Industry Flocks to Nesting
Suited for small- and mid-sized production shops, as well as large shops with custom applications, nested-based manufacturing accomplishes with one machine, in one step, what otherwise takes many machines to perform in multiple steps.
By Karen M. Koenig
It’s often considered simplification at its best. Nested-based manufacturing (NBM) gives flat panel producers the ability to cut various geometric shapes from a single sheet, in one easy step.
Sizing, rabbeting, dadoing, grooving, boring, shaping, etc., are all performed on a CNC router equipped with a high-volume pump. This allows for vacuum chuck nesting of components without custom fixturing. But while not for everyone, NBM is suited for use by small and mid-size production shops, as well as large shops with custom applications.
According to Dave McFarland, Heian product manager, Stiles Machinery, NBM is packaged as a complete manufacturing system. Included are software, tooling, fixturing, the CNC router, material handling, installation, training and integration.
“(NBM) offers several advantages over conventional processing,” says Ken Susnjara, chairman of Thermwood Corp. “First, the capital investment for an automated system is generally less. Using traditional methods, both a panel saw and some type of point-to-point machining center are required. With nested-based, generally a large table CNC router becomes the only major investment.
“With NBM, yield can be better if the proper technology is used,” Susnjara adds. “NBM does not require parts to be aligned along ‘cut lines’ as is required for panel saws. Also, odd-shaped parts such as tops and decks for corner cabinets can be interlocked rather than having to be first cut into rectangles with the saw and then cut to shape using the CNC.”
“NBM also saves a shop time and money by reducing errors and streamlining processes,” says Kris Hanchette, vice president of sales, MultiCam. “Each time you move a part from one machine to another, you can introduce error. NBM allows the part to be fully processed on the CNC router. The user puts a full sheet on the machine and pulls off finished parts that are ready for assembly.”
Small and Large Shops
“(It is ideal for) one to 20-person shops that need to process 15-plus sheets per day,” says Craig Sexton, national router product manager, Biesse Group America. “These cells work excellently with HPL, MDF, plywood, OSB, solid surface, veneers, any type of non-ferrous metal, plastic, acrylic, etc. Although currently it’s primarily being promoted in the wood industry, this style of production has been around 20-plus years in other industries.”
According to Dan Radusinovich, regional sales manager, Masterwood Group USA, a potential nested-based manufacturer is one which “is already using some type of design software; is willing to spend additional monies on necessary design software; is not currently operating a high-production level saw; and is caught in a labor shortage with not enough employees to process all the parts.”
“NBM has potential advantages for all sizes of companies simply because parts produced by nesting cost less,” adds Robert Alsup, National Komo Technology Center program director, Komo Machine.
“The revolution brought to the industry by NBM is that small companies can now be as competitive as the large ones. In fact, the small companies may be getting an unfair advantage because they are not experiencing the high fixed costs that follow large facilities with lots of people,” Alsup continues.
John Ridgway, operations manager at Anderson America Corp., agrees. “A small company will benefit from the addition of NBM the most as it will broaden the horizons of the complete operation. Adding NBM will boost overall output and efficient production while reducing overhead and labor costs.”
“Small shop owners are quick to realize the need for competitive leverage,” says Michael Dupont, Northwood Nestech product manager, Altendorf America. “Technology is their lever. NBM is comparatively inexpensive on a per part basis. Also, the flexibility that NBM affords permits the small shop to diversify easily with very little incremental — or no — increase in investment in personnel or equipment, other than software and tooling in most cases.
“With larger manufacturers going offshore, there will be a rising need for domestically-produced products that have short lead times,” Dupont continues. “Automating a small shop to accommodate these needs is an ideal solution. Coupling a computer and manufacturing software to computer-controlled machinery makes the small shop very competitive. Communication between these small shops and their customers will make it possible for the shop to be the virtual factory from which the customer gets product, components, etc.”
