CONTROL DESIGN Innovator Awards 2006

Hole Control Drills
Down Cycle Time

IT NEVER hurts to ask what’s possible, especially when you can get two innovations at once. So, while drilling holes at 2,200 rpm, slightly melting the surrounding metal, and tapping in bolts that don’t need back nuts is good. Combining several machines and automating this entire process is better.

That’s what engineers at Tubular Products Co. in Birmingham, Ala., thought when they ran across Flow Drill’s technology on the web and at a tradeshow. Craig Armstrong, Tubular’s engineering manager, says his company knew Flow Drill could help it build frames for electric vehicles, such as golf carts, but Tubular also wanted to consolidate several steps in its framing process. As a result, Tubular enlisted Advanced Machine Automation (AMA) to design and build its combined machine. AMA is a system integrator and turnkey design/build company.

Tubular previously used seven separate machines to drill 35-40 holes in the eight pieces of tubing it needs to build its frames. “It used to take five or six separate processes to drill the holes in our frames, but our automated Flow Drill puts all of them into one machine,” says Craig Armstrong, Tubular’s engineering manager. “This dramatically reduced our cycle time by 75-80% from 5-6 minutes per frame to 45 seconds. This means we get all the business because we can pass these savings on to our customers.”

To understand how these huge improvements were achieved, it helps to know how Flow Drill works and how AMA automated it. Flow Drill traditionally is used on standalone, manually operated machinery to drill .021 in. to 2.500 in. diameter holes, in which thin-walled steel, aluminum, or copper tubing is tapped to provide 120% stronger pull-test mountings without backing nuts. Flow Drill’s carbide bits turn the material into a glowing, plastic state, and then 300 lbs of pressure is used to push it into the tube, creating a tappable hole three times longer than the material’s thickness. Most former automated Flow Drill operations had been accomplished with ball screws, servomotors, and drives.

“However, we found that hydraulics hold position more rigidly than ball screws, which can wear and loose their rigidity. Previous electronic and servo technologies wouldn’t hold position either, so we had to use clamps, or build some equipment with bigger, more expensive CNCs,” says Keith DeMonia, AMA’s general and engineering manager. “Hydraulic controls also allow operators to type in value changes, and put in offsets to change position without requiring an act of Congress.”  

Because faster drilling requires more immobility, AMA automates Flow Drill’s usual operations by using hydraulic cylinders with Temposonic’s linear transducers for position feedback, which is fed to Delta Computer’s RMC75-D08 controller. This controller also operates an Atos proportional valve to position the part or sometimes the spindle unit to ± 0.001 in., and hold position during operation, while a Suhner spindle unit running at 2,200 rpm does the actual drilling. The part then moves to a tapping position where Suhner’s automatic tapping head is used. AMA reports its hydraulic solution is about three-quarters as costly as previous methods, and its ± 0.001 in. location offers an acceptable positioning tolerance, even after adding the cost of the hydraulic unit.

 “Now, instead of shipping frame with holes, we’re producing completed parts,” says DeMonia. “So, instead of requiring customers to put these frames in a jig and put in RIV nuts, they can send these frames straight to assembly, and use their own self-tapping screws. This saves an entire production step.”

AMA reports the key to its operation is to tune the controller properly, so there will be absolutely no oscillation or vibration during the cycle. This would instantly shatter Flow Drill’s bit. Used properly, one Flow Drill used on an AMA automated machine will typically produce 8,000-10,000 holes before having to be replaced.

“The reason we need a motion controller is because proportional valves must be constantly readjusted. This is because the part being drilled has forces acting on it, such as the bit touching it and trying to move it, and so the valve has to react quickly enough, and move to apply more pressure or fluid,” says DeMonia. “A typical PLC is too slow to do this because it has to do a program scan, scan for the control, and then say ‘do your stuff’ to the controller. Our Delta motion controller operates more autonomously, and basically says to the system ‘we’re there and in position’ in 0.01 sec. Because it just controls position and doesn’t need a program scan, the controller’s scan time is a lot faster than a PLC.”

Because good ideas lead to even newer ones, DeMonia adds AMA’s automated Flow Drill is already being used to prevent leaks by providing better joints in HVAC unit frames. In addition, AMA just installed this same Delta, Atos, and Tempsonic combination to reducing the time it takes to cut and chamfer hot water heater cores from 5.7 sec to 3.7 sec.