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4 Primary processing

The steps connected with primary processing are:

4.1 Sawing patterns

The coconut stem shows a decrease of physical and mechanical properties from periphery to pith over each cross-section. This property distribution requires an early separation of boards originating from the outer, harder part of the stem, and those from the softer core. By experience, frequent turning of the log during sawing yields the highest recovery of dense material, if broken down with circular or band-saws. The cutting patterns proposed are shown in Figures 19 – 24. Figure 24 depicts sawing patterns applicable when frame-sawing.

Fig. 19: Cutting pattern for coconut logs

Fig. 19

Fig. 20: Additional pattern for cutting purloins

Fig. 20

Fig. 21: Cutting pattern for beams

Fig. 21

Source: FAO, 1985

Fig. 22: Cutting pattern relative to selection and grading

Fig. 22

Source: FAO, 1985

Fig. 23: Cutting pattern for conventional sawmills

Fig. 23

Source: FAO, 1985

Fig. 24: Cutting pattern for frame-sawing

Fig. 24

4.2 Cleaning and ramp-loading of logs

Before loaded onto the ramp, sand and grit must be cleaned from the logs with water and brush, in order to reduce damage or blunting of saws. Depending on the size of the break down saw, the logs may have to be cross-cut again to the required length.

Loading can be done with a forklift, a farm tractor equipped with a frontloader, or manually over a ramp (Photo 28).

Photo 28: Manual ramp-loading of palm logs

Photo 28

4.3 Break down of logs

The logs can be broken down by the following methods:

Splitting 
Handsawing 
Chain-sawing 
Circular sawing 
Band-sawing 
Frame-sawing 

4.3.1 Splitting

The easiest way to breakdown coconut palm logs is to split them with wedges. If this method is applied, the log has to be clamped either on a ramp or with the help of wooden pegs to the ground. Aline is then drawn along the stem to mark where it should be split. Along this line, wedges are driven into the stem approximately 50 cm apart. After the log is split, the inner, highly perishable part has to be hewn out with an axe or adze. The split boards are rough. They can be used for rafters or trusses in sheds and simple construction.

Equipment: - axe
- mallet
- wedges
Advantage: - low labour input
- low investment for equipment
- less time consuming than handsawing
Disadvantage: - only rough material can be recovered

4.3.2 Handsawing with two-man ripsaw

This method has been traditionally applied in many coconut palm growing countries for the ripping of smaller numbers of shorter logs.

Procedure: - prepare a ramp (Figure25)
- fix the log (ca. 3 m long) on ramp with nails or wedges
- mark the planned cuts
- execute sawing (Figure 26)
Equipment: - two-man ripsaw (Figure 27)
- wedges
- hammer, nails, pliers
- filing and swaging set
- ramp
Advantages: - simple technology
- low investment
- recovery rate of about 45 %
Disadvantages: - slow and tedious process
- only shorter lengths can be sawn

Fig. 25: Fixing of coconut log for handsawing

Fig. 25

Source: Quinones et.al., 1983

Fig. 26: Manual sawing of coconut logs

Fig. 25

Source: Juson, 1984

Fig. 27: Two-man ripsaw for coconut palm logs

Fig. 25

4.3.3 Chain-sawing

Chain-saw ripping (Photos 29, 30) yields a higher production rate than manual sawing. However, as with the latter, it is only applicable where a small number of logs is to be converted. The production rate is about 0.04 m3/man-hour. A recovery of about 45 % can be achieved.

Procedure: -fix the log on a ramp
 -set the chain-saw and fix the clamping attachment
 -place the clamping device on top of the log, thus having the motor and handle on top of the log and the bar vertical (Figure 28)
 -push the saw through the log while sawing
Equipment: -ramp
 -chain-saw, min. 10 hp
 -bar min. 60 cm, with sprocket nose
 -chipper chain, spare chain
 -filing and repair set
 -clamping attachment (available with chain-saw manufacturers)
Advantages: -low initial costs
 -portability
 -less laborious than manual sawing
 -higher production rate than manual sawing
Disadvantages: -lower production rate than circular or band-sawing
 -frequent resharpening of chain necessary
 -wide saw kerf

Fig. 28: Sawing coconut logs by chain-saw

Fig. 28

Source: Juson, 19B4

Photo 29: Chain-sawing of palm stems

Photo 29

Photo 30: Chain-sawing of palm stems with guide bar

Photo 30

4.3.4 Circular sawing

Coconut logs have been successfully sawn with circular saws in various countries (Photo 31), and the following recommendations are the result of extensive research work undertaken in Zamboanga. Two alternative set-ups are possible, dependent on volume and area of operation:

-   stationary mill

-   transportable mill.

