Cling’s Aerospace has discovered the right toolholder-retention knob is crucial in properly seating a tapered toolholder in its spindle.
High-speed machining (in excess of 20,000rpm) is often used in aerospace when machining exotic alloys and hard metals such as titanium.
At these speeds, precise and secure seating of tapered toolholders in the spindle becomes even more critical. So much so, that failing to pay attention to this single detail can lead to decreased productivity, less precise machining, reduced tool life, and damaged workpieces.
Often overlooked, even ignored, are poorly designed retention knobs that – when tightened – create a bulge in the small end of the taper that prevents full contact and proper seating in the spindle.
Despite widespread evidence of uneven wear patterns and simple touch-off tests that immediately identify it as a widespread issue, the industry has largely ignored this aspect of machining and, unwittingly, are paying a price for it.
The flaw in the systemShanks of tapered toolholders are ground to a fine finish within very precise, established tolerances, and are also threaded at the narrow end to accept a retention knob. The knob engages 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-$30 part – when tightened, create a bulge in the taper that prevents proper seating in the spindle. Once this expansion occurs, the toolholder will not pull fully into the spindle and so cannot contact upward of 70% of its surface.
The results are manifest 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, run-out, and shallow depths of cuts.
“A lot of aerospace work is really tight tolerance,” says Rex Ausbun at Cling’s Aerospace, a Tempe, Arizona-based company that specializes in complex 4- and 5-axis precision-machined parts. “When you see chatter or vibration, you know there is an issue with the toolholder.”
According to Ausbun, who is responsible for purchasing all the inserts, tools, and other machining accessories for Cling’s Aerospace, “with a tapered toolholder, you want to marry it as tight as possible to the spindle to get as much contact across the entire taper as possible. That way, you are not just hitting at the top of the angle.”
Retention knobs accomplish this; however, Ausbun says that newer CNC milling machines exert significantly more drawbar pressure on the knobs than in the past. This is compounded by the fact that most retention knob manufacturers provide little information on the proper torque required, a factor that can lead to the improper seating already described.
“As CNC machines drawbar tension continues to increase, it puts so much pressure on the weakest link, the retention knob, that it’s bound to come apart. It’s a significant issue, because if the retention knob comes apart while the machine is running, it could cause considerable damage.” Ausbun notes, “You are talking spindles that cost $10,000 to $14,000 a piece, not to mention the downtime. That’s a lot of money.”
High-torque retention knobsTo find a solution, Ausbun discovered JM Performance Products Inc. (JMPP) searching online. In 2009, the company introduced its High Torque retention knob. Invented by the company’s 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 to reach deeper into the threaded bore of the toolholder. As a result, all thread engagement occurs on 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 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.
“When you start checking out different manufacturers as to what they recommend for torque specs on the retention knobs, everyone seems to have a different opinion,” Ausbun says. “I thought it was pretty impressive that [JMPP] went the extra mile and put a lot of research into determining the ideal torque.”
Tool lifeBy increasing toolholder rigidity at higher rpms, the High Torque retention knob can also increase tool life.
Aerospace manufacturing can take a toll on the carbide cutting tools used when machining exotic alloys and hard metals, so cutting tools must be changed more frequently as they dull or break.
“In aerospace, every shop is trying to machine parts faster and aggressively remove more stock, just to stay competitive,” Ausbun says. “This just puts more pressure on the tool.”
With higher-end technical carbide inserts, the cost of tool replacement and lost production time due to frequent changeover can add up quickly.
“Since we changed to the High Torque Retention Knobs, we are not going through inserts like we used to, and we haven’t had any more issues with retention knobs pulling apart,” Ausbun adds. “I’m also not seeing any distortion in the toolholder taper either.”
Try a touch-off testFor those that are not entirely convinced that improper seating of tapered toolholders is even a problem, JMPP suggests a simple 6-step touch-off test. More sophisticated measurement of toolholder expansion (bulge) can also be taken using a taper shank test fixture.
