Tool life addition in jointing, sizing operations

ANDREAS KISSELBACH & DR JUERGEN GRAEF

The range of concepts extends for machining solutions from two to five spindles.

Furniture and kitchens, as a form of expression for individuality and lifestyle, could not be more diverse in their type and construction. Since consumers are increasingly switching from utility and functional objects to lifestyle objects, the demand for quality in terms of materials, manufacturing quality, utility value and design is increasing.

For manufacturing companies, the resulting growing variety of materials with sophisticated surfaces, coatings and structures is essentially decisive for the high demands on the production technologies used in throughfeed technology.

Particularly in view of the processing costs, producers are forced to create their production processes more and more flexibly and efficiently – partly due to the special market and competitive situation in furniture production, which increasingly focuses on the topic of cost optimisation.

Sizing panels

Furniture and kitchen manufacturers increasingly have to deal with issues such as productivity, efficiency, flexibility and quality in order to be successful with their products on the market.

Against this background, the sizing of furniture panels, as a finishing operation before edging, takes on a key function in the entire production process. The line between the required processing quality and the maximum economic efficiency of the overall process is particularly narrow here, and in many cases holds unimagined potential for optimisation.

Particularly in the case of high-quality fronts (with a so-called zero-joint look), in combination with high-gloss and matt coatings, valuable real wood veneers or finish foils, perfect machining of the decorative edges and narrow sides is absolutely essential before edge banding.

The aim is always to achieve an almost invisible glue joint and a tightly closing edge. From an economic point of view, these challenges can only be solved with suitable, perfectly coordinated machining and tooling concepts.

Frequent tool changes and the associated machine downtimes reduce productivity and drive up production costs. An additional cost factor is the resulting stockpiling of replacement tools, because these tools also have to be purchased and constantly available to ensure a smooth production flow.

Tool life

The decisive factor for significantly reducing production costs is, therefore, the use of tools with particularly long tool life. This is actually, a simple task. For many users, however, the question arises as to how this should be possible at all, given the general state of development of current tool technologies.

After all, common tool systems hardly differ from each other at first glance. The magic phrase here is: “tool life addition“.

Perfect edge quality can only be achieved with the described surface materials on chipboard or MDF by circumferential cutting with diamond tools, the so-called jointing. In the course of the cutting process, the used diamond cutting edges wear out, especially in the area of the top layers.

Cutting edge areas that lie outside the tool contact, however, remain unused. With the concept of tool life addition, these unused cutting edge areas can be brought into the quality-relevant machining zone.

In practice, this is done by the axial adjustment of the jointing tool. The result: tools can remain in use over several tool lives. 

An excellent example of how these still sharp cutting edge areas can be used for tool life addition is the specially developed, width-adjustable jointing cutter from Leitz.

By adjusting the width of this two-part tool system, unused cutting edge areas can be brought into use in the quality-forming cutting area of the surface layers when the machining quality decreases.

The adjustment is carried out in millimetre steps in just a few operations. This way, the life of such a tool can be significantly multiplied in comparison to one-piece jointing cutters.

For example, by adjusting the tool six times, the tool life is achieved seven times before the tool needs to be re-sharpened. The operator does not have to correct the spindle position, as the width adjustment of the tool is synchronised with the top and bottom of the panel.

Maintaining accuracy

This is an immense advantage, considering that fewer tool changes and no time-consuming adjustment work are necessary for positioning the tools, thus significantly increasing the productive times.

Practical applications have proven that machine downtimes can be reduced by up to 80% compared to conventional tool changes.

The challenge for the tool manufacturer with such adjustable tools is to achieve the same accuracy as with one-piece tools and the functional reliability under the influence of dust and chips.

A specially developed hydraulic clamping system with user-friendly operation of all functions from above and integrated dust protection guarantees the highest precision and reliability of the tool system.

Since the wear and tool life of jointing cutters is very strongly influenced by the infeed (chip removal), it is recommended to use double hoggers for pre-cutting if the material removal exceeds 0.5 mm in order to protect the quality-relevant jointing cutters.

Depending on the machine configuration, the parts spectrum and the production volume, Leitz has developed different jointing concepts for “tool life addition“ for use in almost all common throughfeed systems. These are concepts ranging from mere jointing with manual width adjustment to fully automatic width adjustment with pre-cutting.

Five-spindle concept

The range of concepts extends for machining solutions from two to five spindles. For individual application, it is important to select the most reasonable machining concept for the customer, so that he can optimally design his overall process and ultimately produce with the greatest possible economic success.

The fully automatically operated five-spindle solution concept is already being used by numerous users. Despite its complexity, with the aid of several tool systems, very impressive savings in the overall process have been demonstrably achieved with this concept.

At the beginning of the machining process, a protective cutter cuts the front edge of the workpiece to the finished size in the counter-rotation and then stops again after only a few centimetres (red).

The double hoggers (orange) working with feed then take over the pre-chipping of the remaining panel length down to a small tolerance of ideally about 0.5mm to the finished contour.

Also working with feed, two staggered jointing cutters produce the finished edge – the first as a rebate cutter, responsible for the bottom edge of the panel (blue), the second for the top edge of the panel (green).

If the edge quality decreases, both jointing cutters, one from below and the other from above, are automatically adjusted by 1 mm by axially adjusting the spindles.

As a result, the previously unused cutting edge areas now take over the processing of the decorative coating. By moving the jointing cutters several times, the desired tool life addition and thus a multiplication of the total tool life is achieved. 

This five-spindle concept can of course be adapted to any range of parts to be produced. If, for example, two different panel thicknesses of 16mm and19 mm are to be machined, then the width-adjustable jointing cutters described above can be used on the two finishing spindles, which then machine one of the two panel thicknesses of 16mm (green) and 19mm (blue).

Re-conditioning needs

The concept of tool life addition as the innovative solution in the area of jointing and sizing brings advantages that almost every manufacturing company in the area of furniture and kitchen production would like to have.

Furniture manufacturers who are looking for solutions to achieve consistently high machining quality, longer tool life, shorter set-up and downtimes, lower production costs and satisfied employees will have to deal with this topic sooner than later.

The topic of jointing concepts and tool life addition is flanked by the re-conditioning of worn or damaged tools. Here, additional sharpening cycles on the tool and thus further savings can be achieved through appropriate professional sharpening.

Finally, it is not unimportant that the sharpening of diamond-tipped cutting tools is carried out by qualified staff and that only as much material is removed from the cutting material as is necessary during the sharpening process.

The professional service that Leitz offers in its more than 120 sharpening services around the globe is designed to conserve resources in this way. Here, the tools delivered are cleaned, sharpened and re-measured so that they can be used again by the customer after a short time, including a measurement report (plug and play).

All Leitz tools are serialised (RFID chip) so that they can be managed individually and that, with future machine generations, even an automatic data transfer between tool and machine would be possible.

With its innovative, efficient and sustainable machining concepts and tool solutions, Leitz proves that economy, flexibility and quality can be combined.

– Mr Andreas Kisselbach is Head of Research & Development at Leitz. Dr Juergen Graef heads the Leitz Technology Centre in Oberkochen, Germany.

 

A protective cutter (L) cuts the front edge of the workpiece to the finished size in the counter-rotation and then stops (red). The double hoggers (orange) working with feed then take over the pre-chipping of the remaining panel length. The wear on the cutting edges is always concentrated on defined areas and the width adjustment results in the tool life addition (R).

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