In practice, production scheduling is part of a complex flow of information and decision making that forms a manufacturing operation’s planning and control systems. Global competition and rapidly changing customer requirements are making efficient production scheduling increasingly more and more important for today’s production and manufacturing environments. The decorated-apparel industry is no exception.
We would define production scheduling as the scheduling of individual customer needs and the control of their flow through the production process, which is defined by resource requirements and capacity constraints.
Bringing reality to theory
A solid production schedule should help in determining whether delivery dates can be met and can identify predictable downtime for maintenance schedules. A proper production schedule also gives production and other personnel an explicit statement of what is expected and in order that supervisors and managers can measure productivity and performance.
Other advantages include minimizing WIP (work in process) inventories, set-up times and overall lead times as well as maximizing machine and production personnel. A good production schedule can identify resource conflicts, control the release of jobs to the production floor, and ensure that all required raw materials—such as blank product and correct ink colors—are purchased and received on time. Additionally, better coordination will increase overall productivity and minimize operating cost.
Traditional scheduling research has done little to improve production-planning practices over the years. What’s more, traditional scheduling models based on operation-research techniques that assume ideal situations are being found insufficient. In reality, actual production systems are filled with uncertainties. In an attempt to bridge the gap between production theory and reality many apparel-decorating companies have adopted a fuzzy scheduling model. Imprecise scheduling parameters in process times and due dates as well as constraints on resources and the custom nature of our business have forced us in this direction. Since internal and external business-environment reality may change dramatically from day to day or even hour to hour, there is a need to respond to the unexpected and modify existing production schedules. Flexibility is paramount, and keeping it simple makes scheduling manageable. Make no mistake that not only is fast and responsive production scheduling the key to supply-chain management, but also that logic enables business-to-business transactions by directly linking customer’s and supplier’s schedules together.
Spreadsheets are the key
Despite the fact that during the last couple of decades many companies in our industry and others have made large investments in the developments as well as the implementation of computerized scheduling software systems, not very many such systems appear to be in regular use. Systems, after being implemented, often remain in use for only a limited time, eventually becoming, for one reason or another, ignored altogether. The real world is somehow different than idealized computer models, and therein lie those fuzzy constraints, shortages of accurate information and those oh-those-sudden changes of direction. There is, of course, the human factor as well. Over- and under-estimating the employees’ abilities, sick days and “just bad” days are difficult if not impossible to schedule around.
Using spreadsheets to model and simulate is the first step towards the design of an advanced planning and scheduling system. Because spread sheets have become so powerful and easy to use, the overall projection of capacities and limitations can be pre-loaded into the operating plan. For years spread sheets have been used to design prototype scheduling systems.
Building a scheduling system requires a structured and disciplined approach. Reports, graphs and charts can easily be created to greatly assist in reality projections. The best part is that these spreadsheets can be completely customized and changed as many times as necessary.
Anybody’s worst nightmare
The following are among the key decisions made easier with a production-scheduling system:
- releasing jobs for production;
- prioritizing jobs that require resources (ink, special stencils and so on);
- assigning resources (people, equipment);
- reassigning resources from one job to another (similar jobs);
- determining when jobs should be started (to meet deadlines); and
- interrupting jobs that should be stopped (rush orders).
Production scheduling deals with the allocation of resources and the sequencing of tasks to produce the particular goods and services. In this case, embellished apparel. Although allocation and sequencing decisions are closely related, it is very difficult to model mathematically the interaction between them.
The production-scheduling system is a control system that is part of a larger, more-complex manufacturing planning and control system. The production-scheduling system is more than a schedule-generation process, be it manual or automated. This system should not be a piece of software, but it should interact with all departments and provide information that all managers need for other planning and supervisory functions. Note that only after the schedule is generated do the manufacturing operations and processes begin.
Weak production control and scheduling invites disaster: Under its direction, the production floor does not know what to decorate, and machine efficiency falls through the floor. Customers don’t get orders filled on time and that spells big trouble. Production scheduling is at least as important as any other part of the production loop, and it can create anybody’s worst nightmare of not handled correctly.
