It has been estimated that over 30% of the materials delivered to a construction site are wasted during construction. This makes the building industry one of the largest contributors of waste to the environment. To curb this inefficiency, the smart building delivery employs Lean Manufacturing Principles.
Dating back to the ancient civilizations, a colony expresses herself through powerful edifices. This trickles down to the construction process as well — the more labor consumed, the stronger the message. Hence, traditional building delivery has become associated with site works. This leads to a very elongated process on the site — with so many coordination issues and back-and-forth.
This write-up takes a cue from the Automobile Industry. The entire delivery process of a building can be simulated offsite; through an Integrated Project Delivery, IPD. This entails the use of Lean Manufacturing Principles summarized at the end of the write-up.
However, buildings are not as repetitive as automobiles or mobile phones.
- The users’ needs vary.
- The context varies.
- The budget varies etc.
Thus, a very important technology that complements Lean Manufacturing is Rapid Prototyping — a subset of Digital Fabrication. This shortens the gap between a virtual design and the real Fabrication.
The advantages of Lean Manufacturing, among others, include:
- Saved Time.
- Fewer Wastes.
- Less Labor — and More Safety — on the site.
- Higher Quality/ Performance etc.
CHOOSE THE PREFABRICATION LEVEL
Come to think of it, a sizable proportion of a conventional building is not manufactured on the site. The doors and windows, the plumbing and sanitary fittings, the steel reinforcements — even the bricks, mostly.
Why then are they not categorized as prefabricated? As we’ll see, there are different levels of prefabrication.
Thus, it is the first choice in a prefabrication workflow — right from the planning stage.
Prefabrication is the process of manufacturing and assembling the major building components at a remote factory, followed by transportation to the construction site, then installation.
By inference, at least 50% of the building components are manufactured offsite — in a conditioned environment.
There are five major levels of prefabrication, at increasing levels of cohesiveness.
- Componentized Systems: this is found in a traditional building. Here, joining is at component-by-component level.
- Panelized Structures: here, the building is broken down into 2D planar elements — walls, floors, roofs etc.
- Modular Structures: here, the building is broken down into 3D volumetric sections. This is recommended for high-rise and big structures.
- Hybrid Structures: this is a combination of panels and modules. Thus, it tends to be more flexible.
- Unitized Whole Buildings: this employs the highest level of cohesiveness. Thus, is only recommended when there are enough machinery and technology available.
RATIONALIZE THE BIM MODEL
Leveraging the IPD to populate a BIM Model (get more info here) – in the spirit of Lean Manufacturing – should we just export the BIM Model to the digital fabricating machines?
No! Not so fast.
The process of Digital Fabrication begins by rationalizing the BIM Model. This entails adding all the joints, parts and pieces…
In a purely digital delivery workflow, there are five stages:
- Inspiration — the Conceptual Design stage.
- Configuration — the Detail Design stage.
- Rationalization — adding all the necessary fabrication details.
- Isolation — exporting to supported formats (e.g. STL), and subsequent conversions and preparations.
- Fabrication — Additive or Subtractive Manufacturing.
Thus, the difference between the traditional and digital workflows starts at the rationalization stage.
The implications of the digital workflow include:
- More time is spent on the (digital) modeling process.
- A thorough knowledge of the joining methods, materials, and every necessary detail is needed — right from the design stage.
- The prefabrication and digital fabrication methods are known.
- The Prefabrication Components (PC) Manufacturers and the Fabricators are part of the design process too — as they’ll be supplying all the necessary fabrication details.
As we will soon see, however, the delivery workflow is not always completely digital. It depends on the prefabrication level.
CHOOSE THE FABRICATION TYPES
Based on the prefabrication level chosen, there are various fabrication types that could be employed. This ranges from Traditional Fabrication to Digital Fabrication. Traditional Fabrication includes such methods as Injection Molding and Investment/Die Casting. Digital Fabrication includes such methods as CNC Machining (Subtractive) and 3D Printing (Additive).
