Medical part manufacturing continues to grow at a healthy pace, and projections are for the global market for medical device outsourcing to reach $40.8 billion this year. Lately there have been increasing opportunities to bid on medical part micro-machining jobs, but your shop is having a tough time winning against the competition. The micro-tools just aren’t turning fast enough to get to that price-per-piece sweet spot and win the job.
If money is no object, invest in a new machine, perhaps a dedicated micro-cutter. What do you do if you don’t have a massive capital expenditure plan?
One suggestion is to adapt what’s already in the shop and use an auxiliary spindle attachment, often referred to as a speeder. Speeders use planetary gears interfaced with the machine’s main spindle amplify rotational motion, often multiplying existing speeds up to 6x. However, speeders can push a machine’s main spindle beyond its wear limits when running at or near maximum revolutions per minute (rpm) for extended periods of time. The resulting thermal expansion can destroy gears and bearings as extra speed generates extra friction. This, in turn, requires more frequent replacement and machine downtime. Speeder use can also induce problems with vibration, tool life, and runout.
While those are options often heard, NSK America’s Michael Shea, product sales manager – industrial; and Greg Nottoli, senior product manager, suggest another solution – auxiliary electric spindles that excel in handling the small features and intricate work of micro-machining.
“When we’re talking about micro-machining, it’s really any tool under 1/8", and more frequently, the end mills, drills, etc., that machinists are using have diameters all the way down to 0.005", so high rpm is necessary for this precision work,” Shea says. “This is where NSK high-speed electric spindles are designed to perform.”
Unlike speeders that require existing gears, wearing them down prematurely, NSK high speed electric spindles feature an integrated motor and spindle, so there are no gears to wear out.
“People are more aware of spindle speeders and often they think they can only achieve the required rpms using this gear-driven tool,” Nottoli says, “NSK offers the HES series of integral motor electric spindles that take away abuse of the machine spindle and the need for gears, removing heat and vibration issues. Machinists using speeders are getting more speed, but by adding in issues of heat and vibration, there are issues with tool life, speeder longevity, and runout.”
Speed without wear
When added to machining centers, NSK’s HES series of spindles – HES510 and HES810 – enable high-speed micro-machining, milling, and small-diameter drilling with improved accuracy, surface finish, and tool life, and less machine abuse. And they are quiet, with some users noting they can’t even hear it running.
“Our high-speed electric spindles interface with BT, CAT, NT, and HSK tool holders, so compatibility is no issue,” Shea notes. “Tool speeds can be increased in 1,000rpm increments up to the spindle’s maximum – HES510 to 50,000 rpm, HES810 to 80,000rpm.”
It should be noted the HES510 is also available in an R8 shank, while the HES810 is compatible with 32mm straight shanks.
And it’s simple to use.
“The HES inserts into the spindle just like a toolholder. The operator connects the electrical cord and air hose – required for cooling the ceramic bearings and delivering air purge to keep chips and contaminants out – and they are set to run,” Nottoli explains. “We are delivering the speed they need, in an easy-to-use system that increases tool life and surface finish while resting the machine’s main spindle. It typically takes less than a minute to hook up the spindle and be ready to run.”
The main spindle must be switched off prior to use. An emergency breakaway connector prevents damage if the machine spindle is switched back on by accident. Design of the completely self-contained high-speed spindle eliminates gears, removing the risk of heat buildup, so it’s able to run at higher speeds for longer periods.
Helping protect cutting tools, the system also has a load meter on the unit’s control box that uses green, yellow, and red lights to determine when parameters require adjustment. If the load becomes too great, the system can automatically shut off the spindle and report back to the CNC control.
Micro-milling applications require small cutting tools run at high rpm to minimize tool breakage and maximize machine quality.
“Micro-machining means small features and tight tolerances,” Shea says. “High spindle speed reduces the chip load which reduces the forces between the tool and the material. High-speed/low-force machining yields less heat, reduces tool deflection, and allows machining of thinner walled workpieces.”
Nottoli agrees, adding that “All this results in cooler machining, superior surface quality, and better accuracy. A micro-tool needs a high rpm value to realize both efficient cutting speed and productive metal removal rate. This is where HES510 and HES810 high speed electric spindles show what they can deliver.”