A plant’s production-scheduling system continues to develop over the years, evolving through the mistakes and miscalculations recognized and corrected. Remember, common sense is one of the most important aspects of effectively simple production scheduling.
Sending up red flags
Sales, administration, prepress, production, shipping and receiving, along with the divisions of each department, must all be considered. Within sales you have customer service. Administration includes order entry, accounting and invoicing, Prepress is art, screen and ink. Don’t forget purchasing. Sound familiar? These are the key components of the production loop and will need to be considered throughout the scheduling process.
After the sale is made, the order will need to be entered into the system. There are any number of order-entry systems on the market from very simple and inexpensive to significantly more complex. My operations have stayed fairly simple based on a number of internal considerations.
The department which performs the order-entry phase must be familiar with general pricing, and production limitations. It won’t matter how many presses you have if you get a job requiring 19 heads and you max out at 18. If a sales order does not fit within predetermined criteria, it should be sent back to the sales person and removed from the schedule until appropriate adjustments have been made. Terms and conditions as well as past-due balances should be examined before processing. These should be built-in protections that send up red flags . . . literally.
After the initial stages of order entry are complete, one should consider the information which needs to find its way to each department. Depending on the software of choice, information should be available for output in the form of various reports which will assist in providing data for many departments. The actual order confirmation and specifications will aid in production.
Pull-sheets or purchase requirements will get product procurement started. The most useful information any order-entry system can provide comes in the form of tracking production. An open-orders report provides an up-to-date list of what is still to be invoiced, or what is still in production. This is particularly useful in making sure everything finds its way through invoicing. The open-order report also serves as an alarm of past-due orders and is useful in revenue projections.
Although over the years specifics have changed, I have always been a big believer in a highly visible, completely accessible, ever flexible scheduling board. K.I.S.S., right? We have an enormous white board that takes up an entire wall in the production office (see simulation, page 58). This office resembles a fish bowl with windows all around for full visualization by the entire staff. Sales, admin, art, purchasing, shipping-and-receiving and all production departments have access to this board.
The layout of the production-scheduling board traditionally would be in a calendar-month format. With today’s decreasing run sizes and increased set-ups, along with minimal lead times, we were forced into two-week format, in vertical progression. As one week ends another is added behind in order to accommodate two weeks at a time. Each press has its own section running horizontally along the two-week period. In our case, we schedule four automatics, four manuals and four embroidery machines. Each delineated section is one day’s worth of production for that specific machine.
Each section on the board will be the location of that machine’s daily jobs. Each job will be earmarked with a job card. The job card has all the details of the work to be done and is created at the order-entry stage. Pertinent information for the job is included on the card: customer, design, number of colors, substrate and, most important, due date.
The production manager places the cards on the board according to the particulars. The job cards are generally placed on the appropriate press with a cushion for due date. The bottom of each card has a color-coded system for determining the arrival of product, art, screens, ink and customer press proofs. The codes are marked off in real time by each of the supporting departments. When all are completed . . . the job can and will run.
The production schedule is a work in progress and changes continually. A daily schedule and requisitions for art, receiving, screen and ink is created by each department head, determined by the main scheduling needs.
Become an expert juggler
Staff is critical to any system of production scheduling. Daily or weekly production meetings with representatives from each department keep everyone on the same page. Checks and balances of a highly visible system such as this one become natural, as everyone is checking everyone. Pretty tough to burn screens without art, or print shirts if they’re not ordered. Production scheduling helps us all understand limitations and capacities making true projections a reality.
The objective is that production scheduling is a part of a complex flow of information and decision making. It is not an isolated optimization problem to be solved. Since production is not a distinct, singular function, there are plenty of variables affecting it. It is expected that a scheduling system should incorporate all relevant constraints in the printing process and should perform suitable activities for a changeable environment, so much so that it can solve unforeseen and unpredictable events. (Hmm. How likely is that?)
There are, however, numerous advantages to the integration of process planning and production scheduling. It must be incorporated with other systems and interactive with real-time changes and adjustments. Bottom line? It’s really just a juggling act, but one that gives you all the talent of an expert juggler.