What are the different types of roller conveyors?
There are a number of types of roller conveyor. The differences in them largely
goes back to how they are powered, how we make the rollers turn.
There are all kinds of specialty conveyors, but most conveyors break down into
two types, belt conveyor and roller conveyor. The primary advantage of belt conveyor
is it can carry smaller items and things with irregular shapes. Roller conveyor struggles
with irregular shapes and prefers boxes, totes, or pallets. Accumulation is something
that roller conveyor does much better than belt conveyor. Accumulation is a whole
other blog but for now, know that accumulation is what roller conveyor does best.
Let us take a look at a few different types of roller conveyor:
- Belt Under Roller
Belt under roller is just what it sounds like, it is a roller conveyor that has a narrow (
usually about 8” wide) belt that runs under the top rollers. The belt is supported underneath
by carrier or lift rollers and is driven by a center or an end pulley drive. This type can be used
as transport conveyor to move thing across a plant. It can also be used for accumulation.
It does both jobs well and can handle light to medium loads.
- CDLR (Chain Driven Live Roller)
CDLR conveyor is generally used for heavier loads like loaded pallets. This conveyor has a
cover (called the chain box) on one side that houses the chains that run between each roller
back to a drive. It is a very positive drive. These conveyors are typically set low so they can
be loaded and unloaded by fork trucks. They also are capable of accumulation.
- MDR (Motorized Driven Roller)
MDR conveyor is relatively new technology although it has been around for over 10 years,
it’s mainstream use has only recently started to pick up steam over the last 4 to 6 years.
This is primarily because the price of this technology has come down to compete with other
forms of conveyor. MDR has no central drive system. There are MDR rollers in the conveyor
where the roller itself is the motor. Yep, there is a wire coming right out of the end of the roller.
That wire goes to a drive card that runs the roller on 24 volts DC. This drive card can be controlled
from a control panel to control speed, direction, and accumulation. The MDR roller drives 2 or 3
adjacent rollers on either side of the MDR roller with drive bands or toothed belts for heavier loads.
MDR is for light to medium loads but there are versions that can be used for heavy loads.
- V-belt Drive & Line Shaft
V-belt driven roller conveyor is driven by pulling an upside down v-belt (flat side up) under
the rollers causing them to turn. Line shaft conveyor has a turning shaft running lengthwise
under the rollers. The shaft has spools on it that turn with the shaft under friction. The spool
turns a drive band that twists 90 degrees and goes up around the roller causing it to turn. Both
of these types of conveyors are becoming older technology. They have lots of parts and have proven
to be time consuming to maintain. I would not recommend them in today’s environment.
How do they compare?
- Price? (Least to Highest)
- Belt Under Roller It has the lower price but more parts and medium capacity.
- CDLR It can carry loaded pallets with heavier loads.
- MDR Costs more because of the built in technology, but it is quite versatile.
- Energy consumption? (Best to Worst)
- MDR Is by far the most energy efficient and it will shut down at idle.
- CDLR Will use the most energy. They are the trucks of the conveyor world.
- Belt under roller Is mid-range technology. Energy consumption is good.
- Ease of maintenance & repair? (Easiest to Hardest)
- MDR No central drive system & easy change rollers.
- Belt under roller There is a belt to deal with, otherwise simple.
- CDLR Usually heavy duty, bigger and heavier parts, lots of chain
- Reliability? (Most to Least)
- MDR Simple equals reliable. MDR is simple mechanically.
- Belt Under Roller Belts are where the maintenance is here.
- CDLR Still reliable but more parts and heavier.
How to know when it is time to replace?
Like anything else, knowing the right time to replace conveyor is a judgment call. The
first place to watch is cost of maintenance. As conveyors age they begin to cost more to
maintain. Another huge consideration is how much it’s maintenance or down time
interferes with your production schedule. In certain situations, production down time
costs may make the cost of new equipment easily worth it.
In general when you start seeing the same repairs over and over like chain replacements
on a CDLR or roller after roller on a roller conveyor, it is time to consider looking at new equipment.
If you do decide it is time to look at new equipment, consult with your equipment provider.
They should be able to not only help you through the process, but they should take a new
look at your application and see it there are any new technologies or design changes that would
benefit your operation going forward.