I seem to remember those hot wire tools that could cut expanded polystyrene - as I remember they gave it a nice smooth surface but I don't think it made it in any way stronger so I don't think your plan would work.

I once had success mending a fridge door shelf with Araldite using some kind of mould to shape it as I needed but I can't remember for the life of me how I stopped it sticking to the mould!

On Wed, 12 Aug 2020 19:57:47 -0300, Nick Odell wrote:

If I were to use a hot wire or hot knife to cut the polystyrene into
new shapes would the hot tool seal the cut surfaces with a melted skin
...

Hot wire works quite well leaving a smooth surface not the fryable,
bobbly, surface of broken expanded polystyrene. I think a hot knife
unless temeprature controlled will either not cut at all or end up as
a very sticky molten mass. The temperature of a hot wire is similary
fairly critcal but easy to adjust by varying the current through the
wire.

... and would that skin give the shape any structural integrity ...

Not that would be noticeable.

... I had been pondering the idea of molding a piece of thermoplastic
sheet to replace a broken part from the refrigerator door and if instead
I could shape a piece of expanded polystyrene it might be a whole lot
easier. But would it have the strength to hold the bottle shelf in
place?

I think that depends on what is broken and the stress it is under. As
packing behind a crack to stop it moving it might work but probably
not as a lug to take the shelf.

Or try very gently melting the poly down and casting it in a mould or
perhaps even moulding it into shape with your fingers. At the
temperatures you can handle it shouldn't be sticky but might be quite
firm.

--
Cheers
Dave.

On Wednesday, 12 August 2020 21:39:02 UTC+1, Murmansk wrote:
I seem to remember those hot wire tools that could cut expanded polystyrene - as I remember they gave it a nice smooth surface but I don't think it made it in any way stronger so I don't think your plan would work.

I once had success mending a fridge door shelf with Araldite using some kind of mould to shape it as I needed but I can't remember for the life of me how I stopped it sticking to the mould!

I don't know if it would work for an epoxy resin, but polyester film (Mylar) can be used to allow release of polyester resins.

This is just idle curiosity so please do not spend too much time on an
answer or an explanation but...

I have just taken delivery of a new washing machine which has left me
with loads of pre-molded expanded polystyrene sections and -erme- a
new washing machine.

If I were to use a hot wire or hot knife to cut the polystyrene into
new shapes would the hot tool seal the cut surfaces with a melted skin
and would that skin give the shape any structural integrity - or will
the pieces just remain as crumbly as they were before? I do not have
many specific ideas about how to use this foam but for instance I had
been pondering the idea of molding a piece of thermoplastic sheet to
replace a broken part from the refrigerator door and if instead I
could shape a piece of expanded polystyrene it might be a whole lot
easier. But would it have the strength to hold the bottle shelf in
place?

Thanks,

Nick

On 12/08/2020 23:57, Nick Odell wrote:
This is just idle curiosity so please do not spend too much time on an
answer or an explanation but...

I have just taken delivery of a new washing machine which has left me
with loads of pre-molded expanded polystyrene sections and -erme- a
new washing machine.

If I were to use a hot wire or hot knife to cut the polystyrene into
new shapes would the hot tool seal the cut surfaces with a melted skin
and would that skin give the shape any structural integrity - or will
the pieces just remain as crumbly as they were before? I do not have
many specific ideas about how to use this foam but for instance I had
been pondering the idea of molding a piece of thermoplastic sheet to
replace a broken part from the refrigerator door and if instead I
could shape a piece of expanded polystyrene it might be a whole lot
easier. But would it have the strength to hold the bottle shelf in
place?

Thanks,

Nick

you can cut EPS with a hot wire but the surface is still porous.
in the model plane fraternity that, or cutting and shaping with knives
and saws and sandpaper, is the way it is shaped.
It has a lousy surface texture so it is normally covered in something
like tissue or even brown paper using PVA, before being painted -
emulsion paint or acrylic is pretty OK.


