Palmako, a Lemeks group-related company located near Tartu in Estonia, has been producing materials for its in-house garden shed and timber construction production since 1997, commercial laminated timber productions since 2007, and pellets since 2013. With four factories, the group has an annual production output of around 51,000 wood houses, 24,000 m³ of impregnated garden timber and 46,000 t of pellets as well as 27,000 m³ of laminated timber. The glulam production was supposed to grow; therefore, in the summer of 2017, the decision was made to replace the second-hand bought and by now slightly ageing glulam production line in its entirety by a new investment, head of production Silver Simenson remembers: "We had simultaneously become aware of a trend towards order-related smaller batches at an increasing demand." For the design, therefore, flexible product changeover was the main focus. Before that a detailed planning process had taken place that fundamentally questioned both the previous plant concept as well as the adhesive system in use.
The result was a highly flexible system for the production of glulam, duo, trio, KVH and log house planks – for batch production as well as order-related production on commission. What is special here is that the design and construction of new system was assigned to a syndicate of specialists which reads like a who's who of the sector: German industry plant manufacturer Minda from Minden was responsible for mechanization, manufacturing control engineering and project management, Kallesoe Machinery, Lem/DK, supplied the high-frequency press, the planing units come from Schwarzbeck, Pinneberg/DE, and Weinig Grecon, Alfeld/DE delivered the trimming machine and finger-jointing unit. The advantage of this solution is self-evident: For every area of the facility, Palmako chose the preferred supplier. All system components are perfectly synchronized and coordinated. Furthermore, the syndicate took over the entire project management including interface coordination.
The lumber used for processing is kiln-dried and unsorted lumber from external suppliers, Simenson explains: "A forklift is loading the lumber in packages at two feed stations." The packages are destacked and isolated layer by layer by means of vacuum lifters. Boards that fail the subsequent moisture measurement are discharged. Afterwards, the heart-side is determined, and a turning station turns the boards according to the classification.
Sorting with dimension changes
Flaws are marked by hand at two different spots. The next position features a metal detector to protect the machines and tools that follow. Next, the marked boards go through a net length measurement, are registered by the production calculator and sorted into a 3-level grade buffer to optimize wood yield. A Weinig Dimter Opticut 450 is automatically cutting out marked spots.
In the next step, the trimmed-out board portions are finger-jointed on the face, glued on one side and pressed into a continuous strand with the Weinig Grecon finger-jointing unit Power-Joint 15. Subsequently, the lamellas that are cut to length are brought into the 3-level curing station.
Fetching cured lamellas from this buffer to the Rex lamella planer by Schwarzbeck and the subsequent glue application unit is done according to the glued truss structure or the press filling specified in production planning. In line with the plant concept designed for small batch sizes, the Rex Bigmaster lamella planer is designed for unmanned operation with fully automated control of all axes. Manual adjustments at the machine that do not take place automatically via control programs can be made outside of the soundproof cabin so that there is no need to enter the security zone. This means that machine operation is not interrupted. Upstream of the lamella planer, there is also a bypass for KVH and log house planks: "KVH can be passed by the high-frequency press. After high-frequency gluing, half glulam beams are fed into the lamella planer a second time and afterwards glued together," Simenson elaborates.
To avoid long press and throughput times, Palmako decided to use a high-frequency press. "With a HF press, gluing is quick, but changing to different dimensions used to be time-consuming up until now," Simenson says. For the new line, Palmako therefore opted for the Vario press by Kallesoe Machinery, Lem/DK: "With its minimal intake width of 240 mm, this press can even press individual glued trusses of this height, and at a throughput width of 1260 mm, different lengths can be processed within the same press cycle." For this, lamellas are aligned at their end faces to fill out the press. Changeover time for a dimension change is shorter, as well, according to Simenson: "Height adjustment of lateral thrust plates is semi-automatic which saves us time."
With a capacity of 150 kW, the "microwave" generator ever so slightly exceeds common household power requirements, Simenson smiles. In fact, however, with a total power rating of 318 kW the power demand can be called moderate when considering the annual output per shift of the HF press of about 32,000 m³. This makes glulam with lamella lengths between 4 and 18 m, thicknesses between 60 and 240 mm and widths between 60 and 1260 mm possible. The feed is continuous. Of course, with every change in thickness or width a new press cycle must be started. The entire press line can be set up and controlled from a central control stand with very little set-up times. Since high-frequency technology merely warms up the glue in the groove and no heat must be inserted externally with great losses, the press line also does not need a cooling buffer – the goods can be forwarded directly from the press to further processing.
Downstream of the press, a fully automated transport takes the pieces to the cutting and finished planing area with an on-site horizontal band saw, a cross-cut saw for single and group cutting and the Rex high-performance finished planer. To optimally process this variety of products, minimum and maximum cross sections and truss lengths, the Supermaster finished planer has a number of flexible options such as the fully automated control of all axes, direct drive of output shafts and rotational speed control. The machine can travel in parallel which not only allows for uniform utilization of the working width but also ensures uniform use of tables and pressure units when processing smaller dimensions. The powerful forward feed can even handle very large trusses with ease while still operating delicately enough for clean machining of smaller dimensions.
The great diversity of components was also an extraordinary challenge when designing the patching station. In order to avoid backlogs especially with small, short components that can be pressed with a high cycle output, two workstations were realized on two levels with large buffer areas.
The fact that the entire plant is designed for both production on commission up to batch size 1 as well as batch production becomes apparent at the discharge of the system. Standard packages are formed with a conventional stacking unit. Flexible customer commissions can be compiled individually from single parts in an area storage space with a vacuum crane according to the package based on planning.
In any case, head of production Sivler Simenson seems to be quite taken with the design: "Compared to what we had before, we can now produce a lot of products more efficiently. There is less special production and a more flexible production is possible."
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