Steam box System for Bamboo Bending Process Hari Nugraha , Ismail Alif Siregar , and Taufiq Panji Wisesa Pembangunan Jaya University, Kampus UPJ I Jl Boulevard Bintaro Sektor VII, Bintaro Jaya Tangerang 15224 Abstract Bamboo is used for many things, such as for building material, furniture and interior products. There are many ways to process bamboo using taraditional methods and conventional manufacturing methods using machines. The structure of bamboo has the same tensile strength as wood and can be used as an alternative to using wood. Bamboo also has better bending properties than wood and using composite and or laminating process bamboo can be processed into laminates or blocks like wood. Because the manufacturing is similar to the process used by wood the materials produced from bamboo can also be variative. Bamboo composite that are shaped into blocks or laminates must be able to be processed using wood techniques such as being milled, sanded down, joined with certain profiles and bended with varying degrees of roundness. The methods used are actually wood process which is steam bending in a steam box. The process of using the steam box to process bamboo uses bamboo shaped as planks. The process still needs to be further examined because the properties of bamboo compared to wood that uses the steam box method is different. Also there needs to be a redesign of the steam box method because of the different property of bamboo compared to wood. The refinement of the steam box design and prototype is hoped to be able to be used by small home industries to innovate their products in the bamboo industry. Keywords: Bamboo; wood; bamboo properties; bamboo bending; bamboo processing; bamboo industry, bamboo furniture, bamboo products, steam, steam box, steaming method. 1. Introduction There is an increased demand on the use of wood and the price of wood also increases (wwf, Asia Pulse Analyst, Tue, 13 April 2004) Also there is the negative impact of illegal logging because of the increased demand of wood. Because of this, bamboo is deemed to be a good alternative to wood because of it relatively quick growth and mature rate. In Indonesia alone there are 159 species out of the world’s 1250 bamboo varieties. Bamboo has been used traditionally as a material to make household products such as rice bowl, bubu (a fishing device) furniture product such as chairs, tables and beds. The bamboo used is still mainly in its natural form which is cylindrical and or has been cut down to strips. The bamboo strips have an advantage compared to wood because of its elasticity and tensile strength has potential to be bended and this has not been exploited. Right now, the processing of bamboo is still to cut and then assembled into some form of product, such as furniture. This convensional way of using bamboo limits its potential. Because the bamboo is now expected to become a replacement for wood, the processing process is also expeted to be 68 | Proceedings “The 1ST UMM International Conference on Pure and Applied Research (UMM-ICOPAR 2015)” like wood processing. One of the process is a composite system or laminated bamboo veneer which is made into planks or blocks. Another way is to take advantage of the bamboo’s ability that is flexible and bendable which can be applied to designs that have organic curving shapes. The technique used to bend bamboo like that conventionally is to use the laminated composite veneer that is bended by a jig. Another way is by putting the raw bamboo inside a steambox, where the moisture content of the bamboo is raised by steaming it to make it more pliable. This method cannot be applied to laminated bamboo strips because of the characteristics of the composite and laminated bamboo. The bamboo laminated composite process needs a long time to prepare, especially during the laminating process where special adhesion materials is added, This research aims to overcome the limitations of convensional bending techniques so that more innovative and unique designs can be produced. 