--
"Socialist governments traditionally do make a financial mess. They
always run out of other people's money. It's quite a characteristic of them"

Margaret Thatcher

In a word, no. The best stuff has a film on it already on the exposed bits,
but is seldom used for consumer grade packaging. It might seal a bit but
its not very strong. Its designed to give under compression for cushioning,
but has poor sheer strength at all. I remember using it for model aircraft
and it split very readily if not sealed.
Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Nick Odell" wrote in message
...
This is just idle curiosity so please do not spend too much time on an
answer or an explanation but...

I have just taken delivery of a new washing machine which has left me
with loads of pre-molded expanded polystyrene sections and -erme- a
new washing machine.

If I were to use a hot wire or hot knife to cut the polystyrene into
new shapes would the hot tool seal the cut surfaces with a melted skin
and would that skin give the shape any structural integrity - or will
the pieces just remain as crumbly as they were before? I do not have
many specific ideas about how to use this foam but for instance I had
been pondering the idea of molding a piece of thermoplastic sheet to
replace a broken part from the refrigerator door and if instead I
could shape a piece of expanded polystyrene it might be a whole lot
easier. But would it have the strength to hold the bottle shelf in
place?

Thanks,

Nick

Vaseline.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Murmansk" wrote in message
...
I seem to remember those hot wire tools that could cut expanded
polystyrene - as I remember they gave it a nice smooth surface but I don't
think it made it in any way stronger so I don't think your plan would work.

I once had success mending a fridge door shelf with Araldite using some
kind of mould to shape it as I needed but I can't remember for the life of
me how I stopped it sticking to the mould!

On 12/08/2020 23:57, Nick Odell wrote:
This is just idle curiosity so please do not spend too much time on an
answer or an explanation but...

I have just taken delivery of a new washing machine which has left me
with loads of pre-molded expanded polystyrene sections and -erme- a
new washing machine.

If I were to use a hot wire or hot knife to cut the polystyrene into
new shapes would the hot tool seal the cut surfaces with a melted skin
and would that skin give the shape any structural integrity - or will
the pieces just remain as crumbly as they were before?

You can cut it with any sharp blade box cutter is my tool of choice. Put
newspaper down to catch the tiny spheres that drop off.

Carve to shape dip in PVA and then you can use it as a mould or make a
plaster cast from it to use as a mould depending which is easier.

Expect to have lots of little polystyrene spheres floating around.

--
Regards,
Martin Brown

On Wednesday, 12 August 2020 at 20:57:52 UTC+1, Nick Odell wrote:
This is just idle curiosity so please do not spend too much time on an
answer or an explanation but...

I have just taken delivery of a new washing machine which has left me
with loads of pre-molded expanded polystyrene sections and -erme- a
new washing machine.

If I were to use a hot wire or hot knife to cut the polystyrene into
new shapes would the hot tool seal the cut surfaces with a melted skin
and would that skin give the shape any structural integrity - or will
the pieces just remain as crumbly as they were before? I do not have
many specific ideas about how to use this foam but for instance I had
been pondering the idea of molding a piece of thermoplastic sheet to
replace a broken part from the refrigerator door and if instead I
could shape a piece of expanded polystyrene it might be a whole lot
easier. But would it have the strength to hold the bottle shelf in
place?

Thanks,

Nick

No. You might make it more useful by dissolving it in solvent, then you can mould or glue with it. It's PS though, a relatively brittle plastic.


NT

On Wed, 12 Aug 2020 19:57:47 -0300, Nick Odell
wrote:

This is just idle curiosity so please do not spend too much time on an
answer or an explanation but...

I have just taken delivery of a new washing machine which has left me
with loads of pre-molded expanded polystyrene sections and -erme- a
new washing machine.

If I were to use a hot wire or hot knife to cut the polystyrene into
new shapes would the hot tool seal the cut surfaces with a melted skin
and would that skin give the shape any structural integrity - or will
the pieces just remain as crumbly as they were before? I do not have
many specific ideas about how to use this foam but for instance I had
been pondering the idea of molding a piece of thermoplastic sheet to
replace a broken part from the refrigerator door and if instead I
could shape a piece of expanded polystyrene it might be a whole lot
easier. But would it have the strength to hold the bottle shelf in
place?

Thanks,

Thanks for all the suggestions which I have taken on board.

Cheers,

Nick