Cutting tool manufacturer Emuge Corp. and OPEN MIND Technologies USA, developer of hyperMILL CAM software, are holding a complimentary Lunch and Learn Workshop on Advanced Strategies for 5-Axis Milling at Emuge North American corporate headquarters and Technology Center, 1800 Century Drive, West Boylston, MA, on June 12, 2019, from 10:00am to 1:00pm. Manufacturing professionals are welcome and encouraged to attend. Registration is limited – click here to register and for more event details.
Emuge and OPEN MIND experts will present strategies on how to reduce cycle times up to 90% and improve surface finishes and tool life by leveraging the latest end mills and CAM software to maximize 5-axis machining. Attendees will have short overviews on the latest cutting tools and software innovations, in addition to live custom milling demonstrations on a Hermle C 42 5-axis mill-turn machining center. Attendees will see a bladed component machined to learn first-hand how Emuge’s Circle Segment End Mills (also known as conical barrel cutters), together with OPEN MIND hyperMILL MAXX Machining performance package, can offer productivity gains when roughing and finishing. A catered lunch will be offered, and a Q&A session will conclude the event.
“Our collaboration with OPEN MIND to develop Circle Segment machining has enabled dramatic productivity improvements for challenging applications, such as in aerospace. We are pleased to demonstrate this leading cutting tool and CAM software solution at the event,” said Bob Hellinger, Emuge Corp. president.
“The Lunch and Learn Workshop is an excellent opportunity for attendees to consult with OPEN MIND and Emuge experts to solve their toughest aerospace milling challenges,” said Alan Levine, managing director of OPEN MIND Technologies USA Inc.
U.S. Navy funding covers modernization of 10 aircraft; option for FY20 would cover up to 35 aircraft.
Boeing Defense, Space & Security has received a one-year contract, which also includes a one-year option for 2020, to continue modernizing the U.S. Navy’s F/A-18 fleet under the Service Life Modification (SLM) program. The $164 million contract for FY19 funds the standup of a second SLM line in San Antonio, Texas, complementary to the line established last year in St. Louis.
“The Service Life Modification program is making great strides as we’ve already inducted seven Super Hornets into the program and will deliver the first jet back to the Navy later this year,” said Dave Sallenbach, program director. “This program is crucial in helping the Navy with its readiness challenges and will continue to grow each year with the number of jets we induct.”
The San Antonio SLM line is scheduled to receive its first Super Hornet in June, and a total of 23 Super Hornets during this contract. The U.S. Navy fleet consists of more than 550 Super Hornets.
In the early 2020s, Boeing is scheduled to begin installing initial updates to the aircraft that will convert existing Block II Super Hornets to a Block III configuration that will include enhanced network capability, longer range with conformal fuel tanks, an advanced cockpit system, signature improvements, and an enhanced communication system.
Attend this free webinar Wed., Jun 19, 2019 2:00pm – 3:00pm EDT, presented by VERICUT Product Specialist Pete Haas.
There is tremendous pressure on machined parts suppliers to deliver more for less, and always on time. Physics-based feed rate optimization enables shops to spend minimal time preparing highly optimized toolpaths that run smoother and deliver big savings at the machine. Feed rate optimization software determines the maximum reliable feed rate for cutting conditions encountered (in simulation) and calculates feed rates to remove material under ideal conditions. In addition to reducing machining times, machined surface quality and tool life are also improved. Using feed rate optimization software that is independent of your CAM system(s) provides the ability to optimize new and existing or legacy NC programs, so they all cut as efficiently as if they were created by a machining expert.
• Discover how feed rate optimization software speeds machining and creates a more efficient manufacturing environment
• Learn what every machine tool and cutting tool manufacturer wants you to know – how to use their products optimally
• Learn how this software can be a great benefit to all NC programmers (experienced, novice, or in between)
• Hear how major aerospace companies use this technology to make better parts faster, even those made from hard or difficult-to-machine materials.
