Dorner Engineered Solution – Recirculating Conveyors
Manufacturing lines require mechanical solutions to facilitate the consistent flow products to maximize throughput, and recirculating conveyors are a common part of these applications.
What are Recirculating Conveyors?
A recirculating conveyor is a piece of machinery that helps move products down a manufacturing line. It optimizes the production process by helping to move products quickly and without error — avoiding backups, redirections, and shutdowns.
Features of Recirculating Conveyors
The basic features of a recirculating conveyor are:
- At least two conveyor belts
- A motor to run the belts
- Side guides and dividers to control the flow of parts
A recirculating table is a type of conveyor that creates space for a product to accumulate, and controls the flow to the next process in the manufacturing line.
A type of accumulation conveyor, its belts must be low-friction, and can be made of either fabric, modular belt or plastic chain.
An accumulation conveyor is a type of recirculating conveyor that contains overflow and buffers items until a machine or operator downstream is ready to receive them, providing automated control of a product along a manufacturing line.
This type of conveyor is an excellent solution for handling overflow and buffering items along the line. It can smooth out fluctuations in product line rates, and singulate products while controlling outfeed rate. An accumulation conveyor is often regarded as crucial for when items from multiple lines must be merged into a unified line.
It requires low-friction belting, made of either fabric, urethane, modular belt or plastic chain.
Dorner has designed accumulation conveyors (also referred to as accumulation tables) that use multiple belts within the same frame to provide more accumulation space than traditional in-line conveyors.
Technical information bulletin the effects of ozone on rubber conveyor belts
The effects of exposure to ozone
Ozone occurs naturally in the upper atmosphere. At high altitude, it acts as a protective shield by absorbing harmful ultraviolet rays. However, at low altitude, the ozone itself becomes a pollutant. Exposure to ozone increases the acidity of carbon black surfaces and causes reactions to take place within the molecular structure of the rubber. This has several consequences such as a surface cracking and a decrease in the tensile strength of the rubber. The actual level of ozone concentrations at ground level, and therefore the level of
exposure, can differ greatly from one location to another depending on geographical and climatic conditions. The general concentration of ozone is from 0 to 6 parts per hundred million parts of air. Coastal areas have particularly high levels of ozone pollution. Ozone also occurs in cities and industrialised areas, when it is formed by the photolysis of nitrogen dioxide from automobile exhaust and industrial discharges, where ozone levels can range from 5 to 25 parts per hundred million parts of air.
Environmental and safety concerns
Belts that do not operate under shelter are especially prone to surface cracking, which can be extremely detrimental in terms of the performance of the belt and its working life.
Even more significant are the environmental and health and safety consequences of the damage caused by ozone exposure because dust particles from the materials being conveyed penetrate the surface cracks and are then discharged (shaken out) on the return (underside) run of the belt.
At first glance, fine cracks in the surface rubber may not seem to be a major problem but over a period the rubber becomes increasingly brittle. Transversal cracks deepen under the repeated stress of passing over the pulleys and drums and, if the conveyor has a relatively short transition distance, longitudinal cracks can also begin to appear.
Again, surface cracking may not initially seem to be a cause of concern but there are often hidden long-term effects.
One of those hidden effects is that moisture and other fluids seep into the cracks and penetrate through the belt covers
down to the carcass of the belt. If the belt is carrying product such as household waste, grain, wood/waste or biomass then the oils and resins that penetrate through to the carcass will cause the belt to swell and distort very badly.
The effects of ultra violet radiation
Ultraviolet radiation causes chemical reactions to take place within rubber and the rapid decline in the ozone layer in the upper atmosphere over the past several decades is allowing an increasing level of UV radiation to reach the earth’s surface. Ultraviolet light from sunlight and fluorescent lighting accelerates deterioration because it produces photochemical reactions that promote the oxidation of the surface of the rubber resulting in a loss in mechanical strength.