Karl Frey, vice president of SCM Group’s Routech Division, agrees. “Small companies can purchase one machine to do all or most of their machining operations. In many respects the technology evens the manufacturing playing field between small and large companies due to the high productivity,” Frey says.
“Mid-size companies,” he adds, “can consider using the NBM method to compartmentalize operations where a programmer and operator are a team, with the second team consisting of finishing and assembly. Large companies can consider NBM for all their custom operations. If they want to make all their product lines custom, with quick ship programs, NBM has many positive benefits to consider.
“As the market goes to mass customization for panel processors, the benefits of NBM will be more readily noticeable,” Frey concludes.
Pros and Cons of the System
“Small companies eliminate the number of processes, number of hands on a piece and number of times a part needs to be handled. Those customers with limited space and payroll levels will most greatly benefit from the one machine, one payment, one man and one footprint advantages offered by NBM,” says Don Dixon, regional sales manager, Masterwood. “Medium and larger companies benefit from controlling the yield per panel better through the high optimization of the NBM process.”
“I believe (another) key point to sell the customer on is just-in-time production and labor savings,” says Steve Hillis, CEO of CMS North America.
“With this method, parts can be produced as needed for a particular item, such as an upholstered sofa or chair, or even a complete custom kitchen. The labor savings come into play by taking the sheet stock to one machine. There are no additional steps needed before the panel is placed on the machine for processing. The manufacturer knows exactly where the part is in production and when it will be completed. It removes the guesswork on when the production pieces needed for final assembly will be available,” Hillis says.
One benefit of NBM, Hanchette adds, is that “shops can work out all the details for their customer and even walk them through a room on the computer before they ever cut a part.”
“The benefits go across the board for all company sizes,” adds Dupont. “(They include) a small footprint with a considerable amount of capability, typically one operator for the full operation, great flexibility with very little set-up time between runs, consistent accuracy and repeatability that is less dependent upon the operator, and the potential for savings based on yield improvements. Even the largest companies can use NBM in flexible work cells or ‘custom’ shops.”
However, manufacturers say, NBM may not be for everyone. “As shops increase in production requirements, they can find NBM to be too limiting in the number of panels they can efficiently process,” comments Danny Thompson, Southeast regional manager, Holz-Her U.S. “In shops that have more uniform parts, using a saw that can cut books of two or more may be more practical.”
Susnjara agrees. “(In) small- and medium-sized companies where a single CNC router running NBM will suffice, the lower investment makes this the best choice. (However,) larger companies running large volumes of standard cabinets might find that the high throughput of a CNC panel saw feeding several point-to-points may offer a better choice.”
Another consideration McFarland mentions, is that horizontal router/drill work must be done off-line. However, he adds, “a dedicated horizontal machine can be run by a CNC operator during the NBM cutting cycle.”
“Construction methods may also be affected, requiring some retraining of the labor pool,” Dupont adds. “Incorporating an off-line dowel drilling and insertion machine can offset the impact. In fact, while the machine is running a sheet, the router operator may dowel parts that were just removed from the machine, thus maximizing his time.”
“Understanding the processes of both standard manufacturing and NBM is the first step in overcoming these issues,” says Hillis. “Understand when to use NBM and when not to. When purchasing machinery, make sure it is capable of being used for NBM and for standard processing methods involving hard fixturing. Flexible machinery can, with easy changeover and setup, reduce the negative aspects.”
Software and Other Challenges
“Without a doubt, software to create the G-code was the greatest hurdle for NBM as a manufacturing concept,” says Mike Cox, Bussellato product manager, Delmac Machinery Group. “The software has since advanced from needing a computer guy on staff and running all night (second shift), to being able to be run by typical cabinet shop personnel.”
“Another major problem involved the time required to turn the ‘design software’ parts into code the routers could make,” adds Thompson. “This was resolved with faster nesting software that reduced the time per part required to nest the parts on a sheet from 7 to 9 seconds per part to less than 4 seconds per part.
