In this section:
Cutting Machines
Basic components
All the machines have the same basic components including:
Receival hopper
Fruit from the field is placed into the hopper where overripe or blemished fruit is removed. The hopper should feed the aligner with a steady even flow of fruit.
Aligner
This aligns the fruit so the cutting head will cut it on the suture line.
Cutting head
Fruit are cut by a single circular blade rotating over the fruit at the end of the aligner.
Stone remover
Cut halves pass through a cylindrical rotating mesh drum with 25 mm square holes. The loose stones fall through the mesh and the halved apricots pass on to the conveyor.
Inversion conveyor
The conveyor that takes fruit from the stone remover to the tray loader is sloped so that only cup-down halves will move up the belt. Fruit lying cup up are unstable and roll back.
Tray loader
Tray loaders work on the principle of collecting the cut apricots on to a vibrating ribbed table that is slightly smaller than the wooden tray. When the table is full a wooden tray is placed or clamped over the fruit and both trays are inverted together. The wooden drying tray is then on the bottom, and when the top tray is removed the cut halves are left cup up on the wooden tray.
Site and installation
The cutting machine should be housed in a shed to shelter it from the weather; rain and direct sunlight are both detrimental to the machine. However, the shed should be well ventilated for operator comfort during the heat of the cutting season.
The shed floor should be concrete, sloped and drained to take away the water used during operation and washing down. Bolt the machine to the floor to prevent misalignment, ensuring that this does not itself twist the frames out of shape and cause running problems. Watch the conveyor belt section especially in this respect.
Site the machine so fruit can be easily received from the orchard, and transferred after cutting to the sulphuring facilities. A platform is needed alongside the hopper to make the working height more comfortable, and it is best if fruit can be transferred directly to this from the orchard trailer to minimise lifting.
Once the site for the machine has been chosen have it permanently wired. All electrical fittings should be waterproof. Install an earth leakage circuit breaker for safety. This is the only way to guarantee operational safety. One of these units should be supplied as standard equipment with every machine sold. Install safety kill switches at the hopper, conveyor and tray loader for operator and mechanical safety.
Critical points in operation
- Poorly maintained apricot cutting machines produce inferior quality dried fruit.
- Time spent ensuring that a cutting machine is in top working condition will more than pay for itself in product quality. If a cutting machine is not correctly adjusted, it is not possible to process ripe fruit. Processing immature fruit must be avoided.
- Each line of fruit can behave differently through a cutting machine. Even fruit from the same trees can behave differently from one season to the next. When operating a cutting machine it is necessary to monitor its performance continually and adjust its setup to maintain a quality cut product.
- Getting the best performance from a cutting machine takes some trial and error. Take a note of exactly how the machine is set before making any adjustments or modifications, in case you have to return to the original settings. No single setup will suit all fruit types and only experience allows the machine to be set up appropriately.
Cleaning
The machine must be kept clean to work correctly, as well as for hygiene. If the machine is going to be stopped for more than 30 minutes wash it down to ensure it works well when restarted. Do not allow it to dry off without first washing it clean, or cleaning will be difficult. Clean the machine thoroughly at least once each four hours of operation. The fastest and simplest way is to use clean water from a hand gun connected by a suitable length of hose to a high pressure spray plant. It is especially important to clean the aligner and other parts with which the fruit comes in contact, but all parts should be washed.
Check belt tensions, blade sharpness and alignments while washing the equipment. Afterwards grease, oil and make any adjustments so the machine is ready for the next cutting session. Ensure that all safety guards are in place during fruit cutting operations.
For both efficient operation and safety stones need to be removed frequently. Catching them in a special tray is recommended, or even a small conveyor or auger to carry them outside the shed may be a worthwhile investment.
Component descriptions
Feed hopper
A single layer of fruit on the creep feed belt is recommended. This will help in grading out over-ripe fruit and stop softer fruit being squashed and reducing machine efficiency and final quality.
It is important to have an operator at the feed hopper. This person can remove fruit unsuitable for cutting and, just as importantly, control the amount of fruit being fed on to the aligner. Making sure a fruit is carried along in front of every wheel on the aligner chain improves cutting efficiency. This is a much preferable way to increase the number of fruit cut to speeding up the machine. Optimum operating speed is about one apricot a second through each cutting blade. Running a cutting machine faster than its design speed will reduce the quality of dried fruit produced.
