Push-Pull Hybrid System

Definition

Hybrid control combines planned upstream supply with downstream pull signals where each part of the material flow has different planning characteristics.

Objective

Maintain required material availability with controlled inventory, defined replenishment signals, practical operating rules and measurable exceptions.

Required Inputs

• Average and maximum consumption
• Lead time and lead-time variability
• Current stock and inventory position
• Safety stock or protection requirement
• Minimum, maximum, order quantity or review-period parameters
• Material value, criticality and demand pattern

Methodology & Control Logic

Define the demand signal, establish the replenishment trigger, determine the target quantity, identify the responsible owner and specify the action when the trigger is reached. Parameters should reflect actual consumption, supply lead time and the required service level.

Calculation / Control Parameters

Inventory Position = On-hand + Open Receipts − Relevant Commitments

Reorder Point = Lead-Time Demand + Safety Stock

Replenishment Quantity depends on the selected control method and may be fixed, variable, or target-based.

Worked Industrial Example

Suppose a routinely consumed MRO item has average daily consumption of 8 units, an average lead time of 10 days and safety stock of 30 units. Lead-time demand is 80 units and the reorder point is therefore 110 units. When the controlled inventory position reaches the trigger, the defined replenishment rule is activated.

Industrial Application

Use the method according to material characteristics. High-frequency, predictable consumption can support visual or pull controls. Variable or critical materials may require explicit planning parameters, safety stock and exception monitoring. MRO and insurance spares require criticality-based treatment rather than a single universal rule.

Decision Rules

• Use actual consumption wherever a reliable consumption signal is available.
• Do not treat physical on-hand quantity alone as inventory position when open receipts or commitments materially affect replenishment.
• Review parameters when demand, lead time, supplier performance or operating conditions change.
• Use criticality and service requirements when selecting protection levels.
• Escalate stockout, overdue receipt and abnormal-consumption exceptions promptly.

Controls & Governance

Maintain controlled master data for item, UOM, lead time, replenishment method, minimum/maximum, order quantity, safety stock and review frequency. Define ownership and approval for parameter changes and periodically compare system parameters with actual operating conditions.

KPIs

• Service Level
• Fill Rate
• Stock-out Rate
• Inventory Accuracy
• Inventory Coverage / Days
• Replenishment Adherence
• Excess and Non-Moving Inventory
• Parameter Review Compliance

Common Errors

• Using obsolete lead times
• Ignoring open purchase orders or reservations
• Applying one replenishment method to every SKU
• Setting arbitrary minimum and maximum values
• Failing to distinguish normal demand from exceptional demand
• Not reviewing parameters after supplier or process changes

Excel / MIS Method

Maintain one controlled row per item with consumption, lead time, safety stock, inventory position, trigger, target, open receipts, open commitments and exception status. Use conditional indicators for items below trigger, overdue receipts and abnormal coverage.

Related References

Inventory Management · Material Planning · Materials Management · Min-Max / Reorder Point Calculator