Our Non-Circular Gears
We manufacture non-circular gears for machines and systems in which individual motion phases are intended to occur at different speeds. The drive can operate at a constant speed. The shape of the gears determines when the output accelerates, decelerates, or changes its torque.
Typical applications include packaging machines, textile machines, printing presses, conveyor systems, assembly equipment, machine tools, and agricultural machinery. We manufacture non-circular gears according to drawings, technical specifications, or an existing sample, either as single units or in small batches.
Non-circular gears in complex machine movements
A circular gear transmits rotational motion with a constant gear ratio. It cannot produce such speed changes based on its geometry alone. To achieve this, additional control systems, servo drives, cam discs, or multi-part mechanisms are often used.
Before commissioning a manufacturing project, several technical questions therefore arise:
Even a slight deviation in shape or installation position can cause the machine to accelerate or decelerate at the wrong point.
Manufacture non-circular gears according to drawings or samples
Relevant manufacturing specifications include, among others:
Geometry and Contour of the Out-of-Round Gear
Type of Tooth Profile
Module and Number of Teeth
Center distance of the gear pair
Quantity
Material and, if applicable, heat treatment
Load and Operating Speed
Installation Orientation and Angle
Out-of-round gears are often used as a matched set. For this reason, we consider not only the individual component but also its function within the assembly. When replacing a part, we determine whether a single gear can be manufactured to match the existing mating gear or whether a new, coordinated set makes more technical sense.
Advantages of Non-Circular Gears with Variable Ratio
The output motion changes even though the motor runs at a constant speed. The speed profile is generated mechanically and does not need to be recalculated during every cycle.
Repeatable sequence with every revolution
The gear profile determines when acceleration and deceleration occur. When properly assembled, this sequence repeats with every revolution.
Compact Design
A properly designed pair of non-circular gears can handle motion tasks that would otherwise require additional gear stages, cam mechanisms, or control components.
Robust Mechanical Operation
The motion sequence is directly encoded within the gear pair. For applications with a consistently constant cycle time, this results in a readily understandable mechanical solution.
Constant Drive Speed
The motor does not need to be continuously accelerated and decelerated. The speed adjustment takes place within the gear pair.
Suitable for recurring machine cycles
Non-circular gears are particularly useful when a defined sequence repeats unchanged over a long period of time.
Use in existing machines
In older systems, the existing mechanical motion principle can be retained without having to convert the entire machine to an electronic drive solution.
Non-circular Gears and How They Work
In a circular gear, the effective distance between the axis of rotation and the point of tooth engagement remains constant throughout one revolution. Therefore, the gear ratio between the input and output shafts does not change.
In an eccentric gear, the effective radius changes during rotation. In one part of the revolution, a larger effective diameter engages; in another part, a smaller one. As a result, the instantaneous gear ratio changes continuously.
During a single cycle, the downforce can, for example:
- start up slowly
- then accelerate
- go through a phase of higher speed
- Slow down before a handoff
- then return to the starting position
The exact sequence depends on the shape of the gear pair. Elliptical and oval gears are types of non-circular gears, but they make up only a portion of this gear group. Other non-circular profiles are also possible when a specific motion profile is required.
The two gears must mesh with each other throughout their entire rotation. For this reason, their geometries are not considered independently of one another. The shape of one gear directly influences the shape of the other.
The angular position is also important. If the gears are mounted at an angle to each other, the timing of acceleration and deceleration shifts. Clear reference markings and documented installation positions therefore make installation and subsequent replacement easier.
Non-circular gears for packaging machines and conveyor systems
In a packaging machine, an eccentric gear can mechanically guide a gripper through several speed phases.
During product pickup, the gripper moves slowly. This allows sufficient time to grasp the product. The gripper then accelerates and transports it to the next station. Just before the handoff, the movement slows down again.
The motor can run at a constant speed throughout the entire process. The varying motion pattern is caused by the shape of the out-of-round wheels.
Other typical applications include:
The application determines the shape of the gear. A motion profile designed for a packaging gripper cannot be applied unchanged to a paper conveyor or an agricultural conveyor system.
Each contour must be derived from the actual machine sequence required.
Non-circular gears for precisely defined motion profiles
The strength of an eccentric gear lies in its fixed and repetitive motion pattern. This characteristic also imposes clear limitations.
The design is more complex than that of a standard round gear. In addition to the tooth profile, the varying radius, the motion path, and the geometry of the mating gear must be taken into account.
Manufacturing also requires the right machinery and carefully coordinated machining steps. The tooth flanks follow a non-circular contour. Therefore, a standard manufacturing process for circular gears cannot simply be applied here.
Other factors to consider when making a selection:
Non-circular gears are therefore particularly suitable when the machine cycle is known, remains constant over time, and is to be executed without continuous electronic adjustment.
Non-circular gears from the manufacturer Dittler GmbH
Non-circular gears, oval gears, and elliptical gears are among the focal points of our gear manufacturing. We specifically cater to companies that are not looking for a standard part from a catalog, but rather need a gear for a specific assembly, a custom machine, or an existing drive system.