EN/ISO 1431 International standards
To scientifically measure resistance to ozone, samples are placed under tension (20% elongation) inside the ozone testing cabinet and exposed to highly concentrated levels of ozone for a period up to 96 hours. At Dunlop the pass criteria is that the rubber sample does not show any signs of cracking after 96 hours (@ 20°C, 50 pphm and 20% strain) inside the ozone cabinet. Every sample is closely examined for evidence of cracking at two-hourly intervals and the results carefully measured and recorded. As a general rule, based on experience, failure to exceed more than 8 hours under test without surface cracking will most certainly mean that the belt will start to deteriorate in less than 2 years. In many cases, particularly in coastal locations, deterioration will begin within a matter of months.
At Dunlop Conveyor Belting we were amongst the very first to introduce mandatory testing to EN/ISO 1431 international standards. As a direct result, special anti-oxidant additives that act as highly efficient anti-ozonants were introduced into all of our rubber compound recipes to provide protection against the damaging effects of ozone and ultra violet.
Always insist that your belt supplier provides written verification that their belts undergo stringent conditional
As often as not, the quality of a belt (including its ability to resist wear) is reflected in its price. It is always worth the effort to check the original manufacturers specifications very carefully and ask for documented evidence of tested performance compared to the relevant international standard before placing your order.
Flexible and efficient: automated line changeovers for the InnoPET TriBlock from KHS
Up to 70% time saved compared to manual changeovers / Molds changed by robots on the stretch blow molding module / Automated adaptation to the label gluing height and bottle diameter
The example of KHS’ InnoPET TriBlock stretch blow molder/labeler/filler block illustrates how automated format changeovers can be successfully implemented. And it shows that beverage producers can combine maximum flexibility with a high level of efficiency.
PET lines today are very rarely configured exclusively from individual machines. Instead, beverage producers want a turnkey system with a small footprint, shorter conveying segments and a reduced maintenance effort and – first and foremost – short changeover times. As part of the holistic, automated line changeovers on its PET lines the InnoPET stretch blow molder, labeler and filler TriBlock satisfies these high demands. Thanks to the new KHS InnoPET iflex automation concept beverage bottlers can now save up to 70% of the time needed for manual changeovers. To this end, various functions were developed for the different segments on the InnoPET TriBlock that considerably increase the level of automation and make manual intervention largely superfluous with a few clicks on the HMI.
Format changeovers by robot
PET bottles are produced in the stretch blow molding module. When formats are scheduled for a changeover, the iflex first triggers the automatic loading of recipes for the heating profile, blow pressure, preform conveying and inspection technology.
The most important new feature on this machine is the mold changeover when the new batch requires a different bottle size or shape. Here, the switch is made with the help of a robot that changes the two side mold shells and base mold fully automatically and very quickly during ongoing production. It removes the previous molds from the stations, places them in the mold set magazine, takes out the new molds and slots them back into the stations without any need for action from the operator. The robot needs just 41 seconds per station for this short, fully reproducible procedure. The time for manual intervention is thus reduced from a previous 95 to just eight minutes. This is further facilitated by automatic bottle base detection adjustment at the blow wheel transfer star with the help of several sensors. All the operator has to do by hand is to start the format changeover and later start the new production run.
Less manual intervention
The time and effort needed for manual work by the operator is also reduced in the labeling module. This is chiefly thanks to automatic adaptation of the label gluing height and bottle diameter. The operator still carries out the toolless changeover of the vacuum drum, brushes and bottle guide parts, however. Nevertheless, two labeling stations can now be converted within 20 minutes.
At the press of a button
In the filler module conversion is fully automatic. Firstly, this avoids handling errors by the operator, and secondly, it prevents the risk of bacterial or microbiological contamination by people entering the hygiene area that would then need foam cleaning. This would delay the changeover by around 30 minutes.
The key components relevant to automatic changeovers are the guides from the filler infeed to the capper discharge that need to be set to the bottle diameter and height. Conical base guides or bottle pockets are used here, for example, where the containers are fixed by simple height adjustment as in a funnel. The discharge conveyor is vertically adjusted by a servomotor instead of being manually cranked; the same goes for the horizontal adjustment of the railings. What’s more, the bottle caps are also changed over automatically, such as when a new beverage features a different cap color from the previous one.
