Manufacturing Process of Cross-Laminated Timber

Manufacturing Process of Cross-Laminated Timber

Introduction

The manufacturing process of cross-laminated timber is divided into nine essential steps. The steps include species selection, material grouping, material cutting, adhesive application, panel lay-up, assembly pressing, quality control and finally marketing and transportation.

To begin with, timber selection, also called species selection, the process involves checking the moisture content, grading the lumber through visual observation and grading and sometimes depending on the structural application testing. Mainly the timber that is fit for CLT is used for the creation of construction grade while at the same time timber that is not fit to be used as construction-grade CLT or appearance grade CLT is used for other different purposes like making of glued laminated timber and plywood (Edskär, Ida & Helena, 32). The main species used for CLT is spruce though many others can be used like Larch, Douglas fir. Some species like Swiss stone pine are very suitable to make a high-quality finish in the outer layer. In this stage also the moisture content is checked and it is recommended that plain boards of between 12 and 45 mm thickness to have a moisture content of about 14.

The second step is the grouping and, in this step, it is ensured that timbers are grouped according to their categories. Timbers with better structural properties are clustered, while those with good aesthetic qualities are also arranged. For instance, during the making of a construction-grade Cross Laminated Timber, the lumber that has high-quality structural properties will be used in the inner layers. In the outermost layers, the timber with high aesthetic qualities will be used (Fell et al. 90). This is different from aesthetic grade Cross Laminated Timber, whereby all the layers are made timber materials of high quality.

The third step is planning. This step is aimed at improving the surfaces of the timber and also improving the performance of the adhesive that is always applied between the layers of the lumber. Planning here can also be done by trimming the top and the bottom surfaces and mostly, the measurements would include 2.6mm and 3.9mm, respectively and this aims at achieving a flat surface (Fell et al. 89). In some cases where only the top and the bottom surfaces are trimmed and, in such circumstances, sides do not necessarily have to be adhered to another substance. Sometimes the planning step involves losing the overall moisture content, although this is not the case most of the time.

The fourth step is timber or lumber cutting, whereby the timber is cut to different lengths depending on where it is going to be used to or depending on the specifications of the client. If it is going to be used to make large equipment or structures, then the lengths to be cut would always be longer and if it is going to be used in shorter structures, then the lengths would still be shorter (Edskär, Ida & Helena, 32). Also, sometimes it can be cut to specific lengths for easy transportation.

The fifth step involves the application of adhesive to the timber and this is done through a machine. During the use of adhesives, necessary precautions need to be taken. For instance, the whole process of application should be airtight to ensure that there are no air gaps and holes in between the layers, the glue and the entire structure. This is because the presence of air gaps and holes makes the whole structure faulty and weak and it will not be suitable for structures that need high strength (Edskär, Ida & Helena, 32-60). To obtain such a timber system without holes and gaps, there is a need for constant and careful application of the adhesives or the glue on the layers because any breaks in between allow air, which leads to the formation of holes and gaps. The resins are always applied mechanically and without contact.

The sixth step is panel lay-up. This is a process that involves sticking different individual layers together. During the stacking of the layers together, one of the precautions that need to be taken is that a larger area of the layers must be bound together (Fernando et al., 60). It is always recommended that about 85 percent of the surface area between the layers must be bound together

The seventh step is assembly pressing. This is the step that involves completing the adhering process and it comprises of two main methods of pressing the layers. The first method is hydraulic pressing, while the second method is the vacuum pressing. They both have their advantages and disadvantages that would make the manufacturer prefer one over the other (Fernando et al., 70). Vacuum pressing is advantageous when pressing more than one CLT panel and can be pressed at the same time and this makes the whole process both time and energy saving. In the case of hydraulic pressing, the advantages include higher pressures that can be obtained and also the pressures placed on the edges can be well specified.

The last step is the quality control stage. This process is always done on the CLT panels and a sanding machine is mostly used to perform this task. The process also involves cutting the panels to suit their specific design. It is in this process that defects are also removed (Fernando et al., 70). The flaws would include large knots, resin and bark pockets. They are always cut out to make the whole thing look neat and well presentable.

Critical Discussion of why the use of Cross Laminated Timber is now on Increase in Different Parts of the World

There are several reasons why CLT is now on the increase in different parts of the world. One of the reasons is the versatility of the timber at work. Cross Laminated Timber can resist compressive forces and this has made it very suitable for multi-story and long-span diaphragm applications. This is because they have less weight compared to other building materials like steel and concrete (Milestone, Scott Nicholas & Paul Kremer, 34). This reduces foundational costs. Another property that makes CLT products very versatile is their ability to be combined with other building materials like glulam beams and this makes them very flexible in design and final finishing of different architectural designs.

