High-tech dovetails

A traditional dovetail joint – however efficient and visually attractive – is also rather difficult to manufacture by hand. So even though it was taught at vocational schools throughout the second half of the 20th century, it is less and less done in real life carpentry.

This is changing now. Because with modern five-axis joining machinery, the tapered dovetail is milled with high-precision even in angled connections. Such a machine – or more specifically, a Hundegger K2i – has now been working at the Schwangler carpentry in the Bavarian town of Petting since July. Master carpenter Andreas Schwangler uses the traditional connection method more and more often thanks to his modern CNC machine.

"No more by hand"

Long-standing timber joinery knowledge and high-tech go hand-in-hand. But what's behind the blue and yellow machine with the “Hundegger K2i” type designation? It is no less than the world market leader’s latest version of the single-component joining unit.
Two gripping arms pick up the timber from the infeed and guide it through the work zone. Multi-purpose units (drilling, milling, triming, marking, ...) execute the worksteps as laid down in the CAD-plan. Human intervention is not necessary.
Key advantage of the world's best-selling joining station is its flexibility. Thanks to the aligned module design it can be upgraded to meet the exact requirements of the customer. Schwangler’s main goal was to achieve a high degree of automation. "In the process of joining, we do nothing by hand anymore", he says.
Apart from the standard sub-table trim saw he ordered his K2i with the following units:

five-axis milling headtwo vertical milling headsthree drilling units (horizontally, vertically, horizontally pivoting) slot unit adjustable block board milling unitthree marking units

Already last year, Schwangler purchased a Hundegger four-side planer. It puts the final touch to the surface of the joined components.

First mill and drill - then plane

Let us join a fictitious beam on its way through the K2i. In this case, it is a secondary beam of a wooden ceiling with sight-grade bottom side. For this, Schwangler uses high-quality glulam. The raw glulam beam is placed in the infeed by a forklift. A cross conveyor moves it all the way back until it impacts the stop rail which represents the machine’s zero baseline. From there, two gripping arms take over. The CAD/CAM data for processing were transmitted to the Hundegger control during work preparation. Schwangler uses software designed by Nussreiner which perfectly communicates with the machine.
As soon as the operator starts the cycle at the control panel, the processing begins. First, the sub-table trim saw makes the front end completely plane. Then follows the dovetail joint. At first, a cylindrical router head cuts the shape of the bung into the wood. The flat knives of the tool leave behind a flawless surface. Slightly grooved, on the other hand, is the side surface of the bung which prevents wood fibers from splintering. The process it is performed with a precision of tenths of a millimeter.

In order to connect it to a staircase, holes for a threaded rod are required which are done by a pivoting drilling unit. The end milling tool produces a pocket which can accommodate the screw head. Now the dovetail bung is also cut on the back of the wood component. While the router machines the conical shape at an angle, a fully automated conveyor belt takes all residues to a hacker.
The joining process itself is now completed, yet the surface is still waiting for its sparkling finish. This is carried out by Hundegger’s automated four-sided planer. The few millimeters of extra thickness has already been taken into account during the CNC machining process. Once the component comes out of the machine it is ready for installation. Manual finishing is unnecessary in just about all cases, "provided the CAD draft was done correctly", adds Schwangler. He and his team are quite experienced in this. But when executing commission joinery orders, the underlying draft must be checked for plausibility sometimes. "Otherwise you get square pegs and round mortises out of the machine", the master carpenter says, smiling.
In commission orders, the dovetail happens to be popular as well. After all, it is a cheap connection that needs no further technical device other than a fully threaded screw (editor’s comment: This also depends on regional wooden building codes).

Mostly roof trusses, sometimes entire houses

Schwangler employs five carpenter journeymen. With his small team he works regionally – usually within radius of 15 km. His main business are roof trusses in single-family homes, larger object and agricultural buildings. With the wood components of up to 30 by 62.5 cm and lengths of up to 20 m it can handle, the joining unit is ideal for these jobs. Sometimes Schwangler gets to built complete wooden houses in MHM-design: To get these patented glueless solid wood wall components prefabricated with millimeter precision, he cooperates with the Koch timber construction company, Ainring/DE.

Only good things to say about the "old one"

There is enough to do for the timber construction contractor. "The order situation is good", says Schwangler as he describes the favourable market conditions which are currently characterized by "low interest rates". In days like these, investing in one’s own machinery just makes a lot more sense. There was never a doubt on Schwangler’s mind, by the way, that the new joining line would be a Hundegger. Twelve years ago, his father had already purchased a Hundegger unit – at that time the previous K2 model. Without much ado, Hundegger dismounted it and took it in for an overhaul. Used equipment designed by the world market leader in CNC joinery is highly sought after and therefore easy to re-sell.

In Petting, on the other hand, a state-of-the art machine does a reliable job now. In a matter of two weeks, the old unit was removed and the new one in place ready to work. With the exception of the automatic disposal, no additional investments were necessary. The unit will have to manage between 1,000 and 2,000 m3 of joined timber a year in the future. Schwangler does not intend to expand his business, yet it is his ambition to remain state-of-the art with his technology. And for that, he is in good hands with Hundegger. "We have been satisfied in the past and we are also now", he says. In this way, Schwangler is well prepared for the future. And he has no reason to believe why commercial fortune should forsake him – as long as he keeps cultivating the art of dovetail making in the foreseeable future.

Facts & Figures: Schwangler

Established: 1970
Company owner: master carpenter Andreas Schwangler
Location: Petting (Upper Bavaria)
Product range: contract joining, roof trusses, balconies, lodges, log cabins, solid-wood wall houses (MHM-system), interior design, construction joinery
Area: majority of orders are within radius of 15 km Employees: 5

Facts & Figures: Hundegger

Established: 1978
Location: Hawangen/DE, 26 branche offices and representations worldwide
Managing directors: Hans Hundegger, Otto Nothelfer, Hans Schillmeier, Walter Fahrenschon
Employees: 400, including 300 in Hawangen
Products: joining plants, cutting and gantry machining equipment, panel cutting machines, planers, solid wood wall lines, profiled wood element lines