Gravity Rollers

 
 
What are Type110 & Type120 Rollers?

Excel Conveyors is a manufacturer of various types of conveyor rollers. There is a division of rollers based on the construction, e.g., Type 110 & Type 120; both are gravity rollers, but Type110 is with circlip locking arrangement, and Type120 is with internal locking arrangement. 

If you are not sure what option to choose, do share your application and we shall help to choose you the right type of Gravity Roller for your selection. Excel Conveyors is an Expert in the manufacturing of Conveyor Rollers and Gravity Roller Conveyors. 

Read Below- Coating options available in Conveyor Rollers

What are RL & SL dimensions of Gravity Rollers? 

Please refer below Drawing . 

RL - Roller Length & SL = Shaft Length. Distance BF should be considered equally. BF is minimum distance between mounting frames. In case spring load mounting arrangement, BF plays important role. 

What are the different sizes of rollers available?

Please refer below chart, which provides the various sizes available in gravity rollers. The buyer has to choose the required roller from the same. Please note 

L* - Max Roller Length 

Steel # = Materials Carbon Steel (MS), Stainless Steel grades SS304, SS316, SS202

Zinc Plating^ - Zinc Plating, Chrome Plating, Powder Coating, polishing, PU Coating, PVC Sleeve

 This chart is available only on the desktop site

Read Below- Applications of Gravity Rollers

What is the load-carrying capacity of conveyor rollers?

The designers and users of gravity conveyors need to understand that the load-carrying capacity of rollers is distributive and not concentric.

It means that the capacity of the roller is not pointed load capacity.  Also the load capacities are indicative because there are a lot of other factors that come in the picture such as the construction of the conveyor. 

Load-carrying capacity is inversely proportional to the length of the rollers. As the length of the roller increases, the roller capacity decreases. Accordingly high width products need more diameter. 

 

Below is the chart of load-carrying capacities.

The Columns headers are lengths of the roller in mm, and row headers are roller types. So a roller of dia.50.8 x 1.6mm thick 600mm length will have a capacity of 150kgs.   The load-carrying capabilities are indicative. This chart is available only on the desktop site



 

 

 

 

 

 

 

 

 

 

Excel Conveyors also provides replacement rollers made to order. Excel Conveyors manufactures Best in Class gravity rollers at the fastest delivery to satisfy your needs at unmatched pricing with uncompromising quality standards. 

Read Below- Design of Gravity Roller Conveyor

Materials available in Gravity Rollers

The below materials are available for Roller Tube.

  • PP - Polypropylene

  • UPVC - Unplasticized Polyvinyl chloride 

  • Carbon Steel - Generally known as Mild Steel 

  • Stainless Steel - Grades SS304  SS202, SS316 

Below materials are available for Roller Shaft

  • Carbon Steel 

  • Stainless Steel Grades SS304, SS316, Ss202                                                                                                                                                                     

5 types of coatings available for conveyor rollers 

Different types of roller coatings are available to protect the rollers from corrosion.

Below coatings are available for Carbon Steel or MS Rollers. 

  • Zinc Plating 

  • Chrome Plating 

  • Powder Coating

  • PU Coating 

  • PVC Sleeve 

Zinc Plating is the most used roller coating because it is the fastest and economical process. 

Chrome plating is an expensive and time-consuming process. 

Powder Coating is also a process which is suitable for gravity rollers. 

Polyurethane or PU Coating avoids metal to metal friction. If you are carrying a metallic machined component on a metal roller, the probability of component damage is very high. PU coating prevents this. PU coating protects the roller from corrosion, weathering, and abrasion. 

PVC Sleeve is a low-cost alternative to PU coating. PVC sleeves of 1mm or 2mm thickness are applied on the rollers to avoid corrosion and abrasion. 

Read Below- Limitations of Gravity Rollers

How Gravity Rollers are mounted in the frame?

