PRF Servo Feeds

Waddington Electronics has delivered industrial control systems and, specifically, computer-driven servo systems to the machine tool and metal stamping industries for over 44 years.

Experience

We have experience with all types of electric, hydraulic, air and electronic servo systems and have implemented them across a variety of applications.

Milestones

Some milestones along the way include: A 16-spindle deep-hole drilling machine that makes transmission shafts for Chevrolet, 5-axis CNC deep-hole drilling machines for making transmission parts for the NATO tank, 3-axis CNC gear-cutting machinery for cutting gears as large as 72 inches in diameter, and a 5-axis CNC gear hobber that, at the time, had never been produced in the United States.

Design

The design of the PRF series of servo-driven roll feeds is based on the cumulative knowledge and experience gained in our 44-year history.

Feed body design is based on a heavy-duty feed frame that is dowel-pinned after alignment, adding strength to the frame and preventing the frame from ever going out of alignment. All bearings are ball type and require no lubrication.

Very low inertia feed rolls and a variety of zero backlash power train designs allow proper selection of feed power and speed characteristics to match the most demanding applications. The brushless servo system allows for extremely high indexing rates; and, zero backlash between the motor and the feed rolls allows very high servo system gain, resulting in exceptional stock positioning accuracy.

Zero Backlash Drive Train

The ZERO BACKLASH direct-coupled drive train approach of the In Line machines has proven itself in hundreds of applications and is free of the shortcoming's which plague servo systems that include gears in the drive train. Gear sets must have some backlash when factory new and only get worse as they wear.

The Belt Driven drive train of the SF, LD, LC, and HD Series feeds offers increased pulling power and a compact overall design, and unlike other feeds we experience no loss of accuracy due to drive train error because the resolver feedback is mounted to the rolls not the back of the motor.

Zero Maintenance

The zero maintenance philosophy applied to all Waddington feeds dictates the use of high reliability brushless motors, tachometers, and position feed- back devices. Additionally, the high mechanical shock encountered in the punch press environment mandates the use of only the most rugged feedback devices.

High-performance Brushless Servo motors eliminate the problems associated with brush arcing and commutator wear during the high rates of acceleration required for press feeding. Brushless design is what makes PRF motors truly maintenance-free. Brush-type motor manufacturers recommend changing brushes after every 5,000-10,000 hours of use, even under the best conditions. Commutators must be repaired or replaced from time to time, and sometimes the entire armature has to be replaced.

Optimum efficiency of the servo system is not obtained by sacrificing positioning performance with the inherent inaccuracy of gear reduction, but by the proper selection of motor characteristics and feed body style.

Position Feedback Devices

Position feedback devices are perhaps the single most important device in the servo system. Optical type encoders were originally chosen for position feedback because of cost and accuracy factors, but were quickly eliminated because the delicate glass disk and critical optical alignments were easily damaged by the shock generated during the punching process. In some applications where the motor is run close to its capacity, the temperature of the encoder can approach 100 degrees Centigrade. Because of the digital nature of the signals coming from the encoder they are sensitive to electrical noise, and thus have limitations on cable length.

Brushless Resolver

Of the many types of position feed-back devices available, none are as noise-, shock-, and contamination-resistant as the brushless resolver. Long used by the military in ship fire control and gun turret positioning systems, the resolver is well proven in high shock and contamination environments. Also, resolvers are less susceptible to electrical noise and lead length requirements.

A quick survey of die protection and electronic cam vendors who manufacture punch press control systems reveals that, in fact, none of them use encoders, due the inherent weakness of this approach when applied to punch press applications.

Anti-backlash Gears

All Waddington feeding machines have anti-backlash gears between the top and bottom rolls. This approach greatly increases stock gripping force and prevents stock slippage during acceleration and deceleration of the feed rolls. Also, the anti-backlash feature of the PRF gear set allows consistent accuracy across the full thickness rating of the feed.

Variety of Pilot Release Options

One of the most important aspects in feeding progressive dies is the need to release the feed rolls during the piloting portion of the press stroke. We offer a variety of pilot release options including our striker bar, high-speed air, belt-driven cam and super-speed servo-driven release mechanisms. Our high-speed air pilot release can operate up to 300 spm on some models and generally up to 250 strokes per minute on all models. The servo-driven pilot release operates up to 1800 spm.

Flexibility for Changing Needs

PRF Feeds come with preprogrammed acceleration rates that cover a variety of applications. To remain flexible in the face of changing customer needs, acceleration rates can be changed in the field to meet those needs, ensuring the feed you buy today will meet the needs of tomorrow.

Warranty

Waddington Electronics stands confident in our ability to deliver the highest quality roll feeds on the market and we back all our roll feed products with a