MTF Linear Motors – An Introduction
Published on : Saturday 04-03-2023
What is a (Magnetic Track Free) MTF linear motor? This article explains the concept and the benefits.
The video link is here - https://drive.google.com/file/d/1xrblgrFfdEvlBruZUBRbYSox_ADUuLbR/view?usp=share_link
Conventionally, if you were to slice a rotary servo motor and lay it flat, you would have, essentially, a linear motor. The rotor with permanent magnets becomes the stationary part of the linear motor (also called the secondary, or magnet plate), and the stator, which contains the coil windings, becomes the moving part (also called the primary, or coil unit).
Linear motors operate with an AC power supply and servo controller, which are often the same as those used for rotary servo motors. The linear motor primary part is connected to the power supply to produce a magnet field. By changing the current phase in the coils, the polarity of each coil is changed. The attractive and repelling forces between the coils in the primary part and the magnets in the secondary part cause the primary to move and generate a linear force. The rate of change of the current controls the velocity of the movement, and the amperage of the current determines the force generated.
ALM Intelligent Technology based in China has bought out a new revolution in linear motors. They proposed the Seidal branded Magnetic-track-free (MTF) linear motor for the first time in industry based on the innovation in the magnetic field theory. Remarkably, the stator does not need the Permanent Magnets in the plate anymore, which can save the massive rare-earth materials. By iteratively optimising the design and the manufacturing craft, MTF linear motor obtained the extremely high force density, operating speed and moving precision.
Seidal has a total of 20 products in the S1, S2 and S3 series. The motors can achieve a maximum speed of 18m/s, the maximum acceleration they can reach is 15G, the thrust range is from 63N to 1500N, and the vertical suction is only 1/3 of the conventional linear motor, which greatly extends the guide life.
MTF linear motors can effectively overcome the disadvantages of large magnet consumption and low magnet utilisation of the conventional linear motor. The stator of the magnetic-track-free linear motor does not use magnets, but the powder magnetic conductive materials. The material has high permeability, high saturation flux and is easy to be manufactured by metallurgical die casting.
MTF linear motors put the magnet inside the stator such that when the actuator moves, the corresponding magnet moves with it. That is, the motor will be excited by the magnet because of the electromagnetic force.
Thus the system becomes similar to a rotary permanent magnet synchronous motor, the magnet utilisation rate reaches 100% and no extra magnet is exposed. As a result, the cost of linear motors is greatly reduced and safety is improved. Compared with high-cost magnetic rail linear motors on the market, Seidal linear motors can save a large amount of rare earth materials and save at least 70% of the cost, especially for long-track linear motors.
Advantages of MTF linear motors
Besides the high speed and precision merits as the conventional linear motor, MTF-LM has the following advantages:
Safer: No magnetic field in stator, easier for assembling, much lower risk for operators
Much smaller attractions force: About ⅓ of the conventional linear motor attraction force can reduce the friction and cogging force significantly, thus to increase the life expectancy and reduce the operating noise.
Much smaller cogging force: Benefited from the low attraction force and the specialised optimising design, MTF-LM can obtain the extremely low cogging force.
Highly adaptive:
With low requirement for the ingress protection, and reduce the EMI grade obviously.
Easier for protection: Not easy to attract the sundries and ashes into the motor, easier for protection.
Highly cost effective: Benefited from the rare earth material saving, MTF is trying to provide the most cost-effective products for customers.
Linear motor applications
Linear motors have wide applications in various fields, including:
1. IC packaging
2. Testing of semiconductor equipment
3. IC patching
4. Photovoltaic panel manufacture
5. Lithium battery manufacture
6. Laser cutting equipments
7. Medical apparatus and instruments
8. Machine tools
9. Optical equipments, and
10. Display panel manufacturers.
How to select a linear motor
1. Define a move profile: Triangular or Trapezoidal
2. Define the load
3. Size the motor and the amplifier
i. From the move profile, we can calculate the maximum speed and the maximum acceleration/deceleration.
ii. From the load we can calculate all of the forces at constant speed and using the move profile all the dynamic forces during acceleration and deceleration.
iii. Once a motor is selected, the weight of the moving parts of the motor are added to the moving weight to calculate a total Peak Force and a total RMS force.
The motor should be able to deliver the peak force and the calculated RMS force should be less than the motor continuous force to ensure a known safety margin. The coil temperature rise can also be calculated to ensure that it is lower than the intended maximum temperature rise. The maximum bus voltage and continuous and peak current can also be calculated and compared to the selected amplifier to be sure the calculated performances can be achieved.
How to get in India
Durga Mechatronics a 40+ year old company is the sole distributor of Seidal MTF – Linear Motors in India. We have trained manpower that can help the company right from the designing stage, the motor sizing, assisting with assembly, final trial and testing, and then after sales support as well. Seidal MTF requires a servo driver to run, which can be sourced from Durga Mechatronics as well. We also can support your company with many other products from various internally recognised brand such as Unitronics PLC & HMI, Danfoss VFD’s, ABB switchgears, Marathon Electric Motors and Bearings from various companies such as NSK, Schaeffler, NBC, etc.
Durga Mechatronics Pvt Ltd, Mumbai. www.durgamechatronics.com