Z94.14 - Operations & Inventory Planning & Control

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SAFETY CAPACITY. The planning for or reserving of excess manpower and equipment above known  requirements for unexpected demand. This reserve capacity is in lieu of safety stock. Syn: reserved capacity procurement.

SAFETY STOCK. (1) A quantity of stock planned to be in inventory to protect against fluctuations in demand and/or supply. (2) The average amount of stock on hand when a replenishment quantity is  received. (3) In the context of Master Production Scheduling, additional inventory and/or capacity  planned as protection primarily against forecast errors and/or short term changes in the backlog.  This investment is often under the control of the master scheduler in terms of where it should be planned. Sometimes referred to as "overplanning"  or a "market hedge." (See HEDGE.) 

SAFETY TIME. The difference between the requirement  date and the planned in-stock date. (See SAFETY  STOCK.)

SCHEDULE. A listing of jobs to be processed through a  work center, department, or plant, and their  respective start and completion dates as well as  other related information. 

SCHEDULED RECEIPTS. (1) A planned order arrival.  (2) Within MRP, open production orders and open  purchase orders are considered as "scheduled  receipts" on their due date and will be treated as  part of available inventory during the netting process for the time period in question. Scheduled receipt dates and/or quantities are not normally  altered automatically by the MRP system. Further, scheduled receipts are not exploded into requirements for components as MRP logic assumes that all components required for the manufacture of the item in question have been either allocated or issued to the shop floor. (See PLANNED ORDER, FIRM PLANNED ORDER.)

SCHEDULE VARIANCE MANAGEMENT. A technique used in on-line MRP systems to evaluate the quality of planner output. The resulting actual schedule is compared to the system-suggested ideal schedule. Variances are highlighted and summarized on an exception basis for management action.  

SCHEDULING. Establishing the order and timing for  performing a task. There are various levels of  scheduling within a manufacturing company. For  example: master production scheduling,  requirements scheduling and material shop floor  scheduling on time. (See MASTER PRODUCTION SCHEDULE, DISPATCHING, PRIORITY.) 

SCHEDULING RULES. Basic rules that are defined ahead  of time for consistent use in scheduling jobs.

SEQUENCING. Establishing an order (priority) in which  a series of tasks or jobs are to be performed.

SERVICE PARTS. Parts used for the repair and/or maintenance of an assembled product. Typically they are ordered and shipped at a date later than  the shipment of the product itself. 

SERVICE PARTS DEMAND. The need for a component to be  sold by itself, as opposed to being used in  production to make a higher level product. Syn: repair parts demand.

SET-UP LEAD TIME. The time in hours or days needed to  prepare before a manufacturing process can start.  Set-up lead time may include run and inspection  time for the first piece.

SET-UP TIME. (1) Time required to adjust a machine  work center, or line and to attach the proper  tooling to make a particular product. (2) Time  required for removing tooling, attaching tooling,  adjusting, cleaning, warm-up, etc. Syn: start-up  time. 

SHOP FLOOR CONTROL. A system for utilizing data from  the shop floor and data processing files to  maintain and communicate status information on shop  orders and work centers. The major sub-functions  of shop floor control are: assigning priority to each shop order, maintaining work-in-process  quantity information for MRP, conveying shop order  status information to the office, and providing  actual output data for capacity control purposes.  (See CLOSED LOOP MRP.) 

SHOP PACKET. A manufacturing order that travels with  the job and includes a group of documents (possibly  coded) such as routings, time tickets, etc. 

SHOP PLANNING. Coordinating material handling,  material availability, and set-up and tool  availability so that a job can be processed on a  particular machine. Shop planning is often part of the dispatching function although dispatching does not necessarily include shop planning. (See DISPATCHING, CLOSED LOOP MRP.)

SHORTEST PROCESSING TIME (SPT). A sequencing rule  where the job requiring the shortest amount of  processing time is produced first. Syn: shortest operation time.

SIMULATION. A computer method for modeling the behavior of a system used in what-if analysis and as a decision tool. Simulation can also be either physical or theoretical. 

