NEO – power magnetic system. Advanced steel holding technology
Magnetic workholding is the simplest and most effective technology for all types of steel working and steel handling tasks. Magnet can realize safe and reliable fixation of practically all kinds and shapes of steel pieces during their machining (magnetic chucks, tables), handling (magnetic lifters, manipulators) and transportation (magnetic conveyers).
Today practically everywhere, where we use steel, a lot of both standard and special magnetic systems are successfully applied.
The most popular are three types of magnetic systems, classified according to the type of magnetic energy source: with electromagnets, with permanent magnets and with the combination of both above.
In this article we’ll describe our new “Neo – Power” magnetic systems with high energy permanent magnets, developed and applied by DVM.
Last decades practically all magnetic systems with permanent magnets were significantly redesigned. This has to do with the application of new rare-earth magnets, mostly NdFeB, which have substituted traditional Ferrite magnets in most of magnetic devices. This substitution has started with just replacing of low energy ferrite magnets by high energy magnets in traditional magnetic systems without changing the correspondent magnetic circuit. Unfortunately, till now in many magnetic devices with high energy magnets this is still the case. In order to understand the disadvantages of such magnetic devices, let us first analyze traditional magnetic circuits with Ferrite magnets.
Magnetic systems with Ferrite magnets.
Magnetic devices with Ferrite magnets were mostly created using so called magnetic amplification principle. Low energy of these magnets did not allow using them as direct source of magnetic flux in order to create reasonable holding force between magnetic device and steel piece. That is why Ferrite magnets were mostly placed between the device steel poles so that their contact surface with poles was three – four times larger than the active pole surface. As a result, magnetic flux, collected from the large pole sides area, was concentrated in comparatively small pole active area increasing magnetic induction on active pole and correspondingly magnetic force between the pole and steel object.
It is quite obvious that blind substitution of Ferrite magnets in such devices with high energy magnets, having already three – four times higher magnetic induction, can not lead to significant magnetic force increase due to magnetic saturation in the steel pole active cross-section.
Another problem here is the necessity to control magnetic force, mostly just switching the device -on and -off. In traditional devices with Ferrite magnets this was realized by dividing magnetic circuit into two equal parts with the possibility of moving one part according to another so that in one position both parts were working together and in another position were compensating each other. Also here the blind substitution of Ferrite magnets by high energy magnets can lead to significant switching force increase, so that some devices can not be switched -on and -off at all.
Magnetic systems with NdFeB magnets.
First that was changed in traditional magnetic systems with the application of new high energy magnets was the structure of the second (control) part of the magnetic system. This part becomes flat with magnets situated perpendicular to magnets in the first part and parallel to the device working surface. Immediately several problems have appeared here.
First, now in the switching system magnets have to move on the steel surface, experiencing high friction, therefore high temperature with significant decrease of magnetic, mechanical and longevity properties.
Second, such magnets situation in the control part, where magnets are supplying flux direct to the working pole, immediately results in changing magnetic flux (induction) distribution along the pole active surface. This distribution just repeats the magnet magnetizing distribution, resulting in so called magnetic side effects.
From the other hand, in order to switch the system off, the control part has to compensate completely the flux of the first part of the system, where still the old amplification principle is used and flux in the pole is distributed differently. As a result, in order to achieve reasonable compensation, the active volume and the energy grade of magnets has to be increased here about 30% without any advantages for the total device application parameters.
It is obvious now that most disadvantages of modern magnetic systems with high energy magnets have to do with characteristics of their magnets, which are just standard and mostly created for standard applications in electrical motors.
Neo Power systems.
These systems were created by DVM with the following main task: realize maximum advantages of high energy rare-earth magnets in static steel holding devices. This task was solved by:
- Developing and arranging production of special high energy magnets;
- Developing special surface covers for new magnets and their covering technology;
- Developing special magnetizing technology;
- Optimizing magnetic circuits of steel holding devices.
Special High Energy Magnets. In the DVM production of special magnets we have created original initial alloys and have changed the magnets sintering technology so that new magnets are different from the standard energy grades definition. This was done in order to reach for concrete alloy the highest possible magnetic induction with just reasonable (not maximum) coercivity. As a result with lower volume of new magnets we can achieve about 30% higher holding force and at the same time decrease magnets production costs dramatically.
New Magnets Cover. We have developed the multilayer magnet covering technology, using metal, plastic and self-lubrication graphite top layer. As a result the friction between magnet and steel surface was decreased 25%, magnetic device switching force was decreased up to 30% and high energy magnets life in static devices increased more than twice.
By introducing special form of magnetizing poles active area and using multi-pulse magnetizing with different pulse amplitudes we have reached the “convex” form of magnetic induction on the magnet surface instead of traditional “concave” form. As a result we have decreased the influence of side effects in magnetic circuits and increased the average magnetic induction on the working pole by 10%. This allowed decreasing the total volume of high energy compensating magnets by more than 15% without decreasing the device holding force.
We have applied different magnets in the main top part (plate) of magnetic system and in the compensating part. In the top part magnets with maximum induction are applied, this allows decreasing the top height (weight) or increasing the total force if necessary. In the compensating part the “convex” magnetized magnets with special low friction cover are applied, allowing lower magnets volume and lower switching force.
The geometry of analyzed magnetic systems can be best described with the the ratio between the active pole width and non-magnetic width between poles (where top magnets are situated) on the device working surface. Computer modeling of new systems shows that with all above described we are able decreasing non-magnetic space between poles about 25% and as a result increase the device active surface and productivity correspondingly.
Neo Power devices
Starting from 2007, DVM is serially producing the following magnetic devices, based on Neo Power system: rectangular and round magnetic chucks, magnetic lifters for flat material, magnetic manipulators for underwater application, separators with permanent magnets, several magnetic devices for special application.