By Larry Thoman
General Manager of Newgy Industries
Since the beginnings of the sport in the early 1900’s, table tennis has used a ball made of
celluloid. Non-celluloid balls have been made in the past, but were never as popular as celluloid
balls. In 2012, the International Table Tennis Federation (ITTF) mandated that in
their sanctioned competitions, a new, as yet undeveloped, non-celluloid ball would be used
as the tournament ball starting July 1, 2014. I will refer to these non-celluloid balls as poly
As part of the ITTF mandate, they also instituted a different acceptable range for the poly
ball’s diameter. For celluloid balls, the acceptable range is from 39.5mm to 40.5mm. For
poly balls, the new range is from 40.0mm to 40.6mm.
This white paper will discuss the compatibility of poly balls with the Robo-Pong line of table
tennis (TT) robots manufactured by Newgy Industries. Many players have wondered if
the larger size of the poly ball will affect how the Robo-Pong robots perform when using
these new balls.
Poly Ball Types & Behavior
Poly balls have begun appearing in the marketplace and most TT brands have released, or
are scheduled to soon release, versions of the poly ball. There are only 5 actual ball manufacturers
at the time of this writing and all poly balls, regardless of the brand, come from
these 5 companies.
Poly balls can be categorized as either seamed or seamless. Seamed poly balls use a similar
manufacturing technique as has been used for decades to manufacture celluloid balls, all of
which are also seamed. Seamless balls use a more recent manufacturing process called rotational
molding, which has not been used previously to manufacture TT balls.
The majority of poly balls available for sale today are of the seamed variety. Most major TT
brands—Butterfly, Stiga, Nittaku, TSP, Double Happiness, Double Fish, Joola, Donic, and
Tibhar— and several minor TT brands—Andro, Adidas, Cornilleau, Giant Dragon, Sunflex—
have seamed poly balls approved by the ITTF. So far, there are 3 brands of seamless poly
balls—XuShaofa, Palio, and Hanno.
Poly balls tend to produce less speed and spin as compared to celluloid balls. However, the
spin tends not to dissipate as quickly so by the time the ball is struck again, the amount of
spin is similar to celluloid and possibly even a little more, especially for longer traveling
shots like chops and lobs. Speed seems to dissipate faster. Poly balls tend to bounce lower
than celluloid and with a flatter trajectory. Slow underspin can hang up or stop as compared
to celluloid’s more forward bouncing behavior. Topspin shots also seem to not drive
as far outward from the table.
I believe many of these differences are explainable by the slightly larger size of poly balls.
Also poly balls tend to be manufactured at marginally heavier weights compared to celluloid
(see chart below). Until January 2016, ITTF allows poly balls to be approved up to 2.82
grams. After that date, they must meet the standard for celluloid balls—2.77 grams.
Another factor is the actual material the balls are being made of. Current seamless balls are
being made from cellulose acetate or cellulose diacetate, close relatives of celluloid, which is
cellulose nitrate mixed with camphor. I am uncertain what plastic is used for seamless poly
balls. But each different material will produce different results due strictly to the individual
characteristics inherent in that material.
Please keep in mind that we are in the beginning stages of manufacturing these new balls.
As such, I believe many of these weight and size variations will improve as the manufacturers
refine their processes to produce a more consistent product. The end product will
probably be a poly ball that is even closer to celluloid performance than today’s iterations
are. In the meantime, the occurrence of balls that don’t meet ITTF specifications is significantly
higher than with celluloid balls. With celluloid balls, it’s unusual to find an out of
spec ball. With poly balls, it’s quite common.
Poly Ball Measurements
To date, I have been able to test 6 brands of seamed poly balls and 2 brands of seamless
poly balls. All have similar measurements, except the XuShaofa Sports seamless balls being
slightly bigger in diameter on average. Here’s the breakdown:
(to view the chart visit www.newgy.com)
As can be observed from this chart, the average diameter ranges from 40.13 to 40.19mm
for seamed and 40.21 to 40.29mm for seamless. It’s significant to note that this average for
seamed poly balls is comparable to the averages observed with celluloid 40mm balls
(seamed) and, prior to 2001, celluloid 38mm balls (seamed). For 40mm celluloid balls, the
average was 39.65~39.70mm. For 38mm balls, the average was 37.65~37.70mm. So we
can see that in all cases so far the average diameter for each ball size was @ 0.15~0.20
above the minimum acceptable range when comparing similar manufacturing processes.
