One of the most fundamental aspects of construction is design. So what is the design process in the construction industry ultimately geared toward? The short answer is: creating a building at a reasonable cost, ensuring that users and stakeholders are happy with it. One such process, DfMA (Design for Manufacturing and Assembly) or prefabrication, with the help of prefabricated construction BIM and modular construction drawings, focuses on simplifying elements of the construction process by manufacturing them off site for a number of valid and profitable reasons, not least that it balances the important facets of cost, quality and performance.
During the latter stages of design, teams may find it difficult to link needs and product specifications to relevant design issues. DfMA, using DfMA modelling and drawings, is generally practiced by design and manufacturing engineers to help simplify parts, processes and product designs. Manufacture and assembly are married in the DfMA approach for optimum efficiency. Like many marriages, DfMA may present complications at some point, but the advantages of reducing labour costs, overheads and materials present a formula for ultimate success. Whether products are created by machines or humans, organisations and individuals prosper with higher profit margins and minimal wastage.
A logical way to look at DfMA would be to consider the following sections: raw materials, machines/processes and assembly of the product. Selecting the most suitable raw materials and the right machines and processes to handle those materials is very important. The process is particularly important to ensure that manufactured products meet design specifications. While assembling the product, DfMA follows a meticulous design review method. It identifies optimal part design of the product and an efficient and cost-effective method for production. It also encourages product design that meets the requirements of designers and other team members.
So, how does it work? A factory deploying prefabricated assemblies, such as MEP (M&E) services, may be remote from the site or located in a close-by area. Effective engineering requires that engineers in a factory are well informed about how assemblies in their factories are conducted. This involves the ability to translate model and drawing details into finished components, knowledge of where assembled parts are located and so on. It also involves a fair amount of planning so that all components that are to be added to the assembly are delivered to the off-site location and stored appropriately for easy access. These processes demand the involvement of the designer, planning teams and also logistics teams. Once these processes are in place, DfMA and prefabricated construction modelling encourages the collaboration between project design and production, making the product more reliable and cost-effective.
Actual prefabricated products may include: a “flat pack”, which is a kit of parts that can be assembled on site easily and quickly. These kits are delivered to the site with those elements needed for a particular part of the construction. For example, in an apartment complex, this would translate to boards and studs, tested and terminated ‘plug and play’ wiring looms, volumetric or flat pack bathrooms and prefabricated services units (comprising boiler and water tank, under floor heating manifold, electrical distribution board, whole house ventilation unit).
After the ‘what’ and ‘how’ of DfMA, let’s look at ‘why’ DfMA is desirable. Specifically, there are ten reasons that make deployment of DfMA advantageous:
There are a number of factors that influence costs and overall savings in costs. Some of the primary methods for reducing costs in DfMA is using fewer parts, removing unique parts and decreasing the labour count for assembly. Other factors include using standard parts and hardware. Using standard parts means that less tools are needed for assembly, thereby reducing cost. This kind of standardisation needs a list of standard parts. Also, when parts are constructed off site, the process is predictable and not susceptible to external features, such as the weather. In addition, a ‘life cycle cost’ on parts can lead to cost savings and addition of value to parts. An example would be fabricating off-site bathroom modules. This has been found to be almost one-third the cost of constructing bathrooms on site.
Other Cost-saving Aspects:
Eliminate Interfaces – Every interface doubles the quantity of data required and increases overall assembly time. DfMA can eliminate this by reducing the number of interfaces.
Part Interchangeability – Similar parts can be used interchangeably to manufacture the product, reducing the number of parts, decreasing assembly time and costs.
One of the primary advantages of DfMA is that it decreases assembly time by enforcing standard assembly practices, such as vertical assembly and self-aligning parts. DfMA-created products quickly and smoothly transition to the production phase, so the time taken for a product to travel from conception stage to ready-for-market stage is reduced. In the DfMA process, vertical, or stack, assembly means stacking up components of an assembly in order, requiring less reorientation of parts, speeding up the process. Self-aligning parts require no adjustment or reorientation. The presence of more self-aligning parts, such as washers, ball bearings and roller bearings, means it is easier for workers to assemble the product.
3. Ability to Test:
Off-site solutions can be considered early on in the project planning phase, with the aid of the BIM (Building Information Modelling) process. BIM can optimise modularisations and standardisations that characterise DfMA, as it is a component-driven tool. BIM helps deliver specifications for prototypes so that they can be extensively tested. Models are tested virtually before investing finances on actual prototypes. With BIM involvement in DfMA, testing prior to construction and the resulting reduction in risk is of great reassurance. Components or entire buildings can be reconfigured and transported to a different site, which means building deconstruction can be safer.