Fruit sizer
These were not supplied on early machines, but they can be added. Many newer machines have a fruit sizer because it does not pay to dry small fruit. The sizer can be a separate section added to the machine, or the aligner can be modified so that small fruit will fall through. The simplest separate size-grader that can be incorporated in a cutting machine is the dual hose grader.
For the most efficient operation the sizer should come before the fruit is fed to the aligner. If sizing is carried out as part of the aligner then, depending on the number of small fruit, some of the alignment wheels will not carry fruit through the cutting blade.
Fruit aligners
Efficiency of fruit alignment depends on the shape of the fruit, and can range from 70% to 95% or higher of correctly aligned fruit (cut on the suture line). Flat-sided fruit will align much more easily than round fruit, so variety has a large impact on the operation of cutting machines.
The length of the aligner also influences the number of fruit correctly aligned. In one trial at 1.8 metres long only 65% of Moorparks were correctly aligned (85% Trevatts) but at 3.6 metres long 80% were correctly aligned (95% Trevatts). A length of 3 to 3.6 metres is recommended.
Aligners work most efficiently when there is an angle of 60 to 70 degrees between the sloping sides, that is 30 to 35 degrees to vertical on both sides. Some early cutting machines with angle iron aligner guides have an angle of 45 degrees each side of vertical; these can be modified to improve alignment efficiency.
It is important to lubricate the chain and shafts on which the alignment wheels are mounted to keep the machine operating at peak effectiveness. If the alignment wheels are set too low in the aligner trough the cutting blade will knock fruit back over the wheel. This results in two fruit being pushed through the cutting blade by the next wheel, neither of which will be cut correctly.
The fruit aligner must be kept slippery where the fruit contacts it if the fruit is to align easily. This is generally done by keeping the aligner clean and wet with water jets that maintain a thin film between the fruit and the aligner guides. Stainless steel is the best material to provide a slippery surface. Polycarbonate or steel that has been polished and then painted with a high gloss paint such as used in the automotive industry is also suitable.
It is important that the cutter spatter guard is functioning correctly. This guard prevents the cutting blade flicking small particles of fruit back on to the aligner and making it sticky. The spatter guard is best mounted independently of the cutting head, so that it does not rise as the blade cuts each fruit.
Cutting head
There are two types of cutting head, single blade and Williams head.
The single blade head is simpler, easier and cheaper to construct. The Williams head, however, does a marginally better job on soft fruit and will handle a greater size range of fruit at any one particular setting. There are more moving parts and more critical adjustments to be made on the Williams cutting head, making it more difficult to use and maintain for correct cutting. Almost all cutting machines are fitted with single blade cutting heads.
It is vital that the blades are kept sharp. Check them at least once a day. Blades can be hand-sharpened using a fine milsaw file.
Blades should be of stainless steel and at least 175 mm in diameter. Overall performance drops off as the blade size is decreased beyond this point. A blade diameter of approximately 225 mm is recommended, but some growers prefer 250 mm diameter blades. If a different blade size is fitted the cutting head must be repositioned along the aligner. Repositioning is also required as the blade wears down during use.
The blade is held over the aligner and rotated so that the bottom of the blade is travelling in the same direction as the fruit. Fruit is carried along by the rotating discs and rolled under the cutting blade. Cutting can sometimes be improved by roughening the surface of the aligner guides onwards from the point where the fruit contacts the cutting blade.
The rotational speed of the blade is critical for correctly cut fruit. The best rotational speed depends on the blade size and the type of cutting head. For a single blade cutting head of 175 mm diameter, a speed of 520 rpm is recommended as a starting point. For a 250 mm blade 450 rpm is best. If the machine is not cutting as it should try changing pulleys by one size up or down to assess if it can be improved.
If stones are hard to remove when using a plain blade try a notched blade. A notched blade has been found to give least stone chipping and a high rate of stone removal. Mount a notched blade so the square edge of the notches does not hit the stone, that is, in the opposite direction to a normal saw blade. Operation in the other direction can result in the production of stone chips, slip stoning and torn rather than cut fruit.
The cutting head must be positioned correctly. The blade should be directly over the centre of the aligner, vertical and run true to the aligner. If any of these are not right it is likely the cut will not meet or will be to one side of the suture line. This results in uneven halves, ragged edges and reduced stone removal.
Badly aligned blades will often slide down one side of the stone. This shaves the stone leaving a brown stain in the fruit that downgrades the fruit at the packing shed.
