By James Swanson and John Mauro
Nested-based manufacturing continues to grow in North America. As an end-user of the technology your market is filled with options, specifications, vendors and brands all doing our part to differentiate, it’s a worthwhile investment of your time to understand what you need, vs. what you want, vs. what one may want you to want.
Throughput and automation level required of your application is a good place to start. Simplifying the process into four workflow categories and assigning some general production levels has proven beneficial for many.
Standard nesting workflow
Here we work from a manual load and manual unload of the machine. The accuracy, and the zero setup nature of nesting earn their keep. Part sizing, shaping, machining and vertical drilling become easy, repeatable and fast. As we calculate time for loading of raw sheets, unloading of finished parts, cleaning and prepping the CNC between machining cycles, some will argue standard nesting trends toward slow and dirty. Within this segment, if we benchmark a 6:30 second processing cycle and 6:00 for loading, unloading, sorting and cleaning we can expect this segment to process approximately 40 sheets in 8 hours.
Outfeed nesting workflow
In this configuration the machine is manually loaded, followed by automatic processing of the sheet, unloading of completed parts, as well as cleaning of the machine table. Second only to justifying the need for a CNC in your shop in general, adding an outfeed system to the machine carries a powerful ROI, often justified as a 20% cost increase to the initial investment machine that generates a 40% increase in throughput.
How? The outfeed machine automates the process that makes a standard nesting machine appear slow and dirty. These processes include unloading, sorting, and cleaning that has to be completed by an operator while the machine sits idle.
With an automated system, after a nest is finished it is effectively pushed off onto and a conveyor belt. During the process the machine table is also cleaned of dust and debris by utilizing a push off sweep device integrated with dust extraction. Residual dust is taken care of by a series of additional collection points above and around the outfeed conveyor.
The key here is to load the next sheet of raw material and start the machine. The operator then moves to unload and sort the previously machined parts from the conveyor belt. Since the machine is already back in operation these tasks no longer negatively impact the overall cycle time of the router, sometimes referred to as a process happening in “masked time.”
It is also common to integrate a barcode printer near the outfeed so the operator is also able to label parts in masked time. Benchmarking an outfeed machine using the same 6:30 processing cycle, and 1:00 for loading and unloading an outfeed workflow solution will process approximately 65 sheets in 8 hours. At this level and above, the nesting machine also begins to take up a position of pacing the operator and the pace of play within the shop.
Throughfeed nesting work flow
This configuration build upon the outfeed configuration and add automatic loading from a scissor lift into the machines responsibility. Whether it is the right or wrong method for a particular application, the fact is that throughfeed nesting currently receives the most interest from the North American market.
That said, we start to see the importance of understanding your application here as throughfeed can be more productive than outfeed, but not always.
Changing materials over on the scissor lift can create non-productive time for the machine. If you require only a few changeovers per shift throughfeed nesting could be for you. If your material color, size, texture, or thickness variation requires numerous changeovers per shift, an outfeed machine may be the more productive choice.
For those with the application matching the strengths of the throughfeed solution, production quantities for this automation level typically achieve 65-75 sheets per shift while also utilizing a barcode printer integrated near the outfeed so the operator can label parts in masked time.
As we create more advanced specifications of these machines and integrate them with construction methods optimized for nesting, it isn’t uncommon for machines to achieve 90-100+ sheets per shift.
Throughfeed nesting workflow with part pre-identification
Here we add a barcode label component to the throughfeed CNC router that automatically identifies the parts within the nest prior to processing, bringing the direct labor requirement to a low point. This system produces at a rate similar to a throughfeed nesting machine while further eliminating the need for an operator to manually identify parts at the outfeed.
As you climb the ladder of automation, your throughput increases and your dependence upon direct labor decreases. It is also important to understand other criteria related to nesting also grow in importance. Your strong understanding of data management and optimization software, tooling, vacuum (not only the quality of the pumps creating vacuum, but more importantly the delivery of the vacuum to the machine) and appropriate dust collection strategies ensure consistent operation of your nesting solution.
Within today’s market, successful nesting is much more than simply buying the machine.
Editor’s Note: Future best practices posted here will include optimization software, 4th-axis nesting, and the advantages gained from the utilization of appropriate tooling and feed speeds, vacuum and spoil board preparation, and dust collection.
About the authors: James Swanson is the Product Manager – CNC for Stiles Machinery. John Mauro is the Regional Director North East Region for Stiles Machinery.
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