As a result of the growing demand to lower the costs of production and the consequent adoption of economies of scale of wooden constructions, the processes of transformation of the beams had to be adjusted, the main ones being:
- standardisation of dimensions.
- the use of laminated wood.
- storage of the beams before being processed.
- automated manufacturing processes.
- cutting centres and CNC milling.
All these operations can result in surface damage, presenting:
- imperfect planing performed.
- yellowing due to storage.
- streaks, micro-bubbles and scratches due to automated processes, transport and processing.
These factors are of course contrary to the policies of quality improvement where, in addition to precision, the operations of surface finishing must be perfect as is the case for impregnation. thus the need to process again the beams in order to prepare the surface so that it is: homogeneous, with a high level of finishing, repeatability and is devoid of intensity variations.
The answer to all this is in the Stromab Kiowa design that has developed a series of machines for the sanding of beams. the sanding operation involves restoring in a practically perfect manner the surfaces of wooden beams abrading a material thickness that can vary from 2 tenths of a millimetre to 2 mm according to the degree of beam damage.
There are several models of machines, they are all fixed bench, and are divided into single-sided machine, multi-sided machines, buffer machines and combined roller-buffer machines.
There are mainly two sanding concepts. The first fig. 1 is with buffer, the second fig. 2 is with roller buffer (or the combi principal).
In the first case the advancing beam meets buffer A which pushes the abrasive sheet E upwards causing the removal of wood. The depth of cut can range from 2 tenths to 1mm (depending on the pneumatic pressure adjustment of the buffer)
In the second case the beam meets roller C which through the cylinder F is pressed against the beam, squaring and adjusting the surface. The depth of cut can range from 3 tenths to 3 mm (depending on the setting of the roller). Continuing the beam meets the pneumatic buffer that performs a second phase. The pneumatic buffer was designed to have the ability to adapt to the surface of the workpiece compensating for any residual geometric errors of surface flatness.
With the combined action of steel roller removal C and pneumatic buffer B it is also possible to obtain a high depth of cut, always ensuring optimal performance, high quality and high speed of execution.
TYPE: KIOWA MODEL: S
A sanding machine for carpentry wood elements such as beams and timber, with sanding machine head from below.
A sanding machine for constant profile wooden elements, such as: beams, planks and beads.
The machine works as follows: the pieces are placed on the inlet idle roller conveyor and taken into the sander, a light barrier recognises the input of the piece, commanding lowering of the upper ram that, leaning against the beam, causes insertion of the feed motion. Underneath the sanding head works the bottom surface of the beam.
With machining completed the upper ram lifts up, the lower pneumatic buffer loses pressure withdrawing from the upper wire of the rollers.
The machine can work both forwards and backwards, in fact introducing the piece from the side of the machine from where it exited, the system recognises it and sets the belt and feed in motion with the correct direction of rotation. This automatic process significantly speeds up processing times.
OVER-UNDER DOUBLE SANDING MACHINE
TYPE: MODEL KIOWA: D
Sanding machine for wooden carpentry elements such as timber and beams, with fixed bench and double sanding head; over and under.
Sanding machine for continuous profile wooden elements, such as: beams, timber and beads.
The machine works as follows: the pieces are placed on the inlet idle roller conveyor and taken to the sander, a light barrier recognises introduction of the piece, commanding lowering of the ram that leaning on the beam causes auto-alignment of the upper sanding head and insertion of the feed motion. Underneath the lower sanding head it works the opposite surface of the beam. At the end of the piece the upper ram is raised placing the machine in stand-by.
To sand the two orthogonal surfaces, simply rotate the beam by 90° to introduce it on the side where it exited. The machine is able to recognise the piece and to repeat the work cycle.
VERTICAL SANDING MACHINE THREE SIDES LEFT-RIGHT-OVER
TYPE: MODEL KIOWA: T
COMBINED ROLLER-BUFFER BUFFER
Sanding machine for wooden carpentry elements such as timber and beams, with fixed bench and triple sanding head; right, left and above
the pieces are placed on the inlet roller conveyor and taken to the sander, the first stage is the sanding of the two left and right sides, the second stage is the sanding of the top of the beam,
the lateral grinding units are equipped with two devices to compensate for dimensional and geometric differences of the beams being worked; the first is a side floating device that allows compensation for error of straightness of the beam, the second is a dimensional floating device that compensates for the error of parallelism of the two sides of the beam.
the upper sanding unit is equipped with a self-levelling device which compensates for any dimensional and geometric differences in the vertical dimension of the beam,
the feed motion of the beam is ensured by a series of motorised rollers and by a motorised belt counter-opposed to the upper sanding head to increase the buffer removal depth it is possible to increase the working pressure which is controlled by an electronic pressure switch that is easily settable on the touch control panel of the machine,
to avoid unevenness in the head and tail of the workpiece being processed, the buffer pressurises and depressurises according to a scale of time calculated by PLC in relation to the speed, corresponding the pressure point when the head of the piece in its advancement is located exactly in the centre of the buffer.
The chamfer group in outlet is very important for the processing of the wooden carpentry beams as it restores the original edges of the beam so that it exits processing completely finished.