Our range of services includes, among other things:
Our quality management system is certified to DIN EN ISO 9001. For in-process and final inspections, we use a physically separate measuring room equipped with 3-coordinate measuring technology.
For recurring custom-made parts, we also ensure traceable assignment of the gear sets. This is particularly important if a replacement part is needed later and the original motion sequence must be maintained.
Non-circular gears as a mechanical solution for variable gear ratios
In this way, grippers, workpieces, paper webs, films, textiles, or conveyor components can be moved at different speeds within a single cycle. The motion profile is generated mechanically and repeats with each revolution.
This solution is particularly suitable for machines with a fixed operating cycle. However, the design, mating gear, center distance, and mounting position must be considered together. Only a properly matched gear pair can produce the intended speed and torque profile.
We manufacture non-circular gears according to drawings, technical specifications, and—depending on the initial situation—based on an existing sample. We can produce single units, small batches, and replacement solutions for existing machines.
Request and Have Non-Circular Gears Manufactured
Please send us your drawing, technical data, or details about the existing assembly via the contact form. For an initial assessment, information regarding the gearing, center distance, material, quantity, and desired motion profile is particularly helpful.
For replacement parts, please also include, if possible, the mating gear, the installation orientation, and any existing documentation for the machine. The more precisely you describe the initial situation, the better we can assess which manufacturing method is suitable for the non-circular gear.
Frequently Asked Questions About Non-Circular Gears and Variable Gear Ratios
What is an eccentric gear?
An eccentric gear is a gear with a non-circular effective profile. As the gear rotates, the distance between its axis and the point of tooth engagement changes. This results in a variable gear ratio. Although the drive speed remains constant, the output speed varies during a single revolution.
Which types of gears are classified as non-circular gears?
Elliptical and oval gears belong to the group of non-circular gears. However, this umbrella term also includes other non-circular gear geometries. The required profile depends on the desired motion profile. An elliptical profile is therefore only one of several possible designs.
How is the motion profile of an eccentric gear determined?
The starting point is the desired motion sequence of the machine. It must be known at which positions the output shaft is to run slowly, accelerate, or decelerate. The required variation in the gear ratio is derived from this information. This, in turn, determines the profiles of the meshing gears.
Why are non-circular gears usually considered in pairs?
The change in the gear ratio results from the interaction of the two gears. Their profiles must mesh with one another throughout the entire revolution and fit the specified center distance. Therefore, a single out-of-round gear cannot be designed in isolation from its mating gear. The existing gear pairing must also be taken into account when selecting replacement parts.
Can non-circular gears replace electronic drives?
With a fixed, regularly recurring motion profile, non-circular gears can produce variable motion without continuous electronic speed control. However, they are not a general substitute for servo drives. If the sequence needs to be changed frequently during operation, a programmable drive solution usually offers more flexibility.
What data is required for the manufacture of non-circular gears?
It is helpful to provide a technical drawing, gear specifications, module, number of teeth, center distance, material, bore, hub, and installation orientation. In addition, the desired speed or torque profile is required. For a replacement part project, the existing mating gear and information on the original angular position should also be provided, if possible.
Why is the angular position important for non-circular gears?
The relative position of the gears determines at which point in the machine cycle the gear ratio increases or decreases. If the gears are mounted out of alignment, the sequence of motion shifts. The gripper or conveyor mechanism could then accelerate too early or too late. Reference marks and documented mounting positions are therefore important.
Can individual damaged out-of-round gears be replaced?
This depends on the available documentation and the condition of the mating gear. If complete geometric data is available and the mating gear is still usable, a single replacement gear may be manufactured under certain circumstances. If the data is missing or the gear pair shows signs of wear, a new, matched gear set may be the better solution.
For which machines are out-of-round gears suitable?
Non-circular gears are suitable for machines that require different speeds within a repeating cycle. These include packaging machines, textile machines, printing presses, conveyor systems, assembly equipment, machine tools, and agricultural machinery. The key factor is the motion requirements, not just the industry.
What are the limitations of non-circular gears?
The motion profile is mechanically fixed after manufacturing. Any change usually requires a new gear profile. In addition, the design, manufacturing, and assembly are more complex than with standard round gears. Both gears must be designed together and installed at the specified angular position.
Are non-circular gears available as individual pieces?
Yes. Non-circular gears are often needed for special-purpose machines, test setups, or as replacement parts. Therefore, we can manufacture them as single units or in small quantities. For machines with a long-term need for replacement parts, it may be advisable to have additional, custom-matched gear sets manufactured.
How do non-circular gears differ from cam discs?
Both solutions can produce non-uniform motion, but they operate on different principles. An eccentric gear transmits rotational motion via meshing tooth flanks. A cam typically guides a follower along a predetermined contour. Which option is more suitable depends on the type of motion, installation space, load, and machine design.