Does the nest meet all production requirements?
When sheet metal nesting every parameter, machine setting, order sequence, or part layout choice impacts nesting productivity – time & material.
There are countless sheet metal fabrication requirements to be considered when placing parts on a CNC punch, laser, plasma, waterjet or router. The design, the fabrication requirements, and the order sequence can have a significant impact on the quality of the nest. How well those requirements are respected when compiling a nest is at the heart of an effective sheet metal nesting strategy.
Let’s look some of the real world demands that these requirements place on a programmer when nesting, and more significantly, the tools and techiques available improve your numbers today.
Can the equipment produce the nest as programmed?
If the programmer does not take into consideration the machine requirements (reach, repositions, tooling stations, kerf allowances, etc.), the production may be stalled or halted to address unforeseen problems. Part quality may suffer, the machine may be damaged, and certainly production time will be lost. Creating a quality nest means taking into consideration the ability to produce it.
Best Practice: You can test a part or a nest’s ability to be manufacturered using the principles of concurrent engineering and test programming and nesting a part before it ever gets to manufacturing.
Does the tool path retain enough material integrity to hold the sheet together throughout the machine cycle?
If the skeleton falls apart before the parts can be off loaded, a potential hazard is created. Parts can come loose, tip up, fall through slats and get damaged. Parts or the machine can be damaged or personal injury can occur to the operator. Ideally, the tool path should be intelligently programmed to accommodate any manner of offloading with no risk.
Best Practice: Intelligent tabbing can be automatically achieved on a part by part basis or by using a minimum size parameter, i.e. all parts under X width get tabbed, to avoid mishaps.
Does the nest reflect the most priority parts?
Material efficiency is often an important priority when nesting. But sometimes, a “hot part” trumps material efficiency in terms of priorities. And even when material efficiency is the priority, are “hot parts” still effectively addressed in the nest? Optimal nests consider the real world manufacturing environment with all of its often competing priorities.
Best Practice: With automatic batch nesting a series of nests – not yet produced – can be discarded, a hot part inserted in the order bucket, then the batch is rerun. Achieving both material efficiency and responsiveness. Another approach is JIT nesting, where each nest is made in real time and reflects all current demand.
Are the individual parts within an order held together in the same or successive nests?
Order cohesion can be critical to managing the downstream production flow. If parts in one order are spread over multiple nests, which could be cut hours apart, the opportunity for part damage or loss increases. A nest should keep parts within one order together and have supporting documentation that identifies the status and location of each part and order for the operator.
Best Practice: Intelligent order management using smart sheet metal nesting software knows which parts belong together in an order and which orders have priority. The software can keep track of whether an order is new, complete or a work in process. Further, and taken to the next level, JIT Kit Nesting addresses the needs of keeping all of the parts of a single assembly together, so they can flow through the shop as a unit. Through intelligent nesting, the material efficiency can be managed to eliminate the end-of-kit efficiency tailoff and additionally reduce material waste.
Does creating the nest pose any potential physical hazards?
Slugs. Loose parts. Floating Scrap. These are all machine operator nightmares and an invitation for machine downtime. If the nest is not created to prevent their occurrence, any savings gained in material efficiency will be lost in rework and repair.
Solution: Again, strategic, automatic tabbing and intelligent nesting with collision avoidance can overcome these obstacles for the programmer and the machine operator.
Did the time spent programming the nest the justify results?
Sometimes programmers spend from 5 to 15 minutes to up to several hours programming a nest. The truth is the programmer’s time is valuable and comes at a cost. Is an extra hour or two creating or manipulating a nest worth the additional material savings? Is there more value-added activities that he or she can be doing that makes a greater contribution to the value of the product? Depending on the cost of the material and the opportunity costs of the programmer’s time, it may be justified. But it is important to weigh all costs – including programming time – when evaluating a nest.
Best Practice: Programming time is just one of the many costs involved in nesting. Automatic nesting can drastically reduce that time and open up other opportunities to improve production with better use of the programmer’s time.
Is the nest meeting the ideal balance between all production requirements (material efficiency, programming time, throughput)?
When looking at the nest, it should reflect the priorities you have set for your production. And each manufacturer has unique standards. If material efficiency is the only criteria, then it should be the most material efficient nest possible. If programming or shop time, throughput, inventory management, or overhead are important, it should reflect these production demands as well. The challenge for sheet metal software is to find that perfect balance based on the priorities – all fo the priorities – you’ve set.
Solution: The optimal nest is a function of all of your priorities – response to change, efficiency, programming time, order priority, order cohesion, and more. Intelligent sheet metal software can dynamically balance these objectives and still keep you in control.
Is the nest material efficient?
I’ve mentioned it a couple times, but it merrits repeating because material efficiency is an important criterion. Does the nest make use of all material saving opportunities? Does the nest calculate part rotations at fixed angles (90, 180 degrees) or does it take full advantage of all angles, i.e. 123.574 degrees, to find the best part orientation. Does it create mirror parts, 180-degree pairs, or parts within holes? Does it take advantage of common cut or common punch situations to save material? Does it take advantage of trim strips through – in the case of punch – clamp repositioning? How does it handle tail off? Even a small percentage increase in material can return large savings.
Best Practice: You should be able to rely on your sheet metal software to answer these questions to your satisfaction. And at the heart of that question is really the power of the nesting algorithm.
In Conclusion
At first blush the concept of a nest may seem simple – just layout the parts on the material, then cut. The art and science of producing the nest in an optimal manner to achieve all of these goals is where the real complexity lies. But, if you’re thinking broadly, taking in to consideration all of the variables, and relying on good, solid tools including a quality sheet metal software package, the complexity can be tamed and your results will meet or exceed your expectations.
What challenges do you encounter when sheet metal nesting? How’s the process working for you? Let us know what you think.
For more information on sheet metal software that thinks about all of these considerations – automatically – talk to Optimation.