Pete has been with CGTech since 2017 and has more than 36 years of manufacturing experience that includes a diverse background in the aerospace, defense, and consumer packaged goods industries. He has a passion for optimizing product development processes with a focus on CNC machining and improving ROI. He spent 20 years as a tool designer, CNC programmer, CNC manager, engineering manager and general manager in manufacturing job shops. Prior to joining CGTech, Pete was a Senior CNC Specialist at TaylorMade Golf, and Director of CAM & Tooling and Director of R&D at Callaway Golf.
Memorial Day, originally called Decoration Day, is a day of remembrance for those who have died in service of the United States of America.
More than two dozen cities and towns claim to be the birthplace of Memorial Day. While Waterloo, New York, was officially declared the birthplace of Memorial Day by President Lyndon Johnson in May 1966, it’s difficult to prove conclusively the origins of the day.
Regardless of the exact date or location of its origins, one thing is clear – Memorial Day was borne out of the Civil War and a desire to honor our dead. It was officially proclaimed on 5 May 1868 by General John Logan, national commander of the Grand Army of the Republic, in his General Order No. 11. “The 30th of May, 1868, is designated for the purpose of strewing with flowers, or otherwise decorating the graves of comrades who died in defense of their country during the late rebellion, and whose bodies now lie in almost every city, village and hamlet churchyard in the land,” he proclaimed. The date of Decoration Day, as he called it, was chosen because it wasn’t the anniversary of any particular battle.
On the first Decoration Day, General James Garfield made a speech at Arlington National Cemetery, and 5,000 participants decorated the graves of the 20,000 Union and Confederate soldiers buried there.
The first state to officially recognize the holiday was New York in 1873. By 1890 it was recognized by all of the northern states. The South refused to acknowledge the day, honoring their dead on separate days until after World War I (when the holiday changed from honoring just those who died fighting in the Civil War to honoring Americans who died fighting in any war).
It is now observed in almost every state on the last Monday in May with Congressional passage of the National Holiday Act of 1971 (P.L. 90 – 363). This helped ensure a three day weekend for Federal holidays, though several southern states have an additional separate day for honoring the Confederate war dead: January 19th in Texas; April 26th in Alabama, Florida, Georgia, and Mississippi; May 10th in South Carolina; and June 3rd (Jefferson Davis’ birthday) in Louisiana and Tennessee.
Red poppiesIn 1915, inspired by the poem “In Flanders Fields,” Moina Michael replied with her own poem:
‘We cherish too, the Poppy redThat grows on fields where valor led,It seems to signal to the skiesThat blood of heroes never dies.’
She then conceived of an idea to wear red poppies on Memorial day in honor of those who died serving the nation during war. She was the first to wear one, and sold poppies to her friends and co-workers with the money going to benefit servicemen in need. Later a Madam Guerin from France was visiting the United States and learned of this new custom started by Ms. Michael. When she returned to France she made artificial red poppies to raise money for war orphaned children and widowed women. This tradition spread to other countries. In 1921, the Franco-American Children’s League sold poppies nationally to benefit war orphans of France and Belgium. The League disbanded a year later and Madam Guerin approached the VFW for help.
Shortly before Memorial Day in 1922, the VFW became the first veterans’ organization to nationally sell poppies. Two years later their “Buddy” Poppy program was selling artificial poppies made by disabled veterans. In 1948 the US Post Office honored Ms. Michael for her role in founding the National Poppy movement by issuing a red 3 cent postage stamp with her likeness on it.
National moment of remembranceThe “National Moment of Remembrance” resolution was passed in Dec. 2000, which asks that at 3 p.m. local time, for all Americans “To voluntarily and informally observe in their own way a Moment of remembrance and respect, pausing from whatever they are doing for a moment of silence or listening to ‘Taps.”
Post time: Jun-24-2019