A CYCLO gearbox uses an eccentric cycloidal disc drive instead of conventional gear teeth to set the bowl-to-scroll differential speed on a decanter centrifuge. Sentrimax services CYCLO-brand gearboxes, including Sumitomo units, by inspecting the cycloidal discs and pins for wear, machining or replacing worn components, and re-balancing the rebuilt assembly to ISO G 0.5.
What makes a CYCLO gearbox different
Most reduction gearboxes use involute gear teeth meshing directly against each other.
A CYCLO gearbox instead uses a cycloidal disc — a specially profiled rotating disc driven
by an eccentric input shaft — that engages a ring of pins around the housing. As the
eccentric drives the disc, the disc’s profile causes it to roll against the pins rather
than mesh tooth-to-tooth, producing the output rotation and, on a decanter, the
differential speed between bowl and scroll. This is a fundamentally different load path
than a planetary gear set, and it wears differently as a result.
Why cycloidal drives show up on decanters
Cycloidal gearboxes are used where a high reduction ratio is needed in a compact
housing, and where tolerance for shock loading matters. Because the load in a cycloidal
drive is distributed across multiple pins engaging the disc profile simultaneously,
rather than concentrated at a single pair of meshing teeth, this design handles the
torque reversals and momentary overloads that occur during centrifuge start-up, upset
conditions, and process disturbances differently than conventional gearing does.
What a CYCLO gearbox service involves
Servicing a cycloidal drive follows the same disciplined process as any other gearbox
at Sentrimax, but the inspection points are specific to this mechanism:
- Cycloidal disc inspection
- Checked for wear on the profile surface that engages the ring pins, and for any
scoring or pitting from contamination or lubrication breakdown. - Ring pin and pin housing inspection
- Each pin and its bore is checked for wear, since uneven pin wear changes how load is
distributed around the disc. - Eccentric shaft and bearing inspection
- The input eccentric and its bearings carry the drive load and are inspected alongside
the output bearings supporting the disc assembly. - Reassembly and balance
- Once repaired, the gearbox is reassembled with the rotating assembly, dynamically
balanced to ISO G 0.5, and put through a test run as part of the overall centrifuge
commissioning.
Rolling contact vs sliding contact: why it matters
Conventional involute gear teeth transmit load through a combination of rolling and
sliding contact at the point where two teeth meet, which is part of why lubrication
film condition matters so much to gear tooth life. A cycloidal drive’s disc-and-pin
engagement is predominantly a rolling contact rather than a sliding one across most of
its load path. That changes both the wear pattern an inspection looks for and the
lubrication demands of the unit — a CYCLO gearbox does not necessarily fail the same way
a worn planetary gear set does, even though the symptoms an operator notices (noise,
heat, backlash) can look similar from the outside.
Lubrication and oil sampling on CYCLO units
Because much of the internal wear on a cycloidal drive shows up first as changes in
lubricant condition rather than obvious visual damage, an oil sample sent for
third-party analysis at the inspection stage is a meaningful early indicator on these
units. Particle content and type can point toward disc or pin wear before it has
progressed far enough to be visible without disassembly.
Precision machining for cycloidal components
Where a cycloidal disc or eccentric shaft is salvageable rather than requiring
replacement, Sentrimax’s machine shop capability — milling, lathe-turning and
precision-grinding — is used to bring the component’s critical surfaces back to
tolerance. Where an exact replacement part is not available, the same engineering
services capability can design and manufacture a reverse-engineered replacement rather
than leaving the gearbox without a repair path.
Sumitomo and other CYCLO-brand units
Sentrimax stocks and services CYCLO-brand gearboxes, including Sumitomo CYCLO units, as
part of its centrifuge gearbox repair capability. Sentrimax is an independent MRO
provider, not affiliated with, authorized by, or endorsed by Sumitomo or any other
gearbox manufacturer — brand names here describe the equipment we service, nothing more.
Documentation delivered with a CYCLO gearbox service
As with any other gearbox type, a CYCLO service comes with the same documentation
trail as the rest of a Sentrimax repair: an inspection report identifying which
components — disc, pins, eccentric shaft, bearings or seals — were found worn and to
what extent, a quotation package covering the approved scope, a post-repair quality
control inspection, and a test run performance report confirming the reassembled unit
runs correctly. That documentation is what lets a maintenance manager verify what was
actually done to a mechanism that is otherwise difficult to inspect visually once it is
back in the housing.
What determines whether a CYCLO unit is rebuilt or replaced
As with planetary gearboxes, the rebuild-or-replace decision on a cycloidal drive is
made component by component: the disc, the pins, the eccentric shaft, the bearings and
the housing are each assessed individually during inspection. A housing in sound
condition paired with a worn disc and pin set is a very different scope of work than
housing damage that cannot be corrected by machining, and the two are not treated the
same simply because both are labeled a “CYCLO gearbox problem.”
