105 replies to this topic

[CFL Mike]

Thanks for the information Ron, on how the magnets and armature interact. The only thing I dont quite understand, is what part of the magnet is considered the lead edge and the trailing edge.

Also just to clarify, "wet press" and "wet charging" are the same thing? Or is "wet charging" a non-exsistent term?

[Ron Hershman]

The leading edge of the magnet is the top edge/tip as the armature rotates in the running direction of the motor.

Wet charging is not a term or process.

More info....

General Information

Ferrite magnets are sintered permanent magnets composed of Barium or Strontium Ferrite. This class of magnets, aside from good resistance to demagnetization, has the popular advantage of low cost.

Ferrite magnets are very hard and brittle, and require specialized machining techniques. Moreover, they should be machined in an unmagnetized state.

Anisotropic grades are oriented in the manufacturing direction, and must be magnetized in the direction of orientation. Isotropic grades are not oriented and can be magnetized in any direction, although some degree of greater magnetic strength will be found in the pressing dimension, usually the shortest dimension.

Due to their low cost, Ferrite magnets enjoy a very wide range of applications, from motors and loudspeakers to toys and crafts, and are the most widely used permanent magnets today.

Manufacturing Methods

Pressing and Sintering:

Pressing and sintering involves pressing very fine ferrite powder in a die, and then sintering this pressed magnet. All fully dense Ferrite magnets are produced this way. Ferrite magnets can be wet pressed or dry pressed. Wet pressing yields better magnetic properties, but poorer physical tolerances. Sintering involves subjecting the material to high temperatures to fuse the pressed powder together, thus creating a solid material. Magnets produced through this process usually need to have some finish machining, otherwise surface finishes and tolerances are not acceptable. Some manufacturers extrude instead of press wet powder slurry and then sinter the material. This is sometimes done for arc segment shapes, where the arc cross-section is extruded in long lengths, sintered, and then cut to length.

[CFL Mike]

Since it seems like you pretty much run the slot cat magnet industry Ron (I know hyperbole, still take it as a compliment) I would really value your opinion. I was reading through this thread earlier, and I think you said, even today you prefer Mura magnets right? Or which ones do like/use most often?

[Gator Bob]

Did Mura sell them as Yellow Dots?

Help - I forget.

Orientation ???

dots face the can bushing ?
with the two dots at the (rear on a AW) side of a Mura C can with the axle clearance cut out ?

Or what?

[Rick]

Be bold, turn the dots one way on one side and opposite on the other. heheheh

[Gator Bob]

Be bold, turn the dots one way on one side and opposite on the other. heheheh

Then paint new dots?