With challenges in operational cost and decreasing availability of good quality natural wood, innovation was the only way to bring the highest quality solid wood products at lower cost.Finger joining, also known as box or comb joining is an innovative way to bring strength in wood with good durability.
Finger jointing is a woodworking joint made by cutting a set of complementary rectangular cuts in two pieces of wood. The best visualization of finger jointing is possible by simply interlocking the fingers of your hands at a ninety-degree angle, hence the name justifies as “Finger Joint”. Finger joint is much stronger than Butt Joint or Lap Joint.
Finger jointing is recognized as the most stable method of creating length joints between two solid wood or wood composite components. It is used to produce very long wood components or to separate out branches and cracks which lower the strength. Using finger joints, it is possible to joint short pieces of wood into one, in principle, an infinitely long strand of wood. Finger jointing results in much higher quality and stronger pieces and components, while dramatically reducing waste in our industry where the cost of raw materials is rapidly increasing.
Finger Jointing is an effective method of utilizing short pieces of lumber and reducing waste. Defect free finger jointed lumber is raw material for many of wood products for structural and non-structural purposes and for transparent or non-transparent finishing. Some of the best quality types of machinery bring value through finger jointing line in manufacturing set up. Through finger jointing, your residue wood will be used to produce a valuable, high-quality product –
– Top Quality Joining
– Very Short Setup time
– Fast, simple setup
It is produced using a longitudinal joint with high initial force (self-clamping), which is then always glued. Because of the constant crossover between the two connected parts it also has a correspondingly high flexural strength. These characteristics mean that it is superior to steel-wood joints as well as other wood-wood joints. Finger jointed components can almost achieve the same strength as components grown in one piece, given the ideal conditions in terms of production and quality assurance. The two most important advantages of finger jointed lumber are straightness and dimensional stability. With short lengths of wood joined into longer pieces, the warping and twisting associated with regular dimension lumber are minimized. The finger-jointing process allows the removal of strength reducing defects to produce a product with higher engineering properties. Great Reasons to Use Finger joined Lumber:
Strength – Finger joint lumber is as strong as, or stronger than conventional dimension lumber.
Stability – Warping, and twisting are significantly minimized.
Straightness – Each piece is straight and true, as any bow or crook is absorbed in the joint.
Nailing Surface – Finger joint studs provide a better nailing surface as wane (bark or inconsistencies) on the edge is minimized along the length of the stud.
Quality Control – Rigorous assurance controls ensure that the joints are tested for strength, water resistance and conformance to standards.
Appearance – Finger joint lumber generally has less prevalence of visually displeasing attributes such as wane and discoloration.
Consistency – It is made from small pieces of high-quality wood ensuring the end product is always of consistent premium quality.
Environmental Friendliness – It reduces waste by salvaging excellent quality wood from short pieces of lumber that would otherwise be discarded. Finger jointing maximizes the value extracted from every tree harvested.
Nowadays a variety of glues are available in the market which is been widely used in Finger Jointing, based on intended use of the final product. Glue for dry use interior applications such as furniture and trim moldings will be different from the glue used for exterior or water resistance applications. The preparation of joints, as well as the adhesive itself, plays a critical role in the quality of the finger jointed product. Most failures of finger jointed lumber are caused by poorly machined and poorly fitted dry joints. The adhesive is a factor in heat and water resistance. However, even the best adhesive available cannot make up for the poor fitting joint. The fit of the dry finger joint must be checked before gluing begins.
Finger Jointing Troubleshooting –
Blades stack/sets – Be sure to check overall blades stack for accuracy. Keep cutter heads in the pair and properly cleaned. Cutter head should be sharpened as a set. Blade set should cut only 0.25mm or 0.010 inches to 0.75mm or 0.030 inches of wood.
Joint Assembly –
End pressure should be set to provide14.0 kg/cm2 – 35.0 kg/cm2 or200 – 500 psi pressure for non-structural joints. Crowder wheels should be aligned to match fingers accurately.
Adhesive Application –
Sufficient adhesive spread will provide a uniform coverage that should cover one-half to two-thirds the length of the finger on both sides in a thin continuous film. Make sure fingers aren’t skipped and that the adhesive is applied to the whole joint, not just the tips of the fingers.If the adhesive is a two-component system, make sure the ingredients are properly mixed.Excess adhesive squeeze-out can cause arcing in a high-frequency tunnel.It also causes adhesive build-up and adhesive waste. Too much adhesive can cause a hydraulic effect in finger joint back off.
I am a fan of modern innovative horizontal mortiser in comparison with the traditional vertical mortiser. The use of automated CNC mortiser reduces the lag in the process. These revolutionized machinery helping our industry with right measured grooves which are key success criteria in the final assembly of wooden components.
Spindle Molder is a stationary woodworking machinery where a vertically oriented spindle drives cutter heads to shape the profiles in wooden components. The spindle has a capacity to adjust according to the required need of the wooden components. The height of spindle is being adjusted in accordance with the thickness/characteristics of wood. The spindle may be raised and lowered relative to the shapers table. The spindle has a capacity to rotate between 3,000 and 10,000 rpm, with stock running in the vertical fence.