Since both the 40 and 38mm celluloid ball markets were mature, it can be postulated that
manufacturers learned that players preferred, and bought, balls toward the lower end of
the acceptable range. Therefore they manufactured them at that size. And it appears as if
they are following that same strategy with these seamed poly balls as all brands measured
are in or very close to that relatively narrow ideal range of 0.15~0.20mm above the minimum
The largest diameter of any ball measured was 40.35mm. Just as we occasionally see a celluloid
ball significantly larger than the norm, this will also occur with the poly balls., but
probably on a more frequent basis until the manufacturing processes used with poly balls
Newgy Robot Ball Channel & Poly Ball Use
The ball channel inside a Newgy robot starts at the bottom where the ball is picked up and
pushed into the channel at the lower end of the Back Panel. Upon leaving the Back Panel, it enters the Upper Guide where it changes direction from vertical to horizontal. It then briefly
passes through the Pivot Guide that determines the side–to-side location of a thrown
ball. Immediately, it enters the Discharge Tube that carries the ball to the robot head and
determines the trajectory (up/down) angle of a thrown ball. Lastly, the ball is pushed into
the robot head where it is captured between the spinning Discharge Wheel and the opposing
Friction Block before being thrown out of the robot through the discharge hole at the
front of the robot head.
I tested a total of 11 Newgy robots, representing all the different models (540, 1040, 2040,
1050, 2050), various ages (from 2001 to 2014), and degree of use (from brand new to well
worn). Measurements were taken at various points throughout the ball channel. The sample
robots exhibited a range of widths at each measured point, some below the average diameter
of a poly ball (40.13~40.29). So it would be natural to conclude that Newgy Robots
would have a problem if any of these measurements were less than the diameter of the ball
passing by that point. But this is not what I found in my research.
There are two factors other than width of the ball channel that determines whether or not a
particular robot can use poly balls without issue. These are discussed below.
Type Of Newgy Control Box
The type of Newgy Control Box (CB) is a significant factor in determining if a robot will run
normally when poly balls are used. There are 3 types of Newgy Control Boxes in use at present—the
digital CB, used with the 1050 and 2050 models; the 3-knob analog CB, used with
the 1040 and 2040 models, and the 2-knob analog CB used with the 540.
The digital CB is by far the most robust in design. Our digital design allows for maximum
torque to push the balls through the ball channel regardless of the ball frequency. This CB
also contains a Ball Jam Alarm that senses the amount of resistance in the ball channel and
then shuts down the motor if too much resistance is sensed. Typically crushed balls or foreign
objects entering the ball path cause the added resistance. But this resistance can also
be increased by having to push a ball that is larger than the width of the channel, as can be
the case with poly balls in some Newgy robots.
There is less torque available with the 3-knob and 2-knob analog CB’s when using lower
frequencies. With the analog control boxes, the normal result of the Ball Feed Motor straining
due to increased resistance is heating up of the motor and lowered ball frequencies. Indeed,
comparing balls per minute at a certain frequency setting is a way for an analog robot
owner to determine if use of poly balls is causing extra resistance in the ball channel as
compared to celluloid balls.
The 2-knob analog CB operates at even lower frequencies than the 3-knob analog CB (because
it was designed primarily for beginners and lesser skilled players). This means at the
low end there is less torque available to push the balls through the ball channel. Also there
is no Ball Jam Alarm incorporated into this CB. If the resistance of the balls exceeds the torque of the motor, the balls will simply stop being pushed up the channel and no alarm
Another difference between our digital and analog control boxes is that balls are pushed in
pulses with the digital design. So the balls are pushed, then there is a rest cycle until the
next push. With analog CB’s, the motor is constantly trying to push the balls through the
robot with no rest cycles, even when extra resistance is encountered. This cycling of pushing/resting
enables our digital CB to better deal with variances in the resistance of pushing
balls through the ball channel.
