FACILITIES MANAGEMENT
ROTARY VERSUS PLANETARY
NATIONAL FLOORING EQUIPMENT
ROTARY VERSUS PLANETARY SURFACE GRINDERS
Planetary grinders were given their name
because the motion of the discs in the base
resembles that of the planets around the
sun. Here, Ed Biggs, regional sales manager
at surface preparation expert National
Flooring Equipment, explains the differences
between planetary and rotary grinders and
how to decide which type to purchase or
rent.
Surface grinders use horizontal discs
mounted with an abrasive material —
usually diamond — to grind and polish
marble, granite or concrete surfaces.
There are two main variants of the
technology, rotary and planetary,
categorised by the configuration of the discs
on their bases. Traditionally, surface grinders
were all rotary - their bases contained two or
four discs that counter-rotated.
Planetary grinders were introduced to the
US in the 1990s. Unlike rotary grinders, their
bases comprise of three small discs — the
planets — which rotate in one direction.
The discs are mounted to a single larger disc
— the Sun — which rotates in the opposite
direction. Contractors are now faced with
the difficulty of choosing between the two
configurations, to work out which would be
most beneficial for the job at hand.
Making the choice
The different configurations of the machines
mean they are each suited to different
applications. Rotary grinders are often the
best choice for aggres sive jobs because
they are gear driven, giving them a high
horse power. Their weight also enables them
to make strong contact with the floor, an
advantage in hard to complete jobs. Rotary
grinders are more able to access corners
because of the square shape of their bases,
compared to the round bases of planetary
grinders.
Although Chinese manufacturers are
beginning to produce gear driven planetary
grinders, the majority are still belt driven.
This, plus the fact that they are lighter than
their rotary counterparts, makes them more
suitable for less aggressive jobs, such as
smoothing out concrete or preparing a floor
for an epoxy coating. Planetary grinders
create smaller scratch patterns, meaning
they can polish floors with greater clarity.
Therefore, contractors who do a lot of
polishing work should consider a planetary
grinder, as it may best suit their needs.
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PECM Issue 33
Where to start
There are approximately 50 manufacturers
of planetary grinders, compared to just three
or four manufacturers of rotary grinders.
This is partly because it’s more expensive
to manufacture rotary grinders, but also
because surface polishing is a very common
task, so there is a high demand for planetary
machines.
If you’re finding it difficult to choose, we
recommend starting with a rotary machine
due to their ease of use. However, if your job
involves a lot of polishing, you may wish to
purchase a planetary grinder to achieve a
high-quality finish. Cost is not a critical factor
when deciding between planetary and
rotary grinders because the two types have
similar prices.
The main factor affecting cost is the size of
the machine. Rotary grinders come in just
two sizes, whereas planetary grinders can be
purchased in many different sizes, giving rise
to greater variation in price.
Contractors must assess their needs before
deciding on which size is appropriate for
them.
With an awareness of the differences
between planetary and rotary grinders and
advice from a reliable supplier, contractors
can more easily purchase or rent the most
suitable machine for their requirements.
www.nationalequipment.com