Julien-Robert Lecadou

ALUF PLASTICS ,INC Lecadou@gmail.com

CUSTOMIZING THE JOB SHOP SCHEDULING USING

MICROSOFT DYNAMICS AX (PART I)

Customizing Job Shop scheduling using Microsoft Dynamics AX

How to implement a production scheduling engine using Microsoft Dynamics AX?

Software version: The first version of this document is about Microsoft Dynamics AX 2009. An update

version for 2012 R3 is underway but could not be released to the public. This is a fruit of an intensive

research.

The standard Microsoft Dynamics AX 2009 production scheduling engine considers the following:

- A Route is a set of multiple operations sequentially executed.

- The link between these operations can be soft or hard.

- Each operation uses a specific work center

- You can have several route versions to manufacture an item.

- And more

In our production environment, a Production Line is a combination of two types of work centers that are

a machine (an extruder) and downstream equipment (tools).We’re currently using a manual production

scheduling system because there are some differences between the production module in Microsoft

Dynamics AX 2009 and our current manual system. The current production routes registered in the

system are just enumerations of operations that are realized simultaneously at the time of production.

This happened because the solution implementers did not have a good understanding of the standard

requirement of the production routing. The result of this mistake was a pure simple abandon of the

production scheduling sub module of Microsoft Dynamics AX 2009. Mainly because it will be too hard to

maintain several thousand of routes.

The attempt of this paper is to show how we have tackled this complex issue of production scheduling

and the lessons that we have learnt.

Part I: Concepts and Fit gap analysis

Key term definition in Production Scheduling Module

The Work Center

Work centers are the resources that are used to complete the production processes. They can be

machines, tools, people, or sub suppliers that contribute to the production of an item. A work center

consists of one or more people and/or machines with identical capabilities that are considered as one

unit for managing the planning of capacity requirements and detailed scheduling. After a work center is

created, you can assign it to specific productions.

Center categories

The Category 1: is composed of extruder and its identification number is the production line number

Category 2: is composed of downstream equipment used to create the shape of the plastics bags, e.g.

The star seal system or the winder.

Category 3: is composed of downstream equipment used to create the bag aesthetic and special

features e.g. the air hole machines and the printing machine.

The Route

The route is a detailed set of instructions that describes how to create a particular item. A route includes operations to be performed, the scheduling sequence, machines and work centers involved, and hours required for setup and run times. A route can also include information about tooling, operator skill level, inspection needs, testing requirements, and so on.

Jobs Jobs are assigned to work centers during the job scheduling process. Job scheduling is the detailed

planning of capacity, and separates each operation into its individual tasks or jobs.

Operation

An operation is a specific task rendered in the manufacturing process. An operation is carried out at a

work center.

Thus a route is a set of multiple operations each on a specific work center at a scheduled time.

About Job Scheduling

Job scheduling is detailed scheduling. It breaks each operation down into its individual tasks or jobs.

These jobs are then assigned to the individual work centers.

Target Production scheduling process

After implementation of the solution, when the job scheduling is run, the system will schedule

the resources needed for the productions based on the priorities that the users have defined in the

parameters setup.

The users can control the optimal capacity of the work centers by setting up a min/max capacity

allowed.

The calculation of the capacity loads for the work centers is conducted by the system during the

scheduling process.

The plastics manufacturing process These are the steps involved in making any plastics bag:

PLASTICS BAG MANUFACTURING PROCESS

1- Extruding plastic film

2- Printing of the plastic films

3- Bag making or “converting”

The intention of this paper is to show the operations and resources used during production process and

how they are scheduled. So we are not going into the details of each operation.

Extrusion of the plastic bag

During the manufacturing, you will always “extrude” the plastic film. Thus this operation is necessary

and always happens. The extruder is a machine and its identification number defines the production line

number.

Printing on the plastic film

You don’t always need to have to press a print on the plastic film that is coming out of the extruder. This

operation will be skipped when a print is not requested by the customer.

The printing machine is a downstream equipment. It is a moveable equipment that can be used at will.

Tips: About work center category

The printing machine is not a primary equipment. During the design phase, the

printing equipment will be used as a work center category 3.

Extruding the plastic

film

Printing on film

Making the bags or

converting

Conversion

The bag making or “conversion” activities sometimes encompasses several processes depending on the

type of bags ordered by customers. This also means that you need to have different tools based upon

the type of bags ordered. And if a tool is not required at one production line, it can be moved to

another one or simply kept aside for future usage.

The gap analysis between the production routing in AX and the plastic

manufacturing process

In Microsoft Dynamics AX 2009 (AX 2009), the route is a sequence of multiple operations. For a plastic

manufacturing process the route could be:

Operation 10: Extrusion and the work center: Extruder (here Ext)

Operation 20: Bag Printing and the work center: Printing machine (here Print)

Operation 30: Bag Making and the work center: Bag machine (here Sep for separator)

Production Route 1

This route is clear and simple but it omits several operations. Let’s keep this simple route for now and

let’s call it Route 1. The Route 1 is the route master and we can have another version of the Route 1

where we don’t use the printing machine and we will call it Route 1.1

Route 1.1 is:

Operation 1: Extrusion and the work center: Extruder

Operation 2: Bag Making and the work center: Bag machine

Thus, when a bag is scheduled to be manufactured, needs a printing job, we will use Route 1 and when

it doesn’t need printing on the bag will use Route 1.1.

This simple example only works when your production process is simple. For example, you have one

type of bag and you can press a print or not.

In reality, this case is not true because plastic bags have different colors, sizes, gussets and other

features such as star seal, air hole and more. The bags can be packed in rolls or separately. Moreover

the plastics bags chemical compositions are not the same. A customer can order 20% of calcium

(CaCO3) bag whereas another will order one with 12% of this calcium. Some plastic bags can have

drawstrings whereas some others don’t need one.

