Jeff Eliott :
An opinion piece from an industry expert that looks at how automotive tier suppliers are increasing capacity by addressing a commonly overlooked flaw in machining
Jeff Eliott :
Automotive Tier Suppliers Increase Capacity 15% without the CapEx
Tier suppliers are increasing capacity by addressing a flaw in toolholder-retention knob design to satisfy reserve capacity requirements of OEMs
Out of concern for potential production disruptions and unexpected fluctuations in demand, OEMs and Tier 1 automotive suppliers prefer sourcing business from lower-tier suppliers that can demonstrate reserve machining capacity. In an effort to meet these requirements, lower-tier suppliers often have no alternative but to invest hundreds of thousands of dollars for additional machining centers and tooling.
However, what if a much smaller investment – infinitesimal even in relation to the interest financing such equipment – could yield an increase in milling capacity across the boards by 15-20%?
While this might sound like it belongs in the category of “too good to be true,” tier suppliers that machine parts can significantly increase cycle times and increase capacity by resolving one of the most fundamental and longstanding problems in machining: improper seating of the toolholder in the spindle.
This small fact robs machining operations of valuable time, affects tolerances and precision, shortens tool and spindle life and even increases power consumption.
Yet despite widespread evidence of uneven wear patterns and simple “touch-off” tests that immediately identify it as an issue, the industry has largely ignored this aspect of machining and, unwittingly, are paying a significant price for it.
Productivity Gains – an Executive Level Decision
“In my role as an executive, anything that reduced costs or improved efficiency got my attention,” says Joe DaRosa, former president at Toyota Manufacturing of Texas.
According to DaRosa, who continues to serve as an advisor to the industry, improper seating of tapered toolholders in the spindle is often overlooked as a factor in the performance and efficiency of CNC milling equipment.
“Companies purchase top-of-the-line machining centers for a half a million dollars or more and buy the most expensive cutting tools, yet they completely ignore the interface between them: the toolholder and the retention knob,” says DaRosa, adding that the purchasing decision for these items often comes down to the lowest priced options, including overseas.
So, when he first learned about an inexpensive fix to a machining problem that even by conservative estimates could increase productivity 15% and tool life even more, he was immediately intrigued.
“If you’re an executive, you’re going to look at this [solution] and see reduced costs and increased productivity; If you are machining operator you will see increased tool life and less frequency of changeover,” adds DaRosa.
DaRosa is referring to a flaw in the design and utilization of retention knobs in tapered toolholders secured by drawbars, such as the popular V-flange, that date back to the original designs first introduced decades ago.
The flaw in the system
Although the shank of tapered toolholders is ground to a fine finish to fit in the spindle within very precise, established tolerances, those that utilize drawbars are also threaded at the narrow end to accept a retention knob. The knob is designed to engage with the drawbar, which exerts a pull force that holds the toolholder firmly in the spindle.
The problem is poorly designed, traditional retention knobs – a less than $20 part – when tightened create a bulge in the taper that prevents full contact and proper seating in the spindle. Once this expansion occurs, the toolholder will not pull fully into the spindle and so cannot make contact with upwards of 70% of its surface.
Perhaps because the shank and spindle are so carefully machined or because the industry has utilized retention knobs on tapered products for decades, this issue has largely been overlooked.
However, the results are manifested in a wide range of CNC milling issues often attributed to other causes: vibration and chatter, poor tolerances, non- repeatability, poor finishes, shortened tool life, excessive spindle wear and tear, run-out, and shallow depths of cuts.
High Torque retention knobs
There are solutions on the market today that address this design flaw. In 2009, JM Performance Products, Inc. (JMPP) introduced its High Torque retention knob. Invented by the company’ founder, John Stoneback, the product works with all existing toolholders including BT, DIN, ISO, and CAT toolholders from 30 taper to 60 taper.
The High Torque retention knob is longer, by design, to reach deeper into the threaded bore of the toolholder. As a result, all thread engagement occurs in a region of the toolholder where there is a thicker cross-section of material to resist deformation.
It also includes a precision pilot to increase rigidity, and is balanced by design. Since even over-tightening of the High Torque retention knobs can still create a bulge, the company provides specifically calculated torque specs based on drawbar pressure.
By combining the High Torque retention knob with the correct torque, spindle contact with the taper is improved to close to 100% every time. This can be verified by simple 6-step “touch off” test (www.jmperformanceproducts.com/toolholder-test.aspx). More sophisticated measurement of toolholder expansion (bulge) can also be taken using a taper shank test fixture.
The solution can even provide V-flange toolholders with the rigidity and concentricity necessary for high speed machining of titanium, aluminum and other metals/alloys without having to turn to HSK or Capto tooling systems that are 2-3 times more expensive.
Eliminating tooling errors
For Dan Carlstrom of Carlstrom Associates, a manufacturer’s rep organization that sells toolholders, milling products and workholding systems, the “light bulb” moment came when he recommended the High Torque retention knob to a customer that was struggling with a boring product he had sold them.
“The customer was having a problem holding size on an aerospace component, so they had to take multiple boring passes and then do a final reaming pass to get this hole to size,” explains Carlstrom. “When they put the High Torque retention knob on the toolholder, the boring tool was able to cut the hole to size, in tolerance, in one pass.”
“They never gave me total cost savings, but needless to say it was significant. It also solved a huge headache for them,” adds Carlstrom.
Carlstrom, who emphasizes that his company does not represent or sell JMPP’s High Torque retention knobs, says whenever he runs a test of his product for a customer he does so with the knob installed to eliminate poor seating in the spindle as a variable that could affect performance.
“When I run an end mill test, a toolholder test, or a boring bar test, I will not run it without the High Torque retention knob, period,” says Carlstrom. “I know it will make my tools, which I get paid for, run properly.”
The ROI in increased capacity
In addition to increasing reserve capacity demanded by OEMs without the capital expenditure for additional machining centers, the increase in productivity as well as decreased tooling costs and set up times can increase revenues that more than justify the cost of High Torque retention knobs.
Although the product costs nominally more than a traditional retention knob, at a conservative 10% increase in capacity, the ROI can be as little as 3 weeks. At a 20% increase, the ROI can be achieved in a week or less.
Furthermore, automotive tier suppliers running 24/7 or having to add extra shifts to meet production demands could scale back, if so desired.
With so much to gain, experts like DaRosa say the issue is simply lack of awareness.
Although automotive manufacturers are already benefitting from implementing the High Torque retention knobs, many consider it a competitive edge so keep the information close to the vest. Others remain unaware – even dismissive – that improper seating of tapered toolholders in the spindle is even a problem that has far reaching effects on machining.
“My entire career, we always looked at cost, not price,” says DaRosa. “So when you get my attention with something that can increase productivity, my direction to procurement is to take a close look at it and not just based on price.”
For more detailed information contact JM Performance Products, Inc., 1234 High Street
Fairport Harbor, OH, 44077; visit www.jmperformanceproducts.com; call (440) 357-1234; email firstname.lastname@example.org.