Why identifying the drive type early avoids wasted diagnostic time
Because a cycloidal drive’s internal wear pattern differs from a planetary gear set’s,
diagnosing a CYCLO gearbox as if it were conventional gearing can lead to the wrong
components being checked first. Confirming the gearbox type — from a nameplate, original
documentation, or a quick inspection — before pursuing an in-depth diagnosis saves time
that would otherwise go toward ruling out the wrong failure mode.
Common CYCLO failure modes
- Disc profile wear. The cycloidal disc’s engagement surface wears
gradually with normal operation and more quickly if lubrication has degraded or
contamination has entered the housing. - Ring pin and roller wear. Individual pins or their rollers can wear
unevenly, changing how load is shared around the disc and accelerating wear at the
pins carrying more than their share. - Eccentric bearing wear. The bearings supporting the eccentric input
shaft carry the full drive load and are a common source of the backlash and noise
symptoms covered on our gearbox failure signs page. - Seal failure. As with any gearbox, a failed input or output seal
allows contamination in and lubricant out, and is often what turns a slow wear process
into a faster one.
How a CYCLO gearbox compares to conventional gearing in service
A conventional helical or worm gear reducer concentrates load at the meshing tooth
surfaces, which is where wear and eventual failure typically originate. A cycloidal
drive distributes load across the disc profile and multiple ring pins simultaneously,
which tends to give it a different service life profile under shock loading — the kind
of momentary overload a decanter can see during start-up or an upset in feed
conditions — compared to conventional gearing carrying the same average torque. This is
a design trade-off, not a guarantee that a CYCLO unit will outlast or underperform a
planetary gearbox in a given application; the right comparison depends on the specific
duty the centrifuge sees.
If your gearbox isn’t a CYCLO design
Not every decanter uses a cycloidal drive. If your centrifuge is showing the symptoms
covered on our gearbox failure warning
signs page but turns out to use a conventional gear train, see our
planetary gearbox rebuild page instead. If it
uses a hydraulic motor rather than any mechanical gear set to set differential speed, see
our hydraulic backdrive service page. For the
full range of gearbox repair options, see the
centrifuge gearbox repair overview.
What to expect if the disc or pins need replacement rather than machining
When wear on the cycloidal disc or ring pins has progressed beyond what
precision-grinding can correct, replacement components are sourced or, where an exact
match is not available, manufactured through Sentrimax’s engineering services and
machine shop. Either path leads to the same reassembly, balancing and test run sequence
as a repair that only needed machining — the documentation simply reflects parts
replaced rather than parts restored.
What CYCLO service looks like when combined with other repairs
A CYCLO gearbox rarely arrives as the only item needing attention. It is common for a
gearbox service to be combined with bowl or scroll repair, bearing replacement, or
seal work on the same visit, since all of these components share the same rotating
assembly. When that is the case, the gearbox work is sequenced alongside the rest of the
repair so that the final balancing and test run reflect the complete, reassembled
machine rather than the gearbox in isolation.
What to have on hand before contacting us
A gearbox nameplate photo, the centrifuge make and model, and a description of what
you have observed — noise, heat, backlash, oil condition or conveyance behavior — are
enough to start a meaningful conversation about scope. If the nameplate is missing or
illegible, that is not a blocker; it is simply something our technicians confirm during
the initial inspection alongside everything else.
Ask about CYCLO gearbox service
If you have a CYCLO-equipped decanter or tricanter showing wear symptoms, an
inspection at receipt confirms the disc and pin condition before any repair scope is
quoted.
Frequently asked questions
How does a CYCLO gearbox wear differently from a planetary gearbox?
A cycloidal drive spreads load across the disc profile and multiple ring pins rather than concentrating it at meshing gear teeth. Wear typically shows up as profile wear on the disc and uneven pin wear rather than the tooth pitting seen on conventional gears, so the inspection checks different surfaces.
Is Sentrimax an authorized Sumitomo service center?
No. Sentrimax is an independent centrifuge MRO provider. We service Sumitomo CYCLO gearboxes and other brands as part of our gearbox repair capability, but we are not affiliated with, authorized by, or endorsed by Sumitomo or any other manufacturer.
Can a CYCLO gearbox be rebuilt, or does it need full replacement?
In most cases it can be rebuilt. The cycloidal disc, ring pins, eccentric shaft and bearings are inspected individually, and only the components worn beyond a serviceable tolerance are replaced. Full replacement is only recommended when housing damage or wear cannot be corrected by machining.
Does servicing a CYCLO gearbox affect the centrifuge's differential speed setting?
A correctly executed rebuild restores the original differential speed relationship, since the disc and pin geometry that produces it is inspected and repaired to specification. Any deviation would be identified and corrected before the gearbox is reassembled and balanced.
What should I check before assuming my gearbox is a CYCLO design?
The gearbox nameplate or original equipment documentation usually identifies it by brand and model. If that is unavailable, our technicians confirm the gearbox type during the initial inspection, since a cycloidal drive's internal construction is visibly different from planetary gearing.
Talk to a centrifuge specialist
Send us the machine details and we will come back with an inspection scope and a quote.