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Old 25th September 2017, 07:05 PM   #11
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
Location: Värsta Götaland
I've decided to make the plastic parts myself.
So I've ordered the new Prusa i3 Mk3 3D printer.

Unfortunately it is not due until November...

Last edited by solhaga; 25th September 2017 at 07:09 PM.
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Old 25th September 2017, 09:37 PM   #12
WrineX is offline WrineX  Netherlands
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Quote:
Originally Posted by solhaga View Post
Thank you, Wrinex.

Did you by the way visit any of the Piet Mondriaan exhibitions this summer?
not that I know of although I live in the Hague
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Old 1st October 2017, 09:42 AM   #13
solhaga is offline solhaga  Sweden
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Default SLAM!

Got some prototypes made of the pole piece holders:

Click the image to open in full size.

Some minor errors: fillet where the vertical part ends in the horisontal part should have had a larger radius and there should be no fillet on the bottom plate.

First try of the mounting:

Click the image to open in full size.

The holders should have the same contour as the pole piece at membrane.

The backside, where the magnets will be mounted:


Click the image to open in full size.


It could of course be good to cover the nuts with some snap-in so it'll be the same contour towards the membrane/gap all the way.

Test mount in the frame:

Click the image to open in full size.

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Old 14th October 2017, 08:31 PM   #14
solhaga is offline solhaga  Sweden
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Default SLAM prototype v2

I'll replace the small aluminium parts with 3D printed:

Click the image to open in full size.

I can then premount a complete two pole piece section (you'll have to ignore the aluminium part here):

Click the image to open in full size.

Another angle:

Click the image to open in full size.

I'll force the sections down the aluminium frame "rail":

Click the image to open in full size.

When in place I'll secure the section at the aluminium frame with a screw though the section and frame.

Hopefully will this be a lot faster and much more secure.
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Old 24th October 2017, 06:53 AM   #15
solhaga is offline solhaga  Sweden
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While waiting for the printer, I'll need some advice from the forum expertise.

The ideal motor looks like this:

Click the image to open in full size.

Simulated flux density:

Click the image to open in full size.

Horisontal plot:

Click the image to open in full size.

Linear and even through the gap.


But the reflexion of the back wave produces all sorts of distortion both in time and frequency when it is mixed with the front wave.

So after a couple of measurements with different back pole pieces, I decided to skip the back pole pieces all together.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

The flux density is now un-linear and varies a lot over the gap.


Now I'm wondering if there a way to disperse the reflexion.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Considerably better linearity over the gap.

But is the back pole piece curved the right way to make the desired dispersian?
Shall it have a larger radius? (Larger radius means greater variation.)
Other thoughts?
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Old 24th October 2017, 08:55 AM   #16
solhaga is offline solhaga  Sweden
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The back pole piece can be straight across the gap to get a linear flux density.
Convex or concave curvatures towards the membrane are easily made from printed plastic details that are glued to the pole piece.
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Old 24th October 2017, 06:27 PM   #17
båndsei is offline båndsei  Denmark
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Hi Solhaga

I don´t use back pole for my AMT´s.
Using back pole increases sensivity and give a much more linear magnetic field.
My idea is to use round bars to omit reflexions .
Use a angle grinder to cut the ends like this:Udklip.PNG

Bernt
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Old 24th October 2017, 07:07 PM   #18
solhaga is offline solhaga  Sweden
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Quote:
Originally Posted by båndsei View Post
Hi Solhaga

I don´t use back pole for my AMT´s.
Using back pole increases sensivity and give a much more linear magnetic field.
My idea is to use round bars to omit reflexions .
Use a angle grinder to cut the ends like this:Attachment 641975

Bernt
Yeah, that's a great idea.
Instead of using a grinder, a 5x5 mm square rod can be used that can have your suggestion glued to it or a concave or a convex or a ...
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Old 29th October 2017, 05:14 PM   #19
solhaga is offline solhaga  Sweden
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As the configuration is MMTMM, the section where the four mid membranes are can have back pole pieces.
This as the reflections have little impact for that frequency interval.
I'm also considering to make the mid membranes to go lower, let's see what properties that will have to change - pleat depth, pleat width and/or foil thickness/width.

Then I will see if the small tweeter membrane in the middle can cope with back pole pieces.
That membrane's properties will of course be changed as well, apart from being shorter of course.

Back pole piece:

Click the image to open in full size.

I will test this in my current motor.
Simulations looks good!

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.



SLAM! two pole piece complete assembly:

Click the image to open in full size.
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Old 4th November 2017, 05:29 PM   #20
båndsei is offline båndsei  Denmark
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Join Date: Dec 2008
Hi Solhaga

I have tried to become member at faktisk.se to make a comment to your SLAM project.
At the registration site you are given a security question to prevent spambots
In SWEEDISH.

A comment to the other site. You can increase the field strength in the tweeter gap using this bar:solhaga bar tweeter.PNG
Are the iron bars saturated ?

Bernt
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