Advantages of CNC in wooden structures
Why is it worth using CNC in construction?
CNC accuracy and repeatability in woodworking
As a manufacturer of wooden structures, it’s crucial for us to accurately reproduce design specifications to within 1mm. The entire prefabrication system eliminates the human factor in beam routing. Thanks to CNC, we can guarantee repeatability even on large roof surfaces.
Why are accuracy and repeatability important? I’ll try to explain this with an example. Please note that this is one important aspect of roof truss accuracy, but there are many more. The graphic below shows a rafter connecting to a wall plate using a notch. The rafter presses against the wall plate with a defined area. This area must be specified by the roof truss designer and cannot be random or too small, as it must transfer vertical loads from the rafter to the wall plate. The graphic illustrates three common situations:
A) The joint is made precisely – the truss will last for years.
B) Poor finishing, too small a contact area – initially, nothing happens, but over time, the wood at the joint with the wall plate will compress under the load until the entire surface of the notch rests on the wall plate. This, however, causes changes in the roof plane, which can cause cracking of the plasterboard in the attic or leaks in the roof covering, causing moisture in the roof deck.
C) The finishing is imprecise, but the carpenter screws the rafter to the wall plate, so to the naked eye, everything looks fine. The problem is only reported by the roofer, who asks for an additional fee for the service, because he has to fiddle around and waste time to get the battens in a flat plane. If the inaccuracy is significant, the interior contractor will also have a problem, as they will have to work extra hard to ensure the drywall grid is flush.
Traditional carpentry joints and modern CNC machining
Traditional carpentry joints—tenons, caps, and dovetail joints—are proven solutions that have proven effective for hundreds of years. They were invented and practiced in a different era, when people had time to stop and think, to craft. In today’s fast-paced world, hand-crafting complex carpentry joints is not economically viable.
Today, carpenters, instead of using traditional joints, use system connectors. Thanks to CNC, we can use traditional joints, which often simply need to be secured with a screw or wooden dowel. This is economically viable because it positively impacts the durability of the truss and significantly speeds up the installation of the truss or other structure due to:
- Fewer system connectors
- The location of elements is predetermined—for example, simply inserting a column tenon into a socket eliminates the need for on-site marking.
- Fewer errors on the construction site—considering the comfortable office environment, decision-making is minimized in challenging construction conditions.
Laser tachymeter measurement in the prefabrication of roof trusses
Another factor that reduces the risk of error and the time of expensive installation is laser total station measurement. Using surveying technology, we can locate the contact points between the wooden structure and the building in 3D space.
The measurement result is a point cloud, which we transfer to a 3D model of the structure to match the truss to the actual, existing building geometry. The measurement report provides the investor with insight into whether the masonry elements are constructed according to the design assumptions. If deviations are significant, we can propose solutions to problems resulting from inaccuracies before processing.
We have successfully developed our own system for locating the pins protruding from the tie beam used for wall plate installation – this allows us to drill the wall plates using a numerically controlled machine. This allows us to position the prefabricated structure on the actual building during the design phase. This shortens installation time and reduces errors in the crucial process of wall plate positioning.
CNC wooden construction processing process – step by step
- Preliminary modeling based on documentation provided by the investor.
- Agreements – Proposed improvements and problem solutions by the roof truss designer.
- Laser total station measurements.
- Measurement analysis and report preparation.
- Matching the 3D model to the actual geometry in consultation with the investor or construction manager.
- Generating numerical information for the CNC machine based on the final 3D model.
- CNC machining
Hundegger K2-Industry – technical parameters of the CNC machine
The elements in our prefabricated structures are machined on a Hundegger K2-Industry machine. For those unfamiliar with this machine, it can be called a “combine.” In simple terms, you insert a beam on one side, select a program, and remove the finished part on the other. The machine can process elements with cross-sections ranging from 20x50mm to 300x450mm. The machine consists of various units.
- A circular saw with a power of 13 kW at 1500 rpm. For comparison, handheld circular saws have around 1.5 kW, and stationary saws up to 3 kW. This ensures high efficiency, effectiveness, and cut quality.
- A 5-axis universal milling machine with a power of 35 kW and adjustable speed up to 5200 rpm, optimal for woodworking. Available tools for this unit include cylindrical cutters, shank cutters, and dovetail jointers.
- The 6-axis milling unit, thanks to ROBOT technology, provides flexibility and significantly increases the possibilities of complex carpentry machining.
- This synchronous unit allows for milling, drilling, and grooving with maximum efficiency. It can simultaneously process two opposing sides.
👉 See the machine’s capabilities in the video: YouTube – Hundegger K2-Industry
Summary – advantages of CNC technology in roof truss production
CNC technology in the production of wooden structures guarantees precision, repeatability, and time savings. It combines traditional carpentry craftsmanship with modern technology, resulting in durable and safe trusses.
For the investor, this means reduced risk of errors and faster assembly, while for the contractor, it means more efficient work and lower costs. This is a win-win solution that should be standard in modern construction.
