Page 27 - MetalForming September 2012
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The challenge: Scheduling these parts through the fabrica- tion facility so that they flow together, a challenge that becomes even more complex when multiple machines are used. The solution lies in JIT kit nesting. Imagine a group of orders sequenced so that order #1 is to be produced first, then order #2, and so on through the last order in the sequence. To move parts through fabrication as quickly as possible, the manufac- turer would like to use all available equipment capacity first for order #1, then for order #2, etc. JIT nesting with order man- agement will accomplish this task and provide an optimal set of nests that ensures the order cohesion is met, producing the orders in the desired sequence at the lowest possible cost.
This method of nesting, called JIT kit nesting, processes each order as a kit of parts that must be fabricated together and flow together through the facility. The flow diagram looks like this:
5 three days before they are required, parts 2 and 3 two days before they are required and finally part 1 one day before it is required. The goal is to produce all parts on time with the least amount of work-in-process inventory.
When a shop produces multiple products using the same equipment, it must produce a large group of parts today and each subsequent day. From this large list of parts made of multiple materials, the shop must create a production plan that will meet the schedule and minimize costs for materials, direct labor cost and setup. The production plan also must respond to any hot parts, schedule changes and machine breakdowns. Further, the plan must be able to transition from today’s requirements to tomorrow’s requirements without sacrificing material efficiency and productivity.
Consider a hypothetical order comprising five parts of three different materials. To simplify, all parts must be completed today. If the parts are to be welded together into an assembly, it would be beneficial to produce all five parts in the same timeframe— achievable with JIT kit nesting that keeps orders together.
MRP/ERP systems often add an order identifier or order number. We then can create a sequence of order numbers that will automatically control the production sequence. Once the orders are identified and placed in a sequence, JIT kit nest- ing can create an optimal finite schedule that meets the overall MRP/ERP schedule, while producing cohesive orders that smoothly flow through manufacturing. MF
Orders are sequenced in shipping or delivery order.
JIT KIT nesting
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JIT kit nesting provides intelligent production-oriented nesting that accomplishes the following:
• Manages flow of parts so that each order is produced together, managing machine load over multiple raw materials to complete the set of parts contained in the order.
• Merges the end of order #1 with the beginning of order #2 to keep material efficiency continuously high.
• Dynamically balances the work load on multiple machines by dynamically assigning work to each machine as it becomes available.
• Responds to changes in schedule and hot parts every machine cycle.
Fabricators that use JIT kit nesting can dynamically man- age their production to satisfy their customer ship dates, with- out using complex scheduling systems not tied to the shop floor. With JIT kit nesting, a fabricator can immediately respond to machine breakdowns, schedule changes, hot parts and other events that impact production.
Nesting Using ERP/MRP Systems
ERP/MRP systems plan orders based on the time it takes to produce a part. Imagine a product made of five parts where part 1 takes one day to produce, parts 2 and 3 take two days to produce and parts 4 and 5 take three days to produce. The ERP/MRP system will launch production of parts 4 and
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