Static Nesting vs Dynamic Nesting
What’s the difference between dynamic nesting and static nesting?
They are two nesting strategies frequently used in 2D or sheet metal fabrication. Both strategies speak to the means and method by which the parts are ordered, arranged or laid out and produced on the laser, punch, plasma, router or other fabrication equipment.
Although they serve the same need of nesting, the differences between the two approaches are striking.
Let’s Review.
- Part Selection – The first characteristic that stands out is the part selection.
- In static nesting, the user selects one part or a few parts and creates one nest or unique part layout. Then he uses that “static” or unchanging pattern of parts repeatedly in cutting one or often many of the same sheets. The net result is a large quantity of the same parts.
- Conversely in dynamic nesting the user works with a large variety – often fluid – selection of parts over an unlimited number of nest or sheets. Each sheet may hold a unique combination of parts – reflected both in their quantity and orientation.
- Part Priority – This is the urgency or immediacy of need for any part and how that priority is reflected in the nests.
- With static nesting, order priority is a secondary or lesser concern. Single parts are produced en masse, as a function of material efficiency or aggregate need. For example, if a quantity of one of a particular part is needed, a whole sheet or many sheets of that single part or a few parts are produced. If more are produced to fill out a sheet than are needed the remainder are scrapped or inventoried.
- With dynamic nesting individual part priority is evaluated – automatically – along with the need for material efficiency. The part orders are managed to insure that the highest priority, often the nearest due date, order is handled first and selected to get optimal material efficiency.
- Response to Change – Change in fabrication or manufacturing comes in many forms. There can be a design change to a part, and order priority change as in a new due date, a sudden rework or hot part, or an equipment problem. Any of these circumstances impact the nests and the users ability to respond to change.
- With static nesting, responding to change can be very difficult. If a part with a new revision is needed, the whole nest needs to be reassembled and reprogrammed. The old, reliable static nest is of no use. If a hot part is needed, it is either run as a single part on a sheet or the static nest is modified to incorporate it. Most often these steps are taken manually or interactively causing delays in production.
- Dynamic Nesting, on the other hand, is built about absorbing fluid nature of production. If there is a new revision, a hot part, a down machine, the problem is addressed in the next nest to be created reflecting the current demand for parts if Just-in-Time nesting. There isn’t an “existing nest” to modify or rebuild. Each new nest is created based on the current circumstances at the time. If Batch Nesting, where a queue of many nests are lined up, the operator can delete any nests not yet produced, the changes integrated, and the nests reassembled in minutes with little or no disruption to production.
- Speed of Nest Creation – This factor is all about the time it takes to create nests. How long does it take to bring in the parts, assemble the orders, layout the parts and create code for the machine?
- With static nesting – and probably the basis for its creation – the static nests can be reused over and over again with little or no time expense. The big time expense is in the – frequently manual – first creation of the nest, and any modification made to it thereafter in responding to change (see point #3 above).
- With dynamic nesting, the process is automatic. The nests can be created in seconds or minutes and still reflect current demand, order cohesion, and material efficiency. The user isn’t tied to creating each nest separately. He can create a batch of nests for a production run, a shift, etc. or can have the machine operator call down one nest at a time (JIT), which reflects current demand. Again, each nest may have a completely unique selection and orientation of parts and part quantities.
- Part Orientation & Quantity – This speaks to the granular nature of the layout of each nest – how many parts, how many different parts, what quantity of each, what’s the orientation of each part, etc.
- Static nesting means the parts are rigid or set in their layout. Per nest the quantity, variety, and orientation are set. They will not vary from run to run of that particular nest. If there are grain constrained parts to be considered, they are locked in place when the nest is built. If there is a large quantity of one part needed, it may be the only part on that nest.
- Dynamic nests are created uniquely. Unless the volume of parts merits several sheets be made with the same nest, the nest pattern isn’t repeated. This opens up the opportunity to change the quantity and orientation of each part on each nest to optimize material efficiency, to retain order or kit cohesion or to meet other demands.
- Automation – This is about how much human interaction necessary to complete the task of nesting.
- Static is well suited for a human or manual creation process. If the nest is considered as a puzzle, it is pretty straight forward to lay out five or fifty of the same part on a sheet. Even if a few parts are introduced into the mix it can still be manageable. It takes time, but it is doable.
- Because dynamic nesting can take into account a much, much larger bucket of parts, look at individual due dates and priorities, evaluate material efficiency needs, consider a full 360° rotation for each part, honor and respect grain constraints on each part, and manage tooling and / or tabbing, it is well beyond the capabilities of most human or manual interaction. The need for nesting automation is essential to juggle all of these needs in a timely fashion with optimal results.
In Conclusion….
So there you have it, a contrast between the nature and process of static and dynamic nesting and their relative applications. We often find that static nesting is a method born of necessity to cut the programming time and still have a respectable material yield. It is only when inventory spirals out of control, or scrap is too high, or changes comes too fast that this work-around becomes unfeasible. Enter automation with dynamic nesting software.
How about you?
What is your nesting strategy? Do you use static or dynamic nesting or a combination? What led you to this choice?
If there is an interest in automation through dynamic nesting, contact Optimation. We can help think through the process and the possibilities with you.
0 comments:
Post a Comment