Any belt or chain drive can transmit motion or power, but it takes a solid metal belt to serve as a conveyor of material, sorter of parts and synchronizer while operating efficiently in harsh environments, temperature extremes and in environments both caustic or corrosive.
Metal belts have been used in commercial applications for more than 30 years. From their beginnings in the space program, the applications for solid metal belts range from small, lightweight units used in precision machinery, to large, steel conveyor belts found in chocolate and food processing, material processing, warehouses, and package sorting facilities.
Metal belts are fabricated from materials often considered inflexible, such as high-grade stainless steel or carbon steel. As such, the belts have unique properties unavailable with more conventional belt materials. Some of the benefits include:
- A high strength-to-weight ratio. Belts of high tensile strength alloys have low mass and inertia. This allows using more of the input horsepower to move product--not the production line--to increase efficiency and reduce operating expense.
- Dimensional stability. Metal belts remain accurate because they do not stretch. Particularly important in precision conveying applications, such as sorting houses, metal belts can easily indicate where product is on a conveyor.
- Easily cleaned. Solid metal belts are inert, non-absorbent and suitable for corrosive environments. Organic acids and detergents do not affect stainless steel belts. Nor do the sharp edges of scraping blades or knives damage them. They feature a long service life, with a sanitary coefficient similar to that of glass or enamel. They comply with the most stringent sanitary requirements.
- Extreme temperature operation. Solid metal belts perform well at 1,100o F in ovens, as well as at -50o F in freezers.
- High electrical and thermal conductivity. Special alloys provide desired heat transfer, electrical conductance or magnetic properties. Material can be maintained on the conveyor at a known temperature, improving the quality and consistency of the finished product.
Metal belts are often used as friction drive belts. Generally speaking, straight power transmission is more easily accomplished with traditional drives, such as chain or V-belts. However, the properties of solid metal belts can be applied in more critical applications.
Some casting applications use a plain solid metal belt--often carbon steel or stainless steel--as the forming base for material being cast. If the surface characteristics need to be modified, coatings such as urethane can be added, which increase the belt's coefficient of friction. Teflon( coatings in a wide range of harness and temperature ratings can increase the belt's release characteristics.
In the chocolate industry, metal belt conveyor lines commonly link mixers, refiners and conches. The belts do not absorb odors or tastes, and there is no risk of flavor cross-contamination.
Laminating applications use metal belts in two ways: with one belt as a base platen holding a single material, or with two belts positioned face-to-face and the laminate material between them. The electrostatic discharge properties of metal belts enhance their utility in laminating applications.
The metallizing industry uses the belts as masking mediums to create package windows, cutoff lines and other custom features of the metallized components of packaging films.
A magnetized carbon-steel belt removes steel chips from the sump in a machine tool. A scraping blade can then remove the chips from the belt surface.
Mail order facilities, media distributors and package distribution centers use automated sorting systems with coded information stored magnetically on a carbon steel belt, which triggers gates or pushers to remove a single item from the belt at a precise location.
Conveyor-accumulators exploit the smooth surface of a solid metal belt. Such systems depend on the strength of the solid belt for conveying, and the low coefficient of friction on the belt's surface allows it to slip easily underneath the product being conveyed and accumulated. This increases the productivity of packaging applications because product can continue being manufactured upstream, even if downstream equipment is off-line.
In addition to endless metal belts, a metal drive tape can be used for reciprocal motion, such as that seen in a robotic arm. Drive tapes usually feature fittings at either end so that they can be secured to the motor and arm assembly. Their low mass and high strength offer durability, quick acceleration and stopping, and near zero backlash.
Perforated metal belts
Perforations can enhance the performance of a metal belt. A range of perforations, from specifically sized holes at fixed locations along the belt, to random "open area" patterns, are common in product dryer systems. Virtually any shape can be cut into the metal belt surface, offering unique tooling nests, which can be co-located with vacuum pressure from beneath the belt to hold parts in place. Applications typically use small perforations to pass steam or liquid through the belt to the material being processed. The use of perforated belts in commercial baking plants reduces energy consumption, resulting in less maintenance, easier cleaning and improvement of total product economy.
A popular misconception is that a solid metal belt is too large, heavy or bulky to maintain easily. Several termination schemes, however, enable the easy use, installation and maintenance of metal belts.
By far, the strongest belt connector is a solid, high-energy beam weld. Most belts are manufactured as endless loops, with the weld in place before installation.