In this type of production environment, it becomes clear that Route 1 and Route 1.1 will almost never

be used. Thus the Microsoft Dynamics AX 2009 scheduling engine will become unusable if a

customization is not made to standard scheduling engine.

What Microsoft Dynamics AX is missing? Here are some details that Microsoft Dynamics AX is missing when it comes to job shop

scheduling in a plastics manufacturing environment:

- While a route is able to assign a specific operation to a work center, it is not possible to

dynamically assign an operation to a work center that is moveable and used when needed.

To put it simple, it is not possible to use Microsoft Dynamics AX 2009 in a heuristics job shop

scheduling.

- There are usually several types of extruders at a production plant that can produce the same

group of bags (e.g. REPRO LINEAR LOW CLEAR) but the downstream equipment (work center

type 2 or type 3) available at one production line would determine which bags can be

produced and which ones can’t be at a given moment.

One will argue that we should use the work center group feature to resolve this issue. The

problem is that grouping extruders and downstream equipment is not possible because these

equipment are moveable, thus the work center groups’ implementation would be problematic.

Moreover, the downstream production unit is different from the extruder production units. The

first is in Case or Rolls (CS/RL) whereas the latter is in pounds (lbs.).

- In general the production scheduling engine uses the data from the Master Planning,

Production, Inventory modules. The jobs are scheduled according to a certain direction. The jobs

can be scheduled forward or backward. But the job scheduling does not take into account

priorities (e.g. customer’s priorities).

- The production scheduling engine of Microsoft Dynamics AX 2009 does not have an expert

system that could learn from the inputs from the domain experts (e.g. the planners or the

operation manager)

- Finally according to the production line configuration, the setup time between one work order

and another will be different.

Illustration

Scenario

Prod Line 1 (Ext A) Bag ={A,B,C} 800 lbs./ h

Prod Line 2 (Ext B) Bag={A,B, C} 500 lbs./h

Tool A Bag={A,B} Setup ext. A= 40 min ; Ext B= 50

Tool B Bag={A,B,C} Setup ext. A= 120 min ; Ext B= 60

Color a= black , b=clear, c=white

WC= Work Center, Prod Line= Production Line; Ext= Extruder;

Job 1 = bag A = 2000 lbs.

Job2 = bag B= 5000 lbs.

Job 3 = bag C= 3000 lbs.

If Job1 is running on the Prod Line 1 with the Ext A and Tool A, it will require a new setup for tool B on

Prod line 1, if you want to run Job 3 on Prod Line 1 after Job1.

But if Job 1 is running on Prod Line 2, you can run Job 3 after Job 1. But, by avoiding the long setup time,

that will be required for Tool B on Prod Line 1, you will run into other problems such as the creation of

scrap because Bag A is Black whereas Bag C is white and you will be using a slower machine.

This simple scenario shows that a rules engine (or an expert system) is necessary for the production

scheduling module on AX 2009.

The Gap between the production scheduling literature and the actual requirements

in the planning and scheduling of the job shop in the plastic bag manufacturing

environment One of the most recurring problems when it comes to job shop scheduling is the tardiness of operations

scheduled. For example a job scheduled for a given time could be delayed because of multiple reasons

such as:

The Setup of the downstream equipment could be longer than expected

Some tools are not available because used by another machine

A Work center breakdown or unexpected maintenance and jobs scheduled on that line

will be delayed.

Unexpected scrap during the precedent jobs

Material not available

The operation research literature is filled with theories that tried to tackle the issues encountered

during the job shop planning and scheduling. The job shops and the shifting Bottleneck heuristic theory

are our favorite theories.

While the shifting bottleneck heuristic theory somehow could help optimizing the job shop scheduling,

there are several constraints that hold us back.

Note: Heuristic is by essence not about optimization. People choose the heuristic job shop scheduling

because they cannot optimize their planning. In that case, the heuristic planning could be considered as

the new optimum.

The shifting bottleneck heuristic assumes that a job will go to one or more machines before the

completion of the production. Based on the setup time and processing time of each job on a designated

work center, it is possible to schedule a job shop to minimize the makespan.

The issues here:

- There is no makespan because it is a continuous production.

- The setup of the downstream equipment (ultimately the setup time) is not done for one

production order but for multiple items that fit the requirement of the current production line

configuration.

- As it was true for the route in standard Microsoft Dynamics AX 2009, the theory only assumes a

fixed route for every item. And the reservation of the work center is done according to the route

(master). The issue here is that the production line is configurable and more than one

production line configuration can manufacture the same bag.

- Finally according to the production line configuration, the setup time between one work order

and another will be different.

Fitting the gap The analysis of the production scheduling in the plastics manufacturing plant and the job shop

scheduling engine in Microsoft Dynamics AX 2009 brought us to the conclusion that the

following feature needs to be added to the standard system.

- The work center proprieties should be enhanced. We should add the following attributes: Min /

Max width, min production starting cost. We should also link the work center type machine to

the preferred downstream equipment.

- The work center type machine (extruders) should also have restricted and preferred materials.

- There will be 2 types of routes. One route considered the master route will be used to list the

different operations needed to manufacture an item and a floating route version that will use

the scheduling engine to be populated.

- A rules engine is needed to handle the different decision rules that are specific to the

organization and the plastic bags manufacturing environment.

- The operation managers and planners should be able to amend the productions (jobs)

scheduled and totally reconfigure the production line.

Conclusion Microsoft Dynamics AX is an ERP system that can be used to create a very flexible and yet powerful

production scheduling system. In the first part of this document we have presented the basic concepts

of the production scheduling and then we have done the fit gap analysis. In the next part, we will

present the modeling of the target solution.