Application note

Curved magnet track

curved magnet track with tm3

Introduction

How does a linear motor move over a curved track? A seemingly complicated question with straight forward answers. Where traditionally different motion systems can be used to follow up on a linear motion, Tecnotion develops curved magnet tracks. These tracks allow more complicated curved movements using a ‘traditional’ linear coil unit.

 

Tecnotion developed the curved tracks to minimize force losses. Electromagnetic design provides low cogging, and by using the right algorithms, allow very smooth motion.
Especially transport and packaging systems can benefit from a curved magnet track. Curved magnets enable the possibility to create a closed track entirely from direct drive linear motor parts. In particular systems with continuous flow and with more motors on one track can achieve higher efficiency using closed loop curved magnet tracks.

 

Customizable

There are existing curved magnet designs at hand, specifying a radius and magnet track width. Large projects with curved magnet tracks are highly customizable thanks to these designs. Depending on specific customer requests, Tecnotion can adapt the design, radius and number of segments required to make any curved track. We will advise the correct radius depending on the coil unit needed. When the radius is too small or the motor is too long, movements will become unpredictably (side-to-side and/or force variations).

unpredictable moving  

Unpredictable moving and force loss occurs when the motor is too long for the curves

perfect fit

Perfect fit with optimal force ratio

table outer radius and motor series

 

Possibilities and opportunities

Curved magnets provide opportunities for transport, packaging and more. Tecnotion’s standard linear motors can be used in a closed track system. Closed tracks allow for continuous workflow and multiple coil units on one track. Giving the potential to use an existing track much more efficient. The individual motors can be driven at different speeds and in different directions. Compared to a traditional conveyor belt, products can be slowed down for quality inspection and/or sorting processes. The product can be sped up immediately afterwards to not disturb over-all workflow. Individual motors can be powered by sliding contacts for maximum versatility. 

Upon designing a curved magnet application, it is important to look at the bend radius. Keep in mind the radius has to be sufficient for the motor to move in a correct way. The minimum magnet-radius (center) of the track is approximately 275 mm. Designs can be optimized by varying in the number of curved magnet segments used to complete a track.

straight magnet tracks vs curved track

Left: Some systems use regular straight magnet tracks to form a curve. Even though the motor will move, movement and vibration become very unpredictable
and a lot of force can be lost in these movements. The magnets are not at ‘set’ distances.
Right: The Tecnotion design has precise placed magnets to provide smooth movement through the entire curve.


Advantages

A curved magnet iron core system provides unique characteristics. What advantages they provide for your system depends on what parts the curved magnet track replaces. There is no direct comparison to be made between any current system and the iron core on a curved magnet track.

 

In short, the curved magnet track is

  • Cost effective and less complex to control by using one motion system to control all movements.
  • Delivers a higher continuous force than a moving magnet solution.
  • Maintenance friendly and mechanically simple compared to a ‘combined system’ of belts and linear motors.
  • Far higher force than a curve made with straight magnet sections.
  • More versatile and free in movement than a transport belt and the possibility to use multiple motors on one track. For this application a sliding contact to power the motor can be beneficial. 
  • Opportunity to use a continuous workflow instead of moving back and forth on a traditional linear motor track.
  • More versatile than a large torque motor, the possibility to use only a 90 or 180 degree curve and multiple coil units.

 

motorlenght vs curve

Lenght of motors in relation to radius of magnet track curve

 

Conclusion

With a curved magnet iron core system it is always important to pay close attention to radius related to motor length. A certain motor length is needed to provide force to the application. This motor length will be the deciding factor in the possible radius. The Tecnotion TM3 (51x91 mm WxH) can for instance be used on a track with a 300 mm outer radius. Small deviations can be made by choosing a different track width and making concessions on the motors’ force. For full flexibility in movement a slide can be used to power the motor, flexible cables are a more limiting option. The Tecnotion TM, TL and TB(W) coil units are very capable when used on a curved track. When using the correct design, power loss is minimal. Usually Tecnotion advises a design with a power loss of 5% or less.

 

Our team of Application Engineers can advise in all your future plans for curved magnet tracks. Do not hesitate to contact us at support@tecnotion.com
or +31 546536300.

 

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