There are various options for mounting the rollers 

Spring-loaded Shaft - The shaft is spring-loaded. While mounting the roller, the shaft is to be pressed and released in the mounting hole. Designers should take note while the design of the roller conveyor that sufficient free distance should be kept between the frames. Lack of the extra distance between the roller mounting frames will make the roller assembly difficult. 

Female Tap - The shaft has a female tap in the shaft. and is bolted on the roller mounting frame. When a large number of rollers are to be installed it is very time-consuming work.  Pneumatic or electric nut runners are useful in such cases. 

Female Tap + Across Flat -  Across flat is used most of the time to apply the spanner. As mentioned above, it is laborious work. 

Across Flat - The roller shaft has across flat and it is placed in the slot of the roller mounting frame. An "L" frame is used to hold the rollers in place in the frame. This method gives the fastest result. 

A conveyor manufacturer has a preset mindset and accordingly the roller mounting option is selected. Across flat option is for applying spanner to the shaft. It is easier to bolt when you can hold the shaft with a spanner. The spanner slot is also important during maintenance. Sometimes due to oil & dirt, the bolt does not open easily. You need to hold the shaft. Across flat is important in such cases.  

What are other types of Gravity Rollers?

  • Curve roller conveyors use taper rollers.  Taper Rollers are conical rollers which make the product movement at curves smooth. Taper Rollers have 2 variety of rollers.

    • ​Fully Metalic - In this roller taper portion is metallic. These are made by bending sheet precisely to achieve the taper roller dimensions.​

    • Polymide - In this roller taper portion is formed using PP molded sleeves. These sleeves are molded according to the dimensions and plugged over each other to form a taper portion. The base roller is metallic.  

  • Split Rollers - Split gravity rollers have a single shaft and two rollers. This is done according to application demand.  It is done most of the time to increase the roller capacity. The shaft is supported centrally to increase load-carrying capacity. 

 

What are gravity rollers? 

Gravity Rollers slide the product freely from a point A to point B. The product moves due to the natural gravitational force.  It is similar to the slider in the children's playground. Children's slide from top to bottom on the slide since the gravitational force is working, and it pulls them back to earth. The higher the top height, the faster, is speed. They are also called idler rollers or free rollers. 

 

Usage 

Various material handling equipments use gravity rollers such as

  • Gravity Roller Conveyors 

  • Roll conveyors

  • Roller Tracks

  • Gravity Roller tables 

  • Gravity Roller Beds 

  • Slider Roller Beds 

    • All the above names are given for gravity roller conveyors. Basically rollers are mounted parallel between two​ roller mounting frames. A gravity roller conveyor without support legs is called a gravity roller track or roller track.                                                                

  • Storage Rack Slide Beds 

    • These are simple storage racks. When the depth of the rack is more, it is difficult to access the last item ... such as carton box, crate pallet. If we use rollers below them, they slide and come to usage as per FIFO or LIFO principle. Rollers make sliding easy. Large pallet storage racks use roller tracks to store pallets like this. In such cases, speed control rollers or brake rollers are also required.                     

  • Heavy Duty Gravity Roller Conveyors 

    • These are roller conveyors but made for high loads such as pallet conveying. ​These rollers have high load-carrying capacity. Excel Conveyors manufactures conveyors required for pallet conveying. Our pallet conveyors and rigid, robust, and fully tested before dispatch.                                                                                                                                                                                                                                                      

  • Flexible Roller Conveyors 

  • Expandable Roller Conveyors 

    • ​A scissor-like mechanism ​​holds the rollers. Due to the scissor mechanism we can close and open the conveyor length.  You can use the conveyor when it is required resulting in space-saving. 
    • There are two options in this roller conveyors -Flexible gravity roller conveyors and flexible powered roller conveyors.                                
  • Floor Roller Conveyors 

    • Similar to flexible roller conveyors, this is a flexible floor conveyor. The floor roller conveyor is to be used on the ground or table. You can fold it and roller when not in use.                                                                                                                                                                               

