Logs should free from any visual defects, such as resin pocket, resin streak, bark pocket, flaws, decay, rough grain, etc. After selection, the logs are shaped to be lumber blocks and then ripped and cut up to the specified size. To attain high-endurance wood products, the sawn timber should perform vacuum impregnation process and kiln drying process.
Moisture Content (MC)
Because the correct seasoning of timber is so critical to ultimate glueline performance as well as long term stability, MC checks are carried out at various stages of the process. Different species will determine the initial specified MC: for successful gluing and many tests are done in the laboratory to determine the best MC or machining/gluing regime in order to ensure ultimate performance. MC testing is done by pin electronic moisture meters, both on surface and internally. The aim ultimately, is to ensure that the total product is at Equilibrium Moisture Content (EMC) when the manufacturing is complete. It means that the external ambient humidity and the internal timber MC are balanced and in harmony. Generally, the MC is 12% or less.
The rough timber laminates are checked for defects. Those that are obvious and go through the piece are docked out. Timber is also checked for conformance to the specifications required to obtain the eventual required finished laminate size. To go through timber grading PT. MBJ has competent grader that holds certification from Balai Sertifikasi Penguji Hasil Hutan (BSPHH) – Ministry of Forestry, Republic of Indonesia.
Where it is difficult to obtain long length laminates adequate for the range of lengths required, fingerjointing of laminates is required. This produces a strong joint that holds the pieces together for the machining and gluing processes. It is also utilised to join pieces together after any observed defects are docked out. PT. MBJ has both Structural and Decorative Fingerjointing Lines.
The next process takes the laminates in the rough through a moulding machine. The moulder cleans all four sides of the laminate to exact tolerances. Speed of machining is critical, as too fast will create a slightly uneven surface which will show too large a glue line later, and too slow a speed will burn the wood. PT. MBJ’s state of the art Weinig and Wadkin moulder has six and eight cutting heads, which in addition to machining all four sides of each laminae a bank of saws can be placed on one of the horizontal heads. These saws can be set so as to rip wide timber to one or more pieces in order to produce the laminae sizes required for the specific dimension.
From the pre-conditioning room, laminates are fed on a conveyor through one of the glue spreaders. Glulam beam is glued with Zero Formaldehyde Resin. It is fully waterproof and has proven long-term performance. Accurate glue mixing machines and scales are used to ensure correct catalisation. The glue is then fed into hoppers mounted at the top of the glue spreader, which spreads the glue at a predetermined rate and consistency.
PT. MBJ only use 'cold presses'. Our presses utilise clamps that are tightened to pre-determined torque settings dependant on the density of the species being glued. Spacing between clamps has also been designed to ensure equal pressures along the length of the boards being pressed.
Boards are through a series of AMITEC Wide-belt Sander which take the surface to 180 grit or as buyer specification.
Prior to selection of a species for gluing, various trials are undertaken to determine performance, adhesion and longevity. This process ensures that timbers that are difficult to glue, have poor stability characteristics, or display drying or defect problems, are not released into the marketplace where future problems may ultimately show themselves.
Various tests are done as part of the PT.MBJ Quality assurance program to ensure the product meets relevant Japanese standards, and some of the more rigorous criteria established by the PT.MBJ laboratory team. These tests are done on pieces cut from actual production slabs, and records are kept of results and processing batches.
- Block shear test - this measures the strength of the fingerjoints by putting stress on the joint until breakage occurs.
- Boil/Water resistance test - 72 hour boiling water immersion test to determine suitability to high humidity and long term water exposure.
- Moisture Content test - finished pieces are again checked for accurate moisture content by "Oven Dry" method.
- Solvent resistance test - after allowing full glueline cure, various solvents and chemicals are used to saturate the surface to determine overall resistance.
- Glue Quality checks - Glue batches are tested and recorded for 'Use by dates' and viability.