September 2008 Edition

Vertical Machining Centers

It Takes a Flexible Attitude to Find Rigidity

Using a VMC’s rigidity to gain large work paid off for a shop that was flexible enough to invest in a new machine

Before Mark Bamberg closes the doors of his Silicon Valley job shop for the night, one of his machining centers begins cutting 760 little housings out of 60"×30" plate-stock. Later, in the night, the eight-hour cycle is finished. If a tool should break, a load sensor detects the problem and the tool changer is instructed to retrieve a tool for a different operation. The machine skips the prior part since it may include a broken tool or have some other type of damage.

The next day, Bamberg’s company, MJB Precision, Campbell, CA, may be setting up 46" OD titanium satellite aperture-filter rings on the same machining center. Or, it could be hoisting a 2,700 lb machine base onto the bed. These are the types of applications where the 40-taper, 10,000 rpm high-torque spindle shows its stuff, hogging material and changing tools with optimized chip-to-chip time. Profiling is accomplished with 1.25" OD roughing end mills, at 200 to 250 ipm or more. Several hours later, the job is done. Rigidity-enhancing machine features, such as box ways, are critical because the part is heavy, and so are the cuts.

MJB is able to do this type of work with the use of its VMC 6535 from MAG Fadal, Chatsworth, CA.

"Most of my competition can do a part the size of your hand, but not everybody can do a part the size of your desk. Our high-torque machine has a big enough work envelope to give us that versatility," Bamberg said. "We can take the side doors off and handle a part up to 14' before we hit the shop wall. We can make heavy cuts and maintain a good finish – more so than with a linear guide machine."

Consistency Breeds Loyalty

MJB has been a Fadal shop since it opened in 1995 with a used Fadal 4020.

"All of our machines performed well and have good value, starting with our first machine, still running today," Bamberg said.

He said that it’s the size range of his seven machining centers that positions his company where he wants it. MJB’s customer base includes manufacturers in the defense, aerospace, machine tool, semi-conductor, and medical device industries. MAG Fadal vertical machining centers currently operated by MJB include a 3016, 3020, 4020, and 6030, as well as the high-torque 6535.

Jobs range from parts for military ground support equipment and satellite devices, to components for laser-cutting machines. The semi-conductor work runs the gamut, according to Bamberg. Batch size is from hundreds or thousands of production pieces to one-off machine bases and prototype work. Value-added manufacturing engineering and part programming is another advantage.

"We are also certified Mil-45208-A. Not many shops in the valley have that," Bamberg said. Certification from the annually-renewed audit helps MJB win defense work, and is a credential that is a competitive advantage when selling its services to any industry.

Faster Cutting Speeds Equal Profitability

"The profitability factor is what sold us on the Fadal 6535. It’s a cost-effective machine that keeps us competitive in the marketplace, and its box-way design gives us the productivity and accuracy we need," Bamberg said. "Repeatability is right around 0.0002". The thermally-controlled ball screws – Fadal’s Cool Power – keeps everything stabilized when we go from cool mornings to hot afternoons here."

Double-mounted extra-large 63mm ball screws also help to ensure accurate positioning.

MJB can profitably cut machine bases on the 6535 that weren’t feasible on its smaller machine. The rigidity of the 6535, with its wider columns, saddle and base, and the fast spindle increases cutting speeds 10 to 30 percent compared to its previous machine.

"The material removal rate improvement with the high-torque machines is radical. You can see the role of rigidity, when you’re cutting fast, in the part finishes," Bamberg said. "We can machine the tough exotics, too – Inconel, covar, monel, and high-nickel stuff – for our defense and medical device customers. Many job shops won’t touch these materials."

Virtually all machining program preparation is done off-line by two full-time programmers at MJB, with frequent use of DNC drip feeding of data to the Fadal machine controls.

"My whole crew, on the shop floor and in the office, are a huge asset to this business. Our machine operators average five to 10 years of experience each, and they’re a hard-working group of guys," Bamberg said. "The Fadal machines have been the other major part of our success. The old cliché is that you have to spend nine dollars to make one dollar. It’s true, but when you focus on getting the most machining capability for the money, then you’re creating the best situation for making money." MAG Fadal

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