Supply Chain Scheduling 

APS and Supply Chain Scheduling

Advanced Planning and Production Scheduling, APS, and Supply Chain Management, SCM, are becoming increasingly important in manufacturing companies, as they look to enhance their enterprise applications to take account of real-time status of suppliers, customers and their own plant.

There is a need for tools that will enable companies to react in a timely manner to events both upstream and downstream of their position within each of their supply chains.

Preactor 400 APS, 500 APS, 600 APS and Enterprise build on the finite capacity production scheduling core of Preactor to meet these needs. Planning and production scheduling across the supply chain, is a relatively new concept. It is an extension of other technologies that have been used to try and improve efficiency, such as Electronic Data Interchange, EDI, and SCM systems. Both EDI and SCM foster closer relationships between the companies within a supply chain, but it tends to be a one way relationship. For example EDI is primarily a way for a company to place orders on their suppliers. The ability of the supplier to produce the components is taken for granted, and for some, the advent of EDI simply pushed the necessary stock of components back up the supply chain. SCM goes a step further, but its major application areas have been in controlling stock in multiple warehouses for Fast Moving Consumer Goods (FMCG) and food/drink manufacturers. In this role SCM attempts to maintain the required stock levels whilst deciding how, and from where, to fulfill particular customer orders.

Again the assumption is made that the stock/capacity exists to supply the customer orders. Both EDI and SCM place their demand on their suppliers, without taking much account of the supplier's capacity. It is for this reason that any supply chain solution must have at its heart a proficient APS system.

Without it, production scheduling becomes the weakest link in an SCM solution.

Preactor systems are enabling tools. They are there to enable you to get more from your existing applications such as SCM and ERP systems. Preactor APS systems do this in a number of ways depending on the version purchased:-

• Enabling ERP through pegging the allocation of materials between orders generated by MRP
• Complex Production Scheduling Rules
• Order Promising and Supply Chain Scheduling

Enabling ERP

The Enablement of ERP systems by providing an accurate, 'bucketless', finite capacity model of the plant, so called 'Capacitated ERP', is described in the Preactor Scheduling Solution page. In Preactor 400 APS this is taken one step further. An ERP system take sales orders and blows through the Bill of Materials, BoM, for each to produce a number of purchase orders for bought-out components as well as works or shop orders for in-house manufactured items for each level of the BoM.

In a simple process to make bicycles an order is created for the required number of frames and wheels as well as the one for the assembly of the completed bicycles. These are timed to start at the required-by time less the lead-time. However if one of these orders is delayed, as in the example here, then this invalidates the start time of, in this case, the assembly order.

Preactor 400 APS has its SMC feature to peg or allocate materials between orders based on the BoM structure provided by the ERP system.

When Preactor schedules it knows the relationships between orders so it can take this into account when deciding when operations can start. If there is delay to a producing order as in this case, then downstream consuming orders are delayed also.

The user can also set up pegging rules that controls the allocation of materials where more than one alternative exists. This type of matching consuming batch and producing batch quantities is common in the defence industry where it is allowed for one producing batch to feed more than one consuming batch but it is not allowed for more than one consuming batch to take materials from more than one producing batch otherwise traceability is compromized.

Another example is to 'match' customer orders with completed product based on one or more attributes of the batch. For example a company may make 'widgets' that vary in 'quality' from one batch to the next. Customers may also have different requirements in terms of quality to be delivered, for example, Customer A will only accept grade 1 widgets while Customer B will accept grade 2, but the company will also ship Customer B grade 1 widgets if there are no other grade 2 batches available.

SMC rules have also been used to reduce the handling required in a beverages company. The existing system took packed product from the end of packaging lines to one or more warehouses. Sales orders were then picked from the warehouses into containers for delivery. The Preactor pegging rule checked first if it was possible to pack containers directly from the end of the packing lines, and if not then product in a warehouse is allocated instead thus reducing double handling costs.

Complex Production Scheduling Rules

Preactor 400 APS offers the same scheduling algorithms as P300 FCS, but also has the unique Preactor Open Planning Board, OPB system. The OPB is supplied with a simulation based scheduling engine with built in optimization rules such as, select the shortest setup time, minimize work-in process, etc. Customized rules can also be added using any ActiveX Automation compatible programming system, such as Visual Basic. Fundamentally the OPB will allow all the interactions that can be achieved with the mouse and keyboard in the Preactor Sequencer to be automated via ActiveX Automation methods. The power and flexibility of this approach will enable Preactor 400 APS solutions to be developed for any requirement and to simplify the most common scheduling needs. Some scheduling rules are in-built and data driven such as resource specific preferred sequence. An example of the use of this rule is shown here.