In both cases, the set-up is made up of:

-   headrig (main saw or breakdown saw)

-   breast bench (resaw)

-   log skid

-   dipping tank.

The saw, whether transportable or stationary, should be roofed (thatch, corrugated iron, or other) to protect the operating staff, timber, and equipment against sun and rain. To reduce stifling heat, the shed should be airy, preferably open on the sides. The log-yard, like the sawmilling area, should be cleared of vegetation, well-drained, and be covered by a layer of gravel or compacted material, which prevents the build-up of mud during rainy seasons. The dipping tank is essential to provide temporary protection of sawn timber against fungi and insects for the duration of seasoning. It can be made of old oil-drums cut in half lengthwise and welded together, or a trough dug into the soil and lined with plastic, or a plastic-lined wooden trough. Stationary mills might be equipped with a concrete trough. The dipping tank has to be protected by a roof to prevent the dilution of the preservative by rainwater.

Photo 31: Circular saw headrig (note the wide gullets in saw-blade)

Photo 31

Procedure:

The logs are loaded from the log-yard to the log skid. In order to facilitate later grading, only one category of logs (butt logs, middle logs or top logs) may be loaded and sawn at a given time. The logs should preferably be green in order to facilitate sawing. Prior to sawing operations, the saw has to be properly aligned, the saw-blade hammered, and the teeth sharpened (Astell,1981). The saws should either be tungsten-carbide (TC) tipped or equipped with stellited inserted teeth. The saw guides have to be properly set. They can be made of hardwood, even hard coconut wood. Watering of the saw-blade during sawing has proved helpful in order to reduce the heating of the blade due to friction, and to reduce the clogging of sawdust in the gullets.

The logs are cut according to the sawing pattern chosen. The slabs are sorted out for production of small items such as tool handles, novelty items etc., or for firewood or charcoal. The boards are passed over to the breast bench for edging. After edging or resawing, they are treated in the dipping tank (Chapter 7). Prior to dipping, it is advisable to brush off the sawdust, which otherwise may prevent proper surface treatment in the dipping tank, and which may also settle there, thus binding the preservative and reducing its effectiveness. After dipping, the boards are sorted according to thickness, size and quality (grading) and stacked in the seasoning shed.

Equipment:

The choice of equipment depends on the size of the operation. In Table 5 two examples are given. The feed speed depends on the thickness of the boards and the revolutions per minute (rpm). With these set-ups the daily production (1 shift of 6 effective working hours) can be achieved as given in Table 6. These are average figures based on ca. 80-year-old palms of the San Ramon Tall variety in Zamboanga. The recovery depends very much on height and diameter of the palms, on sweep, number and depth of harvesting steps.

Table 5: Data on circular sawmill for coconut wood conversion

Sawtype Engine Teeth Saw-blade Saw gauge Rpm Feed speed 
 (hp)Type no.Dia (mm)(mm-BWG)min 1m/min
Stationary mill       
Headrig100TC* 2313705,18–677015–20
Breastbench75TC 489104,19–8122030–45
Transportable mill       
Headrig100ins** 1911204,19–868010–15
Breastbench100*** ins 137603,18–9120025–35

*   Tungsten Carbide tipped

**  Inserted teeth

*** Both saws driven by same motor

Table 6: Daily recovery rate from circular sawmills

Milltype  Input Output Recovery 
 No. logsm3m3%
Stationary mill50–6017–216–734
Transportable mill2593–434

4.3.5 Band-sawing

Coconut logs can be sawn in conventional band-saw mills (Photo 32). All band-saw blades should be stellited. Due to their bending over the wheels, they can not be TC-tipped. The feed speeds to be applied in breaking down the logs range from 10 – 25 m/min; for edging or resawing feed speeds of 20–40 m/min can be applied. Recovery in band-saw milling has proved to be the highest with up to 50 %.

