Often used by warehouses that are trying to minimize warehouse space and ensure proper FIFO rotations, on demand replenishment means that product is only moved to a pick location if the computer already knows that there is a need for that item. If you have limited picking space on the floor, you may need to keep the bulk of your items elsewhere until there is a demonstrable demand for those items to be brought down. Likewise, if you're concerned about maintaining FIFO rotations strictly, this process will ensure that no new items are brought to the floor until the older items are already out of the way.
Top Off
Top off replenishment is generally used to maximize utility during downtimes. Instead of having pickers and replenishers working the floor all at once, your warehouse replenishment team can come in between picking waves and top off items to a pre-determined threshold. The only time you will need to disrupt this process is if there is an unexpected surge in demand for a single product that requires replenishment before the next top off period. This is especially effective if you have teams rotating through different sections of your warehouse, so the replenishment team can follow behind them and top off.
Routine
With routine replenishment, your replenishment activity will be also be driven by order activity. In this case, you set a minimum threshold that will trigger a replenishment work order. While this method is highly efficient, it is also requires more real estate if you use fixed forward pick locations.
All three of these warehouse replenishment methods can be highly effective in the right environment. Depending on the amount of space, staffing and time you have, you may choose one style over another. While routine replenishment has become a standby for many industries, it is not always the best fit for companies with limited resources. You should consult with an expert to determine which style will be best suited to your warehouse layout and order dispatching system.