The screen shows a schedule generated for a series of processes. There are four products, white, yellow, pink, and red and five processing operations carried out sequentially on each of the process lines. The changeover times from one product to another are very different with the ideal sequence being white, yellow, pink then red. Here we have forward scheduled without using the preferred sequence rule. The black bar between the operations is the changeover time calculated from the changeover matrix.

Using the Preactor 400 APS rule, you are able to minimize the changeover times depending on the length of the 'look ahead' window. This is the time period that is used by Preactor when scheduling to decide whether a batch should be included in the minimization process. This shows the same orders after re-sequencing using the preferred sequence rule. Now similar products have been 'batched' together to minimize changeover time.

Preactor 400 APS offers both parallel and sequential loading rules. The OPB also has an 'algorithmic sequencing control language', ASCL that provides a means by which any logic can be created to provide the required sequence of loading.

ASCL was used to create the 'Product Specific' standard rules in Preactor. In this you can select one of a number of rules that can be assigned to a product or can be global for all jobs in a scheduling run. These product specific rules include Forward, Backward, Min WIP Forward, Min WIP Backward, and a number of 'Theory of Constraints' type rules that combine backward/forward and buffering techniques.

Almost any production scheduling logic can be created with the scheduling engines available to Preactor 400 APS. This is just one of the reasons why Preactor has been used in so many different types of planning and scheduling applications in many different business sectors.

Order Promising and Supply Chain Server

Order promising and remote enquiries to enable multi-plant scheduling are examples of additional functionality available in the Preactor family. The Preactor BoM Exploder, PBX, option is available to Preactor 500 APS. It provides functionality primarily for exploding sales orders into manufacturing and purchase orders during an order promise. PBX is not meant to replace an existing ERP system.

It enables ERP by providing an 'in-memory' capable and available to promise function (CTP/ATP) from within the Preactor Master Scheduling System. The in-built material allocation rules and clean-up routines within PBX ensure that materials remain under control during an order promise.

Supply Chain Server

The Preactor Supply Chain Server (SCS) is essentially a separate Preactor installation that operates in conjunction with other Preactor systems, viewers and other packages such as ERP/MRP systems. It operates continuously and responds only to electronic enquiries from other systems, sending back messages and maintaining information the content of which will vary according to the configuration in which it has been set up. It is a background process in that it has no graphical displays such as Gantt charts or sequence overview, has no scheduling buttons or reports. It can run on the same computer as another Preactor system or it can run on a separate computer over a network. Communication may be through shared directories on a PC network or E-mail.

Preactor 600 APS is a package that includes Preactor 500 APS, for the planner to manipulate and interact with the schedule, and a Preactor SCS to hold the live schedule and respond to electronic CTP enquiries.

This schematic shows how SCS, P500 APS Master Scheduling System, PBX and ERP system can pass data between them using batch files or event driven messaging. It allows remote ATP/CTP enquiries to be made on a live production schedule that the SCS holds. The Planner has access to the schedule through the normal interface of a Preactor 500 APS Master Scheduling System, can re-sequence, carry out 'what ifs', generate reports, and accept new orders from an ERP/MRP system. Preactor viewers can be used for shop updates to be sent to the SCS or to display Gantt charts and reports. A Preactor viewer, a device running say MS Outlook, a WAP phone, or an ERP system can also make ad-hoc enquiries in order to offer an expected delivery date for an order based on the current live schedule.

Multi-Plant Planning and Production Scheduling

Linking Preactor 600 APS systems together can expand this electronic enquiry system further to cover many plants or by linking companies in a supply chain. For example you may have a system where you wish to optimize the location of manufacture of an order based on various business rules (e.g. cost) including when an order can be shipped from each of several 'competing' plants. In the scenario a number of CTP enquiries would be sent and, based on this real-time replies, make a more informed decision on where to use capacity.

Preactor Enterprise

Preactor Enterprise is a multi-license product designed for companies who are going to implement Preactor at multiple plants. PE comes with one control license and a number of run-time licenses which can be run either as a Preactor 500 APS or SCS. The control license is used to create and modify the configurations to run on each of the run-time licenses. It then compiles these configurations. Run-time systems are typically installed at each plant where Preactor is to be used and will only run compiled configurations created and compiled by the PE control system.

The advantage to the end user is that:-

• The cost of ownership is significantly lower than buying anything more than 3 Preactor 500 APS systems.
• Additional run-time licenses can be purchased later as required.
• The control PE system has control over the features and functionality at each plant.