Photo 32: Band-saw

Photo 32

4.3.6 Frame-sawing

Frame-or gang-saws consist of a frame which carries a number of parallel blades, which can be preset at varying distances. The blades have a heavier gauge than band-saw blades, but they are considerably thinner than those of circular saws. Since they are used straight, their teeth can be TC-tipped. Frame-saws have been developed to breakdown small-diameter logs. The frame moves up and down while the log is pushed through, and the entire log is converted to planks in one go (Photos 33 – 35). Coconut palm logs are broken down in two steps (Figure 24 above).

Photo 33: Frame-saw (infeed)

Photo 33

Photo 34: Frame-saw (outfeed)

Photo 34

Photo 35: Frame-saw blade

Photo 35

4.3.7 Comparison of different saws

The different saws are compared in Tables 7 and 8.

Table 7: Technical data of different saws

Table 8: Advantages and disadvantages of different saws

Advantage/Disadv.Circular sawBand-sawFrame-saw
Kerfwidesmallsmall
Speedlowhighesttow
Surface qualitylowbetterbest
Recoverymediumhighlow
Sawing pattern can be individually selectedyesyesno
Production ratelowhighhighest
Standard of technologysimplehighmedium
Investment costslowhighhigh
Maintenance costs for machinerylowhighlow
Know-how and traininglittlemuchlittle
Sawdoctoring skillshighhighmedium
Sawdoctor equipment costshighmediumlow
Maintenance costs for sawshighmediumlow

Important  
  • Never keep more than several days' log supply in log-yard, since coconut palm stems decay fast!
  • Select mill type dependent on size of operation and know-how/expertise available!
  • Coconut wood can only be sawn effectively with TC-or Stellite-tipped teeth!
  • Always clean logs of sand and mud before sawing!
  • Fresh logs are sawn more easily than dry ones!
 

4.4 Resawing and trimming

Resawing is done with standard resaws, be they circular or band-saws. For the saw-blades and their maintenance see Chapter 4.5. For trimming, the installation of a radial armsaw has proved most useful.

4.5 Cutting steels and saw maintenance

One of the reasons that coconut stems have, as yet, rarely been converted into lumber on a larger scale, is their peculiar texture. In a very soft parenchymatous tissue strands of hard, sclerenchymatous vascular bundles are embedded. While the parenchyma easily gives way and disintegrates into fine particles during sawing, the sclerenchyma celIs in the vascular bundles are very hard and abrasive. The sawing of both tissues together results in rapid blunting of conventional saw-blades. Various techniques have been applied to prolong the life of the saw teeth. Results are:

-   circular and frame-saw blades should either be

-   band-saw blades should be stellited

-   the gullet size has to be increased in order to facilitate the removal of the very fine sawdust during sawing.

The increase of gullet size on a given saw diameter automatically results in the reduction of the number of teeth (for solid tooth nomenclature refer to Figure 29).

Fig. 29: Solid tooth nomenclature

Fig. 29

Four different steel types are used for the processing of solid timber, namely:

-   mild steel (MS)

-   high speed steel (HSS)

-   tungsten carbide (TC)

-   stellite (ST).

Their advantages, disadvantages and uses are discussed in Table 9.

Table 9: Comparison of cutting steels

 Steel 
 MS HSS TC ST 
Advantage cheaplonger lasting than MSvery wear resistant and longest lastingwear resistant
Disadvantage no wear resistance expensive maintenance 
Use light woodlight wooddense wood wood based panelssoft wood, dense wood

Tungsten Carbide comes in ready-made, preground bits, which are to be silver-soldered into recesses in the saw teeth. After soldering the bits must be top, face and side-ground. They are available in various qualities. For coconut wood the use of grade ISO K30 is advisable. It is tough and lasts long, but is also brittle.

Stones or bullets in the stem, as well as dropping the saw-blade on concrete flooring, may result in breaking of the tips.

For the tooth shape, the following angles have afforded successful sawing with circular saws:

-   Hook angle: 20 – 25°,

-   Top clearance angle: 20°,

-   Sharpness angle: 45 – 50° (Figure 29).

