system for holding together a pack of metal laminations

[arivel]

Hi everyone .
to understand what it is I thought the best thing is to attach a link . in link 502574 it says what I want to do.

https://www.eng-tips.com/viewthread.cfm?qid=504815

if, on the other hand, you don't want to read, I'll explain briefly and in simple terms that it is a direct current electromagnet with a ring to close the return path of the magnetic field.
I stopped in front of a problem.
I have to create a cylinder starting from a package of laser cut laminations and then I have to stack them together, in the end they have to be turned on the lathe.
I don't have clear ideas on how to keep them together, I'd like to know how they do it in the industry that builds electric motors.
for example, I remember that years ago I disassembled an engine and the rotor was made up of a pack of very thin laminations joined together but I didn't understand how the job was done.

 

[Gr8blu]

If the lamination geometry is pre-cut via laser (or mechanical punch) then turning them in a lathe after assembly will negate a large chunk of the core loss protection that is a result of the interlaminar insulation (core plate coating) because the cutting tool on the lathe will "smear" one lamination into another at the exposed outer edge. What this means in simple terms is that the resulting assembly will have higher core loss, which ultimately means less efficient. In industry, the pre-cut geometry is (almost) always the final geometry.

As to holding the laminations together - the basic method is a compression clamp, applied over the axial length. This can be done by having a thicker material shaped as a ring at each end, with some form of threaded rod inserted through both plates and the laminations, with a nut on each end. How much force is required to keep the core from moving depends on the diameter and length of the cylinder and the intended rotational speed. Dividing the force by the amount of tension an individual stud/nut can develop will give the number of studs required. For really long cores, be sure to take a look at the resonance characteristics of the stud as it hangs suspended between the two end plates - because the chances are good that the lamination doesn't actually contact the stud itself (i.e., there is a clearance).

Converting energy to motion for more than half a century

 

[arivel]

I'm not sure I understand what you wrote in the first part of your speech.
the laminations are arranged longitudinally so their surface is parallel to the axis of the cylinder.
there is no electrical insulator between the laminations because they have to work with direct current.

 

[Gr8blu]

Hmm. Common industrial use in rotating machines orients the lamination sheet so that the thin edge is radial with respect to the axis of the cylinder. The larger "flat" surfaces are oriented perpendicular to the axis. This is because the desired flux path (in a rotating machine) is radial - not horizontal. To reduce eddy current and core loss (which means flux traveling parallel to the axis), the lamination sheets have a substance on them called "core plate", which is either an organic or inorganic composite. The thickness of the core plate is typically 0.00012 inch (0.003 mm) on each side of the sheet, regardless of actual sheet thickness.

For non-rotating machines (i.e., transformers), the generalized construction orients the thin edge of the sheet toward the air gap. Example: a "C" shaped core will appear as a flat surface when looking at it and seeing the "C", but will look like sliced bread when looking from one of the edges. For a toroidal core, this means having the sheets oriented with the thin edge radial to the axis (and a hollow center to the cylinder). The basic idea in all cases (including the rotating machine) is to make it easier for the magnetic flux to travel in the direction you actually want it to go, rather than some other way.

My best guess for restraining a stack of laminations arranged with the thin edge parallel to the axis of the cylinder is to develop some sort of retaining ring - probably in a non-ferrous material - that can be used to "grab" one end or the other. To machine a fit for the ring, you'd have to simply clamp the pack (pressing through the larger flat side of the lamination, not along the thin edges) in a radial direction somewhere away from the eventual ring mounting surface.



Converting energy to motion for more than half a century

 

[edison123]

Magnetic iron laminations have silicon and are extremely tough to machine. That's why they are punched or laser cut and rarely machined.

Not sure why do you need to machine them. A few photos or pictures here might help.

Muthu

http://www.edison.co.in

 

[EdStainless]

This is not AC and not Si steel.
These are high purity iron and this is for an electromagnetic core.
OP simply needs a shape that this material is not available in, in low quantity.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[waross]

You mentioned mixing materials with different saturation points.
A magnetic circuit may be visualized as series resistors.
Each cross section of each material may be considered a resistor.
The thinner the cross section the higher the resistance.
The air gap will have a relatively very high resistance.
In some magnet designs the air core dominates.
Once a section of magnetic material saturates the effective resistance to increased magnetomotive approaches the air core resistance.
The ratio of the change will be several thousand to one.
Realistically, the flux density will be limited by the air gap and the lowest saturation material section.
Note that a material with a lower cross section but high saturation point may saturate before a material with a lower saturation point but a larger cross section.

Rather than trying so hard to optimize materials, try this.
Using the saturation point of an easy to source section such as shafting, increase the diameter of the air gap to develop more magnetic force.
Use a length of off the shelf, steel shaft and a length of heavy wall steel piping.
Machine the top and bottom from mild steel plates.
That is, compare the magnetic properties of asy to source shapes and vary the dimensions to develop the force that you desire.
In a sketch that you posted previously, you showed the central core necking down at the air gap.
That may push that portion into saturation.
Possible you intended to run a section in saturation as an easy way to achieve a stable field.
With part of the magnetic circuit in saturation, the effects of voltage variation may be reduced by a factor of several thousands.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

Visualize this:
A round section such as a shaft inside a heavy walled pipe.
Both ends closed by steel plates.
Now a slot will be machined in one end plate to accept the voice coil.
The larger the diameter of the slot, the greater force on the voice coil for a given flux density.
The larger the diameter of the slot, the greater current in the coil for a given flux density.
More area of air gap to magnetize.
For a one off design, you can save a lot of money by choosing cheaper material and increasing the dimensions.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[arivel]

arrangement in the radial plane with respect to the axis of the cylinder ?.
it is true that in my case there is no electrical insulation between one lamination and the other but their surface is not perfectly rectified so I fear that a very small layer of air between one lamination and the other always remains, causing small air gaps that add up to each other, lowering the intensity of the total flow.

 

[arivel]

hello waross .
what material do you recommend?

 

[waross]

Google is your friend.
Look at readily available steel shapes and check their magnetic properties and prices.
Solid pole pieces are common for DC fields. (Or were years ago. I am not sure what is current now.)

--------------------
Ohm's law
Not just a good idea;
It's the LAW!