Fill ’er up

Sept. 1, 2003
Coupling absorbs vibration to keep auger on schedule.

Auger systems using direct drive servomotors for blending and filling food pouches and packages are an improvement over stepper motor and traditional clutch/brake systems, resulting in increased speed, repeatable filling accuracy, and reduced system maintenance.

Operating at up to 120 fills/min, these new servodriven systems, when equipped with Zero-Max CD couplings, are able to fill dry products with repeatable accuracy into one pouch or package. The rapid start/stop augering motion is smoothed out by the coupling, so there is no undesirable resonance or vibration during operation. These high-speed filling cycles are programmed to fill accurately to specified weights within a gram, eliminating expensive product giveaway.

Spee-Dee Packaging Machinery Inc. is the innovator of these servo-driven augering systems. Designed for integration into a complete filling line, the auger is mounted vertically in the form/seal system, taking up much less floor space than horizontal systems. The vertical design with 10- and 16-gal feeding hoppers on top also facilitate the high-speed fill cycles within the line.

“We tried other couplings when using stepper motors in our systems years ago,” reports Timm Johnson, vice president of sales/marketing for Spee-Dee. “None was rigid enough; when tested, the couplings developed resonance problems. So we went to the CD couplings on all our servomotors. They gave us the torque rigidity we needed.”

Smooth operation of the augering system is critical to achieve the highest fill rates with repeatable accuracy. These are governed by ingredient consistency and flow, diameter and length of the auger, and the speed at which the auger turns, controlling the torque or pressure and governing food ingredient flow into a pouch or package.

“In designing these auger systems, we carefully calculate desired fill rates for specific ingredients and package sizes, which dictate auger diameter and length and other important variables such as motor requirements. All these systems are designed to operate at top speed without problems so they can perform 24/7 with as little downtime and maintenance as possible. The coupling dampens any tendency of vibration or resonance, which can throw off or interrupt the filling cycles,” says Johnson.

Ideal for this type of servomotor application, the CD coupling has many of the best features of other coupling designs with one notable exception — its patented composite disc pack. While the CD coupling transmits torque similar to any conventional coupling, the composite disc pack does a better job of dampening backlash and shock without the coupling fatiguing, which can occur in a fast-moving system with high cycle rates.

The coupling has a unique open-arm disc design made of highly durable composite disc material. This design absorbs and cushions any tendency for vibration or resonance from the servomotor’s intermittent motion. The motors are Bosch Rexroth servos, 2 kW, 0 to 1,400 rpm. Connecting directly to the servomotor shaft at one end, the CD coupling connects on the other end to a self-aligning ball bearing attached to a middle support plate. The bearing assembly connects to the auger. One auger is employed per filling line. There are single, twin, quad, and as many as 10 dual auger setups designed by Spee- Dee Packaging.

Operating torque for each auger varies depending on the consistency of the ingredients, their volume, and the size of the auger tooling, which ranges from 5 in. to 5 ft. According to Johnson, these systems accelerate from 0 to a maximum 1,400 rpm, with the coupling capable of handling top torque loads of 3,785 in.-lb.

Another benefit Spee-Dee experienced with the coupling was that it allowed for use of a single-flex, single-disc model. These are less costly and do the work of most other double-disc designs. Aligning the coupling in the setup is easy, requiring no special alignment tools, according to Johnson. The clampstyle hub model allows for fast installation by tightening only one screw on each hub of the coupling.

“We’ve had no problems with backlash or vibration using the CD couplings,” reports Johnson. “We’ve been using them for more than four years with several hundred in the field.”

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