The concept of ‘flying factories’ is not new: many of a pop-up nature have been tried, but generally involve a shed of some sort into which conventional equipment and machines are installed, products manufactured and the whole installation later dismantled and removed when the specified task is complete.
The mobile factory being developed here is different: each component part of the manufacturing process is designed for transportation, the main elements in this case, being a mobile sawmill, a portable planing machine, the proposed dowel lamination press itself and a CNC cutting machine sized to fit - and work - inside a standard a shipping container. A portable electricity generator to power the various machines is also part of this ‘train’ of equipment, with a HIAB truck used to transport the smaller items and later its jib used to move the completed dowel-lam panels. The key phases of manufacture can be listed as follows:
Felling of trees and cutting into standard log lengths;
Milling of the logs in portable sawmill to produce over-size boards lengths for the DLT panels;
Drying of the boards in solar-powered kilns;
Strength grading of the boards;
Planing of the kiln-dried timber boards;
Fabrication of standard-size dowel laminated timber panels - lay-ups of the softwood boards into lamellae and holes drilled to accept the hardwood dowels;
CNC machining of panels
The importance of each piece of equipment being separately mobile is to ensure that even the remotest sites can be accessed and for the factory to be established as close to the forest/felled timber as possible. Also that a constant cycle of forestry, manufacturing and construction activity can be maintained in a planned sequence: with locations around the country, the use of the mobile factories needs to be carefully planned to travel efficiently from place to place. Some elements of the ‘train’ need to be mobilised in advance: for example, the portable sawmill needs to travel ahead in order to process the logs from the forest and the kiln too is needed at that stage since, once milled, the slow drying of the boards requires both time and care.
Once kiln-dried, the moisture content of the boards can be measured and, if within acceptable MC parameters, planed. The boards can then be strength-graded to ensure they meet acceptable standards. A hand-held acoustic grading instrument is used for this purpose. The boards are sorted into graded bundles and the lay-up of the lamellae can take place - either into stacked plank, cross laminated or diagonally laminated panels. Once the necessary holes are drilled in pre-determined positions, hardwood dowels can be inserted. The resulting panel can be finished using the CNC machine to trim edges and produce cut-outs and routed channels for cables, plumbing, etc. They are then ready for assembly into new homes and community facilities. The conventional process is to carry out phases 2-7 in centralised facilities, often distant from the forest resource. In Europe, the sawmill and the panel fabrication/CNC machining facility are frequently situated adjacent to each other, minimising the embodied energy required in transportation between the two. As previously indicated, however, there are - as yet - no large scale commercial manufacturing facilities for either CLT or DLT in the UK and the likelihood of either possibility emerging in the foreseeable future is subject to three significant challenges: the level of investment required that has hitherto not materialised; the time taken to assess market demand and the output necessary to make any such facility commercially viable; the time required to design, build and deliver the bespoke equipment needed - most likely from an existing European-based manufacture; and, finally, the possible impact of Brexit on the sourcing, prices and possible tariffs on both the equipment and timber supply (if not home-grown). In the face of these uncertainties, the potential to utilise the home-grown timber resource efficiently and in an environmentally-responsible way becomes significantly more attractive. The mobile factory concept addresses each issue: it involves a vastly reduced capital investment risk; the small-scale, transportable dowel lamination press(es) can be designed and manufactured in the UK; and the timber supply and panel manufacture can become localised operations. With no capital investment needed from individual communities in the mobile factory (they lease or rent the equipment), panel manufacture costs are kept low. Using timber from local forests means no heavy transportation costs with consequent negative impact on fragile road infrastructure and embodied energy levels. This, together with the possibility that the community itself owns the land the new affordable homes will sit upon, means that two of the largest costs in house building (land and structure), if not removed altogether, are vastly reduced. The concept of the mobile factory reverses the conventional construction industry approaches that have long since proved inadequate in tackling the twin issues of depopulation and expensively-built but poor quality homes in remote rural areas. The proposition may be considered disruptive, but it is an innovative practical solution to an endemic problem. Importantly, it devolves responsibility for community sustainability to the communities themselves. In empowering the people who live in these locations to build their own homes to high spatial and thermal standards, it is not so much the factory that is given wings, it is the quality of life and economic potential that can enable them and their communities to soar high above the primary challenges that have until now been so detrimental to their continued existence.