There are two other causes of stone shaving. The weight on the blade should be light so that it can lift over the stone. An adjustable counter balance at the back of the cutting head is used to achieve this. Some machines do not have a counter-weight; if stone shaving is a problem in this case it would be advisable to add this modification to the machine. Fruit maturity and size determine the weight of counter balance required to optimise cutting.
It is often necessary to reduce the weight on a newly-sharpened blade to prevent shaving the stones and leaving chips in the fruit. The small brown chips bleach in the sulphur house to look and feel like sand in the dried product. If blade sounds as if it is sawing wood, then it is certainly shaving or chipping the stones.
Worn blades can cause stone shaving. As the blade wears it becomes thinner, allowing it to flex and slide down the edge of the stone. When this happens replace the blade.
During operation it is advisable to have a continual dripping of water on to the cutting blade. This lubricates the cutting blade and helps keep it clean. It also keeps any apricot flesh that builds up on the blade soft so it is easily removed when the machine is washed.
Stone removal
It is unlikely a cutting machine will achieve 100% stone removal. The stone removal rate varies with variety, and stones are generally harder to remove early in the season. Stones are normally more difficult to remove from immature fruit than from fruit that is firm but ripe. Some growers have also found that stones are more difficult to remove from fruit out of a cold store than from fruit harvested and cut immediately.
For tips on improving stone removal see the previous section on cutting heads.
Clean the stone removal screen often for optimum performance.
Sometimes the stone removal rate can be improved by decreasing the slope of the stone removal screen, however, this normally increases fruit damage. It is preferable to get fruit through the screen as quickly as possible to minimise damage. The screen is designed only to allow loose stones to fall through the mesh, not to actively knock stones out of halves.
Fruit orientation conveyor
Fruit orientation conveyors work best if kept clean, but they should not be wet while the machine is in operation. To clean the belt properly it needs to be scrubbed with a stiff brush.
Adjust the slope of the belt to achieve as many correctly oriented halves as possible. A wire with a crank at each end, offset by 90 degrees to each other, can be placed across the inclined belt so that fruit halves in the cup down position will pass under and others will be tipped down the inclined belt.
If removal of stones is a problem, the orientation conveyor provides a location for a worker to manually pick out stones. This will relieve some of the workload from people operating the tray loader.
Tray loader
The equipment developed to do this job accumulates fruit on a tray in the cup down position and then inverts this on to a wooden drying tray. The unit is not perfect, and a considerable amount of manual labour is still needed to help accumulate the fruit on the loading table and transfer it to the wooden drying trays.
The designs are developments of the original SA Department of Primary Industries tray loader. The descendant machines can be more easily operated by two people and have a convenient place to temporarily hold the filled wooden trays. This latter point is important as it allows any stones not previously removed to be manually picked out.
It is preferable not to use water on the tray loader section of the machine while in operation. Water tends to wash the centres out of the fruit, downgrading the dried quality. If water must be used keep the amount to a minimum. It is important also to have a small gap between the ribbed chute and the ribbed tray loader table to prevent water running down on to the tray loader table. The tray loader must, however, be cleaned frequently for ease of use. Food-grade silicone release agent is available and can improve the performance of the tray loader by providing a slippery surface that stays clean for longer.
Tray loader operators must be careful to prevent fruit packing too tightly on the trays, especially at the bottom edge. It is important that the clamps that hold the long edge of the tray are set accurately to prevent fruit sliding down to the bottom end of the tray when it is inverted. If this is allowed to occur, fruit will be squashed into each other causing them to stick together during drying.
Lubrication
Grease is generally better than oil for machine lubrication as it is not washed away as easily on those parts where water is used. However, make sure that no oil or grease contaminates the fruit. It is important to keep the machine well oiled to prolong the life of the many moving parts, particularly the aligner chain, cutting head and shaker mechanism on the tray loader. Apricot juice contains a considerable amount of acid that will eat out seals and bearings if they are not regularly cleaned and lubricated.
Trouble-shooting guide
The following is a guide to the possible causes of some problems that can occur when operating a cutting machine.
