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Old 21st Nov 2022, 12:35 pm   #1
Mike Phelan
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Default Microwave waveguide mica.

Hi Folks,

We've had our Schneider microwave for many years now - yesterday the bulb finally went kupat so i replaced it.

When I was looking in, I saw thet the mice sheet by the waveguide had started to look a bit black so needed replacing.

As the item was quite old now, the ones I saw on Amazon weren't the right size, so:
  • Can you cut a larger one to size and drill a hole for the screw successfully?
  • When they look black, does the performance deteriorate?
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Old 21st Nov 2022, 2:11 pm   #2
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Default Re: Microwave waveguide mica.

Measure the time for a cup of water to get from ambient to the boil to assess power reaching the job in hand. Or run the thing for a short time while and check the temperature of the mica quickly afterwards. It has low thermal mass and 600W passing through it. If it's not hot, it must be OK.

Mica is usually punched to shape and to make holes. I assume drilling would work with support behind it for the drill to continue into.

David
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Old 21st Nov 2022, 2:34 pm   #3
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Default Re: Microwave waveguide mica.

the biggest problem is going to be if it becomes conductive and starts sparking. I've ordered bigger ones and cut them down, using my hole punch to make a nice hole.
My panasonic here has a plastic waveguide cover as does this 1900W commercial microwave at work
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Old 21st Nov 2022, 2:54 pm   #4
Richard
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Default Re: Microwave waveguide mica.

Hi.
They get darker as they draw in grease etc, and eventually either fall apart or arc and burn. Often when they arc the arc will travel down the wave guide and damage the magnetron antenna so it's worth changing before this happens.
You can buy a sheet of mica, or any larger wave guide cover and cut one out.
I used to use a stanley knife and steel ruler, with the mica on a cutting board.
Shape rounded corners with a sanding block.
Holes are easy to make with a punch or drill bit.
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Old 21st Nov 2022, 3:35 pm   #5
Mike Phelan
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Default Re: Microwave waveguide mica.

Thanks, folks, I'll have a look at all these replies.

Quote:
Originally Posted by Radio Wrangler View Post
Or run the thing for a short time while and check the temperature of the mica quickly afterwards. It has low thermal mass and 600W passing through it. If it's not hot, it must be OK.
It gets quite warm.
Quote:
Mica is usually punched to shape and to make holes. I assume drilling would work with support behind it for the drill to continue into.
David
I've no problen with drilling and cutting; didn't know of doing this would weaken it in some way.

Quote:
Originally Posted by McMurdo View Post
the biggest problem is going to be if it becomes conductive and starts sparking. I've ordered bigger ones and cut them down, using my hole punch to make a nice hole.
My panasonic here has a plastic waveguide cover as does this 1900W commercial microwave at work
I'll drill this on a wooden block when I get it - it's not conductive (yet!)

Quote:
Originally Posted by Richard View Post
Hi.
They get darker as they draw in grease etc, and eventually either fall apart or arc and burn. Often when they arc the arc will travel down the wave guide and damage the magnetron antenna so it's worth changing before this happens.
You can buy a sheet of mica, or any larger wave guide cover and cut one out.
I used to use a stanley knife and steel ruler, with the mica on a cutting board.
Shape rounded corners with a sanding block.
Holes are easy to make with a punch or drill bit.
Thanks, Richard my thoughts exactly.
I'll get a larger sheet from Amazon, drill on a wood block and cut with my ubiquitous Stanley Knife and round the edges with some glasspaper.
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Old 21st Nov 2022, 3:39 pm   #6
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Default Re: Microwave waveguide mica.

I vaguely remember reading something about cutting sheet-Mica with ordinary scissors, _underwater_ .

Mica being fragile, the scissors create their cut by micro-fracturing the mica; the underwater thing being to absorb the shock energy of the micro-fracturing and stop the mica delaminating in the area round the cut.
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Old 21st Nov 2022, 4:18 pm   #7
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Default Re: Microwave waveguide mica.

Hmmm ... interesting.
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Old 21st Nov 2022, 5:24 pm   #8
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Default Re: Microwave waveguide mica.

May I ask if you find a suitable link(URL) to source sheet mica you share it, please?

Good luck!
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Old 21st Nov 2022, 8:03 pm   #9
Richard
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Default Re: Microwave waveguide mica.

Quote:
Originally Posted by PaulDarzi View Post
May I ask if you find a suitable link(URL) to source sheet mica you share it, please?

Good luck!
A search on ebay for "microwave wave guide cover" finds 1000s, many of which are the universal sheet you cut to shape.

Richard
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Old 21st Nov 2022, 8:26 pm   #10
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Default Re: Microwave waveguide mica.

Quote:
Originally Posted by Richard View Post
A search on ebay for "microwave wave guide cover" finds 1000s, many of which are the universal sheet you cut to shape.
Richard
I've done this exact thing, many times...
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Old 21st Nov 2022, 9:13 pm   #11
PaulDarzi
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Default Re: Microwave waveguide mica.

Quote:
Originally Posted by Richard View Post
Quote:
Originally Posted by PaulDarzi View Post
May I ask if you find a suitable link(URL) to source sheet mica you share it, please?

Good luck!
A search on ebay for "microwave wave guide cover" finds 1000s, many of which are the universal sheet you cut to shape.

Richard
Thank you muchly.
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