Considering the highest speed of the spindle and resistant to cutters with the running wood in opposite direction, the foundation of these types of machinery must be very solid. These are some of the fundamentals which are assumed to be considered in building a right process layout for manufacturing shop floor. The electrification for all these woodworking machineries needs to be balanced in context with overall manufacturing capacity on the shop floor. The mounted motor in these types of machinery is usually connected to spindle driver through flat belts.
Mortising is an act of putting a hole or recess into one item so that a tenon can fit inside of it. The technique gets its name from the mortise and tenon joint, one of the most commonly used joints by woodworkers. Through this method, two pieces of wood are usually connected at a 90-degree angle. If one wanted to build a table, they would have to mortise a leg before attaching it to the top. A mortising machine uses a motor to drill a rectangular or square hole into a piece of timber.The user attaches a drill bit that corresponds to the size and shape of the hole they need to the motorized rotator on the machine. When they turn the machine on and place the bit on the timber, it creates a clean, symmetrical hole that is ready for a tenon. Depending on the project, the user may want more or fewer rotations per minute. A mortising machine also has a base that clamps onto the timber so that the wood stays still while the hole is put in place. Some models offer bases that swivel so the user can rotate the piece of timber and drill holes in different areas, without having to take it out and reposition it.
There are three main types of mortising machines: the square chisel, the horizontal (or slot) and the chain. The square chisel model resembles a drill press in its fixed style. It contains a chisel that ensures clean and straight edges and a drill that creates the hole. The horizontal mortiser has a router mounted on its side, and a workpiece attached to a multi-axis sliding table. This type of machine is best for floating tenons, which are created when two pieces of wood have corresponding mortises that must be attached via a third piece of wood. Chain models are best for large scale construction projects. They use chainsaw-style rotating cutters that simultaneously hold onto and cut the piece of wood.
The motor mounted in these types of machinery are usually connected to spindle driver through flat belts. In lower RPM machinery V-belts are also been used. In some of the smaller machines, the router or the cutter is directly mounted on the motor. The decision on these machine designs is dependent on various parameters – speed of the motor, the length of the drill, width and depth of the wood processing and flexibility needed to move the component or machine as needed.
Decision to use flat belt, V-belt or circular belt depends on these base parameters –
Flat Belt – Moderate amount of power, two pulleys are not more than 10m apart.
V – Belt – Great amount of power, two pulleys are very near to each other.
Circular Belt – Great amount of power, two pulleys not more than 5m apart.
The wooden components for solid wood doors and windows, the stiles, and rails are the components running as a frame for the wooden shutter. The process that wooden stiles and rails go through are –
- Components of right height, width, and thickness. The initial raw components usually have a margin which will go into further processing (Wood Seizing, Wood Planner) to achieve a final size of finished products. The margin over the final size is the cost which is required to ensure, we have the required bandwidth to turn the raw wooden components into a high quality finished wooden product.
- The wooden stiles and rails are sized to right length by using Milter Saw (Wood Seizing)
- Post right length the width and thickness are been designed to right dimension by using the wood planer.
- The grooves in stiles and rails are been processed through spindle molder or four cutter/specially designed machines to fit the wooden panels.
The process that wooden panels go through are –
- The thickness of wooden panels is usually lesser than the stiles and rails. This also depends on the final design and the concept of finished products. Being thinner in its thickness, the sensitivity in operating on these wooden panels brings real excitement to make it right. The length of the panel is being shaped using same Milter Saw.
- The width of the wooden panel is an interesting area where it solely depends on the width, design of an overall door shutter. The recommended approach to building a solid wood panel is to join multiple small wooden panels to a bigger panel. The smaller panels are machined on spindle molder of four cutters where tongue and groove are being built to join the small wooden panels to a bigger panel.
- The glue or the adhesive been used in these joints plays an important role. The industry like us has done good research in partnership with adhesive manufacturers to get at the right formulation of adhesives.
- As the length of wooden panels components is set on Milter Saw, the final thickness of wooden panels is shaped up in Wood Planner.
- The post designing final thickness of wooden panels the panels is been raised using spindle molder machine. The panels are being raised in such a way that the final thickness of panels is been lowered at the edge to fit into the groove designed for the stiles and rails.
Quality check of components post machine work is an important activity prior to assembly for the final product. Assembly of final product works where right components are brought to the assembly area. The components need to be qualified for final assembly in its dimensions which include length, width, and thickness. Comparatively less skilled good carpenter should be able to complete an assembly when components are properly manufactured to its final size.
Wooden components are put together to assemble a final product, where all tongue and groves are put together with right marking. A specially designed adhesive is being used while assembling all the products together. Usually, these adhesives are water resistance and quick dry ones. The grip in the wooden joint is made stronger with these adhesives and dowels.
With advancement in technology, various CNC assembly machines are being used to assembling huge quantity of wooden products with sustainable quality. These machines are equipped with hydraulic/pneumatic pressure to ensure tight joints in the assembly. These joints are being drilled for dowels in assembling the final products. The dowels need to be ensured to pass through both the components creating joint in a final product.