Aligner
Fruit does not roll in trough:
- fruit too soft
- sprocket or disc loose on shaft
- wheels set too low in aligner trough
'Clunk' noise from disc drive:
- insufficient lubrication of disc/ sprocket shafts and pins
- incorrect sprocket alignment
- incorrect alignment of drive sprocket for extended pin chains
Cutting head
Fruit cut to one side:
- cutting blade not over centre of aligner trough
- aligner trough sides bent, loose or built up with rubbish at cutting head
- worn bushes or bearings in cutting head
- not enough counter balance weight (blade too heavy)
Fruit not aligned to suture line:
- naturally round fruit (no remedy)
- dirty aligner trough
- too much fruit on aligner (should be only one fruit per wheel)
- aligner too short (recommended 3 metres long)
- wheels set too low in aligner trough
Fruit not cut fully round:
- blade set too high
- blade set too far back from end of aligner
- blade blunt
- blade allowed to lift too high
- too much counter balance weight (blade too light)
- too much water on aligner
- insufficient grip on aligner sides under the cutting blade
Blade blunting rapidly:
- blade set too low
- blade set with insufficient counter balance weight
- blade travel limit stop set too low
Poor stone removal:
- off-suture cutting
- too much counter balance weight
- blade scallops too shallow due to sharpening or wear
- blade set too high
- blade blunt
Stone removal drum
Drum will not turn:
- seized support wheel
- oil/ grease on drive belt
- overloaded with fruit
- drive jammed with stone
- needs cleaning
Conveyor belt
Fruit won't move up belt:
- belt needs cleaning
- too much build up of round fruit and/ or halves with stones at base of belt
- belt worn
Tray loader
Fruit won't move down:
- insufficient vibration
- tray surfaces sticky from dried apricot juice
- wear in hinges or vibration transfer blocks
- eccentric drive loose on shaft
Fruit sticks to tray:
- insufficient vibration
- grooves in tray filled with debris, needs cleaning
- surface rough due to wear
Fruit packing too tightly on to tray:
- too much vibration
- bent or warped drying trays
- inadequate operator skill
End of season shut down
Thoroughly wash down the whole machine using a scrubbing brush and water, then carry out the following to protect the machine between seasons.
Creep feed belt:
- thoroughly wash down
- oil and grease appropriate parts
- relieve tension on conveyor belt, making sure the release is even on both sides
Aligner:
- turn machine over by hand and oil every individual extended pin and disc sprocket shaft
- oil and grease appropriate parts
- cover the aligner to keep direct sunlight off any plastic components if fitted
- remove the oil reservoir wicks (if fitted) to prevent oil from dripping out on to the floor
Cutting head:
- grease appropriate parts
- clean blade thoroughly and store in a dry position, wrapped in an oily rag
Drive module:
- oil or grease appropriate parts
- cover electric motor if likely to get wet
Stone basket:
- remove basket and store in dry, dark place
- oil or grease appropriate parts
Conveyor:
- run for a few seconds a day after last washing to prevent the belt sticking to the rollers
- Release tension on the belt, making sure that the release is even on both sides
- cover the conveyor belt to protect from direct sunlight
- oil belt joiner if not continuous belting
Tray loader:
- oil or grease appropriate parts
- cover all plastic areas to protect from direct sunlight
- release tension on vibrator drive belt
Between-season maintenance
Between seasons, there are some parts that should be checked to ensure that they are in good enough condition to run for the whole of the next season. If there is some doubt then replacement parts can be ordered in and kept in stock in case a breakdown does occur during the season. This will reduce down time.
Any problems that developed or became evident during the season should be fixed well in advance of the next season, as it is unlikely there will be enough time once the next cutting season has started.
Pay attention to the following areas.
Chains and sprockets: Check for excessive wear; chain slippage or locking can occur with badly worn parts. Take special note of the wear on the extended pins of the aligner chain.
Belts: Check for cracks or breaks appearing in the belts. It is always a good idea to keep spare belts on hand, in case of a breakage during the season.
Cutting blade: The cutting blade may require regrinding to deepen the notches during the off season. If the machine does a lot of work, a change during the season may also be necessary. Cutting efficiency will decline once the blade is less than 175 mm diameter, with the ideal being around 225 mm.
Bearings: Check all bearings for wear and dry running. The most important ones to keep in good condition are those on the cutting head, crank arms and drive module.
Aligner chain wear strips: Replace these strips when the side links of the chain have worn grooves into them to such a depth that the rollers on the chain are touching it. Running the machine in this condition increases chain wear.
Tray loader: Oil and grease appropriate parts.
Main frames: The machines are generally made out of mild steel in fruit non-contact areas. As these areas get wet during both the operation of the machine and washing down keep a careful watch for rust.