Another reason for the continued and extensive use of CLT is design flexibility. Cross Laminated Timber is flexible in that it is easy to increase its thickness. This mostly is done in cases where longer spans are needed and also where there is a need for a few interior support elements like pillars. This at the end of the day, reduces the overall cost of buying these supporting materials. The ability of CLT to allow for an increase in thickness gives it better characteristics in terms of energy efficiency and thermal performance. Thermal performance has always been determined by the coefficient of heat transfer, which directly relates to the thickness of the timber (Mohamadzadeh, Milad & Daniel, 54). Another property that makes CLT flexible is its ability to be manufactured using a CNC machine. This is because the CNC machine gives precise and exact tolerances and allows the panel joints to fit even tighter and this at the end of the day results in better energy efficiency for the structure.

CLT also has several environmental advantages that make it be on the increase in different parts of the world.  There is little air pollution, basically because of less greenhouse gas emissions. Generally, the manufacturing of CLT involves less waste production, and the little waste produced can also be reused to make other things. The whole manufacturing process is energy-friendly because wood manufacturing requires less energy. CLT also has the advantage of fast installation simply because most of the panels are prefabricated and roof and wall elements can be pre-cut (Morandi et al. 65). Insulation and finishes can also be applied before installation, reducing demand for skilled workers on site. Also, CLT is mostly used because of fire protection property. Due to their thick cross-section, they do not burn quickly, but instead, they just char and this protects the whole wood from being entirely and burnt soon.

Drawbacks concerning the use of CLT on the Project

The use of Cross Laminated Timber on the project has several limitations. The limitations include higher production costs. Compared to stud walls, CLT requires a little bit more raw materials and this, to some extent, makes the use of CLT on the project to be expensive (Stenson et al., 76). Also, there is a limited track record. Since CLT is a new material, it is not commonly used in many building projects. This, therefore, calls for more research that needs to be done to establish the suitability of the CLT. More studies would mean extra expenses and also more time to research and to integrate the new practices.

Another limitation of CLT is that the cost of plumbing and electricity may increase. This is because one cannot have cavities to insert the pipes and wires. Having the holes will only weaken the whole structure and make lose its strength and durability. Also, there is a limitation in the height of the structure (Stenson et al., 76). Cross Laminated Timber does not allow for very tall building structures. Restriction to the climax is a disadvantage to the business because of the cost since it is more economical to have more rooms or more structures under one building.

Health and Safety Issues

When it comes to construction of any building or any structure, safety and health issues are very important. CLT has negative impacts on people’s health to some extent. Cross Laminated Timber products, especially flooring products, have a high level of formaldehyde. High levels of formaldehyde release carcinogenic gas that can cause respiratory disorders and difficulties in breathing on people using these products (Talamini, Gianni & Mengyu, 65). Thousands of people have been affected by these products and they have experienced these respiratory disorders.

Another health issue about CLT is noise. The manufacturing process involves the use of heavy machines that produces a lot of noise (Talamini, Gianni & Mengyu, 65). This noise can pose a lot of health challenges to individuals operating these machines, for instance, they may develop hearing problems like, for example, due long-time exposure to these noises coupled with negligence of not using protective gear, eardrums of these individuals may be destroyed.

Safety measures include wearing protective gear. The operators of the machines need to wear protective equipment to prevent or protect themselves from the loud noises produced during the production and manufacturing process of the cross-laminated timber (CLT). Also, there are other factors, such as earthquakes, that need to be taken into consideration (Vidal et al., 78). These natural disasters occur without any warning and can never be predicted; hence proper safety measures need to be taken during the construction process. Tests need to be done on the CLT to determine their resistance ability to earthquake forces.

Fire safety is also of utmost importance. In as much as CLT resists fire, it is not as resistant as steel and concrete. Thus safety precautions need to be taken into consideration to prevent any possibility of occurrence of fires. The panel should be made thicker to make the spreading of fires difficult (Vidal et al., 78). Besides, construction of the board should be made in such a way that it is airtight to reduce the fire’s ability to spread

Recommendation

For the CLT project to work well, there is a need to conduct thorough research on the suitability of the Cross Laminated Timber. The study will significantly help to come up with the right thickness of the panel depending on the height of the building, several rooms and also the capacity of the room.

Conclusion

In conclusion, CLT is now on the increase in different parts of the world in a range of building types such as offices, residential houses, and even industries. This is because of the many advantages of CLT which include, cost-effectiveness, flexibility and environmental friendliness. There is a prediction of continued use of these products as long as safety precautions are going to be adhered to, to overcome the limitations of the CLT.