Wear Of The Ball Channel
The remaining factor in determining if use of poly balls will affect a particular robot’s performance
is the amount of wear inside the ball channel. It is considered normal wear and
tear for the balls to wear a groove in the sidewalls of the channel. This happens with celluloid
balls and it will happen with poly balls.
As balls are pushed through the channel, the balls are pushed in a slightly staggered manner
so that each ball is almost always in contact with one sidewall or the other. This constant
rubbing of the balls against the sidewalls wears a groove in them. And the longer this
wear takes place, the deeper the grooves becomes. This creates extra space for the ball and
this extra space varies widely with each individual robot.
What typically happens inside the ball channel is that the most wear occurs in areas that
are the narrowest. So these narrow openings will enlarge over time and resistance is lessened.
Recommended Procedures For Use Of Poly Balls
What was learned from the above examination of the various factors that may affect how
well individual Newgy robots handle the poly balls, is that no one factor by itself is normally
a cause for concern. Rather it is an accumulation of resistance that determines whether or
not a robot will properly handle a poly ball. Correct one or two factors and a robot that was
not initially operating properly with poly balls may well start operating the way it should.
When fully loaded, the ball channel of Newgy Robots contains 11 balls. It is the overall resistance
in the Ball Feed Motor of pushing these 11 balls through the channel that is the
primary determinant. Pinch points in the channel, ball roughness (from dirt and/or the
powder that is on new balls), balls that are exceptionally large in diameter, and ball channel
parts that are not worn all contribute to increasing the overall resistance of pushing balls
through that channel.
When this resistance surpasses a certain maximum, the Ball Jam Alarm activates and ball
delivery stops (or in the case of the 540, the balls just stop). Additionally, with analog robots,
slow ball frequencies provide less torque to the motor for pushing balls through restrictions
and can cause Ball Jam Alarm activation where higher frequencies would not.So the overall goal should be to reduce this resistance as much as possible. Some recommendations
will apply to all models and some to only specific models.
For All Models
The most important action that robot owners should take when they first start using poly
balls in their Newgy robot is to thoroughly wash the balls in soapy water, rinse and then
dry them before using them in the robot. Newgy has always recommended this, even for
celluloid balls. This helps remove dirt and the gritty manufacturing powder that is left on
the balls during manufacture and once removed, the resistance of pushing those balls
through the ball channel is reduced.
After washing the poly balls, it is further recommended to rubdown the balls by running
them through the machine at high frequency. Just like a break-in period for a new car, there
is a break-in period for new table tennis balls and your Newgy robot. This is especially important
for analog robots and even more important for the 540 model. The easiest way to
accomplish this is to hang a box or similar object on the head of the robot and then turn ball
speed to low and Ball Frequency (or Wait Time) to the fastest rate. The balls will be ejected
out of the robot, hit the bottom of the box, then roll out of the box and back into the Ball
Bucket or Ball Trays. Let the robot continue feeding itself like this for about 15-20 minutes.
This rubdown procedure also helps to begin breaking–in the ball channel parts on new robots.Another way to break-in new balls, either celluloid or poly, is to only put in 12–18 new
balls at a time along with at least the same number of well-worn balls. In such case, you can
usually get away with not washing the balls or doing the rubdown procedure.
The next thing is for robot owners to weed out balls that are significantly bigger than the
average diameter. The easiest way to do this is to simply roll each ball up and down the ball channel of the Back Panel. Balls that stick more at particular points in the channel as compared
to the majority of the other balls should be weeded out and not used in the robot.
As a side note, 2040 & 2050 owners also have a ball gauge that is integrated into the two
Ball Dams that come with their robots. However, this gauge may not work at all with poly
balls, or will work differently. For older 2040/2050 robots, the ball gauge hole was almost
exactly 40.0mm in diameter, so no poly balls should fit through that hole unless they happen
to be at the very minimum allowable diameter. For newer 2040/2050 robots, the hole
was increased to 40.6mm so all poly balls will fit through that hole, but it is less useful for
identifying balls that are significantly larger than the norm.