Prefabricated elements made off site go through a great degree of quality control and therefore end up being more consistent. Snagging, or remedial works, take less time. Modules constructed off site can be continuously improved on and standardised. The automated approach of prefabrication improves quality and efficiency. The use of fewer parts and multifunctional parts in a product means that there are less chances of breakage or misalignment, resulting in greater efficiency. DfMA also determines the capabilities of each process step, which is the ability of a process step to work within a specification. A design’s correct process capability helps the design team be better informed and select technology and sequences more efficiently. In this way, wastage is almost completely eliminated and so is a lack of materials and labour. Sequencing of trades and reworking is regulated and controlled, reducing some of the more common delays on site.
5. Design Schedules:
Parts handling can have a decided impact on design schedules. Parts must be designed keeping handling in mind. The design should strive to reduce the possibility of parts becoming entangled or stuck together. Easy parts handling will not need special tools or fixtures for assembly. Easily identifiable parts can also speed up the handling process. Parts designed for interchangeability will also help maintain design schedules. Interchangeable parts reduce part numbers, simplifying the assembly operation. Designs that have left-handed and right-handed parts increase confusion and complexity. Avoiding these designs can also help stick to design schedules. Types of buildings suited to repetition, such as school buildings, budget hotels and hospitals can benefit from DfMA, limiting build time on site and improving the adherence to design schedules.
Health and safety on construction sites is a critical project planning issue and one that absorbs a lot of effort. As there are usually so many teams on site, usually within confined spaces, the risk of accidents increases. In comparison, controlled factory environments, where prefabrication work is carried out allows control of health and safety levels as there is usually more space and fewer external considerations required for other trades or construction teams that may be operating in the same space.
7. Site Space:
DfMA can also benefit sites with complex logistics, limited space and limited access, such as airports or city centre locations. Even in cases where sites are not based in busy urban areas, the actual building constructed may not have the ability to house storage or handle delivery of raw or semi-prepared materials. Additionally, prefabrication off site leads to less material and labour on site, and therefore more space on site.
8. Meeting Volume Needs in the Future:
Projects that involve repetitive elements in the structure, such as schools, hotels, hospitals, colleges, malls, supermarkets, etc., can benefit significantly from DfMA. The DfMA process can limit build time on site by providing certain repetitive elements for these projects, since once the design is chosen for a repetitive element, it can be easily replicated for large quantities.
There are also opportunities to fulfil volume needs in the future through the application of operational management (total quality management) tools.
9. Resource Availability On-site v Off-site Manufacturing:
A major feature that contributes to why off-site construction benefits stakeholders is the fact that it relieves skills shortages. The process of DfMA or prefabrication of a variety of elements enables construction in another environment, needing less investment of labour than traditional on-site processes and addresses the shortage in this area. Off-site construction leads to fewer skilled people being required on site, and even then, it is for a different skillset, one of final assembly rather than the design, manufacture and more intricate assembly of components.
Greater productivity is another benefit of off-site construction, which results in reduced time, higher quality and lower cost of projects. This means that DfMA and off-site construction is more productive per unit of input than on-site construction.
10. Simplifying Manufacturing Activities:
DFMA simplifies and optimises the manufacturing process, especially through modules. Modules in product design resulting from prefabrication simplifies manufacturing activities such as inspection, testing, assembly, purchasing, redesign, maintenance, service and so on.
- Modules add versatility to the redesign process, help testing before final assembly and enable the use of standard components to reduce product variations.
- The use of multi-functional parts enables several functions to be executed by just one part and thus reduces complexity of procedure.
- Problem identification and assembly operations are simplified with the use of prefabrication.
- Inventory is simplified, and maintenance and servicing processes are improved.
Separate and self-contained modules require fewer tools, disassembly time is reduced and so is overall repair time.
- Assembly is simplified with self-aligning and self-locating parts, such as projections, indentations, chamfers, molded keyways, etc.
- DFMA minimises parts for interconnections. Interconnected parts are flexible and are used to connect two other parts. Harnesses ensure that distinctive connectors avoid misalignment.
- Multiple solder and cleaning steps can be avoided.
The manufacturing process can be designed to focus on smooth material flow; reduction of number of material moves; use of easily controlled processes; reduction of welding, brazing, etc.; performance of similar operations at the same time; and separation of manual and mechanised operations.
It can be concluded that there are a number of advantages in going the DfMA way, but primary among them are: cost, speed, testing, efficiency, design schedules, safety, site space, volume needs, resource availability on and off site and simplifying manufacturing activities. Ultimately, a DFMA solution starts by understanding the end product – site, brief, specifications, constraints and key drivers, considers the range of suppliers and systems available, creates many parts of the finished product in the factory, minimises on-site labour and keeps clients and customers happy.