  • Castor Wheel Roller Trolley

    • It is a usual castor wheel trolly. Rollers are fitted on the top of the trolly.  Due to this material loading and unloading from the trolley is easy. ​                                                                                                                                                                                                                                      

  • Powered Roller Conveyor

    • These powered roller conveyors, where rollers move by means of a chain, belt, or any other external media.​                                                  

  • Spiral Gravity Conveyor

    • Spiral gravity conveyor is a space-saving option​ to bring the material from the top floor to ground easily. Rollers are mounted between inner and outer helix to bring the carton box or crate down from the top floor.                                                                                  

  • Belt Conveyor Support Roller

    • Belt conveyors need support rollers on the return path. Gravity rollers are used in such cases.​

    • X-ray machines have infeed and outfeed roller conveyors. Gravity rollers are used in such cases.X-Ray Machine Roller Tables                       

  • Belt Over Roller Conveyor 

    • Flat Belt Conveyors also use rollers below the belt. Rollers make sliding contact with the belt, which reduces the power required to drive the belt. ​                                                                                                                                                                                                                    

  • X-Ray Machine Roller Tables 

    • X-ray machines are found at various places such as airports, temples, hotels, or any mass gatherings place. The infeed and outfeed conveyor ​​is a type of gravity roller conveyor.

Gravity rollers are the most used conveyor rollers - Because there is no electricity or any power required to run the conveyor.           Gravity Conveyors run on the gravitational force of the earth. When a product is on the gravity conveyor, it slides due to gravity, to the other end, which makes it a power-free conveyor to use. 

Apart from this, the user-friendliness of the gravity roller conveyors makes it the most loved conveyor. The user needs no training and maintenance required. Any layman person can just start using it from the first day of installation. 

Difference Between Conventional [ machined ] & new Gravity Rollers.

The construction of rollers is simple. It consists of below significant components.

  1. Roller Tube 

  2. Roller Shaft 

  3. Bearing Housing 

  4. Ball Bearing 

  5. Bearing Locking arrangement. 


Conventional Machined Rollers

This method involves the full machining of all the parts. Due to this, the parts are needed oversize. The round pipe thickness is 3 to 4mm for a diameter of 50mm. The bearing housing is fully machined so raw material dimensions are higher adding cost to roller. the same is applicable to shaft.

Since the bearing housing is press-fitted and welded inside the pipe it needs to be perfectly machined. The round pipe step machining is done. When the bearing housing is outer sides machined it is press-fitted inside the pipe and welded.  When both sides welding is done, the bearing housing inner diameter machining is done.  During machining operator needs to take care so that the inner diameter axis of both sides is the same. Any mistake may occur a rework in the roller. The shaft also needs to be machined fully. 

In spite of all the care taken it is a challenge to assemble the rollers when the quantity of production is in thousands. During the assembly stage lot of challenges arise such as bearing not fitting, welded not cleaned properly. 

The conventional method involves precise machining resulting in expensive and time-consuming methodology for bulk production.  

New Gravity Rollers

This new gravity roller involves thinner pipes, molded bearing housing, and least machining.  

The nylon molded bearing housing is directly press-fitted in the thin pipe. Only the sizing of the thin pipe is required in this case. Due to molded bearing housing, deviations are absorbed resulting in faster assembly.  The bearing housing is press-fitted on the hydraulic machine which ensures a complete assembly. 

How roller conveyors are made?

The construction of the gravity roller conveyor is very simple. It consists of a roller mounting frame and support legs. An "L" angle or a "C" frame works as a roller mounting frame.  Support Legs are bolted to the roller mounting frame. Rollers are installed using various roller mounting options, and the conveyor is ready to use. The L angle or C frame is readily available, and one can easily make the gravity roller conveyor

Excel Conveyors are one of the prominent supplier of conveyors & rollers. We take pride in supplying 32000nos rollers in a short span of 4 years. Quality, consistency, and delivery makes us one of the best manufacturers in India for Conveyor Rollers.   

 
What are Gravity Roller Conveyor Design Calculations?