SINGLE-LEVEL BILL OF MATERIAL. Shows only those  components that are directly used in an upper-level  item. It does not show any relationships more than  one level down.

SINGLE-LEVEL WHERE USED. Lists each assembly in which  a component is directly used and in what quantity.  This information is usually made available through  the technique known as "implosion."  SKU. (See STOCK KEEPING UNIT.)

 SLACK. A priority rule for sequencing jobs based on  slack time. (See SLACK TIME.)

SLACK TIME. The difference in calendar time between  the scheduled due date for a job and the estimated completion date. If a job is to be completed ahead  of schedule, it is said to have slack time; if it is likely to be completed behind schedule, it is  said to have negative slack time. Slack time can be used to calculate job priorities using methods such as the critical ratio. In the Critical Path Method, total slack is the amount of time a job may  be delayed in starting without necessarily delaying the project completion time. Free slack is the amount of time a job may be delayed in starting without delaying the start of any other job in the project. (See CRITICAL RATIO.)

SOURCE DELEGATED INSPECTION. An approach to procured quantity parts that delegates final part inspection to the supplier. The customer validates the supplier's capabilities by approving the supplier's quality system rather than inspecting each part or samples of a lot.

SOURCE INSPECTION. Inspection at the source of supply (e.g., the vendor) instead of inspection following items receipt.

SPLIT LOT. A manufacturing order quantity that has been divided into two or more smaller quantities usually after the order is in process. Lots are sometimes split so that a portion of the lot can be moved through manufacturing faster. This portion is called the send-ahead.


STAGING. Pulling of the material required for an order from inventory before the material is needed. This action is taken as a protection from inaccurate inventory records, but leads to increased problems in inventory records and availability.

START TIME. The calendar time a job starts being manufactured on a machine or in the facility.

STOCK KEEPING UNIT (SKU). Represents an item at a particular location. For example, if a product is stocked at several locations, each combination of product and its stocking location is a different SKU.


STOCKOUT. The lack of materials or components which are needed to be on hand. (See BACKORDER.)

STOCKOUT PERCENTAGE. A measure of the effectiveness with which the inventory management system responds to actual demand. The stockout percent can be a measurement of total stockouts to total line item orders or line items incurring stockouts to total line items in the system. (See CUSTOMER SERVICE RATIO.)

STOCK STATUS. A periodic report showing the inventory on hand and possibly the inventory on order and sales history.

SUBASSEMBLY. An assembly which is used as a component at a higher level in another assembly. (See COMPONENT.) Syn: intermediate.

SUBSTITUTION. The use of a non-primary product or component, normally when the primary item is not available.

SUMMARIZED BILL OF MATERIAL. A form of multi-level bill of material which lists all the parts and their quantities required in a given product structure. Unlike the indented bill of material, it does not list the levels of assembly and lists a component only once showing the total quantity used.

SUPER BILL OF MATERIAL. A type of planning bill, located at the top level in the structure, which ties together various modular bills (and possibly a common parts bill) to define an entire product or product family. The "quantity per" relationship of the super bill to modules represents the forecasted percentage popularity of each module. The master scheduled quantities of the super bill explode to create requirements for the modules which also are master scheduled. (See PLANNING BILL OF MATERIAL, MODULAR BILL OF MATERIAL, COMMON PARTS BILL OF MATERIAL.)


SUPPLIER DELIVERY PERFORMANCE. Delivery performance by a supplier can be measured in two ways: (1) On-time performance - parts delivered on-time against a demand line giving credit for partial quantity shipments. This is generally used for interval measurement, i.e. purchasing performance to the assembly line. (2) Fill rate performance - parts delivered on time and to the complete quantity requested either as a result of 0% or 100%. Fill rate is usually used for performance to an external customer.

SUPPLIER PARTNERSHIP. A strategic supplier management approach whereby the number of suppliers to a company is reduced and parts are bought from a smaller member of selected supplier partners. Long term agreements are used to develop a framework between the customer and supplier. This creates a mutually beneficial team approach to the procurement relationship, leading to reduced costs and lead times.

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