Nestled in the foothills of the Swiss alps, sits one of the most advanced prefab construction
factories in Europe.
Renggli, a 100 year old firm, builds high-performance, energy-efficient, modular structures.
They use a variety of machines to automate construction like CNCs, suction cup lifts,
robotic saws, tilting tables, gantry cranes and more.
I had a chance to visit the factory last month and it’s fair to say that I was blown away
by the precision of their construction, the high quality of materials used and, of course,
the robots in their assembly line.
In this video, we’re going to walk through their steps of modular construction and the
pros and cons of their process.
The first machine is this platform system adopted from the automotive industry.
Forklifts load drywall, timber, sheathing and other large materials onto this base.
They are separated into categories and stored on these shelving racks.
As material is needed inside the factory, it is automatically retrieved from these shelves
and carried down this highway system.
Renggli’s factory operates like an Amazon warehouse.
Every piece of material is tagged with a unique barcode.
This allows every component to be tracked, easily located and retrieved by machines.
They also have a huge storage facility with tagged lumber and engineered wood waiting
to be used.
Such an advanced construction facility needs highly detailed BIM models to drive their
process.
BIM stands for Building Information Modeling.
Digital 3D models are loaded with information like the size and location of every part and
piece.
Renggli knows how large each wall panel is, how many pieces of lumber go into building
it, how many nails are used, where electrical boxes are located and more.
BIM models allow them to think of buildings as a kit of parts.
They can also plan the sequence in which the panels are built in the factory and assembled
on job sites.
The second robot used is a CNC machine which stands for computer numerical control.
Gypsum boards and wood panels are lifted from the shelving racks and brought to these tables.
They slide into the sealed off CNC machine and are cut with router bits.
Data from BIM models dictates the dimensions of each piece and the location of electrical
outlets and plumbing.
When the cuts are complete, the table slides out.
Suction cups carefully lift the pieces to another platform.
I was shocked by how little waste was generated during this process.
Thanks to the BIM models, cuts are optimized for maximum output.
All the small waste pieces are collected in bins and recycled, if possible.
I was also surprised by how clean and dust-free the entire process is.
The CNC machine is connected to 2 exhausts; one for gypsum dust and another for wood dust.
Two large tanks outside the factory store this dust until it is disposed of safely.
Wood dust is actually burned in winter and used to heat the office and factory.
This closed loop recycling reduces landfill waste.
The third machine is an advanced Hundegger saw.
Large pieces of wood, some 40 feet in length, are fed into this fully automated machine.
It can cut wood in 5 axes as well as drill screw holes, cut notches, mortise and tenon
joints and punctures for electrical and plumbing.
Once again, data from BIM models dictates the cuts.
Because precision is so important in off site construction, Renggli only uses engineered
wood like glulam beams.
They cannot use warped pine studs with large knots.
All the lumber needs to be perfectly straight and have consistent widths and thicknesses.
Unique barcodes allow tracking and retrieval.
All the dust from the Hundeggar saw is also suctioned away, which keeps the factory floor
clean.
The fourth type of machine is a butterfly table.
Workers build wall, ceiling and floor panels on these tables by attaching the milled glulams,
sheathing and drywall.
When it’s time to work on the opposite side of the panel, the tables flip 90 or 180 degrees
with hydraulic lifts.
It takes just 90 seconds to flip these tables over and safely lower them on the opposite
side.
It’s a simple but extremely useful device.
Automating the repetitive task of flipping panels can prevent any potential injuries.
Another cool aspect of these tables are metal pins that act as guides for wood studs.
The pins automatically move to the right positions, which makes assembly easier.
The fifth machine is a gantry crane system that spans the entire length of the factory.
It carries building panels from one assembly table to another.
Workers add thick mineral wool insulation in the stud bays and a layer of wood fiber
insulation on the exterior faces.
They also attach drywall to the interior faces with a nail gun.
Plastic tubing for wires is also installed in the wall panels.
While most of the other areas were fully automated, this final assembly section was still reliant
on manual labor.
However, unlike typical job sites, it was so organized and clean.
Every station had a supply cart that was fully stocked.
They had dedicated people making sure no one ran out of supplies.
It isn’t easy or cheap to build such an advanced modular factory.
In order to compete with traditional construction, they have to be extremely efficient.
They cannot afford to have people waiting around for materials or instructions.
They need to run like a well oiled machine.
Once the panels were complete, they were lifted by cranes and flipped in the vertical position.
Panels are stacked on transport platforms and draped with plastic.
They are heat sealed to protect them from moisture.
Outside the factory, they had rows of protected panels waiting to be transported to job sites.
Unfortunately, the plastic cannot be reused in the factory again but they send it to a
recycling plant.
As you can tell, I was very impressed with the way their factory was run.
They have successfully managed to rethink construction and turn buildings into a kit
of parts.
David Renggli, one of the owners of the company, spoke about the importance of accurate BIM
models on my podcast. 6:25
David referred to the BIM model as a digital twin.
He uses it to extract a material list and buy raw materials early.
He is able to guarantee customers a certain price, unlike traditional construction that’s
more susceptible to price fluctuations.
Renggli is also able to build panels faster and better.
They don’t have to worry about exposure to rain, snow and other elements.
Another advantage is the ability to hire older and more experienced workers in the factory
since indoor working conditions are not as harsh.
They are also able to minimize waste because of careful planning and execution.
The final advantage is the sustainability of wood construction.
I usually get a lot of flak for saying this, because there’s an unfortunate misunderstanding
that wood and mass timber construction equals deforestation.
This isn’t true.
Wood has a much lower carbon footprint than concrete and steel.
Renggli only uses sustainably harvested wood, where a tree is planted for every tree cut
down.
They only use rapidly growing softwood and not hardwood.
Renggli also takes sustainability a step further.
Their factory and office are powered by solar panels almost all year round.
Renggli has brought age-old wood construction techniques to the modern era with robots and
automation.
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Let's end this discussion with some of the disadvantages of modular construction.
Renggli uses stone wool, which has a high carbon footprint.
They build well insulated, air-tight buildings with massive walls, floors and ceiling panels.
These buildings require less energy to run over their lifetime, but they have high initial
carbon footprints.
Their construction technique is obviously more expensive than the stick building tbecause
they used high quality engineered wood, triple glazed windows, 10 inch thick insulation and
more.
Finally, as successful as Renggli’s process is, construction is a very difficult industry
to automate because every project is
so individualized.
CLIP 33:00
I hope our industry embraces modular, off-site construction more and starts thinking of buildings
and an assembly of products.
It’s going to take a while and it’s going to be messy, but with companies like Renggli
proving that it can be done, there’s hope.
Be sure to check out my entire conversation with Daivd Renggli on my podcast channel.
I’ll link it up here.
Also let me know what you think about off site modular construction and how it can disrupt
the construction industry here in the States..
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