Designers make calculations to ensure that the rollers are suitable for the product given.

The product properties should be studied carefully. Before you start the design you should have complete information about the product to be handled and what is the conveyor expected to do. 

Shape of the product.

The base of the product should be even at the bottom. Protrusions and projects at the bottom will make the bottom surface uneven. The even surface products are suitable to run on roller conveyors.  A refrigerator is not even at the bottom. It has got leveling pads at the bottom. The leveling pads will enter the gap between rollers. So it is not the right product to run on roller conveyors.​​

Weight of the product.

The product should have evenly distributed weight in it.  It might happen sometimes that the product may have unevenly distributed weight inside it. It is called the eccentric weight. In such cases the product behavior is different.

Imagine a box that is half full of soap bars as shown in the image below. In such a case, the center of gravity of the box may change during the travel of the box on roller conveyor. This is because the box portion ( with weight) will try to enter the gap between the rollers ( since weight is more there). It will result in shifting and falling of soap bars into the empty space. 

To avoid this, a smaller roller pitch is required, so the box may not enter the gap between rollers. 

                                                                                                                                                 

Load on the rollers

Load on the rollers need to calculated properly.  The load-carrying capacity of the product is important. The product has length and width. The rollers are mounted at the right angle to the length of the product.  By doing this, "roller length" will be shortened and load on rollers is distributed on more rollers.

 

e.g. A box of 400x500mm and weighing 50kg is to be carried on gravity roller conveyor.

If we consider box to travel along the width, 

roller length =  550mm

roller pitch =  100mm

No of rollers below box = Width / roller pitch = 400/100 = 4nos

Load on each roller = Weight / No of rollers = 50Kg / 4 = 12.5kg

If we consider box to travel along the length

roller length =  450mm

roller pitch =  100mm

No of rollers below box = Length / roller pitch = 500/100 = 5nos

Load on each roller = Weight / No of rollers = 50Kg / 4 = 10kg

It means that when the box travels along the box length, the roller length is short and load carrying capacity is also less. 

After calculating the load-carrying capacity, the roller can be selected based on the load-carrying capacity chart as above.

Working Conditions 

whether there will be impact load during working?  w the product receives on the roller conveyor - by forklift, manually, EOT crane. What is the impact load of that?        

                                             

Type of Industry & Environmental Conditions

e.g., dusty & oily conditions need to be considered during selection.​ It is advisable to consider these situations in detail. The excessive dust may enter the bearing seal, resulting in damage to the roller.

  

Conveyor construction

 Conveyor Construction should be capable to take the complete load. The impact load also needs to be considered while conveyor construction design.   

                                                                                                                                                          

Conveyor Slope

Weight of the part, Inclination & length of the conveyor play an important part here. The height of the conveyor at both ends should be within ergonomic limits. 

                                                                                                                                                                                      

Operating temperatures 

The conveyor rollers are suitable to work in the temperature range - 10degrees to 80degrees. This is because there are limitations to Bearing operating temperature & Materials used in Roller construction.

Bearing Working temperatures are mainly dependent on the grease used in bearings. The generally available bearings are not suitable below -10 degrees and above 90degrees. 

 

The Type 110 And Type 120 series rollers have nylon molded bearing housings which are not suitable to use beyond 80degrees. 

    

Limitation of gravity rollers & conveyors. 
  • It is challenging to handle higher weights on gravity conveyors. Higher loads get higher speeds with little inclination, which may result in accidental damages at the working place. Proper safety arrangements and speed control rollers or brake rollers reduce the unexpected occurrences drastically. 

Safety arrangements such as stoppers at unloading ends are a must. Speed control or brake rollers reduce the speed of the rollers. Installation of the speed control rollers is well before the unloading end so that there is sufficient time for the product to stop.  There are two types of speed control rollers. Internal speed control rollers, which are inside the roller. Outer speed control roller installation is between 2 rollers. Speed Control Rollers are a must for heavy-duty pallet roller conveyors, since they work like gravity roller conveyor brakes.
 

