Gravity roller conveyor is often referred to as gravity conveyor, roller conveyor or just plain old conveyor. Conveyor in its most basic form is made up of an outer framework and a series of rollers fitted within that frame over which goods can be rolled from point A to B. 

The movement of the goods can be completed manually, by gravity or by electrical power. Manual power obviously requires the intervention of an operative(s), gravity requires some prior specific design work whilst electrical requires more investment. It’s a sort of horses for courses trade off as to which form of conveyor you actually require. Either way there are several options of conveyor that can be considered but it is best to avoid a costly error by consulting experts first.

Roller conveyor can be laid out on the floor or on top of workbenches. This means that no leg supports will be required to support the conveyor. You will often see assembly benches set out in production areas with staff assembling goods and then moving those goods on by hand down a roller conveyor line. To move goods down the roller conveyor line by gravity, you will require leg supports that can be set at a variety of heights to promote the 'gravity effect' that is required to move goods from different points, with no more than an initial push to start them on their way. Electrically powered roller conveyor can obviously take out the manual effort and gravity reliance of the previous systems. This is where the rollers are now moved by an electrical source. A combination of electric and gravity systems can also be employed to provide the necessary speed of operation that may be required between different sections of the conveyor system. It is important to employ a stop mechanism or barrier to ensure that at the end of the 'journey' the goods don't just fall off the conveyor causing safety or damage issues. 

Roller conveyor can be supplied with different framework materials:

• Mild steel
• Aluminium
• Plastic
• Stainless steel

The actual rollers themselves can be manufactured from:

• Mild steel
• Stainless steel
• Plastic

The selection and combination of materials are arrived at by establishing a number of factors like weight capacity, operating environment and the available budget. Mild steel is the most popular material and generally speaking the most cost effective, although the final choice is also dependant on the weight of the goods to be conveyed. Plastic conveyor also comes in two distinct forms - roller or skate-wheel. The skate-wheel system is the lighter of the two in terms of capacity but offers the ability of the conveyor to turn goods through a tighter radius on corners or bends. Sometimes a combination of the two types working in tandem can provide the best system answer.

The roller capacity is worked out by dividing the overall weight of a product to be conveyed by any three rollers … three being the minimum 'under product' requirement at any one time supporting the load. As an example, if the product weighs 100Kg then each roller will need to have a minimum capacity of 33.33Kg. Generally speaking the higher the weight capacity, the larger the diameter and the wall thickness of roller will be required. The 'fitting three rollers' at any one time under your product load sometimes takes a bit of working out. Products often differ in size and weight variation, so you will need to consider all the physical differences across the product range to be conveyed. Assistance is readily available from conveyor suppliers to help determine the correct configuration.

The point of contact between the product load and the top of the rollers also needs to be carefully considered as obviously an uneven, ribbed or non-uniform product base may have difficulty in rolling smoothly down the line of conveyor. Sometimes awkward shaped goods will have to be mounted on a pallet base, contained in boxes or cartons to ensure they’re able to roll smoothly and safely.

Maintenance and replacement of damaged rollers also needs to be considered. The most cost effective way of mounting rollers within a framework is by securing them in place with a length of rod that runs through all of the roller spindles outside of the framework on either side of the conveyor. This however means that replacement of a single roller requires all of the rollers to be removed from the framework to access one individual roller. A spring loaded roller system allows individual rollers to be removed independently and this can make for much faster and easier access. Obviously, this also makes them easier to clean and maintain.

The overall conveyor system can be designed with bends, corners, transfer sections and a number of other specialised accessories to suit individual requirements, so it’s advisable to seek the best possible guidance when designing a conveyor system. 

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