Jewelery magnetic polisher - Handmade by CMS

Fixed electromagnets will not have this effect. However, it should also work to some extent.
Note that at the maximum RPM - 3400rpm, the magnetic field changes 13,600 times per minute, at the moment the inverter is set to 42Hz which gives 2400rpm which is almost 10,000 anyway.
I'm afraid the electromagnets could get hot. After all, each switching on and off causes a "current-voltage" surge, but I may be wrong.

This solution would significantly reduce the size of the machine.

CMS wrote:

After all, each switching on and off causes a "current-voltage" surge, but I may be wrong.

Eddy currents in the cores ... will do their job Here, a rotating magnetic field is generated mechanically, and this has great advantages (e.g. simple speed control of the drive motor). Marcin and ask the recipient how would fine steel shot work instead of needles. It seems to me that the frictional resistance on the bolt would be lower than on the pins.

The shot will not penetrate the processed material, which by definition has many small details. Needles squeeze into the smallest nooks and crannies.

CMS wrote:

Needles squeeze into the smallest nooks and crannies.

Apparently so, but pellets of 0.2 mm? It's almost like sand, and sometimes I give small details for sandblasting. If the shot worked, maybe he would build such a machine (I do not make rings ).

I think that if pellets were better than needles, jewelers would use pellets .
You see, the pellet only hits, and the needle hits the tip and at the same time rotates in some plane and as if it will make a scratch on a polished element. So we have not only stroke but also friction. The shot, on the other hand, "only" hits. The sand works well because it has sharp edges, except that it is much finer than the mentioned 0.2mm.

very nice machine, i have been looking for something like this for a long time to clean, can you tell what thickness did you use magnets? I can see that the plate is 20cm, what magnets to use with a diameter of at least 50cm or more?

Neodymium magnets 30mm diameter 5mm thick.

I have a few comments.
First of all, I definitely don't like the use of chipboard as a material for both the housing of the device and the turntable. The casing does not give off heat, and in my opinion, the turntable will develop a hole in the shaft over time and the drive will have a lot of runout. You don't write anything about the ramp, that is, the slow acceleration of the engine. Without it, your mounting, due to high overloads caused by engine acceleration, will loosen the (single-point) mounting of this plate over time, and no super glues will probably help here. In my opinion, it is also fatal to mount the engine itself. One time it is attached to the chipboard, and secondly, it is attached to the bottom while the rotating disc is at the top of the engine. It is asking you to use a motor with a flange mounting so that the rotating element is as close to this mounting as possible. Then the arm of the centrifugal force of the rotating plate on the motor mount is shortened. And one more thing - do you know what temperature resistance class is the motor winding currently in? I am asking because I do not know if the thermal protection of this motor is adequate for this class. And since I'm still at the engine, I will refer to the following remark from one of my colleagues:

robokop wrote:

A commutator motor would be cheaper

Could you write about exactly what type of engine do you mean? Because as far as I know, these engines have a very high rotational speed, in the order of several thousand revolutions and a tendency to diverge. In an extreme situation, that is when the control fails, which is not a problem in such a housing, and if the device works in idle mode (without a container with metal needles), as a result of the rotating system reaching very high rotations, this disc could break and with it also the housing of the device. Normally, in such an engine, any rotating parts that could burst are located inside the metal housing of the engine. There is only a pulley on the outside that can handle much more rotations.
Regarding the inverter, I think it should have more space around it for ventilation, and it should rather be shielded.
Another thing is the ventilation grille. If it is assumed that temperatures in excess of 80 ° C can develop in the equipment:

CMS wrote:

If for some reason (despite the fans running) the motor reaches 85 °

then, PVC ventilation grilles should not be used, which can operate at a maximum temperature of 70 ° C:
https://www.iwentylatory.pl/kratka-wentylacyj...zem-i-plastikowa-siatka-o-160-mm-biala-x13211

CMS wrote:

The polisher was also supposed to be simple at first, and a beautiful, almost factory-made product came out.

Yes, assuming it is only about the external appearance of the device. For me, the beauty of factory devices lies not only in the aesthetically finished housing, but also in the technical solutions used.

Forgive me, but based on my superficial observations about this project and what you wrote below:

CMS wrote:

I don't know anything about it. When a colleague asked if I would build it, I had no idea about the existence of such devices. I do not have a comparison with any other polisher, so I do not know what their advantages and disadvantages are.

I just designed and built what they asked me for.

I only feel sorry for the buyer of this device.

I would like to add that my comment to Kol. Robokop concerned specific commutator motors used in washing machines (mentioned above), and not this type of motors used in a general sense.

CMS wrote:

robokop wrote:

One more very important thing. The disc with magnets sticks to the motor axis on the screw - with a right-hand thread. When switching to "left", it will unscrew ...

I thought about it. Between the disc and the pulley, there is a silicone washer of the pulley diameter. After 6 hours of testing, nothing has loosened. And as if you can always drip blue thread glue.

A few days ago I spoke to the owner of my "work". The polisher has been working almost non-stop for a year now. Also, all your fears were, not to say unfounded, but strongly exaggerated.