“The other major problem, which can still be an issue, is the ability of some machines to hold small parts in place. This has been solved by some router and software companies in a variety of ways,” Thompson says. Solutions include: larger vacuum pumps and vacuum supply lines, larger plenums under the vacuum tables and dual zones for vacuum tables. Also improved are: the monitoring of inches of mercury of vacuum as sheets are machined; the optimization of cutting processes via software to always cut the smallest parts first; and software designed to place small parts to the middle of sheets.
Dave Wright, Masterwood regional sales manager, also notes improvements in vacuum systems. “The vacuum systems were rarely adequate in the early years. Now, smaller and more compact machines offer proper vacuum, a work area which allows for easier part access and part removal. (Also,) early flat table routers didn’t have the boring heads or the feed speeds which are available now,” Wright says.
“(Another) truly difficult challenge was the requirement to deal with partial sheets, sometimes called ‘drop,’ left over from a job,” adds Susnjara. “This material represents real cost. However, developing a simple method of handling it presented a major technical hurdle.
“We had to develop an electronic description of all the parts we wanted to make, send this to the CNC machine control, scan the drops we wanted to use, have the machine control develop the nests for the exact material sizes being used and then develop the required CNC programs to cut those nests. We were able to develop a method for defining an area on a sheet that is not usable. The control then nests around this area using only good material.
“A cabinetmaker may now be able to purchase material with surface defects at a substantial discount and automatically nest around the defects, dramatically reducing material costs,” Susnjara adds.
Further Machine Developments
“On the machinery front, the advent of ‘flow through’ fixturing, dynamic tool change and the adaptation of multi-spindle drills to CNC routers, virtually eliminated machine set-ups. Every sheet processed on the machine could be a different group (nest) of parts,” Alsup says.
“Concurrently, the design software programs developed the ability to generate electronic part drawings automatically. The integration of software and machine technologies provided the ‘zero set-up’ basis for NBM,” he adds.
“To be truly effective,” Hillis says, “the machine has to be able to hold down small parts positioned at any angle in the nest. This is an area that the original style of NBM machines,the roller hold-down type, had problems with. The traditional roller hold-down machines work well for parts positioned lengthwise on the table, but they do not fully address the complex nests that can be created with today’s software.
“By requiring the end user to position parts in one direction material, yield can be lost. With the new software capabilities, the machine is required to cut both small and large parts positioned at any angle on the table. To do this, high volume vacuum pumps were added to the routers along with a vacuum system and plenum that would accommodate the air flow. Couple these features with the new higher cut speeds available and you have a machine that is ideal for NBM,” Hillis continues.
Radusinovich adds that increased horsepower, higher feed rates and an increased capacity in the working zones have also improved the process. On the horizon, he says, are more advanced bar coding capabilities plus more routers with close to zero chip-to-chip time.
Cox details further developments. “Since NBM requires the router motor to be cutting for much longer periods without rest, liquid cooling of the spindle has become a necessity to preserve bearing life. In addition, improvements have been made in material handling systems to facilitate the unloading and loading process to increase the production output. A machine that can rout at 2,500 inches per minute but sits idle while being loaded and unloaded is a waste of technology.
“Full tool coverage is another aspect of NBM that is often overlooked,” Cox adds. “If a tool can’t reach, then the software must alter the nest to accommodate the machine tool. Yield and processing time will suffer.”
“Control technology,” Dupont says, “has also provided accuracy and repeatability, even at high machining speeds. Digital servo drives precisely model and control the axes and accurately keep them synchronized at all times.
“Newer generation controls with PC front ends make it easy to incorporate the machinery into the factory network. This facilitates sharing information between the design office and the factory floor. Errors are reduced, turnaround time is reduced, and numerous other benefits follow,” he continues.
“The industry continues to embrace this new technology at an amazing rate,” adds Ridgway. “Future developments will always be based upon a sound technological foundation and will proceed along that direction. Stay tuned for more on this in the coming months.”
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