weight

To weight something in manufacturing means to add mass to an object in order to alter its physical properties, balance, or performance characteristics. This is a deliberate operation, not an accidental loading. A machinist might weight a rotating shaft to correct imbalance, or a product designer might weight a handle to improve ergonomics and control during use.

Weighting takes many forms depending on the application. In precision spindle work, small tungsten or lead inserts are fitted into the rotor to reduce vibration caused by mass asymmetry. In injection molding, metal inserts or dense polymer pellets are added before the mold closes to achieve a target finished weight or to lower the center of gravity. Textile machines often use shot or sand contained in pockets sewn into fabric rolls to increase their effective mass and stability during operation.

Common weighting materials and methods

The choice of material depends on space constraints, corrosion risk, and precision required. Lead and tungsten are traditional choices because they are dense and machinable. Steel shot, concrete, and even water-filled chambers serve in applications where cost matters more than precision. Permanent weighting is typically fixed by adhesive, press fit, or mechanical fastening, while removable weighting uses clips or pouches to allow adjustment on site.

Weighting differs from ballasting, though the terms overlap. Ballasting usually refers to adding inert bulk for stability (as in ships or crane counterweights), while weighting is more often applied to smaller components where precise mass distribution or balance is the goal. A vibrating screen might be ballasted with concrete blocks for foundation stability; a motor rotor is weighted to eliminate runout.

Problems arise when weighting is done incorrectly or incompletely. Uneven weighting can introduce new vibration rather than cure it. Metallic inserts can migrate or corrode if not properly sealed. Operators sometimes weight equipment without documenting the change, leading to confusion during maintenance or when the machine is relocated. Correct weighing requires measuring imbalance first, then adding mass at the point of greatest offset.