A sprocket is a toothed wheel or gear that interlocks with a chain, track, or other perforated or toothed material. It's commonly used in machinery and vehicles to transmit rotary motion between two shafts where gears are engaged with the chain, allowing the motion or power to be transferred from one part to another. Plastic sprockets are found in various applications, such as drive systems, conveyors, water treatment plants and poultry processing. They come in different sizes and tooth configurations depending on their specific use and the machinery they are part of.
Eliminating Lubricants – due to the natural lubricity of plastics and self-lubricating grades, often plastics sprockets can operate without additional external lubrication.
Dirty & dusty conditions – plastics that have good abrasion resistance, such as Polystone 7000 and Sustamid, are more tolerant to non-ideal operating conditions.
Low Friction – Plastic-on-metal combinations result in low friction than metal-on-metal, and therefore low drive forces/energy.
Reduced wear – when dissimilar materials are combined, such as plastic-on-metal, there are lower wear rates on both the plastic sprocket and metal chain.
Lightweight – This can be advantageous in weight sensitive applications, as well as reduced energy consumption.
Quieter Operation - Plastic sprockets will provide quieter operation compared to metal sprockets. The reduced noise can be beneficial in noise sensitive applications.
Corrosion Resistance - Plastic sprockets are often resistant to corrosion from moisture, chemicals, and other environmental factors. This makes them ideal for use in damp or corrosive environments.
Cost-Effective - Plastic sprockets can be more cost-effective to manufacture than metal sprockets. They can also offer cost savings in terms of reduced maintenance and longer lifespan.
Dotmar has qualified engineers that can provide direct support with plastic sprocket material selection.
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Roller Chain Sprockets
Traditional roller chain sprockets provide many benefits over steel sprockets.
Water Treatment
Driven main shaft sprockets in a non-metallic sedimentation tank main shaft
Conveyor Chain Sprockets
Generally used in food, beverage and packaging applications.
Modular Belt Drive Sprockets
Both moulded and custom machined to suit a square. These can be both fixed and floating for tracking and alignment of belts.
Split Sprockets
To facilitate installation and removal where it is not possible or practical to install a sprocket from the end of the shaft.
Customised Mounting
This roller door drive sprocket is an example of customised mounting.
Material selection is a critical consideration when choosing a plastic for sprockets, as it directly impacts the performance, durability, and maintenance requirements of these components. Here are some key material selection considerations for plastic sprockets:
Load
The load or power to be transmitted is one of the most important criteria in selecting a suitable material, as well as taking into consideration the number of teeth that are engaged to transmit the load.
Impact
Impact loads such as hard or soft starts, will influence material selection. This loading can also influence the type of mounting requirements.
Temperature
The surrounding temperature for both short- and long-term exposure is important, as materials can withstand higher temperatures for short term periods compared to long term or constant exposure, which in turn affect their load carrying capacity.
Wear and Abrasion
Abrasive conditions provide different challenges to clean environments, and therefore the material selection, which can include Sustamid and Polystone 7000.
Lubrication
Consider whether the application allows for regular lubrication or requires dry-running. In some case lubricants can attract dirt and dust, which can have a detrimental effect, therefore selecting an engineering plastic that can run dry can be beneficial.
Corrosion & Chemicals
If the application is in a corrosive environment, the chemical resistant of the material must be considered, to ensure there is no degradation of the material properties and therefore ability to perform.
Regulatory Requirements
Does the application have regulatory requirements such as food contact, drinking water, anti-static or flame retardant. The food industry may also require materials to be metal detectable, x-ray detectable and/or visually detectable by being coloured blue.
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