A log cabin changed it all

Vorarlberg is a popular tourist destination not only because of the beautiful scenery and the Lake Festival. The architecture – particular that of timber construction – also attracts several thousand visitors to the “Ländle” every year. The habitat is ideal there: It combines ambitious planners, courageous builders and high timber craftsmanship. In the midst of the Bregenzerwald region, a master carpenter has just started up new Hundegger joining machine – the Robot Drive.
For years, Harald Berchtold has been considering investing in CNC joining technology. This spring the time was right – for two reasons: “With the Robot Drive, Hundegger has finally put the perfect machine for my purposes on the market. But what actually triggered the investment was a high-quality log cabin with a rather complex larch facade I had to build”, says Berchtold as he drives up to this object.

Wood perched at the end of the gorge

It is pouring down with rain as the master carpenter from Dornbirn makes his way up the Rappenloch gorge. The Ebnit district is located at the end of the impressive gorge. Perched high above the valley is the new log house. The scaffolding is still there, but the facade is already completed. The architect has intended for horizontal larch boards to be put up. At the corners of the house they alternately protrude by an inch. Without question, this looks impressive. But behind the ventilated facade, the massive log house planks will undoubtedly settle. “I think this log cabin is an ideal wood construction. The whole added value was achieved within the carpentry. But you have to get the details right, because planks will always give way a few millimeters”, says Berchtold as he leads the way to the house.
At the gable, the peculiarities of the log cabin become most evident. The ridge beam rests on the log house planks. The gap to the window structure with its vertical wood beams is so wide, it could easily accommodate a ping pong ball. The facade has to cope with this kind of settlement behaviour. To facilitate this, Berchtold attached vertical battens with a dovetail profile to the logs. All around the house, they connect to the larch planks with a dovetail groove. Only the bottom planks are fixed with screws. Now the dovetail battens can slide along the facade planks according to what the settlement requires.
The building at an altitude of 1100 m has yet more remarkable details. Berchtold even produced a special ship deck style wooden floor. Its but slightly brushed spruce wood planks will gently complement the feet that walk on them. Besides the beautiful flooring surface also the walls are worth a second look. Their corners are cut to mitre. End grain thus escapes the eye.

Flexibility and precision count in the Ländle

With the picturesque surroundings, all of the aspects described make the high-end log cabin a perfect textbook reference. Its high quality is the perfect passage to the aforementioned Hundegger Robot Drive unit. So we head back to the town of Schwarzenberg and enter the joining hall of the family business. When the new hall was planned and built twelve years ago, space for a CNC joining unit was provided at the head end.
Two years prior, Hundegger had introduced the K2 joinery machine. This has revolutionized joinery in many companies, but for Berchtold it was not the right tool yet. It was not until Arno Gaggl, Hundegger‘s sales manager for Austria, invited him to pay a visit to Hawangen early this year that Berchtold‘s enthusiasm was sparked. Gaggl showed him the brand new Robot Drive. “The machine offered everything I possibly needed. The six axle arm makes machining from all sides possible – without turning the workpiece”, says Berchtold emphatically.
However, the carpenter from the Bregenzerwald was not completely happy with his investment. Components with smaller dimensions had a tendency to sag while being machined. Although the deviation was only 1 or 2 mm, it became immediately visible at mitered corners. These are typical teething problems of a newly developed machine. So what to do?
Hundegger holds on to the philosophy that customer‘s suggestions are a valuable drive for machine development. “For this we need carpenters like Harald Berchtold. Constructive criticism helps us to perfect the equipment”, says Gaggl. For small-sized wood components the carpenter from Vorarlberg suggested a simple solution: The workpieces protrude freely into the work zone and are processed by the six- or five-axle arm. The deflection increases with the square of the protrusion. So the point of machining was shifted much closer to the holding rollers. Based on this experience, Berchtold praises the implementation of the solution. “The technicians at Hundegger were very interested in fulfilling my wishes.”

Also made for staircase construction

Not only the new joinery machine catches the eye in the joining hall in Schwarzenberg. What is remarkable about the Berchtold‘s carpentry is the depth of value added production. The roundwood comes from the Bregenzerwald which is still purchased at the forest roadside. A sawmill in the neighboring village does the custom-cutting. The lumber is then kiln-dried in Schwarzenberg. Berchtold has two vacuum dryers and a high-end planing unit on his premises. “The aim of all this is flexibility. If the client wants to have dimensions that are not available on the market, I will satisfy him”, says Berchtold. This dedication to flexibility is certainly one reason why the improved Robot Drive now fully convinces him.
The Hundegger plant is bound to not only process softwood. For staircase production is in fact an important mainstay of the twelve-man business. On the large lumber yard not only spruce and fir wait to be processed, but also oak, cherry, ash, elm and a number of other coloured hardwoods. So far, they are processed on a four-axis machining center. “A fifth axis would be useful ... ,” says Berchtold pensively. Is Hundegger‘s Robot Drive up to that? “Sure. I‘m not worried about accuracy. This is just a question of the right tools.”

Austrian carpentries geared towards CLT

Berchtold‘s Hundegger unit carries the type name Robot Drive 1250. It is designed for the maximum cross-section in this machinery class: 30 by 125 cm. “All Robot Drives that have so far been installed in Austria operate in this size category”, Gaggl explains. The reason is simple: 1.25 m machining width allows for joining cross-laminated timber elements. In Austria being the CLT-boom country, hardly any master carpenter can neglect that product. For easy handling, Berchtold‘s Robot Drive also has an automatic lifting table for this purpose. This is where stacks of lumber and laminated timber wait to be machined one by one.
The output of Berchtold‘s joining unit is complemented with an exceptional device. A series of pneumatic cylinders were added to fix wall and roof elements. For this Berchtold uses con-struction timber with double tongue-and-groove joints. What stands out here is the connection means: A wooden dowel with the shape of an “8” fits exactly into the holes which the Robot Drive has milled on the edge of the wood elements. “This gives me the option to implement solid wood constructions and thus keep added value production in my company”, says Berchtold.

Carpentry Gerhard Berchtold – Facts

Established:1911
Management:Harald und Manfred Berchtold
Location:Schwarzenberg
Employees:12 Products & services:Wood constructions (single and multi-family houses, public and commercial buildings, renovations, extensions, facades), staircases

Hundegger – Facts

Established: 1978
Managing Directors: Hans Hundegger, Otto Nothelfer, Walter Fahrenschon, Hans Schillmeier
Employees: 400, including 300 in Hawangen/DE
Product range: joining plants, cutting and gantry machining equipment, panel cutting machines, planers, solid wood wall lines, profiled wood element lines