As mentioned earlier, a major shortcoming of the traditional workflow is wastages. This is because most traditional techniques are subtractive.
Unlike the traditional fabrication, digital fabrication is a direct outcome of the BIM Model… Nonetheless, digital fabrication can also be subtractive. A typical example is CNC Machining.
Therefore, the only additive fabrication method is 3D Printing. Visit 3dhubs to get a full breakdown of all the 3D printing techniques currently available. Thus, 3D printing is a more economic fabrication technique. However, it is still replete with its shortcomings:
- The available materials are still limited.
- The strength of the final material is not always as high as the other methods.
- The precision is not always as high as that of other techniques.
- The cost savings are often offset when the prefabricated components get numerous…
Therefore, 3D printing is more recommended for fabricating complex parts, that are not much in quantity.
In summary, the choice of the prefabrication technique is directly informed by the level of prefabrication. This, in turn, is informed by such factors as budget, end users, client’s preferences etc.
It is no more a surprise to see a huge building spring up within a month. The reality is that over 90% of the time had been spent outside the construction site. The design lab, the shop floor, the PC manufacturers’ factories etc.Thus, there are four major steps in a prefabrication workflow: Design, Assembly, Transportation, and Installation.
On-site Installations becomes an exhibition of a thoroughly planned process. No more an elongated process — at the mercy of climatic factors…
The primary advantage of prefabrication is time savings on the site. This easily lends itself to reduced labor on the site. It equally brings about more safety on a construction site.
However, the duration of the time spent on the site is dependent on the level of prefabrication. The more cohesive the fabrication level, the lesser the time spent. Componentized Systems take the longest time, while Unitized Whole Building takes the shortest.
To even save more time on the delivery, those aspects of the construction that would be done the traditional way — such as the foundation — are done simultaneously with the shop floor assembly.
Depending on the level of sophistication, such tools as Robots and Automated Cranes could be employed for the site assembly.
The entire installation/assembly on-site can be simulated using such tools as Autodesk Navisworks Manage.
A well-planned building delivery should not exceed a month on the site.
High-rise buildings in China, Japan, and many other parts of the world have been executed within a shorter period of time.
LEAN MANUFACTURING PRINCIPLES
Toyota has been recognized over the years as the world’s greatest manufacturer. Out of the challenging circumstances she found herself at the inception stage, she has over the years, birthed what is popularly known today as Lean Manufacturing. ‘The Toyota Way’ has been broken down into 14 principles and its veracity has been proven beyond the Automobile Industry.
***This is Extracted from The Toyota Way: 14 Management Principles from the World’s Greatest Manufacturer
by Jeffrey K. Liker.
- Base Your Management Decisions on Long-Term Philosophy, Even at the Expense of Short-Term Financial Goals.
- Create Continuous Process Flow to Bring Problems to the Surface.
- Use Pull System to Avoid Overproduction.
- Level Out the Workload (Heijunka).
- Build a Culture of Stopping to Fix Problems, to Get Quality Right the First Time.
- Standardized Tasks Are the Foundation for Continuous Improvement and Employee Empowerment.
- Use Visual Controls, So No Problems are Hidden.
- Use Only Reliable, Thoroughly Tested Technology That Serves Your People and Processes.
- Grow Leaders Who Thoroughly Understand the Work, Live the Philosophy, and Teach It to Others.
- Develop Exceptional People and Teams, Who Follow Your Company’s Philosophy.
- Respect Your Extended Network of Partners and Suppliers, by Challenging Them and Helping Them Improve.
- Go and See for Yourself to Thoroughly Understand the Situation (Genchi Gembutsu).
- Make Decisions Slowly by Consensus, Thoroughly Considering All Options, Implementing Rapidly (Nemawashi).
- Become a Learning Organization Through Relentless Reflection (Hansei), and Continuous Improvement (Kaizen).