Up to 70% quicker
We can see just how important the new iflex options are on the KHS InnoPET TriBlock in particular when it comes to highly flexible beverage filling if we take a look at the total time saving: depending on the specific changeover routine on site, this amounts to approximately 95 minutes. The remaining manual tasks only take eight minutes on the stretch blow molding module and 20 minutes on the labeling module. On the filling module format changeovers have been fully automated and are completed without intervention in a matter of seconds. All told, changeovers are now implemented in less than a third of the time previously required, allowing beverage producers to look forward to a high degree of flexibility and efficiency.
Innoline Flex Control: everything under control
The Innoline Flex Control line management system is essential if the iflex is to function properly and its potential be fully exploited. It takes over the tasks of line and order management from the beverage producer’s ERP system and orchestrates the automatic changeover of the machines. The basic idea is to help the operator to always do exactly the right thing.
By integrating the Innoline Flex Control web GUI into the HMI, data is displayed on the machine operator panel. The operator sees which processing program must be selected when and which materials are needed where to produce the respective current version of the order sequence that has been tactically planned by the system. With the automated iflex variant, this is triggered by the simple press of a button. On the guided iflex version the system clearly prompts the operator through the various steps and provides straightforward instructions for all action that needs to be taken manually.
A guide to the types of belt edge
Used in rubber conveyor belts
Because of advances in technology and the types of materials used to manufacture rubber multi-ply conveyor belting there is often confusion concerning belt edge types.
This information bulletin is designed to provide up-to-date guidance and clarification. There are basically three types of edges available: moulded edge, (cut and) sealed edge and (plain) cut edge.
Many years ago, moulded edges were the norm because cotton was used as the reinforcing fabric in multi-ply belts.
A moulded edge was necessary in order to prevent moisture penetrating the cotton fabric and causing it to rot.
However, since the inception of synthetic ply belt carcasses using polyester and polyamide, this problem effectively no longer exists. As a consequence, belts without moulded edges are now the most commonly used.
Moulded edges can only be created when a belt is manufactured (assembled and vulcanised) to an exact width, usually a specific width required by the end-user. A small strip of non-reinforced rubber is attached to the side of the carcass during the calendaring of the belt. The strip is formed as an integral part of the belt during the vulcanizing process. This typically provides 5 to 15 mm of rubber on the belt edge without fabric reinforcement.
Moulded edges do not provide any structural advantage and can be susceptible to damage if the belt wanders off-track.
Non-reinforced rubber can easily be cut off so when a belt with moulded edges gets damaged, large pieces of rubber are often torn off.
Most ‘non-stock’ belting in special grades (fire resistant for example) and/or non-standard sizes are made to order at the specific width requested by the customer. These will therefore naturally have moulded edges unless the widths and length combinations requested by the customer allow belts to be slit (cut) from a wider, more cost-efficient production width.
To maximise efficiency of production, standard productionbelts are usually made as wide as the production machinerywill allow and are then subsequently cut to narrower widths.At Dunlop we automatically create belts with sealed edgesusing a special cutting process involving cutting knives thatrotate at very high speed. The heat created by the friction ofthe rotating knives melts the carcass fibres and the rubberon the edge of the belt, effectively creating a seal. This isreferred to as a ‘cut & sealed edge’ or simply ‘sealed edge’.Apart from a better visual aspect, the sealed edge means thatthe belt is not sensitive to moisture penetration and cantherefore be used in wet conditions and is better suited tolonger-term storage outdoors.
Belts with cut edges are produced in the same way asdescribed previously but are cut (slit) using conventionalrotating knives. A ‘cut edge’ is therefore not sealed.At Dunlop we do not recommend the use of unsealed (raw)cut belt edges as wet conditions and outdoor storageconditions can cause water to enter the carcass from theedge due to capillary forces. Although the carcass fibres arehardly affected, moisture can cause vulcanising problemswhen making splice joints.
Steelcord Construction Belts
All steelcord belts are manufactured to a specific set ofspecifications which fully embed the steel cords and aretherefore only available with moulded edges. In the caseof steelcord and steel reinforced fabric ply beltingit is necessary to use moulded edges in order to preventmoisture from causing the steel to corrode over time.
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