I have written about the benefits of manufacturing solutions based on nesting (see March/April issue) and sawing (see July/August issue) systems. In this article I will compare both and help you decide which one may be the right solution for your shop. If you expect a clear vote for one or the other, you will be disappointed. However, after you have read this article, you will be able to determine for yourself, which is the right system for your production.
Both systems have their strengths and weaknesses, and this article will explain the main arguments.
Capacity
The capacity of both cutting solutions is affected by the cutting pattern, the board size, the cutting speed and the book height (meaning the number of boards that can be cut at the same time). For cabinet parts or similar components you can expect to process approx. 50 boards per eight (8) hour shift and increase to 80 sheets with the right automation. A panel saw can process substantially more panels. Even the smallest beam saw can cut 100 single panels (no book cutting) per shift and an angular plant will cut up to 1,500 panels in a single shift.
Space
An entry level-nesting machine will require a minimum of 200 ft., 10% less floor space than a panel saw. You have to add at least 50 ft. for a CNC drilling center to the saw solution to drill and route the parts the same as a nesting machine. Once you are considering a nesting solution with automatic outfeed to increase capacity, the space difference becomes insignificant. If you need more than one nesting machine to meet your production, a panel saw with a CNC drill will become the less space demanding solution.
Investment
You can purchase an entry-level nesting machine as well as starter panel saw for about $70,000. Once you consider automatic off-loading for your nesting machine you can easily double that investment. This would then cover the cost of the additional CNC drill required for the solution with a panel saw. For larger production capacities where multiple nesting machines would be required, a panel saw solution with a CNC machine is, in most cases, more cost effective.
Automation
A wide range of automation solutions is available for these technologies. The first to be considered is typically part labeling, which is easier to implement on a saw; in the most basic version you already deal with one part at a time, which makes labeling easy. On a nesting machine you have to either put the labels on the full sheet prior to cutting (when their position is difficult to determine) or you have to apply the labels after the parts are cut. Any good labeling solution on a nesting machine requires some sort of automation.
Labour
A nesting solution is typically designed for a single operator; whereas a panel saw solution with a CNC drill that is run at capacity will require two operators. The processing cycle on a nesting machine is relatively long, which allows the operator to complete other tasks, such as horizontally drilling and doweling fixed shelves.
Capability
In general the saw/CNC combination offers a higher capability than a nesting machine. A panel saw in combination with a CNC router gives the operator a vast array of materials, porous and non-porous, that he can cut and process. Furthermore, this type of system offers greater processing options, i.e. grooving, four-side processing, postforming cuts, stress release cuts or the cut of strips for your edgebander (laminate or solid wood).
Production costs
Apart from the labour cost, which can be offset by the difference in production capacity, the two systems show a significant variation in production costs. The tooling costs and energy consumption for the nesting system is at least 50 per cent higher per part than for a panel saw solution. The nesting process removes at least twice as much material to separate the parts. This also increases the dust collection requirements; and the need for all parts to be held down continuously by vacuum during the nesting process, requires a much larger vacuum system than a CNC router. A nesting solution also requires the periodic machining and replacement of the spoil board.
Material
Both systems handle laminated particleboard or MDF very well, since these are virtually airtight and allow a good hold with the vacuum system on a nesting table. Once the materials get more porous or have a somewhat uneven surface (very open grain veneer, ply- wood etc.), it becomes more and more difficult for the vacuum system to hold the materials, whereas the mechanical hold-down by the pressure beam of the panel saw is not affected at all. Small parts or corrugated panel will also create problems on a nesting system.
Production concept
The single biggest advantage of the nesting solution is the fact that it cuts and drills parts in one step and eliminates the handling required between the panel saw and the CNC drill, but this comes at the expense of production capacity. By combining two production steps into one production cycle one loses the capability of parallel processing and therefore a shorter production cycle.
Yield
Yield is an important factor and the main reason for the development of the nesting solution, which was originally developed in the textile industry. There is a 20 per cent yield improvement when taking the same round component and processing it with straight cuts or ‘nesting’ it into the same sheet.
The more rectangular parts you have in your production, the less significant the difference will be. Another factor influencing the material yield is the waste due to the actual cutting path. A typical saw blade thickness is 5 mm or less, which accounts for a waste factor of approximately 2 per cent with average cutting patterns. The waste when using a nesting machine depends on the diameter of the router bit. Most common are router bits of 3/8" or 1⁄2", which reduces the yield by about 4 per cent.
Software
Both machine concepts require software to run most efficiently. The nesting solution requires the cutting and drilling information to be combined in order to generate a nesting pattern for each individual order. The part sizes are determined when the designer specifies the layout with the consumer and the drilling patterns are assigned according to the rules specified when the design and manufacturing software was originally set up. The panel saw solution could be set up in a similar fashion by sending cutting patterns to the saw and individual drilling patterns to the CNC drill, which are called up manually or by barcode. A more common set-up is sending the optimized cutting patterns to the saw and maintaining the drilling patterns separately. Drilling programs are called up manually or via barcode, but they can still be adjusted through variables on the plant floor if necessary.
Form and size of parts
The panel saw with a CNC router has the least restrictions in regard to the shape, form or size of components and you can virtually duplicate any operation on the part that you can do manually. This can also be done on a nesting machine, but will require considerably more effort for setup and specialized hold-downs. However, most non-rectangular shapes will have a higher yield, if processed by a nesting machine (see criteria yield), but smaller parts are better cut on a panel saw.
As you can see from the above overview there is no easy answer as to which production solution is right for you. As a general rule we can say that a small cabinet shop will benefit from a nesting solution because it will require less space, less labour and the lowest investment. As production requirements increase things are much less clear-cut, but as volume goes up, the unit production costs go down with a panel saw and CNC drilling solution. To find out the right production concept for you, you have to carefully evaluate each of the above aspects to determine their importance in your particular case. For example you can create a list and rate each aspect one by one. If the nesting concept is advantageous mark “N” behind the criteria, if nesting is very beneficial note “NN”. If the saw/ drill combination is more favorable put “S” or “SS” behind the criteria. If both concepts have the same value, mark the criteria with “0”. When you have marked all criteria count the “N” and “S”. “SS” or “NN” count double. The process with more counts will be more likely to fit your requirements. This is of course only a very rough guideline. Please talk to your consultant or machine supplier for a more detailed evaluation.
As a final point, keep in mind that ‘today’s’ nesting machine can also become ‘tomorrow’s’ CNC machine in a saw/router solution.
Christian Vollmers is the president of HOMAG Canada Inc. He can be reached at Christian.Vollmers@homag-canada.ca or visit the website at www.homag-canada.ca
