speeds of 4,000 m/min (13,000 sfm) and a feedrate of 16.8 m/min (660 ipm), the “salt and pepper” porosity plaguing its customer’s cast aluminum engine blocks was almost completely eliminated, and resulted in a metal removal rate 2,143 mm³/min (130 cubic in./min). 

 

Use of advanced high strength steel alloys have made turbocharger components a challenging automotive application area that suppliers like Iscar are addressing with technologies such as the Helido HD line of inserts. Image: Iscar MetalsClick image to enlargeAutomotive-ated
Walter and Sandvik Coromant each offer their own suite of such automotive-oriented cutting tools, many of which might be successfully applied by shops machining cast iron, aluminum, and alloy steels in general purpose applications. So too does Iscar. Automotive industry manager Oleg Eliezer says much of the activity in this area comes as a result of vehicle lightweighting of everything from car bumpers to suspension components. Engines especially are being asked to output more horsepower using less fuel, a goal that typically calls for high strength materials such as CGI and heat-resistant steels. One good example of this is the austenitic alloy used in turbocharger housings, which often must perform at temperatures up to 1100° C (2012° F) and cannot be machined cost-effectively with conventional cutting tools. 

Iscar has responded to this challenge with its MS32 grade of CVD coated carbide. According to Eliezer, MS32 provides an excellent balance between hardness, toughness, and abrasion resistance, making it suitable for both rough and finish milling in dry, wet and even MQL (minimum quantity lubrication) machining environments. And like its competitors, Iscar is seeing broad use of PCBN inserts among engine manufacturers, who must contend not only with CGI and similarly tough grades of iron, but are faced with machining hard thermal spray materials such as CBC (cylinder bore coatings) applied directly to aluminum engine blocks as a replacement for traditional liners. 

Many additional examples exist. Iscar has developed special TriDeep drills for holemaking operations in sintered metal camshafts, as well as new geometries of Grip  inserts for turning and grooving friction-welded steel pistons. Sandvik Coromant is now offering one-shot boring tools that can rough and finish piston bores in a single pass, and be adjusted for wear on the fly. Walter’s line of Titex X·treme are used for oil hole galleries in crankshafts and off-centre holes on crankshafts. Any or all of these might perform superbly in a job shop environment, making the message here a simple one: just because it says “automotive” in the catalog or web page doesn’t mean you should discount it for use with aerospace, medical, or energy component machining. SMT

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