Attention should be paid to the bite. In order to obtain maximum production before blunting, the bite should be as big as possible. Too large a bite, on the other hand, can cause carbide breakage in the tooth tip. The bite recommended is between 1 and 1.3 mm per tooth.

Stellite is available in rod form and has to be fused under heat on to the base metal of the saw tooth. Three methods can be used for its application (FAO,1985):

-   A drop of molten stellite can be applied to the swage cup.

-   A large deposit of stellite can be melted on to the end of a saw tooth which has been ground back slightly. The stellite is then formed with dies so that it looks similar to a swaged shaped point.

-   Molten stellite can be poured into a ceramic mould around the tooth point. This gives a finished point similar to the second method.

Of these methods, the last is most expensive in terms of initial investment, but saves on the expensive stellite rods. The other two methods, which are more commonly applied, tend to waste a considerable amount of stellite in grinding, since the stellite blob on the tooth point has to be top, face and side-ground (equalized). The stellite grade to be used for coconut wood is Grade 6 (red tipped rod). Cobalide 3 and Eutector 9000 have given good results.

TC-tipped teeth have to be ground with the help of diamond grinding wheels, which are very expensive compared to the conventional silicon carbide types used for stellite and high speed steel. The diamond wheels are available in different grades dependent on the percentage of diamonds.

For proper maintenance of saws an appropriately staffed and equipped saw doctor shop is indispensable. The equipment depends on the type of saws used. The recommended standard equipment is as follows:

-   face/top grinder

-   side grinder (for band-saw equalizer)

-   hammering bench (for band-saw roller-stretcher)

-   anvil

-   welding set

-   soldering set

-   tools like hammers, straight edges, gauges

-   spare blades

-   TC bits or stellite rods

-   silver solder.

Photo 36: Band-saw blade grinder

Photo 36

Inserted teeth can be used in smaller operations with transportable circular sawmills. They are available ready-made and can easily be replaced when worn out. They are wear-resistant and need only face grinding. It can be done with a hand-gulleting machine after removal of the saw-blade from the rig, or with a portable “jockey” grinder, which can be clamped on to the saw-blade while on the rig.

Important  
  • Proper maintenance of saws has a direct influence on:
    - output and thus on economics
    - surface quality!
  • Proper training of saw doctors is indispensable!
 

4.6 Peeling and slicing

Coconut logs can be peeled and sliced. However, due to their anatomical structure the veneer sheets tend to split and break along the vascular bundles, either immediately after peeling, or after drying. Therefore, they can only be used as core veneers.

Thus, peeling and slicing have for the moment no relevance for the industrial use of coconut palm stems.

4.7 Chipping for wood-based panels

The fibrous vascular bundles make good raw material for particle board, gypsum-or cement-bonded panels, or medium-density-fibreboards (MDF). During the process of chipping and hammer-milling the parenchymatic tissue disintegrates into a fine dust. It is preferable to achieve a good segregation of these unwanted fines and the bundles. Segregation techniques are presently developed. The economics of wood-based panels made from coconut timber have yet to be proven.

4.8 Utilization and disposal of waste

During the entire operation of felling and processing of coconut stems, proper waste disposal is of paramount importance in order to prevent the rhinoceros beetle (Oryctes rhinoceros) and palm weevil (Rhynchophorus schach oliv.) from breeding. Both insects can create havoc in newly established plantations.

From the crown, the edible heart (palmito) can be carved out and used as a vegetable. In larger replanting schemes it might even be considered to can and export this delicious and highly prized palm heart.

The fronds and the discarded top portion of the stem should be burnt in the plantation after drying. In most cases removal and later charcoaling is not economical since the charcoal recovery and its quality are low. Slabs, on the other hand, make good charcoal. If not converted into smaller wooden items, they can be cut into shorter billets and converted to charcoal after drying. The sawdust has to be removed regularly from the saw (Photo 37). With its high starch and sugar content, it is a good substrate for growing edible mushrooms. Laid out in beds undershade, and covered with banana leaves, the padi straw mushroom (Volvariella spp.) has been cultivated successfully.

Photo 37: Sawdust accumulation under circular saw

Photo 37

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