CNC Machining Marine Nesting "Stringer System"
Boatbuilders who produce hulls benefit from CMS' powerful and efficient nested based plywood machining solutions for boat carcass ribs and stringer components, which result in improved yield, easy machinability of typically difficult to hold parts, elimination of the many production templates required, their storage, greatly increased labor savings, and the reduction of in-process inventory.
To avoid repetition, see also the "Wood Nesting" sector, where the fundamentals of nesting are covered.
Karat - nested based machining in a cell
Karat, CMS' moving table class CNC machining center, provides a double table solution for nested based work. Karat here is shown with an automatic infeed device to load full sized sheets onto each table. After the machining cycle has finished, another vacuum take away device, with high density vacuum cups, removes all the parts at one time and places them onto a roller take away system. The table works with a vacuum waste board and following the machining cycle, it sweeps away any scrap into a scrap take away system and vacuums up any remaining dust.
AVANT - auto infeed, double working spindle, extended unload areaBoat hull production typically requires an interior carcass skeleton of ribs and stringers for structural support. These components vary in shape and complexity, but with today's powerful CAD/CAM software solutions, including "true shape" nesting capability, in which the software accommodates non-linear edges into its calculation, design, best layout possible for parts, and optimization of material, are within the reach of almost any sized company.
CMS' Avant, its moving gantry class machining center with CMS' unique flow through vacuum belt system, as shown in this photo, is provided with an automatic infeed system so that stacks of material are available and automatically fed in to Avant as needed. Avant is capable of working with various sized sheets automatically and adjusting the vacuum holddown depending on the sheet size. After Avant aligns the sheet, it vacuums it in place securely through the remainder of the work cycle and carries out its range of high speed routing, slotting, sawing or drilling operations. This Avant is also equipped with double independently CNC controlled working units, so that, where possible, routing on two parts may occur at the same time, or making a tool change on one spindle, while the other is working. This Avant also has an extended belt providing an unloading area and easy part removal.
For additional information regarding the technical manner in which Avant holds entire sheets with its belt, the cutting process involved and machine capabilities, please refer to the "Wood Nesting" sector.
Avant - flow through belt, unloading belt, roller holddown system
When multiple sheets have an identical layout and cut pattern, Avant's unique roller holddown system makes it possible to cut them in stacks. Avant's vacuum belt provides the flow through capability to move the stack through the machine and the vacuum to hold the bottom sheet. Avant's special roller holddown system provides the pressure to keep the stack of sheets together during machining so that they don't slide over each other, making it possible to machine parts from 2, and sometimes more, sheets at a time. Avant's roller holddown system also automatically adjusts so that if a special working unit, for example drilling or sawing unit, needs additional space, machining processes which comes before the routing, Avant widens out the roller holddown system and then following that work reduces the space again, keeping the rollers as close as possible. Each of Avant's double set of rollers is itself a double set and controlled for automatically raising and lowering related to where the edge of the sheet is, so that it never rolls into the stack of sheets to disturb them, but places its additional double roller on top of the sheet just after an edge passes under it. Avant's roller holddown system is also perfect for the "real" world, in which sheets may have some surface warp in them, making it difficult or impossible to hold them down, yet Avant's roller holddown system holds them under pressure during the machining cycle.
Nested stringers & ribs - "true shape" nesting
Nesting of stringers and ribs for a boat's carcass can be perfectly accomplished with today's CAD/CAM software with the enhanced capability of "true shape" nesting technology, in which all the parts for a particular order or group of orders can be optimized for best yield, while at the same time, their placement within the nest can be optimized without regard to typical rectangular nesting boundary methodology and 3rd phase part rotation of rectangular shapes within unused portions of a sheet. "True shape" nesting permits edge recognition and movement of nonlinear edges within other nonlinear available spaces to achieve the best rational layout possible, a perfect combination for panel nesting applications and CMS' CNC nesting solutions.
Outfeed options - unloading belt or full sheet vacuum unloading device
When it comes time to unload the parts from nested sheets, CMS provides a range of options. This photo shows a separate unloading table with access from 3 sides, where parts can be separated from the nest and off-loaded to skids, or CMS' special full sheet unloading device with continuous vacuum surface, making it possible to off-load the entire sheet at one time when cycle times might be too short to permit unloading during the machining cycle.
Laser ID marking - part/order management and assembly information
To keep track of the many rib and stringer parts machined from each sheet and to make sure they end up with the correct order and in the correct location in a specific carcass, CMS provides laser ID marking technology. In this photo is shown CMS' laser ID marking unit placed at the infeed section and integrated with the work cycle. While the machining center is carrying out its processing work on the sheet, CMS has placed a 2D, high speed, CNC controlled laser marking device at the infeed section, and located over the infeed rollers. The laser marks each part that will be cut from the sheet, in a predetermined location, with the information necessary to identify it for the order with which it goes and its carcass location, so that groups of parts move together through production and parts are ultimately located easily and placed at the correct position within the carcass.
Large wood boat stringer system
Boat carcass stringer systems can be very large, as shown in this photo.
Hybrid lamination stringer systems
A hybrid process is also the choice of some boat builders, in which they unite a wood stringer system with a fiberglass liner and encapsulate the stringer system, combining the strength and flexibility of wood, and its sound deadening quality, with the benefits of fiberglass, resulting in a quieter, more sturdy boat.
Large stringer systems
Large boat structures, as well, implement stringer components for structural strength.
Courtesy of Vectorworks Marine, one of CMS' customers providing special solutions and support for marine industry engineering, tooling and large laminations:
Ribs / Bulkheads
Ribs design can also be adjusted to include bulkhead considerations, in which passage openings are placed and other structural elements can be attached by the use of grooves.
Ribs & Stringers nested layout
The photo shows a high density layout for a stringer system in which there is very little unused material left.