THINK IT THROUGH – Sometimes the tightest nest isn’t the best strategy. Please read this article from Modern Metals by SigmaNEST Product Strategy Manager, Kevin Keane
Think it Through – Sometimes the tightest nest isn’t the best strategy.
However, there are big tradeoffs to nesting. Is it possible to want something other than the absolute best yield? Is there a way to be more strategic and effective for when, why and how parts are nested? Let’s examine some scenarios where the tightest nest is not the best strategy.
SEEKING MATERIAL STABILITY
Each material type has unique properties. Some cutting processes can relieve internal tension in the material, while others introduce stress into the material. In these cases, if there isn’t enough space between parts, it will lead to a weak skeleton that may be inclined to flex or twist. This can result in parts that move or shift position during cutting, thereby degrading the quality or even causing the part to be scrapped. Nesting software must be able to manage part spacing to adapt to different cutting processes and materials. Smart programming allows users to create parameters that work best for material type or thickness, or that automatically modify spacing in X or Y directions or prioritize cutting in relation to clamps and holders.
KANBAN AND MIXED JOBS
For shops that use Kanban methodologies to stage parts between operations, it might make sense to nest parts on the sheet in a specific order to maximize productivity overall. The minor sacrifice of extra used material pays off by improving timing, scheduling accuracy and reducing labor costs.
One of the most powerful and profitable ways to maximize the value of nesting is to mix parts from different orders that call for the same material. However, there is a practical limit. Scattering 20 pallets near the cutting machine in order to stage parts for subsequent operations creates confusion at that station and starves the work downstream, where workers are waiting for the rest of the assembly. A better practice may be to group parts in the quantity that maintains the flow in all operations. The right nesting software should facilitate processing timing and good material yield.
PRIORITIZING DUE DATES AND SECONDARY OPS
It is common to have several jobs moving through the shop floor, each with its own trajectory and deadline. Some of these parts may require more downstream operations once cutting is complete. Nesting only for material yield can cause a shop to suffer if the right parts don’t get to the right workstation at the right time to make a delivery date. The power of nesting can create a more efficient order for cutting and secondary processes while saving time and customer relationships. The ability to see and use delivery dates when programming jobs is crucial, but a nesting solution that can juggle deadlines, next operations, internal capacity and the inevitable disruption is through the shop floor, each with its own trajectory and deadline. Some of these parts may even better.
Lights-out processing with a second work shift to maintain production can be very profitable. That is, if the machines keep running. One way to keep more machine uptime is to nest and cut more conservatively when there is no operator available to rectify small issues. Spacing parts carefully to avoid risks of part tipping or cutting head collision can go a long way toward ending costly trips for a repair crew.
NESTING FOR INVENTORY
Most shops have inventory that consists of different sheet sizes as well as remnants from earlier jobs. Pursuing the best yield above all else can result in never using up remnants, depending on their size and shape. Nesting software that encourages operations to enter and organize inventory, see what’s available and select it at the right time will make use of remnants so they don’t become a logistical and financial burden. Minimizing the effort of chasing inventory can be a huge saving.
Each machine has its own unique strengths and weaknesses, imposing its own restrictions on the production process. Narrow parts may need to be placed lengthwise over multiple slats of the cutting table on a oxyfuel, plasma, laser or waterjet. Punching machines may have tooling index angle limits, which means parts must be nested at an angle compatible with the tooling. If a machine has a drop door or parts chute, the parts may need to be rotated, processed and aligned correctly to take advantage of the automatic part removal. The pairing of nesting software and the machine is a primary concern.
NESTING THAT FITS
If the material is cheap (which is rarely the case anymore), it may not be worth the extra effort to chase every percentage point of yield. If the material is more valuable, the effort pays for itself. It makes sense to prioritize nesting on the materials that cost the most.
Company needs will change over time as new cutting machines are added and new ERP and management systems need to work in tandem with a nesting solution. Operations could expand to include press brakes or tube lasers. Material lead times could change, requiring software to alert management when inventory is running low. Any of these changes affect an entire operation from end to end.
Nesting is data. The right nesting software can be a powerful and adaptable tool for optimizing workflow. It comes down to the right nesting strategy — even if the tightest nest isn’t the top priority.