VFDs Speed Production, Ease Maintenance for RMG/FELM Wire Processing Customers

Rockford Manufacturing Group/Fastener Engineers Lewis Machine (RMG/FELM), is one of the nation’s leading designers and manufacturers of wire processing equipment and systems.

Customers employ RMG/FELM equipment to fabricate metal wire rods for use in applications ranging from wire shelving systems to concrete reinforcing rods.

The company’s advanced straightening and cutting machines consist of five sections:

• The Feed Roll
• The Straightening Arbor
• The Cutter Mechanism
• The Extension Assembly, a track and wire support system that supports the wire prior to cutting
• The Release Assembly, a device that activates the cutter when the wire reaches a preset length

AC Drives Deliver Customer Benefits
Incorporation of AC variable frequency drive (VFD) technology into three of the process segments has permitted RMG/FELM to develop a coordinated straightening and cutting system delivering the following customer benefits:

• Significant production increases
• Substantial maintenance savings
• Fully adjustable speed control
• Simplified adjustments
• Quiet operation

These benefits combine to significantly lower machine operating costs, allowing customer to realize a faster payback when justifying new machinery, according to Mike Kern, RMG/FELM Project Engineer.

Additionally, incorporation of the drives has allowed RMG/FELM to eliminate many costly and troublesome interconnecting transmission components, according to Kern.  This improved machine efficiency means that more power is available to produce work -- straighten wire -- while less heat is generated, Kern said.

The drives also provide real-time operator feedback, according to  Kern.  “On our RMG/FELM Model 28, which utilizes the Yaskawa F7 AC Drive, we remote mount the drive display or keypads on the operators control station, so that the operator can view the drive’s actual speed and current. This is very useful in copying or correcting setups and in detecting tooling or machine wear.”

AC Drive Eliminates Feed Roll
In the RMG/FELM Feed Roll section, wire stock is drawn in from a turntable, unwinding unit or from an inline wire drawer and undergoes the first phase of straightening in preparation for processing.

For example, on the RMG/FELM Model 16  Straightening and Cutting Machine, this is accomplished in dual four-roll feedheads powered by two 1.5 hp AC motors.  Speed is controlled by a single 3 hp Yaskawa V7 AC Drive.

This electronic gearing allows the two feed units to act as one while eliminating the power transmission components that had tied these units together in the past.

In this section, the drive’s ability to provide electronic speed control eliminates the need for mechanical variable speed transmissions and hydrostatic drives formerly used in feed roll applications -- along with the transmission maintenance and oil and filter replacement formerly required.

Additionally, the VFD permits easy reversing of the motor in the event of a jam or to make machine adjustments, according to Kern.  The drive is also used to jog feed stock forward and back -- providing a big assist in the threading process.

RMG/FELM Single-Offset Arbor
The Arbor Section accomplishes the final straightening of the wire to prepare it for processing in the cutting section.

The ability of the VFD to match the speed of the straightening arbor, helps maintain a consistent feed-to-straightening ratio,  which is critical to the quality of the final product, according to Kern.  At the same time, acceleration and deceleration speed ramps, along with DC injection braking, provide uniformly controlled starts and stops.

On the RMG/FELM Model 16, the state-of-the-art single-offset arbor utilizes a 10hp AC motor and a Yaskawa Model V7 Drive with custom software for DC injection braking, which allows  the arbor to be stopped quickly for safety reasons and to eliminate “burn off’ of the wire.

Exclusive “Clutchless Cutter”
Historically, cutting sections have required a clutch assembly to develop sufficient torque to accomplish the cutting operation.

These clutch assemblies were expensive and required significant maintenance.  Additionally, a flywheel was often required to provide smooth cuts and to aid in torque generation.

RMG/FELM engineers, however, are utilizing VFDs to replace the clutch assembly formerly required.  This patented “clutchless cutter” technology increases production levels by as much as 30 percent, while eliminating numerous moving parts and significantly reducing maintenance expenses, according to Kern.

Demanding Requirements
Requirements in the Cutter Section are demanding.  Sufficient torque must be generated in a single rotation of the motor for the knife to cut through steel wire stock up to 3/8” diameter.

To accomplish this, the motor must accelerate to full operating speed from a complete stop in only .1 second.  It must then switch instantly from full operating speed to “stop” after the cut is made and hold the blade in position within a few degrees of where it originally started.

This is accomplished through application of a Yaskawa F7 AC Drive to the 3hp motor to provide VFD control of the cutter shaft in a manner that permits up to three cuts per second.

Meeting Customer Production Requirements
Through the application of variable speed drive technology, Rockford Manufac-turing Group/Fastener Engineers is able to offer its customers straightening and cutting systems which deliver superior performance and production, coupled with reduced maintenance.

These are machines that are matched to our customers’ needs,” said Kern.  “They deliver significant production increases, fully adjustable speed control, and substantial reductions in maintenance.”

Technical Papers - VFD Basics