The next thing that all Newgy robot owners can do is to manually adjust the top of the Back
Panel by loosening and then tightening the two interior screws that attach the Upper Guide
to the Back Panel:
After loosening these screws, retighten them while you pull or press outward on the sidewall
with one of your hands as you’re tightening the screw with your other hand. Doing this
often gains 0.5mm or more to the channel width at that location. It also helps, if your (older)
robot has screws with a head larger than 5.28mm in diameter (the size used on current
robots), to replace the screws with smaller head ones. Order 2000-328A screws from
Newgy or you may find similar screws at a local hardware store.
Some robots, particularly older ones, can be improved for poly ball use by changing out the
Friction Block and the Friction Block Bushing in the head. Not only will this replacement
reduce resistance to the Ball Feed Motor, but it may also correct or improve the ball trajectory.
For a few robots I tested, this was an essential adjustment, as the ball trajectory was
quite erratic when using poly balls—balls would be ejected up, down, off to the side, but
rarely straight ahead. After making this adjustment, ball trajectory went back to normal.
Order a current 2040-192A Friction Block and 2050-193 Friction Block Bushing. Replace
these parts by following the disassembly/assembly instructions in your Owner’s Manual. If
you no longer have your Owner’s Manual, you can download one at:
http://www.newgy.com/support-downloadable-instructions-manuals.aspx. This is espe-cially important on older robots with Friction Block Springs instead of Friction Block Bushings.
You can order these parts from your Newgy Service Center.
For Ball Bucket Robots (540, 1040, 1050)
To increase the space between the hub of the Pickup Wheel and the inside surface of the
Ball Bucket, there is a very simple fix. First, loosen the two wing nuts that hold the robot
onto the Ball Bucket. Then place a small spacer about 1.5 mm thick between the bottom of
the locating tongue on the rear of the Back Panel and the top edge of the Ball Bucket:
The locating tongue is the part of the robot that has the serial number label on it. The white
spacer underneath it is a small piece of cardboard (a typical credit card is 0.75 mm thick).
After making this adjustment, I noticed an immediate reduction in the straining noises
coming from the Ball Feed Motor and from the balls being pushed through the robot. This is
a simple adjustment that is highly recommended for all Newgy robots with a Ball Bucket
when poly balls are used.
For Robo-Pong 2040 models
Older Robo-Pong 2040 models have a Clear Front Cover on them that has angular corners.
2040’s that have this type of Clear Front Cover may experience problems with balls damming
up in the ball trays to the right of the robot:
This ball damming problem can be greatly reduced, if not eliminated entirely, by changing
the Clear Front Cover to the current design that has a rounded shape. You can order the
improved version of this part by contacting your Newgy Service Center and requesting part
Our tests revealed that our current production models work well with the poly balls. No
significant issues were observed when using the latest models as several improvements
were made in preparation for the poly ball’s introduction. Things can always be improved
further and Newgy will continue to work on, and incorporate, these improvements into our
Older Newgy robots may exhibit various issues with handling the poly ball. The biggest factor
is how worn the ball channel is. We expect that most older Newgy robots will already
have significant wear in the ball channel and will handle the poly ball OK. Older robots that
don’t have significant wear may need some of the adjustments as described in the Recommended
Procedures For Use of Poly Balls section.
All Newgy robot owners should be diligent at performing the washing and rubbing down
procedures when using any new balls, poly or celluloid. Furthermore, owners need to keep
the playing area clean and occasionally re-wash the balls to prevent dirt and grime from
accumulating on the balls.
The above conclusions are based on what we’ve been able to test so far. We’ve gone to
great lengths to test a variety of Newgy robots old and new and examine how well they perform
with as many different types of poly balls as we’ve been able to get our hands on. As
more brands of poly balls become available, we will continue to update this white paper
should the test results change our conclusions and recommendations.
check out the graphs and diagrams here: