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IWF ATLANTA REGISTRATION 2_19_24
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Christian Vollmers: Maximizing your nesting performance

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Nesting is not a new technology and the woodworking industry is not the only industry using it. Originally invented in the leather industry to optimize the yield from each piece of leather, the nesting process became very popular in the woodworking industry in the early 1980s. The nesting process provides unique advantages, which make the technology well suited to small start-ups as well as established mid-size production shops.

Because of its popularity there are many suppliers offering a wide range of solutions, which can be confusing not only to the first-time buyer, but also to experienced professionals. Here are some of the many criteria that determine what might be the right machine for your application?

  • What capacity do I require?
  • Do I need a drill block?
  • What is the right table size?
  • How many tools do I need?
  • What kind of software do I need?
  • How much vacuum do I need?

All of these questions are important and need to be answered prior to a purchase decision to avoid surprises later.

In this article I would like to focus on only one of these questions – What is the production capacity of the machine? How many sheets will be cut at the end of the day or shift? To answer this question we have to recap the process of nesting.

  1. Prepare and position a new panel on the spoil board.
  2. Select and start the program.
  3. Run the program with all drilling, grooving and routing operations.
  4. Clean the nested panel.
  5. Remove, sort, check, label and stack the cut parts.
  6. Clean the spoil board

This sequence of steps has to be repeated for every sheet that has to be nested. In addition tools and spoil boards have to be re-surfaced or replaced in intervals that depend on the materials and patterns cut.

The necessary time for each step depends on many factors, for example:

Process step 1

The placing of a panel depends on the size and weight of the panel and whether the panel can be placed manually or if a hoisting device like a vacuum lifter is required. Are the panels stored beside the machine or do they have to be located in the warehouse and transported to the machine every time?

Process Step 3

The time required for the machining process depends on the size of the nest and whether special profile tools are used e.g. for the manufacturing of doors. Is the nest cut in one or two steps to reduce the cutting pressure and optimize the hold-down of smaller parts? How many holes have to be drilled? What is the speed of the machine or what type of tool is being used for what type of material? For the production of case goods even the construction method of the cabinet will have an influence on the processing time. To cut the nest for a cabinet using blind dado will take more time than a cabinet that will be doweled.

Process step 5

Again the size of the panel has a significant impact on the time necessary to unload the machine bed. The number of parts, the time spent on inspection and the complexity of sorting/ stacking the finished components are all factors that make this process step very time consuming. The application of labels to identify parts will extend this time even further.

Looking at the three process steps I described above, it becomes apparent that the biggest opportunity for capacity improvement lies in the last process step. After the machining of the panel is completed, the cut parts have to be manually removed from the machine table. The machine (your investment) cannot produce until the operator has completed that task. With the addition of an automatic push-off device the complete panel (all parts Maximizing your Nesting Performance still surrounded by the skeleton/ frame) will be pushed off the machine table onto an outfeed conveyor. The machine table is quickly cleared, the next panel loaded immediately and the program started. This way the operator can remove, sort, check and optionally label the cut parts from the outfeed conveyor while the machine is already processing the next panel. With the right pusher system the spoil board can also be cleaned (step 6) while the complete nest is pushed off the machine table.

The following calculation is based on what I see happen in shops every day. The times are averages and they will illustrate the influence of an automatic push out device. Let us assume we process kitchen cabinets out of 4' x 8' melamine chip board.

To place the board onto the machine and to load the program takes approx. 30 seconds. To run the machining program will require about four (4) minutes, while the offloading of the parts and removal of the waste pieces will take another three (3) minutes. With 30 seconds to clean the spoil board the total cycle takes eight (8) minutes for a completely manual operation.

By using a system with automated push out device, the loading of the board and the program selection will still take about 30 seconds, and the machining will also still require the same four (4) minutes. But instead of the time consuming off-loading of the single parts and waste pieces, the whole nest will be pushed off the machine and the spoil board cleaned in 30 seconds. The entire cycle takes only about five (5) minutes.

Let us look at what effect this has on the numbers of sheets produced during the day. The manual nesting cycle takes eight (8) minutes, which translates into 7.5 sheets per hour or 60 sheets per day (assuming 8 hours per day). Now we have to consider down time for replacement of tooling, re-surfacing and changing of the spoil board and some preventative machine maintenance as well as breaks for the operator. From experience we say that a machine in this environment will be available for production about 85 per cent of the time. Fifteen per cent is spent on the maintenance items listed above. This reduces the daily production total from 60 sheets per day to 51 sheets per day.

With an automatic push-off and cleaning system, where the overall cycle time is reduced to five (5) minutes, the output can be increased by 31 sheets per day, an astounding 60 per cent performance gain.

By moving the processed parts as quickly as possible from the machining to a holding table, the nesting router can be back in production 60 per cent faster. There are also automated feeding systems to load new sheets onto the machine table, but the time difference between automatic and manual loading is insignificant and the output of the nesting machine is not affected.

For cabinet shops that have a demand of 30 sheets or less per day a stand alone nesting machine will easily meet the current demand as well as allow sufficient room for future growth. Companies that have a demand of 50 sheets or more will need to consider a nesting system with push-off capabilities.

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