2. Material and Methods 2.1. Literature Study According to Dransfield and Widjaja (1995) bamboo consists of 50 % Parenkim, 40 % fibre and 10 % connecting cells (veins and sieve tube). To process bamboo, we must need to know its physical properties, Ginoga (1977) explains that some aspects can influence the physical properties of bamboo, such as the age, height, diameter, thickness, and water content of the bamboo. Bamboo’s resilience towards the elements of nature is still one of the determining factors in the use of bamboo as a functional product. The susceptibility of bamboo towards termite also affects the use of bamboo. There are bamboo species that have resistance towards termite according to the research by Jasni and Sumarni (1999). bamboo atter (Gigantochloa Atter) and bamboo Apus/Tali (Gigantochloa Apus) have good resistace towards termite, so they can be used for functional product or construction materials. The method that is used for this research is experimental for the process of applying the steam box methode on bamboo. Using this experimental method, the application of the steam box methode will be modified to suit the structure of the bamboo compared to the wood steam box process. The experiment process will include the following: The designing of the steam box, the length of time of the steaming process, the maximum pressure achieved by the steam box, the maximum water volume that has been absorbed by the bamboo, and the maximum bend (radius) that can be achieved on the bamboo using this process. The bamboo that will be exerimented upon is Betung bamboo and Gombong bamboo, because these two are the most prolific species in Indonesia. The bamboo results of this experiment will be used to design and refine and can hopefully be used as a material to make a functional product. The following will be studied on the experimental method: 1. Experiment on making the Steam Box a. System and mechanisme b. Steam pressure regulation c. Temperature and amount of water 69 | Proceedings “The 1ST UMM International Conference on Pure and Applied Research (UMM-ICOPAR 2015)” d. Design of the shape of the Steam Box e. Making of the Steam Box Prototype 2. Processing the bamboo using the Prototype Steam Box a. Experimenting on time, water content and temperature of the bamboo b. Maximum bamboo bend radius 3. Aplication of bended bamboo a. Classification of the degree of the bend b. Making of prototype product from the bended bamboo 2.2. Wood Bending Using Steam Method To bend bamboo using steam method we can look at a research done by [7] where he bends wood using a steam box. This method can be used on different wood shapes and sizes. The best wood to use this method is White Oak. The Veritas® Steam Bending Instruction booklet (2011) explains in detail the making and usage of a steam box. There are three characteristics of wood that needs to be fulfilled so that the steam box method can be applied. 1. Wood must have a plasticized characteristic, the bending process will be more succesfull if the wood material is soaked and wet, before the drying process. 2. For the wood bending process to succeed, the drying process must be air dried. Kiln dried wood cannot be used for this process. 3. Before the bending process can be initiated, the wood must still be in steamed condition Figure 2.2-1. Wood bending apparatus. Source : Veritas® Steam Bending Instruction booklet (2011) Tabel 2.2-2. Table of wood species and the smallest radii that can be achieved using the steam box bending method Source : Veritas® Steam Bending Instruction booklet (2011) Species Smallesr Radii Oak (red and white) 2* Hickory 2* Elm 2* Walnut 3* Ash 4.5* Cherry* 6* Mapie** 8* 70 | Proceedings “The 1ST UMM International Conference on Pure and Applied Research (UMM-ICOPAR 2015)” The wood material that can be used must minimal have an MC (Moisture Content) of 20 %30 %. If the wood doesnt have the specified MC, it can be added by submerging the wood in water for a couple of weeks to increase the MC. The steaming process can be applied at steam temperature which is 100 °C and with a pressure of 5Psi in 45 min 60 min. Figure 2.2-3. Steam box machine used to steam wood before the bending process Source: Veritas® Steam Bending Instruction booklet (2011) 2.3. Bamboo Bending Using Steaming Process Bamboo has different character and morphology compared to wood, where bamboo has sections and the fibres is porous and is inline vertically, and also has a tough outer skin layer. Using the bamboo unique morphology, the experiment on using the steam box process will be for: a. Whole bamboo cylinder b. Whole bamboo with outer skin layer peeled c. Bamboo strips with intact outer skin layer d. Bamboo strips with no outer skin layer Figure 2.3-1. Whole bamboo cylinder Figure 2.3-2. Whole bamboo with peeled skin 71 | Proceedings “The 1ST UMM International Conference on Pure and Applied Research (UMM-ICOPAR 2015)” Figure 2.3-3. Bamboo strips with outer skin Gambar 2.3-4. Bamboo strips with peeled skin The dimensions of the bamboo’s that will be used for the experiment is as follows: a. Bambo diameter ± 4cm b. Bamboo length ± 100cm c. Bamboo thickness ± 0,2-0,4cm (For bamboo strips) d. Bamboo width ± 4cm (For bamboo strips) 2.4. Steam Box Design The design of the bamboo steam box will be based on the wood steam box principle. The basic working principle of the steam box can be explained using the following diagram.