  • Similar to higher weights, it is challenging to carry lighter loads. It is because the lighter weights do not slide easily on the rollers, as there is no or very little gravitational force generated.

In such cases ultra free rollers are required. Apart from this, the higher inclination is needed to move the product. 

  • Uncontrolled speedsThe speeds may be slow or fast. You cannot stop the product intermittently and then release it. It is difficult to pass the product at the same speed along full gravity conveyor length. 

  • Length Limitations - The gravity conveyor requires slope to enable the product to slide from top height to lower height. Due to this, for lower product weights and higher inclinations, longer lengths are not suitable.

In spite of all the limitations, gravity roller conveyors are the most widely used conveyors all over the world.
  • Easy to Use
  • Easy to maintain
  • User friendly
  • No Power Required.
  • Easy to move
  • No Training required.
  • Easy for Installation 
  • Low Cost 
Gravity Roller Conveyors are easy to use. There is no pre-knowledge about the conveyors required. Any layman can use the gravity conveyor with the same ease and effort as others. The operators are safe while working with Gravity roller conveyors. There are no safety hazards working with light-duty gravity roller conveyors. Heavy-duty gravity roller conveyors require safety measures but they are very easy to implement. 
Gravity Conveyors require no external power. They are Cost-Effective & Budget-friendly conveyors that provide quick results. 
Which are the industries where gravity rollers are used?
It is difficult to find an industry that does not use gravity conveyors. They are used in all industries across the globe except in some industries. Every industry small or big tries to utilize the free power to make most of it. Gravity Roller Conveyors are the first choice of factory owners.
  • Automotive & Allied Industries
  • Chemical
  • Food & Bakery
  • Milk & Dairy
  • Pharmaceuticals 
  • Electronics 
  • FMCG 
  • Warehouse & Storage
  • E-Commerce

Excel Conveyors is a renowned manufacturer in India for gravity roller conveyors as well as powered chain driven roller conveyorsThe gravity roller conveyor price offered by Excel Conveyors is best in the industry. Contact us now!!!

What are the options for Gravity Rollers?

Gravity Rollers do have some options. But their usage is very limited. They have fewer benefits and more constraints. They are used only when gravity rollers can't be used. 

 

  • Ball Transfer Units - They are used generally when the direction of the product is not straight. The gravity rollers can transfer the product only in a straight direction. Ball transfer units have balls which can run in any direction. In factory layouts or during the production, there are processes where the use of ball transfer units is inevitable.   

  • Skate Wheels - Skate wheels are easy to run and are free than gravity rollers. They need little inclination to move the product. This is one of the reasons for their usage. 

  • Roller Tracks - They are generally used for FIFO racks in assembly areas of automotive and allied industries. During the assembly line, the operator needs to feed with stock items. The FIFO racks are made of ABS Coated pipes and roller tracks are installed on them as per crate size. But over the period it is found that the maintenance cost of roller tracks is high compared to full-width gravity roller tracks.

  • Chutes  - are also used in some cases where sharp inclination enough to slide the box is found. Before the use of spiral gravity conveyors, chutes were in use. This is one of the good options.

  • Conveyor Wheel - Moulded low-cost wheel. Suitable to run at higher slopes. 

What are other types of Conveyor Rollers? What are Powered Rollers? 

Gravity Rollers have limitations, as we have seen above. 

 

Powered Rollers have drive options which control the motion of the roller. e.g. A sprocket drives the rollers. Other drive options that are available in powered rollers are groove pulley, timing pulley, and poly vee pulley. You can read more information at the powered rollers page.

© 2017 by Excel Conveyors 

About us

Excel Conveyors,  manufacturer of Conveyor

Rollers as well as Conveyors.

 

We are known for the Fastest Delivery at Competitive Pricing.

Contact us at

Excel Conveyors 

Plot 14, S Block, MIDC, Pune, India

sales@Econveyors,in Call- 0091 9822957645